 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

OFFICE OF           

PREVENTION, PESTICIDES,

AND TOXIC SUBSTANCES

March 31, 2008

MEMORANDUM:

Subject:	Formaldehyde:  Toxicology Disciplinary Chapter for the
Registration Eligibility Decision (RED) Document. 

To:	Sharon Carlisle, Chemical Review Manager 

Antimicrobials Division

From: 	Timothy F. McMahon, Ph.D.,  Senior Toxicologist

	 Antimicrobials Division

	

Attached is the Toxicology disciplinary chapter for formaldehyde for the

Reregistration  Eligibility Decision Document. 

Table of Contents

1.0	Hazard
Characterization........................................................
...............................4

2.0	Toxicology
Data....................................................................
.................................10

3.0	Data
Gaps....................................................................
...........................................11

4.0	Hazard
Assessment..............................................................
..................................11

	4.1	Acute
Toxicity................................................................
.............................11

	4.2	Subchronic
Toxicity................................................................
...................12

	4.3	Prenatal Developmental
Toxicity.............................................................19

	4.4	Reproductive
Toxicity................................................................
...............21

	4.5	Chronic
Toxicity................................................................
........................22

	4.6
Carcinogenicity.........................................................
.................................24

	4.7      Combined Chronic
Toxicity/Carcinogenicity..........................................33

	4.8
Mutagenicity............................................................
..................................34

4.9
Neurotoxicity...........................................................
...................................43

4.10	Metabolism and
Pharmacokinetics........................................................
..45

4.11	Special
Studies.................................................................
...........................46

5.0	Toxicity End Point
Selection...............................................................
..................67

	5.1	 Summary of Toxicological Doses and
Endpoints......................... ........67

				

Dermal
Absorption..............................................................
......................67

5.3	Classification of Carcinogenic
Potential..................................................67

6.0	FQPA
Considerations..........................................................
..................................69

7.0	Summary of toxicological doses and
endpoints...................................................70 

8.0	Toxicity Profile
Tables..................................................................
.........................71

9.0 
References..............................................................
.................................................94

1.0	HAZARD CHARACTERIZATION

Technical grade formaldehyde (37% a.i.) has a moderate order of acute
toxicity in experimental animals via the oral and dermal routes
(Toxicity Categories II and III). Inhalation toxicity studies on
formaldehyde are extensive and include both acute exposures and longer
term exposures. Toxicity from acute exposures is characterized by
pathology of the respiratory epithelium and has been observed in rats
exposed for 4 hours to a concentration of 10 ppm (Bhalla, 1991), while
longer term exposures of rats (3 ppm for 6 hours/day for 5 days) also
results in respiratory tract lesions (Buckley et al., 1984).  Repeated
exposure to 40 ppm formaldehyde for 6 hours/day, 5 days/week for 13
weeks results in mortality in 80% of B6C3F1 mice whereas exposure to 20
ppm formaldehyde for the same time period produced no mortality
(Maronpot et al., 1986). Formaldehyde is a severe eye and skin irritant
(Toxicity Category I) and is positive for dermal sensitization.  

In one repeated dose (90 day) oral toxicity study in the rat 
irritability, weight loss, hair loss, yellowing of teeth, and decreased
food consumption were observed at 0.6% formaldehyde in male Hotzman
rats.  In another 90-day oral toxicity study in the rat (Johannsen et
al.,1986), decreased body weight gain was observed at 100 mg/kg/day in
male Sprague-Dawley rats.. In a 28-day drinking water toxicity study in
rats (Til et al.,1988), decreased protein and albumin levels in blood
plasma and histologic changes were observed at 125 mg/kg/day in rats..
In a 90-day oral toxicity study in non rodents (Johannsen et al., 1986),
reduced body weight gain was observed in beagle dogs at 100 mg/kg/day. 

	In a 90-day inhalation toxicity study in the rat (Woutersen et al.,
1987) a marked increase in the number of labeled nasal epithelial
showing clear squamous metaplasia and hyperplasia was observed at 12
mg/m3 formaldehyde administered 6 hours/day for 5 days/week. In another
90-day inhalation toxicity study conducted by the Chemical Industry
Institute of Toxicology, formaldehyde was administered to 20 mice and
rats at concentrations of 4, 12.7, or 38.6 ppm (4.96, 15.74 and 47.84
mg/m3, respectively), for 6hrs/day, 5 days/week for 13 weeks. The
systemic LOAEL was 12.7 ppm (15.74 mg/m3), based on body weight decrease
and nasal erosion. 

Developmental toxicity of formaldehyde by inhalation has been examined
in the open literature.  Saillenfait et al. (1989) exposed
Sprague-Dawley rats to 5, 10, 20, and 40 ppm formaldehyde 6 hours/day on
gestation days (GDs) 6–10.Ddams exposed to 40 ppm exhibited reduced
body weight, indicative of general toxicity. This exposure concentration
also led to a significant decrease in fetal body weight (FBW). There was
also a slight, albeit statistically significant, decrease (from 5.61 to
5.35 g/litter) in male FBW in dams exposed to 20 ppm formaldehyde.   No
other significant signs of fetal malformations were reported., In a
similar study, Martin (1990) reported the effects of exposure of
Sprague-Dawley rats to 2, 5, and 10 ppm 6 hours/day on GDs 6–15. Food
consumption and dam weight gain were reduced significantly in dams
exposed to 10 ppm formaldehyde. These studies  indicate that inhalation
of formaldehyde is unlikely to be teratogenic at maternally toxic doses,
although high doses may generally be fetotoxic. 

In a dermal developmental toxicity study by Overman (1984), pregnant
Syrian hamsters were administered 0.5 mL formaldehyde (37% a.i.) 2
hrs/day from gestation day 8 through 11. Treatment had no effect on
maternal weight gain. The treatment did not influence fetal C- R length.
Mean fetal weight was slightly increased in experimental animals, but
the difference was not statistically-significant. No skeletal
malformations were found and no other malformations were observed.

Reproductive toxicity of formaldehyde was examined. In one study   (MRID
00143291), formaldehyde (40% a.i.) was provided to Beagle dogs in the
diet at concentrations of 0, 3.1 or 9.4 mg/kg/day on gestation days 4
through 56. There were no formaldehyde-related effects in any of the
parameters other than   pup weights, which were lower by group in
litters of dams exposed to formaldehyde Cassidy et al. (1983)
administered single oral doses of 100 or 200 mg/kg to five male Wistar
rats/group. Testes from these animals and 20 controls were excised and
examined for spermatogenic abnormalities 11 days after dosing. Although
no significant toxicological effects of formaldehyde on total sperm
counts were observed at either tested dose, an increased incidence (19%)
of testicular sperm head counts was observed in rats exposed to 200
mg/kg-day formaldehyde. The percentage of abnormal sperm heads also
significantly increased (5%) in the 200 mg/kg-day dose group compared to
controls. These data suggest that formaldehyde can induce morphological
abnormalities in the germ cells of male experimental animals at dose
levels that did not significantly affect testis weights or sperm counts.

	Chronic toxicity and carcinogenicity of formaldehyde has been examined
in several studies.  In one study (Kerns et al., 1983), groups of F344
rats and C57BL/6 x C3H F1 (B6C3F1) mice (approximately
120/sex/concentration) were exposed to 0, 2.0, 5.6, and 14.3 ppm
formaldehyde gas, 6 hours/day, 5 days/week for 24 months. Lesions in the
nasal cavity were the primary formaldehyde related effect in both mice
and rats throughout the study.  However, examination of the
histopathology tables also suggested an increase in mouse lymphomas and
rat leukemia in female animals. 

In a chronic toxicity study conducted by Battelle, Pacific Northwest
laboratories B6C3F1 mice (5/sex/group) were exposed to one of five
concentrations of vaporized formaldehyde for a period of 6 hours per day
 at target concentrations of 15, 25, 50, 100, and 200 ppm (18.59, 30.98,
61.96, 123.93, and 247.85 mg/m3). Mild supportive rhinitis was observed
in the 18.59 mg/m3 dose level dose level while necrosis and sloughing of
the mucosa in the turbinates, trachea, and proximal bronchi were seen
the 61.96 mg/m3 animals. Male and females rats exposed at 15 ppm
formaldehyde exhibited increased bone marrow hyperplasia beginning at 20
months It is  not known if bone marrow hyperplasia  may be indicative of
a myeloproliferative or lymphoproliferative disorder, or a regenerative
response to gross tissue injury at the point of entry. Squamous cell
carcinoma (SCC) was also observed at the two highest dose levels in this
study. 

The Chemical Industry Institute of Toxicology (CIIT) performed a second
bioassay on inhaled formaldehyde in 9-week-old male F344
(CDF[F344]/CrlBr) rats (Monticello et al., 1996). The rats were exposed
6 hours/day, 5 days/week for 24 months to 0, 0.7, 2.0, 6.0, 10.0, and
15.0 ppm. Nasal neoplasms included SCC and polypoid (transitional)
adenomas and were similar in morphological characteristics to those
described in the Kerns et al. (1983) chronic bioassay. The incidence of
SCC was increased at 6 ppm and above, with a NOAEL of 2 ppm for this
effect. 

	In a chronic toxicity study in the rat (Kamata et al., 1997), male
Fischer 344 rats were exposed via the inhalation route to formaldehyde
(37% a.i.) at concentrations of 0, 0.3, 2, or 15 ppm (0, 0.4, 2.5, or 19
mg/m3), 6hr/day, 5 days/week. A highly nonlinear response for SCC and
proliferative lesions in the nasal cavity was observed in animals
exposed to 15 ppm formaldehyde, while animals in the 2 ppm group showed
a statistically significant increase in some epithelial lesions.

In studies by Hauptmann et al. (2003, 2004), retrospective cohort
mortality studies of U.S. workers involved in the production or use of
formaldehyde was examined.  These studies were   large epidemiology
studies, and  provided individual quantitative exposure estimates for
the workers. The NCI cohort consisted of 25,619 workers (88% male)
employed in any of the 10 plants prior to 1966; the current follow-up
analyzes 8,486 deaths (178 attributed to lymphohematopoietic malignancy
and 9 to nasopharyngeal cancer). A detailed exposure assessment was
conducted for each worker based on exposure estimates for different jobs
held and tasks performed (Stewart et al., 1986).  Exposure estimates
were made using several different metrics - peak exposures, average
intensity, cumulative exposure, and duration of exposure. Respirator use
and exposures to formaldehyde particles and other chemicals were also
considered. Significant increases in relative risk for
lymphohematopoietic cancer were observed primarily for myeloid leukemia
and Hodgkin’s disease and for the peak exposure and average intensity
exposure metrics. For the nasopharyngeal cancers, significant trends
were observed for the cumulative and peak exposure metrics.

	

	 

Based of the on going development of the science to predict carcinogenic
potential of formaldehyde within EPA, OPP has decided to present the
formaldehyde cancer risks for the pesticidal uses using both the
existing 1991 IRIS cancer unit risk of 1.3 E-5 per (µg/m3) and the CIIT
biologically-based dose-response (BBDR) model until any new cancer
estimates are fully peer reviewed.  OPP also acknowledges the wide range
in cancer risks using these approaches and will coordinate with other
offices in EPA on the outcome of the upcoming peer review process on the
carcinogenicity of formaldehyde.  The formaldehyde IRIS assessment is
scheduled to be begin internal review in May 2008 and is scheduled to 
start external peer review in January 2009. Because formaldehyde air
concentrations approach those associated with ocular and respiratory
tract irritation, the risk mitigation measures to be implemented in the
meantime for the pesticidal uses will be based on mitigating the
non-cancer effects at a limit of 0.01 ppm.  It is believed that this
level will reduce exposures sufficiently such that the cancer risks
would not be of concern.  The EPA  process of regulating pesticides
allows for reevaluation at any time if new information from the peer
review process of the carcinogenic potential of formaldehyde warrants.

Formaldehyde’s mutagenicity has been examined in a variety of in vitro
and in vivo test systems. In a bacterial reverse mutation test (MRID
00132156), formaldehyde (2%) was tested at concentrations of 0.001,
0.01, 0.10, 1.0, or 5.0 µL and found to be negative. In a second
submitted study (MRID 00132157), formaldehyde (2%) was tested at
concentrations of 3.0, 15.0, 75.0, 150, or 300 µg/plate and found to be
positive in the bacterial reverse mutation assay. Formaldehyde caused a
positive response (3.2-fold increase) on tester strain TA98 without
metabolic activation. A 1.9-fold increase was observed on TA98 with
metabolic activation. Also, increases of 2.2-fold and 1.7-fold were
observed on tester strain TA100 with and without activation,
respectively. In an in vitro mammalian chromosome aberration test (MRID
00132168), formaldehyde (37% formalin), was tested on Chinese hamster
ovary cells at concentrations of 28.43, 37.91, or 50.55 nL/mL. The test
article caused a significant dose-dependant increase in the frequencies
of chromosome aberrations in the Chinese Hamster Ovary cells, both with
and without S-9 activation. One submitted study (MRID 00132169), tested
formaldehyde (37%) for Unscheduled DNA synthesis (UDS) in Primary rat
liver hepatocytes. The test material was tested at concentrations of
0.0005, 0.001, 0.005, 0.01, 0.02, or 0.04 µL/mL and found to cause no
significant increase in UDS in rat hepatocytes. 

In published studies, formaldehyde has shown both positive and negative
results in the Ames Salmonella assay (Donovan et al., 1983; Connor et
al., 1983, 1985;  Frei et al., 1984; Fiddler et al., 1984; Oerstavik and
Hongslo, 1985; Takahashi et al., 1985; Schmid et al., 1986; Zielenska
and Guttenplan, 1988;  Le Curieux et al., 1993; O’Donovan and Mee
(1993) Watanabe et al., 1996; Dillon et al., 1998; Ryden et al., 2000;
Wilcox et al., 1990; Jung et al., 1992; Marnett et al., 1985; Mueller et
al., 1993).

	Temcharoen and Thilly (1983) examined the capacity of formaldehyde to
induce forward mutations to 8-azaguanine resistance in S. typhimurium TM
677, a his+ revertant of TA 1535. Both toxicity and mutagenicity were
obtained at formaldehyde concentrations of 0.17 mM in the absence of S9
and 0.33 mM in the presence of S9 Dillon et al. (1998) employed
Salmonella strains TA102 and TA104 because they are more sensitive to
oxidative mutagens. Formaldehyde was mutagenic in both strains, as well
as in TA100. However, the authors reported that the mutagenic activity
was not reduced in TA104 in the presence of S9 from either
Aroclor-induced male Fischer F 344 rats or male B6C3F1 mice. 

	In another study, formaldehyde induced forward mutations to
trifluorothymidine resistance in mouse lymphoma L5178Y tk+/- cells both
in the absence and presence of rat liver S9 (higher concentrations
required for effect with S9). Both toxicity and mutagenicity were
abolished when formaldehyde dehydrogenase was incorporated in the
exposure medium (Blackburn et al., 1991).

ions greater than 200 M and a reduction of radiation-induced breaks
(indirect measure of DPX) at 50 M. Formaldehyde-induced DPX were
repaired 24 hours after the compound was removed from the culture.

	

	In vivo, no treatment-related increase in either micronuclei or
chromosome aberrations were observed following  intraperitoneal exposure
to formaldehyde at 0, 6.25, 12.5, or 25 mg/kg. (Natarajan et al. (1983)
).  Similarly,  chromosomal analysis of spermatocytes at metaphase I did
not reveal any chromosomal lesions in Q strain mice injected
intraperitoneally with 50 mg/kg of the compound (Fontignie-Houbrechts,
1981).   Exposure of male and female Fischer F-344 rats to 0.5, 6, or 15
ppm (0.6, 7.4, 18.5 mg/m3) formaldehyde by inhalation for 6 hours/day
for 5 days showed no increases in either SCE or chromosome aberrations
at any dose level (Kligerman et al. (1984) )  . 

In a neurotoxicity screening battery (Malek et al., 2003a), rats were
exposed to 0, 1.0, 2.5, or 5.0 ppm (0, 1.23, 3.08, or 6.15 mg/m3)
formaldehyde for 2 hours and locomotor activity was assessed for 1 hour
in an open field 2 and 24 hours after termination of formaldehyde
exposure. Reductions in horizontal movements (crossed quadrants) were
observed after two  hours at 1.0 ppm. In another neurotoxicity study
(Malek et al., 2003b), rats (10 per group) were exposed at 0, 0.1, 0.5,
or 5.0 ppm (0, 0.123, 0.615, or 6.15 mg/m3) formaldehyde for 2 hours and
open field behavior tests were conducted on each animal 2 hours after
formaldehyde exposure. Significant reductions in motor activity in males
were observed at 1.0 ppm after 2 hours. In a third neurotoxicity study
(Pitten et al., 2000), adult male Wistar rats were exposed to 0 ppm, 2.6
ppm (0.25% formaldehyde solution to yield 3.06 ± 0.77 mg/m3 ), or 4.6
ppm (0.70% formaldehyde solution to yield 5.55 ± 1.27 mg/m3)
formaldehyde, 10 minutes/day, 7 days/week for 90 days. The animals were
assessed for performance in the maze every seventh day, at least 22
hours after the exposure on the previous day.  Neurotoxicity was
observed at 2.6 ppm,   based on statistically significant performance
errors as compared to the control group and increased run times through
the maze. In a behavioral and neurotoxicity study conducted by Boja et
al., 1985, Sprague-Dawley rats were exposed to either air or
formaldehyde at concentrations of 5, 10, or 20 ppm (6.20, 12.39, or
24.79 mg/m3) via inhalation for 3 hours on two days. Exposure to 5 ppm
(6.20 mg/m3) formaldehyde resulted in statistically significant
decreased motor activity within 15 minutes 

	From the ATSDR Toxicological review on formaldehyde (ATSDR, 1999),
formaldehyde is rapidly metabolized primarily by formaldehyde
dehydrogenase, a widely distributed enzyme present in all tissues,
particularly nasal mucosa. Unmetabolized formaldehyde can form
cross-links between proteins and between protein and DNA. Jeffcoat et
al. (1983) examined disposition of dermally applied formaldehyde in
rats, guinea pigs, and monkeys and observed between 5-8% excretion in
urine of rats and guinea pigs and 0.7-1.5% excretion in feces. Excretion
in monkeys was less than 1% of the applied dose by all routes. Trapped
expired air constituted the largest percentage of excretion in rats and
guinea pigs (21-24% of the administered dose).



2.0	TOXICOLOGY DATA

  SEQ CHAPTER \h \r 1 The available toxicology data for Formaldehyde is
listed below.

Table 1. Toxicology Data for Formaldehyde

Test	Technical

	MRID	Required	Satisfied

870.1100	Acute Oral Toxicity    

870.1200	Acute Dermal Toxicity

870.1300	Acute Inhalation

870.2400	Primary Eye Irritation 

870.2500	Primary Dermal Irritation 

870.2600	Dermal Sensitization	00058054, 00065508

00058054, 00065508, 00159395

Open Literature

00058054, 00065508, 00159395

00058054, 00065514, 00159392

40161103, Open Literature	yes

yes

yes

yes

yes

yes	yes

yes

yes

yes

yes

yes

870.3100	90-day oral (Rodent)

870.3150	90-day oral (Non-rodent)

870.3250     90-Day Dermal (Rat)  

870.3465     90-Day Inhalation (Rat)	00124677, 00134114, Open Literature

Open Literature

-

00082134, 00149755, Open Literature	yes

yes

yes

no

yes	yes

yes

no

yes

870.3700	Developmental Toxicity (Rat) 

870.3700	Developmental Toxicity (Rabbit)

870.3800	Reproduction	00082136, 00123769, 00123770, 00164652, Open
Literature

-

00143291, Open Literature	yes

yes

yes	yes

no

yes

870.4100a   Chronic (Rodent)

870.4100b   Chronic (Non-rodent)

870.4200a   Carcinogenicity (Rat)

870.4200b   Carcinogenicity (Mouse)	Open Literature

-

00143288, Open literature

Open Literature	yes

no

yes

yes	yes

yes

yes

870.5100	Mutagenicity – Bacterial Reverse Gene      

                    Mutation assay        

                                

870.5385	Mutagenicity – Bone marrow chromosome 

                    aberration test (Mouse)                      

870.5550	Mutagenicity – Unscheduled DNA synthesis 

                    in primary rat hepatocytes                    
00132156, 00132157, Open Literature

-

00132169	yes

yes

yes	yes

no

yes



870.6200     90-day neurotoxicity (Mammal)	

Open Literature	

yes	

yes

Metabolism

870.7600     Dermal penetration	Open Literature

Open Literature	yes

yes	yes

yes



3.0	DATA GAPS

 90-day dermal toxicity study (rodent)

  Developmental toxicity in non –rodents

  Mutagenicity – Bone marrow chromosome aberration test (mouse)

4.0	HAZARD ASSESSMENT

Acute Toxicity

Adequacy of database for Acute Toxicity: The acute toxicity database for
formaldehyde is considered complete.  Technical grade formaldehyde (37%
a.i.) has a moderate order of acute toxicity in experimental animals via
the oral and dermal routes (Toxicity Categories II and III). Inhalation
toxicity studies on formaldehyde are extensive and include both acute
exposures and longer term exposures.  Toxicity from acute exposures is
characterized by pathology of the respiratory epithelium and has been
observed in rats exposed for 4 hours to a concentration of 10 ppm
(Bhalla, 1991), while longer term exposures of rats (3 ppm for 6
hours/day for 5 days) also results in respiratory tract lesions (Buckley
et al., 1984).  Repeated exposure to 40 ppm formaldehyde for 6
hours/day, 5 days/week for 13 weeks results in mortality in 80% of
B6C3F1 mice whereas exposure to 20 ppm formaldehyde for the same time
period produced no mortality (Maronpot et al., 1986).    Formaldehyde is
 a severe eye and skin irritant (Toxicity Category I  and is positive
for dermal sensitization.  

The acute toxicity data for Formaldehyde is summarized below in Table 2.

Table 2.  Acute Toxicity data for Formaldehyde technical a.i.

Guideline Number	Study Type/ Test substance (% a.i.)	MRID

Number/ Citation	Results	Toxicity Category



870.1100

(§81-1)	

Acute Oral – Guinea Pig 

Purity 37.3% - Formaldehyde

	

00058054	

LD50 = 260 mg/kg	

II



870.1200

(§81-2)

	

Acute Dermal – Rat

Purity  37.3% - Formaldehyde

	

00058054	

  SEQ CHAPTER \h \r 1 LD50 = 300 mg/kg

	

II



870.1200

(§81-2)

	

Acute Dermal – Rat

Purity  37.0% - Formaldehyde

	

00159395	

LD50 > 4.9 mL/kg (4.53 

            g/kg)	

III



870.1200

(§81-2)	

Acute Dermal – Rabbit

Purity  37.3% - Formaldehyde	

00058054	

  SEQ CHAPTER \h \r 1 LD50 = 240 mg/kg

	

II



870.1200

(§81-2)

	

Acute Dermal – Dog

Purity  37.3% - Formaldehyde

	

00058054	

  SEQ CHAPTER \h \r 1 LD50 = 550 mg/kg

	

II



870.1300

(§81-3)

	

Acute Inhalation – Mouse and Rat	

See Open Literature studies in Toxicity Profile for Formaldehyde



870.2400

(§81-4)

	

Primary Eye Irritation 

Purity  37.3% - Formaldehyde

	

00058054	

Severe eye irritant	

I



870.2500

(§81-5)	

Primary Dermal Irritation 

Purity  37.3% - Formaldehyde

	

00058054

	

Formation of vesicles with superficial necrosis or nodules.

	

I



870.2600

(§81-6)	

Dermal Sensitization – Guinea pigs

Purity 40.0% - Formaldehyde

	

40161103	

Extreme Sensitizer	

NA

NA – Not Applicable

4.2	Subchronic Toxicity

Adequacy of database for Subchronic Toxicity: The database for
subchronic toxicity consists of  guideline and open literature studies.

870.3100	Subchronic (90-day oral) Toxicity – Rat 

In one 90-day oral toxicity in the rat (MRID 00124677) formaldehyde (37%
a.i.) was administered orally at 0, 0.3, 0.6, 1.2 or 2.4 % to 10 male
Holtzman rats/dose. A NOAEL was established at 0.3% while the LOAEL was
0.6%, based on irritability, weight loss, hair loss, yellowing of teeth,
and decreased food consumption. 

ehyde concentrations ≥ 0.50 %, believed due to decreased food
consumption.

870.3100	Subchronic (28-day oral) Toxicity – Rat

In a 28-day oral toxicity study in the rat (MRID 00134114), formaldehyde
(60% a.i.) was administered to 10 male Sprague-Dawley rats/dose at
concentrations of 0, 79, 158 or 316 µg/kg/day, once daily, 5 days/week
for four weeks. 

Statistical evaluation of overall body weight gains and total food
consumption revealed no significant differences between the control
group and test groups. The appearance and behavior of the test rats were
comparable to those of the control rats. No pathological findings
associated with the oral administration of the test substance were
observed.

One rat exposed to158 uL/kg/day died during the 4th week. Autopsy
revealed a pale, mottled liver. Three rats receiving the high dose of
formaldehyde showed slight salivation during the 4th week of the study.

870.3100	Subchronic (90-day oral) Toxicity – Rat

In an oral subchronic toxicity study conducted by Johannsen et al.
(1986) Groups of albino Sprague-Dawley rats (15/sex) were administered
the equivalent of 0, 50, 100, or 150 mg/kg-day paraformaldehyde (95 %
a.i.) in their drinking water for 91 consecutive days. Rats were
observed at frequent intervals for behavioral reactions. Body weights
and food and water intake were recorded on a weekly basis. Hematology
(HCT, Hb, total and differential leukocyte counts), clinical chemistry
[blood sugar, BUN, ALP, glutamic oxalacetic transaminase (GOT),), and
urine analyses (color, appearance, pH, specific gravity, sugar, protein,
and microscopic elements) were conducted on 10 male and 10 female rats
selected from each test group. Tissue weights were recorded for the
adrenals, gonads, hearts, kidneys, livers, lungs, and thyroids.
Histopathology was performed on a set of over 20 tissues and organs from
rats in the high-dose and control groups.

No deaths or abnormal reactions were observed in rats administered
formaldehyde for 90 days.  Significant reductions in weight gain were
observed in both sexes at 150 mg/kg and in male rats given 100 mg/kg.
There was a dose-related decrease in liquid consumption in both male
rats (9%, 18%, and 31%) and females (13%, 22%, and 30%) administered
formaldehyde in their drinking water. There were no overall differences
in mean food intake or feed efficiency in rats at any test level, thus
reductions in body weight gain are considered to be a reflection of
systemic effects of formaldehyde. No statistically-significant
differences were observed in hematologic parameters in any treated rats.
No specific treatment-related effects were observed on any organ or
tissue, including possible target organs like the kidney, liver, and
lung. Clinical chemistry and urinalysis studies failed to indicate any
necrotic effects on muscle, kidney, liver, or heart. No differences were
apparent between absolute or relative organ weights of treated rats. No
treatment-related pathological changes were observed microscopically.

A systemic toxicity NOAEL of 50 mg/kg/day for males and 100 mg/kg/day
for females was established while the systemic NOAEL was set at 100
mg/kg/day for males and 150 mg/kg/day for females, based on decreased
body weight gain.

870.3100	Subchronic (90-day oral) Toxicity – Rat

Til et al. (1988) evaluated the oral toxicity of formaldehyde and
acetaldehyde in a subacute study in Wistar (Cpb:WU; Wistar random) rats.
Groups of rats (10/sex/dose) were exposed to acetaldehyde or
formaldehyde at 0, 25, 125, and 625 mg/kg-day or 0, 5, 25, and 125
mg/kg-day in drinking water for 4 weeks. The control group was comprised
of 20 rats of each sex, and, to account for potential effects of
decreased water consumption in treated animals, an additional control
group of 10 male and 10 female rats was given drinking water in an
amount equal to the amount of liquid consumed by the group given the
highest dose. Fresh solutions of test concentrations were prepared
weekly and stored at 4 ºC until used.  Endpoints examined included food
and water intake, body weight, daily observations for condition and
behavior, organ weights, hematological and clinical chemistry
parameters, urinalysis, gross pathology, and histopathology. Weights
were recorded for all major tissues.  Histopathological examination was
restricted to the established major target tissues: liver, kidneys, GI
tract, and nose (six standard cross sections). Examination of the GI
tract was performed in all dose groups and included the tongue,
esophagus, and stomach.  Histopathology for the other tissues was
performed on high dose and control animals. 

“The rats appeared to be healthy throughout the study, and no effects
on growth occurred despite significant decreases in food and water
intake that occurred at the high dose (125 mg/kg-day). Yellow
discoloration of the fur occurred in the rats on the high dosage from
week 3 onwards. There were no significant changes in hematology among
the exposed groups except for slight (not statistically different)
increases in packed cell volumes in the water-restricted group and in
high-dose males. The high-dose groups of the formaldehyde-exposed and in
the water-restricted controls had slightly increased urine density, but
again this was not statistically significant. Plasma TP and ALB levels
were decreased in the males of the highest-dose group. No changes in
tissue organ weights occurred with the exception that relative kidney
weights were slightly increased in the females of the high-dose group. 
Gross pathological findings were restricted to the GI tract and revealed
a thickening of the limiting ridge of the forestomach in all animals
exposed at the highest dose that was accompanied by a yellowish
discoloration of the mucosa. These latter changes were not observed in
the acetaldehyde-exposed animals. Treatment-related histopathological
changes were seen in the GI tract only. As shown in Table 5-29, slight
(8/20) or moderate (12/20) focal hyperkeratosis of the forestomach and
slight focal atrophic gastritis occurred in animals of the high dose
groups only. One female had moderate focal papillomatous hyperplasia. 
No histopathological changes were observed in any animals of the lower
dose groups. The study established a LOAEL and NOAEL for epithelial
changes in the GI tract of male and female Wistar rats exposed to
formaldehyde in drinking water of 125 mg/kg-day and 25 mg/kg-day,
respectively. ”

870.3150	Subchronic (90-Day oral) Toxicity in nonrodents – Dog

In a 90-day oral toxicity study in non rodents (Johannsen et al., 1986),
paraformaldehyde (95% a.i., aqueous) was administered to four Beagle
dogs/sex/dose at doses of 0, 50, 75, or 100 mg/kg/day. 

No deaths or abnormal reactions were observed. Significant reductions in
weight gain were observed in both sexes at 100 mg/kg/day. Treated
animals had reduced food consumption and feed efficiency even at the
lower dosages (50 and 75 mg/kg/day) which did not depress weight gain.
Hematological values from treated dogs fell within normal limits. No
specific treatment-related effects were observed on any organ or tissue,
including possible target organs like the kidney, liver, and lung. 

The NOAEL was 75 mg/kg/day while the LOAEL was established to be 100
mg/kg/day for both males and females, based on reduced weight gain.

870.3465	Subchronic (90-Day Inhalation) Toxicity 

An earlier cross-species study examined changes in lung tissue resulting
from continuous exposure but did not evaluate effects on the nasal
mucosa (Coon et al., 1970). Animals were exposed to 3.7 ppm formaldehyde
(4.6 mg/m3) for 90 days. Five species of animals were studied: male and
female Sprague-Dawley and Long-Evans derived rats (15), male and female
Princeton-derived guinea pigs (15), male New Zealand albino rabbits
(three), male squirrel monkeys (Saimiri sciureus) (three), and purebred
male beagle dogs (two). Blood samples were taken for hemoglobin (Hb)
concentration, hematocrit (HCT), leukocyte counts, and serum levels of
blood urea nitrogen (BUN), aspartate aminotransferase (AST), alanine
aminotransferase (ALT), alkaline phosphatase (ALP), and LDH. Sections of
heart, lung, liver, kidney, and spleen were fixed and examined from each
species (details of method not provided). Brain, spinal cord, and
adrenal tissue also were examined in monkeys and dogs as well as thyroid
from dogs. Liver and kidney sections were stained for reduced
nicotinamide adenine dinucleotide, lactate, isocitrate, and
ß-hydroxybutyrate. Tissue sections of the nasal mucosa were not
examined in this study.

Hematological parameters were unaffected by formaldehyde treatment. The
lung tissue of all species exhibited interstitial inflammation after 90
days of formaldehyde exposure (detailed description not provided).
Formaldehyde-treated rats and guinea pigs also had focal chronic
inflammation in heart and kidney tissue sections. However, the authors
were uncertain whether the observed changes to heart and kidney were due
to formaldehyde exposure.

870.3465	Subchronic (6-Week Inhalation) Toxicity 

In a 6-Week inhalation toxicity study (MRID 00149755), Fisher 344 rats
– 10/sex/dose; Syrian golden hamsters – 10/sex/dose; and Cynomolgous
monkeys – 6 males/dose, were administered formaldehyde (4.96% a.i.) at
concentrations of 0, 0, 0.20, 1.00, or 3.00 ppm equivalent to 0, 0,
0.19, 0.98 and 2.95 ppm, respectively, for 26 weeks. 

 

Treatment-related effects during the study were not seen. Compared to
controls, monkeys receiving 1.00 ppm showed increased incidence of dried
material around the nose, increased incidences of hoarseness and
congestion. 

Body weight

showed significant differences (p ≤ 0.01) from week 2-26 compared to
controls. 

Organ weight

Organ weights for monkeys and hamsters were not significantly different
compared to controls. Male and female rats in the 0.2 ppm group had
significant mean heart weight depression (p ≤ 0.01) compared to the
control. Males in the 3.0 ppm test group had significantly (p ≤ 0.01)
depressed mea absolute heart and kidney weights compared to the
controls, but the relative weights of these same tissues were
significantly increased for these same rats. Females in the 3.0 ppm test
group had significantly (p ≤ 0.01) depressed absolute heart weights
with the mean relative heart weight significantly increased (p ≤
0.01). For the 3 ppm group, the mean absolute and relative liver weights
were significantly depressed (p ≤ 0.01) compared to the controls. 

Gross and Microscopic Pathology

In monkeys, hamsters and rats, no abnormalities were seen in or
attributable to formaldehyde vapors. 

870.3465	Subchronic (90-Day Inhalation) Toxicity - Rat

In a 90-Day inhalation toxicity study (Woutersen et al., 1987), male and
female albino SPF Wistar rats (10/group) were exposed to 0, 1, 10, or 20
ppm formaldehyde (0, 1.23, 12.3, or 24.6 mg/m3), 6 hours/day, 5
days/week for 13 weeks. Rats were checked daily and weighed weekly.
During week 13, blood samples were taken for Hb, packed cell volume, RBC
count, and a differential count of leukocytes. Urine samples were taken
for density, volume, pH, protein, glucose, occult blood, ketones, and
appearance. At sacrifice, blood samples were taken and analyzed for ALB,
creatinine, glucose, TP, BUN, and the enzyme activities (AST, ALT, and
ALP). GSH and protein content were determined in liver homogenates.
Organs were examined and weighed: adrenals, brain, heart, kidneys,
liver, lungs, ovaries, pituitary, spleen, testes, thymus, and thyroid.
Three longitudinal sections of lungs, trachea, and larynx and six
standard cross sections of the nose were taken for microscopic
examination. Two rats per exposure group were similarly treated for 3
days and sacrificed 18 hours later, and nasoturbinates were dissected to
measure cell proliferation. Nasoturbinates were removed, cultured with
[3H]-thymidine for 2 hours, and processed for autoradiography.

No gross pathological changes were seen upon autopsy, but body weights
decreased in the both male and female rats at the 20 ppm treatment
level. Of the organs weighed, 6 of 11 organs had significantly increased
relative rates in male rats exposed to 20 ppm formaldehyde (not
detailed). Relative brain weight was increased in female rats at the
same treatment level.

Clinical chemistry parameters of liver and kidney function and
hematological parameters were also measured after the 13-week treatment
by Woutersen et al. (1987). Compared to controls, activities of AST,
ALT, and ALP were significantly elevated in plasma from the 20 ppm
treated male rats (by 124%, 132%, and 126%, respectively, p<0.05). Total
plasma protein was reduced to 95% of controls in the same animals.
Although there was an observed increase in BUN in male rats treated with
1 ppm, this was not considered a treatment effect.  Furthermore, no
statistically significant differences were seen for these parameters in
female rats at any concentration level. Likewise, plasma ALB, plasma
creatinine, plasma glucose, total liver protein, GSH, and relative liver
weight were unchanged in all treatment groups. 

Cell proliferation was measured in the respiratory epithelium of rats
treated for 3 successive days to the same treatment levels of
formaldehyde, 0, 1, 10, and 20 ppm. There was an increase of 37.6% in
[3H]-thymidine incorporation (indicating proliferation) in visibly
metaplastic epithelium resulting from exposure to 20 ppm formaldehyde,
compared to a level of 2.8% seen in unaffected tissue. However, there
were only two rats per treatment level.

Statistically significant increases were seen in focal respiratory
epithelial hyperplasia and keratinization in both male and female rats
at the highest treatment level (20 ppm). Male rats also had
statistically significant increases in observed respiratory epithelial
squamous metaplasia, focal olfactory epithelial thinning, and rhinitis.
Both male and female rats treated with 10 ppm formaldehyde showed
statistically significant increases in squamous metaplasia,  

hyperplasia, and keratinization of the respiratory epithelium.

Disarrangement of the respiratory epithelium was only significantly
increased in female rats, but this change was observed at both the 10
ppm and 20 ppm treatment levels.  Although some lesions were observed in
animals treated with 1 ppm formaldehyde, their incidences were not
statistically significant and the findings equivocal. A systemic
toxicity NOAEL was established at 1.2 mg/m3 and the LOAEL was fixed at
12 mg/m3, based on a marked increase in the number of labeled cells,
practically all of which were present in areas of the epithelium showing
clear squamous metaplasia and hyperplasia.

870.3465	Subchronic (90-Day Inhalation) Toxicity 

Appelman et al. (1988) studied the effects of bilateral intranasal
electrocoagulation damage on susceptibility to inhaled formaldehyde in
male SPF Wistar (Cpb: WU) rats. Rats were exposed 6 hours/day, 5
days/week for 13 or 52 weeks to 0, 0.1, 1.0, or 10 ppm (0, 0.12, 1.24,
or 12.4 mg/m3) formaldehyde. These concentrations were chosen because
the various short-term studies performed in this laboratory showed that
formaldehyde was non-cytotoxic to the nasal mucosa at levels of 0.3,
1.0, and 2.0 ppm, slightly cytotoxic at 3 and 4 ppm, and strongly
cytotoxic at 10 and 20 ppm (Woutersen et al., 1987; Zwart et al., 1988;
Wilmer et al., 1987). Further, because nasal tumors have only been found
at exposure concentrations that also induced severe degenerative,
hyperplastic, and metaplastic changes in the nasal epithelium (Squire
and Cameron, 1984; Griesemer et al., 1985), Feron et al. (1984) and the
investigators at the TNO-CIVO Toxicology and Nutrition Institute
postulated that formaldehyde at a subcytotoxic concentration was only a
very weak initiator without promoting activity. Appelman et al. (1988)
used an electrocoagulation method in this study to evaluate if damage to
the mucosa followed by compensatory cell proliferation might render the
epithelium vulnerable to subcytotoxic levels of formaldehyde. One half
of the rats used in the study (10/group) were damaged bilaterally and
then subjected to the first 6-hour exposure to formaldehyde at
approximately 20–26 hours after the electrocoagulation procedure. Ten
undamaged rats/group were also exposed at each concentration for either
13 or 52 weeks.

General condition and behavior was monitored daily. Individual body
weights were recorded at the start of exposure, once weekly during the
first month, and monthly thereafter. Blood samples were drawn on all
interim sacrifice rats to measure plasma ALB and TP, and the activities
of AST, ALT, and ALP. Blood samples drawn on rats of the 53-week
sacrifice were examined for Hb, PCV, and differentials. Urine samples
collected at the second sacrifice were examined for volume, density, pH,
protein, glucose, occult blood, and appearance. The livers of all
animals were weighed. The left lateral lobe of each liver was used to
determine hepatic protein and GSH content in postmitochondrial
fractions.  Additional organ weights obtained for animals in the last
sacrifice included adrenals, brain, heart, kidneys, lungs, pituitary,
spleen, testes, thymus, and thyroid. Histopathological examination
included six standard cross-section levels in the nose, livers of all
rats killed at 14 weeks and of all control and 10 ppm exposed rats
killed in week 53, larynxes, tracheas, and lungs of all rats of the
control and 10 ppm exposed rats killed in week 53, and organs and
tissues of control and 10 ppm exposed rats with an undamaged nasal
mucosa killed in week 53.

Yellow discoloration of the fur occurred in all animals of the two
highest exposure groups.  Growth retardation was observed in the animals
killed with or without damaged noses after 2 weeks exposure to 10 ppm
formaldehyde. No toxicologically significant findings in the body
weights or organ weights of any animals in the other exposure groups
were observed. No relevant differences between groups were found in any
of the hematological or urinary parameters with the exception of
frequent oliguria (p < 0.05) in the top exposure group without nasal
coagulation and killed in week 53. Three-way ANOVA revealed a
significant increase in TP content of the liver in rats with damaged
noses as compared to rats with undamaged noses, and there was a
significant negative correlation between the formaldehyde exposure level
and TP in these same rats. Hepatic GSH were positively correlated with
both nasal damage and age of the animals. 

The systemic toxicity NOAEL was established at 1.24 mg/m3 while the
LOAEL was 12.4 mg/m3, based on body weight retardation, incidence of
oliguria, and incidence of lesions of the respiratory and olfactory
epitheliums for damaged and undamaged animals.

870.3465	Subchronic (90-Day Inhalation) Toxicity – Mice and Rat

In a 90-day inhalation toxicity study conducted by the Chemical Industry
Institute of Toxicology, formaldehyde was administered to 20 mice and
rats at concentrations of 4, 12.7, or 38.6 ppm (4.96, 15.74 and 47.84
mg/m3, respectively), for 6hrs/day, 5 days/week for 13 weeks. 

No adverse effects observed in the 4 ppm group. At 12.7 ppm, a decrease
in body weight and evidence of nasal erosion in two exposed rats was
observed. Ulceration and necrosis of the nasal mucosa seen at 38.6 ppm
resulted in termination of exposure after 2 weeks. The systemic NOAEL
was 4 ppm (4.96 mg/m3, LDT) while the systemic LOAEL was established to
be 12.7 ppm (15.74 mg/m3), based on body weight decrease and nasal
erosion.

870.3465	Subchronic (90-Day Inhalation) Toxicity 

In a 90-day inhalation toxicity study (Citation not available),
formaldehyde was administered to 25 rats at concentrations of 0.0098,
0.028, 0.82 or 2.4 ppm (0.012, 0.035, 1.03 and 2.97 mg/m3,
respectively). 

At 2.4 ppm there was a significant decrease in cholinesterase activity;
at 2.4 and 0.82 ppm, there was proliferation of lymphocytes and
histiocytes in the lungs and some peribronchial and perivascular
hyperemia. There were no significant findings at the two lower
concentrations. The systemic activity NOAEL was 0.028 ppm (0.035 mg/m3)
and the Systemic LOAEL was 0.82 ppm (1.02 mg/m3), based on proliferation
of lymphocytes, histiocytes in the lungs, perivascular hyperemia. The
cholinesterase (ChE) NOAEL was 0.82 ppm (1.02 mg/m3) while the ChE LOAEL
was 2.4 ppm (2.97 mg/m3), based on a significant decrease in
cholinesterase activity at this dose level.

4.3	Prenatal Developmental Toxicity

Adequacy of database for Prenatal Developmental Toxicity: The database
for developmental toxicity of formaldehyde is considered incomplete with
a developmental toxicity study in non-rodents being unavailable. The
database consists of three submitted and two open literature studies in
rodents. 

870.3700a        Prenatal Developmental Toxicity Study – Mouse

Marks et al. (1980) carried out a developmental toxicity study of
formaldehyde in CD-1 mice in which 29-35 pregnant animals were gavaged
on GDs 6-15 with aqueous formaldehyde (containing 10-15% methanol) at
74, 148, and 185 mg/kg-day. Seventy-six controls were gavaged with water
alone. All dams were sacrificed on GD 18 and the number of implantation
sites in each uterine horn were counted. The high-dose of formaldehyde
was toxic to the dams, as indicated by the deaths of 22 of 34 mice
before GD 18. Thus, the dose of 148 mg/kg-day was a NOAEL for maternal
toxicity in this study. However, it is unclear to what extent an
estimated concurrent dose of up to 75 mg/kg-day methanol may have
contributed to this toxic response. To assess the developmental toxicity
of formaldehyde, live fetuses were weighed individually, sexed, and
examined for external, visceral, and skeletal malformations. Fetuses of
surviving high-dose dams and of those of other groups did not show an
increased incidence of malformations. Therefore, Marks et al. (1980)
concluded that formaldehyde did not induce fetal abnormalities and that
the 185 mg/kg-day dose level was a NOAEL for the developmental toxicity
of formaldehyde. Neither were the fetotoxic effects of methanol apparent
under the subject experimental conditions.

The maternal toxicity NOAEL was established to be 0 mg/kg/day and the
maternal toxicity LOAEL was 74 mg/kg/day, based on decreased body weight
gain. 

870.3700a        Prenatal Developmental Toxicity Study – Rat

Sallenfait et al. (1989) report a comprehensive and well-documented
developmental study in Sprague-Dawley rats. Pregnant rats were exposed
beginning on GD 6 in order to cover critical stages of development
(e.g., implantation and major organogenesis). Female Sprague-Dawley rats
(25/group) were exposed to 0, 5, 10, 20, or 40 ppm formaldehyde (0,
6.15, 12.3, 24.6, or 49.2 mg/m3), 6 hours/day on GDs 6–20. The onset
of pregnancy was determined by the presence of sperm in a vaginal smear.
Dams were exposed to formaldehyde in a dynamic flow chamber and
formaldehyde concentrations were determined to be 5.17 ± 0.51, 9.92 ±
0.88, 20.04 ± 0.88, and 38.96 ± 3.70, respectively. Dams were weighed
on GDs 0, 6, and 21 and sacrificed on day 21. Upon examination, uterine
weights, fetal weights, sex ratio, and the number of implantation and
resorption sites, live and dead fetuses were recorded. Fetuses were
examined for external malformations and cleft palate. One half of viable
fetuses were sectioned to assess soft-tissue alterations. The other half
were fixed, stained with Alizarin Red S, and examined for skeletal
alterations.

Body weight gain of dams and body weight of male and female fetuses were
reduced by exposure to 40 ppm formaldehyde to 49%, 78%, and 81% of
control values, respectively (p<0.01) (Saillenfait et al., 1989).
Reduced weight gain in dams remained significantly decreased when
uterine weight was accounted for (p<0.01). Mean fetal weight of male
pups was reduced at maternal exposures of 20 and 40 ppm formaldehyde
(5.53 g and 4.42 g versus 5.61 g in controls). Decreased fetal body
weight in females was only seen at 40 ppm (4.27 g versus 5.24 g in
controls.). All other pregnancy endpoints were unchanged by formaldehyde
exposure (e.g., uterine weight, implantation and resorption sites, live
fetuses, dead fetuses, and sex ratios). No major malformations were
noted in fetuses. Some minor soft tissues and skeletal anomalies such as
dilated ureter, missing sternebrae, extra fourteenth rib, and
rudimentary thirteenth rib (statistics not given), were reported.
However, these effects occurred at similar frequencies in control and
treatment groups. The incidence of delayed ossification of the thoracic
vertebrae was 8.7% in fetuses from the 40 ppm exposure group versus 1.8%
in controls. However, this difference was not statistically significant.
Overall, formaldehyde was not embryolethal or teratogenic in the studies
and only exhibited fetotoxic effects at exposures of 20 ppm and above.
These are levels where there was a significant decrease in fetal body
weight.

The maternal toxicity NOAEL was 24.8 mg/m3 and the LOAEL was established
to be 49.6 mg/m3, based on decreased body weight gain. The developmental
toxicity NOAEL was 12.4 mg/m3 and developmental toxicity LOAEL was
established to be 24.8 mg/m3, based on reduced fetal weight gain.   

 

870.3700a        Prenatal Developmental Toxicity Study – Hamster

Experiments by Overman (1985) were aimed at examining the compound’s
potential for inducing systemic effects in laboratory animals via the
dermal route; in this case, the potential of topically applied
formaldehyde to induce teratological effects in the progeny of pregnant
Syrian golden hamsters. The shaved dorsal surfaces of lightly
anesthetized dams were treated with a single dose of 0.5 mL 37%
formaldehyde for a 2-hour period on any one of GDs 8, 9, 10, or 11,
after which the skin was washed thoroughly with water to remove any
remaining compound. Fetuses were dissected from sacrificed dams on GD
15, fixed in Bouin’s solution, then examined for visceral
malformations or skeletal abnormalities.  Treatment had no effect on
maternal weight gain. The treatment did not influence fetal C- R length.
Mean fetal weight was slightly increased in experimental animals, but
the difference was not statistically-significant. Two fetuses from the
same litter after treatment on day 8 were significantly smaller than
their litter mates (>3 SD below mean). The same was true for 2 fetuses
from different litters after treatment on day 10. One fetus of normal
size treated on day 10 had a subcutaneous hemorrhage in the dorsal
cervical region. No skeletal malformations were found and no other
malformations were observed.

 4.4	Reproductive Toxicity

Adequacy of database for Reproductive: The database for reproductive
toxicity of formaldehyde is considered complete with one study in the
rat and one study in the dog. 

870.3550	Reproductive Toxicity - Dog

In MRID (00143291) Hurni and Ohder tested the developmental toxicity of
formaldehyde in 9 to10 pregnant beagle dogs who received the compound in
the diet on GDs 4-56. Commercial grade formaldehyde (as a 40% solution)
was sprayed on the pellets prior to feeding. Each animal was allotted a
diet of 300 g of chow (reduced to 200 g 1 week prior to term) that was
promptly consumed (within 5-10 minutes) before the formaldehyde
volatilized appreciably.  The concentrations of formaldehyde in the chow
were 0, 125, or 375 ppm, equivalent to doses of 0, 3.1, and 9.4
mg/kg-day, respectively. Dams were allowed to deliver normally and
weight gain, gestation length, the number of litters, litter size,
number of live pups, number of pups surviving through weaning, and pup
weights weekly for the first 8 weeks were monitored as indices of the
potential reproductive/developmental toxicity of formaldehyde.  There
were no formaldehyde-related effects in any of the parameters other than
progressive pup weights, which were lower by group in litters of dams
exposed to formaldehyde. A developmental impact of formaldehyde was
evident in this strain of dog under the conditions of the experiment.
The pup weight decrements were 6.3% for the low-dose dams and 12% for
the high-dose. However, no internal or skeletal malformations were
observed in any of the 264 live-born and 20 still-born pups, suggesting
that formaldehyde had no developmental toxicity in beagles at ingested
concentrations as high as 9.4 mg/kg-day.

870.3550	Reproductive Toxicity – Rat 

Cassidy et al. (1983) administered single oral doses of 100 or 200 mg/kg
to five male Wistar rats/group. Testes from these animals and 20
controls were excised and examined for spermatogenic abnormalities 11
days after dosing. Although no significant toxicological effects of
formaldehyde on total sperm counts were observed at either tested dose,
an increased incidence (19%) of testicular sperm head counts was
observed in rats exposed to 200 mg/kg-day formaldehyde. The percentage
of abnormal sperm heads also significantly increased (5%) in the 200
mg/kg-day dose group compared to controls. These data suggest that
formaldehyde can induce morphological abnormalities in the germ cells of
male experimental animals at dose levels that did not significantly
affect testis weights or sperm counts.

4.5	Chronic Toxicity

870.4100a	Chronic Toxicity – Rodent

In a chronic toxicity study conducted by Battelle, Pacific Northwest
laboratories, B6C3F1  

mice (5/sex/group) were exposed to one of five concentrations of
vaporized formaldehyde for a period of 6 hours per day for a total of
ten exposures.  The target concentrations were 15, 25, 50, 100, and 200
ppm (18.59, 30.98, 61.96, 123.93, and 247.85 mg/m3).

Concentrations of 123.93 mg/m3 or greater produced 100% mortality. The
highly irritating nature of this chemical was evident microscopically in
all dose levels examined, ranging from minimal to mild supportive
rhinitis in the 18.59 mg/m3 dose level dose level, to necrosis and
sloughing of the mucosa in the turbinates, trachea, and proximal bronchi
in the 61.96 mg/m3 animals.  

Differential weight gains of both male and female mice at 18.59, 30.98,
and 61.96 mg/m3 was significant as compared to the controls. At 123.93
and 247.85 mg/m3, only female mice showed significant weight loss, as
the early mortality of the males precluded obtaining any meaningful
data.

870.4100a	Chronic Toxicity – Rodent

Kamata et al. (1997) evaluated the effects of inhaled formaldehyde in
male F344 (F344/DuCrj) rats (32/group) exposed for 28 months.
Formaldehyde exposure was generated by metering 37% formalin (containing
10% methanol) into a sprayer in a glass bottle and diluting with room
air. Concentration in the chamber was monitored twice daily by the
acetyl acetone method. Exposures were for 6 hours/day, 5 days/week at
nominal formaldehyde concentrations of 0, 0.3, 2.0, and 15 ppm.  Actual
levels (mean ± SD) were 0, 0.3 ± 0.07, 2.17 ± 0.32, and 14.85 ± 2.22
ppm. Rats in the 0 ppm group were noted to inhale methanol at the same
concentration (4.2 ppm) as the 15 ppm group. A room control, no-exposure
group was also included in the study. All animals were observed for
clinical signs once a day during the study. Body weights and food
consumption were recorded weekly. Five animals per group were randomly
selected at the end of 12, 18, and 24 months and surviving animals at 28
months were sacrificed for hematological measurements [Hb, RBCs, PCV,
MCV, mean corpuscular hemoglobin (MCH), MCHC and WBCs], biochemical
determinations (TP, ALB, BUN, ALP, AST, ALT, glucose, albumin/globulin
ratio, phospholipids, triglycerides, and total cholesterol), and
pathological examinations. Wet weights were taken on brain, heart,
lungs, liver, kidneys, spleen, testes, and adrenal gland of each rat.
Histopathology was performed on all moribund or dead animals and those
at specified sacrifices on all gross lesions and the following tissues:
pituitary, thyroid, nasal cavity, trachea, esophagus, stomach, small and
large intestines, prostate gland, urinary bladder, muscle, femur,
sciatic nerve, spinal cord, and mesenteric lymph nodes.
Histopathological sections were obtained from five anatomical levels,
but these did not correspond to the typical levels taken in other
bioassays. Most notably, section Level B was anterior and not posterior
to the incisor teeth.  The incidence data for nasal histopathology were
not reported with respect to section level location with the exception
that the nonproliferative lesions and tumors reported were described to
occur predominantly at Levels B and C.

Yellow discoloration of the coats occurred in animals exposed at the 2
and 15 ppm levels.  Significant decreases in body weight and food
consumption were observed in the high concentration (15 ppm) group
throughout the exposure period. Mortality rates at the 28th month were
59.6% in the room control group, 45.5% in the 0 ppm group, 31.8% in the
0.3 ppm group, 55.9% in the 2 ppm group, and 88.3% in the 15 ppm group.
In the 15 ppm group, the first death occurred after 6 months and a total
of 20 rats died by the end of 24 months.  Rats started to die from the
19th month in the 0 ppm group with a total of eight animals dying
spontaneously in that group by the end of the study. No abnormal
compound-related hematological findings were observed. A statistically
significant decrease in triglycerides was observed at the 12-month
sacrifice, and a similar trend (though not statistically significant)
was observed in animals at the high concentration (15 ppm) at the 18-
and 24-month sacrifices. Absolute liver weight was significantly reduced
in these same animals and the relative liver weight was decreased at the
18th month sacrifice. Relative adrenal weights were increased in the
animals exposed at the high concentration at the 12-month sacrifice. No
other remarkable observations were made.

Macroscopic and histopathological findings were limited to the nasal
cavity. Squamous cell metaplasia without epithelial cell hyperplasia was
increased in animals exposed at the 2 ppm level and was likely masked by
the proliferative lesions observed in the animals exposed at 15 ppm. It
was difficult to discern a duration-related trend in any of the data due
to the concurrent mortality. The total number (across all scheduled
sacrifices and unscheduled deaths) of proliferative lesions observed
with an increased incidence at the 15 ppm level included (* indicates
significance at p < 0.01 level): squamous cell metaplasia with
epithelial cell hyperplasia (29 %*), epithelial cell hyperkeratosis (26
%*), papillary hyperplasia (2%), SCC (13 %*), and squamous cell
papillomae (3%). The total number of squamous cell metaplasia with
epithelial cell hyperplasia was also increased (7 %*) in the 2 ppm group
but by only 4% in the 0.3 ppm group(not statistically significant).
These results are similar to those reported above for the CIIT 2-year
bioassays performed in F344 rats and are consistent with those of
Woutersen et al. (1989), who exposed Wistar rats for 28 months. A highly
nonlinear response for SCC and proliferative lesions in the nasal cavity
was observed in animals exposed to 15 ppm formaldehyde, while animals in
the 2 ppm group showed a statistically significant increase in some
epithelial lesions.

The systemic toxicity NOAEL was established to be 0.4 mg/m3 and the
LOAEL was established 2.5 mg/m3.

Carcinogenicity

Adequacy of database for Carcinogenicity: The database for
carcinogenicity consists of one submitted and six open literature
studies. 

870.4200a	Carcinogenicity – Rat

In a carcinogenicity study (MRID 00143288), rats were repeatedly
subjected to subcutaneous injections of 1 cm3 of an aqueous formaldehyde
solution at 0.6% to 0.8%. With 0.4% to 0.5% aqueous formaldehyde
solutions it was possible to inject subcutaneously once or twice a week.
Subcutaneous injections of 1 cm3 of a 0.4% aqueous formaldehyde solution
were continued on 10 rats once a week for about 1 year and three months.
 

0.6% to 0.8%: Necrosis,  formation of an ulcer, while the area around
the injection spot formed a tuber which was very difficult to heal

0.4% - 0.5%: rare occurrence of an ulcer.  After two to five months
after having stopped the injections observations revealed the occurrence
of sarcomas either at the injection spot or in the internal organs of 4
out of 10 of the rats.  

870.4200a	Carcinogenicity – Rat

In a carcinogenicity study in male Fischer Rats, Tobe et al. (1985),
administered formaldehyde at concentrations of 0, 0.3, 2.0 or 15 ppm (0,
0.37, 2.48 or 18.59 mg/m3, respectively) in aqueous solution methanol, 6
hours/day, 5 days/week for 28 months. The exposure at 15 ppm was tested
for 24 months. A positive control – 3.3 ppm methanol and a nonexposure
(NE) control were also used. 

During the exposure running noses, running tears and crouching were seen
in the 15 ppm dose group. These symptoms decreased as the number of
exposures increased. Hair around the abdominal region was observed to be
yellow in color and bleeding from the forelimbs was seen. Yellow
discoloration of abdominal hair was also seen in the 2.0 ppm dose group
although it was light. Significant suppression of weight gain and a
decrease in the amount of food gain were seen in the 15 ppm dose group.
20 of 24 animals in the 15 ppm dose group died in the 24 month dosing
period giving a high death rate of 88.3%. 

Recognizable tumors were observed in the 15 ppm group from the 420th day
onwards and tumors were recognized macroscopically in eight animals by
the 24th month. Squamous cell carcinoma was recognized in 14 rats and
pappiloma in 5 rats. Unclassified carcinoma was seen in 1 rat in the
nonexposure group which died on the 825th day. 

No neoplastic changes were seen in the 0.3 and 2.0 ppm and exposure
control dose groups. Excessive secretion was seen in the nasal cavity,
rhinitis accompanied by desquamation, squamous epithelial metaplasia and
epithelial cell hyperplasia were recognized in the 0.3 and 2.0 ppm dose
groups and these were significant in the 15 ppm dose group. 

A decrease in the T-GLY and a decrease in liver weight, assumed to be
changes accompanying decrease in food intake due to formaldehyde
exposure were seen in the 15 ppm dose group. However, these changes were
not accompanied by histological changes.  

 

870.4200a	Carcinogenicity – Rat

Takahashi et al. (1986) studied the effects of formaldehyde in an
initiation-promotion model of stomach carcinogenesis in male outbred
Wistar (Shizuoka Laboratory Center, Shizuoka) rats. Rats (n=17) were
given 100 mg/L of N-methyl-N¹-nitro-N-nitrosoguanidine (MNNG) in
drinking water and a diet supplemented with 10% sodium chloride for the
first 8 weeks as an initiation phase. This was followed by 0.5% formalin
in drinking water for 32 weeks as the promotion phase of the protocol. A
comparison group (n=10) was given stock water and diet without any
supplementation for the first 8 weeks followed by 0.5% formalin in
drinking water for 32 weeks. Animals were observed daily and weighed
once every 4 weeks.  Histopathology was evaluated on the stomach and
other tissues in the peritoneal cavity.

Body weight gain was reduced by exposure to MNNG with sodium chloride,
and formaldehyde exposure during the promotion phase exacerbated this
effect.  Histopathological investigations were restricted to the GI
tract. Formaldehyde was shown to statistically increase the incidence of
lesions in the forestomach and stomach in the animals initiated with
MNNG with sodium chloride as compared to controls receiving no
initiation.  Increases in papilloma in the forestomach, adenomatous
hyperplasia in the fundus, and adenocarcinoma in the pylorus were
observed. Histopathology in the animals receiving formaldehyde alone for
weeks 9 through 32 showed only an increase in forestomach papillomas
without any lesions reported for the glandular stomach. The adenomatous
hyperplasia was defined as proliferative, noninvasive mucosal lesions,
and the adenocarcinomas as well differentiated and composed of typical
glandular structures demonstrating a tubular pattern and cellular or
structural atypism without metastasis. No definition of criteria for
papilloma diagnosis was provided. The findings in this study are
inconsistent with those of Til et al. (1989) who found no evidence of
carcinogenicity in a 2-year bioassay at comparable concentrations
(assuming 37% formaldehyde in formalin results in 0.19% formaldehyde in
this study). As discussed above, the differences may be due to
differences in the strains of rat or in the diagnostic criteria. The
lack of more than one test concentration precludes dose-response
analysis of this study and provides only a stand-alone LOAEL of 0.2%
formaldehyde in drinking water. The lack of consumption data precludes
an estimation of dose in mg/kg-day.

870.4200b	Carcinogenicity – Mouse

In a study conducted by Iversen (1986), the possible carcinogenic
potency of formaldehyde in classical skin painting experiments (at
concentrations comparable to those used in pathology laboratories) was
evaluated. 

Formaldehyde was topically applied to the back skin of hairless hr/hr
Oslo mice. The animals were divided into five groups and the study
design was as follows: Group I – 200 µL of a 1% solution of
formaldehyde (40% a.i.) in water was applied twice weekly. Group II -
200 µL of a 10% solution of formaldehyde (40% a.i.) in water was
applied twice weekly. Group III – 51.2 µg of DMBA
(Dimethylbenz(a)anthracene) in 100 µL acetone was applied once
initially and nine days later followed with 200 µL of a 10% solution of
formaldehyde (40% a.i.) in water, the latter being applied twice weekly.
Group IV - 51.2 µg of DMBA in 100 µL acetone was applied once
initially and nine days later followed with 17 nmol of TPA
(12-0-tetradecanoylphorbol-13-acetate), the latter being applied twice
weekly. 16 male and 16 female mice were utilized for the first four
groups and observed weekly for 60 weeks. Group V – 176 mice were
treated with 51.2 µg DMBA once and given no further treatment. The
animals were observed once weekly for 80 weeks. 

All animals in groups II and III (10% formaldehyde – treated) were
autopsied and all organs, including the brain, were inspected for any
sign of pathology. Tissue pieces were fixed in buffered formaldehyde and
histological sections of the brain, nasal mucosa and lungs were
subsequently made. Any signs of carcinoma, papilloma or any other tumor
were observed for. Lungs were observed for inflammatory lesions and the
presence of any alveolar macrophages. The epithelium in the nasal mucosa
was investigated for possible metaplasia or dysplasia. 

All animals in group I survived the whole experiment with one of them
developing an infected atheroma of the skin. Apart from this one
observation, there were no pathological lesions, either macroscopically
or microscopically. Animals in Group II generally had a slight
hyperplasia of the epidermis. A few animals had small skin ulcers or
scratches, and in two animals small nonspecific granulomas were observed
in the lungs. There were no signs of lesions in the brain or any other
organs in the animals belonging to this group. No signs of metaplasia or
dysplasia were seen in the nasal mucosa either. In group III one animal
died accidentally in week 26, but histologically only epidermal
hyperplasia was found. Three animals in the group had lung adenomas and
11 of 32 animals had neoplastic growths on the skin, altogether 3
squamous cell carcinomas and 22 papillomas i.e. 25 skin tumors. The
first three papillomas were observed in week 10 following treatment.
There was no evidence of brain or other tumors, nasal dysplasia and no
increase in number of alveolar macrophages. Group IV animals showed an
increase in mortality. At 20 weeks there were 80% surviving animals
which decreased to 40% by week 40. At termination (week 46), there were
only 11 animals surviving of the original 32. At week 20, all the
surviving animals in the group were papillomabearing. No carcinomas or
sarcomas were observed. Almost all of the 176 animals in group V
survived the experiment. Altogether 225 skin tumors developed on 85
animals, 6 of these being squamous cell carcinomas. Two animals
exhibited lymphosarcomas at autopsy. 

Formaldehyde alone gave no tumors while there was a significant
enhancement effect of painting twice with 10% formaldehyde subsequent to
painting once with DMBA as compared to DMBA alone. There was no
significant difference between tumor yields in the two groups mentioned
above. There was a significant difference between DMBA followed by TPA
on the one hand, and the other two combined treated schedules on the
other. Neither 1% nor 10% formaldehyde in water applied topically twice
a week on the back skin of hairless mice had any observable carcinogenic
effect on any of the observed organs of mice. Mice painted with 51.2 µg
DMBA in acetone followed by 10% formaldehyde application, demonstrated a
significant tumor enhancement and shortened latency times. 

870.4200b	Carcinogenicity – Mouse

This carcinogenicity study by Iversen (1988) is a repeat of an earlier
study (Iversen, 1986) conducted by the same author but in this case
topical applications of formaldehyde were evaluated using SENCAR mice,
an animal model bred for maximum sensitivity to chemical tumorigenesis. 

A group of 16 male and 16 female SENCAR mice (Group A) were topically
administered 100 µL of reagent grade acetone on the skin of the back
twice a week. Another group of 32 animals (Group B) was treated with 200
µL 4% formaldehyde (10% formalin) in water twice a week. A third group
(Group C) was administered 51.2 µg DMBA in acetone once followed by 200
µL of 1% formaldehyde (2.5% formalin) twice weekly. A pooled group from
previous studies (Group D – 176 mice) which had been treated with 51.2
µg DMBA was used as a historical control to compare with the SENCAR
mice. A control group (Group E – 96 mice) was given a single
application of 51.2 µg DMBA in 100 mL acetone. The last group (Group F)
was administered 51.2 µg DMBA in acetone followed by 200 µL of 4%
formaldehyde (10% formalin) twice weekly. 

The animals were observed for 58 weeks for skin tumors and all animals
were autopsied. Specimens were collected from all skin lesions and from
obvious pathological lesions observed in the internal organs. Tissue
pieces were fixed in 4% buffered formaldehyde and histological sections
made. Statistical assessments were made on the basis of the crude
incidence of skin tumors with the results being represented as tumor
rates (the percentage of tumor-bearing animals in relation to the number
of animals alive at the appearance of the first tumor related to time)
and tumor yields (the cumulative occurrence of all skin tumors related
to time) in all groups. Differences in tumor rates were assessed using
the method of Peto (1974) and differences in tumor yields were assessed
using the method of Gail et al. (1980). Final tumor yields were also
assessed with the chi-square method, which was also utilized to compare
differences between the groups with regards to lung adenomas and
malignant tumors. 

There was no difference in mortality rates among the treatment groups.
There was a negligible tumor rate in SENCAR mice treated with acetone or
with 4% formaldehyde alone (Groups A and B). Group C (DMBA followed by
1% formaldehyde) produced 26% tumor bearing animals and the time to
tumors were slightly shorter (21 weeks versus 32 weeks before 50% of the
final tumor rates were reached) than those administered DMBA alone.
Group D (single application of 51.2 µg DMBA) animals produced 42%
tumor- bearing animals while Group F (DMBA followed by 4% formaldehyde)
produced 44% tumor-bearing animals and the average time to tumor seemed
to be somewhat shorter (20 versus 32 weeks) than seen in the group given
DMBA alone. There was a significantly higher tumor crop in the SENCAR
mice (Group E) than in the hr/hr Oslo mice (Group D).  There was a very
significant difference in tumor rates between Groups A, B and Group E
while there was no difference in tumor rates between animals of Group E
when compared separately with Group C and Group F animals. There was a
very significant trend seen with DMBA followed by 4% formaldehyde as the
most effective tumorigenic protocol. 

 to Group E (36 tumors in 32 animals). The difference however, was not
significant according to the chi-square method (χ2 = 1.7859 with 1 DF,
0.20 > p > 0.10). 

χ2 = 3.8065, 1 DF, 0.10 > p > 0.05). Hence, there was a slight tendency
for formaldehyde to reduce the number of skin carcinomas provoked by
DMBA. 

The experiment with SENCAR mice gave results similar to those observed
in the hr/hr Oslo strain (Iversen, 1986). Formaldehyde has no
tumorigenic effect of its own, but may slightly enhance DMBA induced
tumorigenesis, manifested in a tendency to shorten the latency period
(for tumor rates) and provoking a slightly, but not convincingly higher
number of tumors (tumor yield). In regard to malignant skin tumors,
formaldehyde tended to be anticarcinogenic.  

870.4200b	Carcinogenicity – Mouse

In a study by Krivanek et al. (1983), formaldehyde in a 50:50 acetone:
water vehicle was tested for its ability to initiate and/or promote
tumorigenesis in CD-1 female mice. In addition, a repeated exposure skin
irritation pretest to determine irritating and nonirritating doses of
formaldehyde was also undertaken by the authors. 

In the skin irritation pretest formaldehyde was applied to approximately
1 square inch of shaved skin on the back of 30 female CD-1 mice at
concentrations of 0.1 (0.1%), 0.5 (0.5%), 1.0 (1%), 2.0 (2%), 5.0 (5%)
or 10.0 (10%) mg/100 µL in a acetone: water mixture. The 0.1 and 0.5
mg/100 µL doses were applied daily, except for weekends, for three
weeks while all other doses were applied daily, except for weekends, for
two weeks. Skin responses were observed daily on weekdays. 

Initiation treatment consisted of a single application of 5 mg
formaldehyde (10%) in 2.5 µg TPA (Phorbol myristate acetate) with the
control for this treatment being 50 µL acetone/2.5 µg TPA. Two weeks
subsequent, promotion treatments were initiated with the promoter
potential of formaldehyde being tested at concentrations of 0.1, 0.5 and
1.0 mg/150 µg BaP (Benz (a)pyrene). The dose used to test formaldehyde
as an initiator as well as promoter was 5 mg formaldehyde/1.0 mg
formaldehyde. The control for this group was 5 mg formaldehyde/100 µL
acetone. Promotion treatments were administered thrice weekly for 26
weeks to groups of 30 female CD-1 mice following which the animals were
held for an additional 26-week recovery period. Body weight
determinations were made biweekly during the promotion treatment and
monthly during the recovery period. Skin test sites were observed daily
during promotion and biweekly during the recovery period. Skin nodules
were chartered monthly while mortality was recorded upon occurrence. 

Observations made during the skin irritation pre-test showed that the 10
mg dose produced moderate skin irritation after 2-4 applications,
characterized by drying and cracking of the skin (fissuring), sloughing
and papules. The 2.0 and 5.0 mg doses produced mild to moderate skin
irritation after 4-5 treatments while the 1.0 mg produced mild
irritation during the second week of treatment. The 0.5 mg dose level
exhibited slight skin irritation potential which was reversible after a
brief rest period. No skin irritation was observed in the 0.1 mg dose
group after three weeks of treatment. Based on the results of the skin
irritation pre-test, doses of 0.1, 0.5 and 1.0 mg formaldehyde were
selected for evaluating the promoter potential of formaldehyde. 

Body weight curves for the initiation-promotion study indicate no
significant differences between the four representative groups:
acetone/TPA, BaP/TPA, 5 mg formaldehyde/TPA and 5 mg formaldehyde/1.0 mg
formaldehyde. Mortality was low in all but the positive control group
ranging from 2-5 per group. Eight positive control mice died or were
sacrificed in extremis due to large ulcerated tumors. Skin nodules were
seen in 3/27 mice in the acetone/TPA group, 5/28 mice in the
formaldehyde/TPA group and comparison of these groups for initiator
potential of formaldehyde revealed no significant difference. In the
positive control group (BaP/TPA) 29/29 mice had at least one skin
nodule. The incidence of nodules was 3/27 in the BaP/acetone group, 7/27
in the BaP/0.1 mg formaldehyde group, 2/28 in the BaP/0.5 mg of
formaldehyde group and 1/25 in the Bap/1.0 mg formaldehyde. However,
Fisher’s exact test analysis indicated no statistical difference
between these groups. There were no mice with skin nodules in the
formaldehyde/formaldehyde and formaldehyde/acetone groups. In addition,
the positive control group BaP/TPA exhibited the earliest time-to-nodule
onset when compared to other groups. Only animals in the positive
control group developed malignant tumors – squamous cell carcinomas.
There were no statistically significant differences between the test and
control groups as indicated by Fischer’s Exact Test. 

 Minimally irritating solutions of formaldehyde do not initiate nor
promote skin tumors. Formaldehyde does not act as a complete tumorigen
when evaluated in the mouse skin painting test. 

 

870.4300 Carcinogenicity- Rat and Mouse

Kerns et al. (1983) exposed about 120 animals/sex/species (Fischer 344
rats and B6C3F1 mice) to 0, 2, 5.6 or 14.3 ppm, 6 hours/day, 5 days/week
for 24 months. Five animals per group were sacrificed at 6 and 12 months
and 20 per group were killed at 18 months. At 24 and 27 months the
number sacrificed is unclear. The studies were terminated at 30 months.
From the 12th month on, male and female rats in the highest dose group
(14.3 ppm) showed significantly increased mortality compared with
controls. In the 5.6ppm group, male rats showed a significant increase
in mortality from 17 months on. Female mice showed generally comparable
survival across dose groups, as did male mice, but the male mice as a
whole showed increased mortality because of housing problems. Squamous
cell carcinomas were seen in the nasal cavities of 51/117 male rats and
52/115 female rats at 14.3 ppm (HDT) by experiment's end (as many as 35
carcinomas had been identified in males by month 18 based on EPA
analysis notes and Kerns (Chart 8). At 5.6 ppm, 1/119 male rats and
1/116 female rats showed squamous cell carcinomas of the nasal cavity.
No such tumors were seen at 0 or 2 ppm. Polypoid adenomas of the nasal
mucosa were seen in rats at all doses (0 ppm: 1/118 M, 0/114 F; 2 ppm:
4/118 M, 4/118 F; 5.6 ppm: 6/119 M, 0/116 F; 14.3 ppm: 4/117 M, 1/115 F)
in a significant dose-related trend, albeit one that falls off after a
peak. Among the mice, squamous cell carcinomas were seen in two males at
14.3 ppm. No other lesions were noteworthy.

Non-guideline     Carcinogenicity – Hamster

Dalbey (1982) examined the effects of inhaled formaldehyde alone for a
lifetime or combined with diethylnitrosamine (DEN) in an
initiation-promotion study design using male Syrian golden hamsters. The
hamsters were housed continuously in stainless steel cages and exposed
in whole body chambers, 5 hours/day, 5 days/week for a lifetime. Two
groups of hamsters were included in the study of inhaled formaldehyde
alone: 132 untreated controls and 88 male hamsters exposed to 10 ppm of
formaldehyde. The study of formaldehyde and DEN interaction involved
five different groups. DEN, administered subcutaneously, was used as the
initiator or primary carcinogen. Formaldehyde was generated by
paraformaldehyde sublimation and monitored by colorimetric analysis.
Fifty animals served as controls; another 50 were exposed to 30 ppm
formaldehyde, 5 hours/day, 1 day/week for life. The third group
consisted of 100 hamsters treated only with DEN (0.5 mg) once per week
for 10 weeks. The fourth group received an exposure to 30 ppm of
formaldehyde 48 hours prior to each weekly injection of DEN for 10 weeks
followed by weekly formaldehyde exposures (5 hours/week) for life. The
fifth group was given weekly 5-hour formaldehyde exposures (30 ppm) for
a lifetime but beginning two weeks after the last DEN injection.  In the
formaldehyde-only study, tissues were prepared by hematoxylin and eosin
(H&E) staining and histopathological evaluations were carried out on two
transverse sections of the nasal turbinates (otherwise not specified),
longitudinal sections of larynx and trachea, and all lung lobes cut
along the bronchus prior to embedding. Respiratory tract tissues in the
combination study were stained with Wright’s stain and rendered
semitransparent by a clearing technique for subgross evaluation under a
dissecting scope. Areas of dense nuclear staining were scored as tumors.
Nasal turbinates were fixed, decalcified, cut, stained, and cleared for
subgross evaluation. At least 10 lesions observed on the subgross level
in each tissue of each treatment group were examined microscopically.

	

In the formaldehyde-only (10 ppm) experiment, mortality was reduced in
hamsters (p < 0.05) relative to unexposed controls. No tumors and little
evidence of toxicity to the nasal epithelium were observed. There was no
increase in rhinitis, and hyperplastic or metaplastic areas were each
observed at an incidence of 5% relative to none in the controls. While
these data are somewhat difficult to interpret given the lack of
information on the location of the nasal sections, they do suggest that
the hamster is less susceptible to inhaled formaldehyde since F344 rats
chronically exposed to ≥10 ppm (Monticello et al., 1996) exhibited an
increase in SCCs, and Wistar rats exposed to 10 ppm for 28 weeks
exhibited significant epithelial disruption (Woutersen et al., 1989).
Differences may be due to dosimetry, as is evident for mice (Chang et
al., 1983), or tissue sensitivity, or both.

In the initiation-promotion protocol with DEN, weekly exposures to
formaldehyde alone (30 ppm once per week) did not influence mortality.
Treatment with DEN alone significantly (p < 0.05) increased mortality
above that of untreated controls, and mortality was further elevated (p
< 0.05) in the two groups exposed to both DEN and formaldehyde relative
to DEN alone. Actual group size was 27 for concurrent DEN and
formaldehyde treatment and 23 for formaldehyde given after DEN because
of unplanned mortality resulting from an exposure accident at 48 weeks.
No tumors were observed in untreated animals or those receiving only
formaldehyde. DEN treatment alone resulted in a high incidence (77%) of
tumors. All tumors observed were classified as adenomas. Lifetime
exposure of animals treated with DEN and formaldehyde did not increase
the number of TBA above those given DEN only. The number of tumors per
tumor-bearing animal (TBA) was significant only in the group given
formaldehyde prior to each DEN injection and only in the trachea and not
in larynx or lung. An adjustment of the tumor incidence for age at death
may have increased the statistical significance further. The author
concluded that the relation of the time of exposures to formaldehyde to
the DEN appeared to be significant, noting that the formaldehyde
exposure resulted in an increase only when administered 48 hours prior
to each injection.  These findings may be due to a cytotoxic effect of
formaldehyde on cell proliferation as later shown by Monticello et al.
(1996) for rats.

	

 

870.4300	Combined Chronic Toxicity/Carcinogenicity – Rat and Mouse

In a combined chronic toxicity/carcinogenicity study (MRID 00143289),
Rats (Fischer 344)  and Mice (B6C3F1) were administered 0, 2.0, 5.6, or
14.3 ppm (0, 2.5, 6.9, or 18 mg/m3) formaldehyde via inhalation, 6
hrs/day, 5 days/week, for up to 24 months. 

From exposure weeks 3 to 103, mildly (15 to35 g) decreased body weights
(p<0.05) in male and female rats (6.9 and 18 mg/m3) were observed.
Animals in the 2.5 mg/m3 exposure group had sporadically reduced body
weights (p>0.05) throughout the exposure period.  Male and female rats
in the 18 mg/m3 exposure group exhibited significantly increased
mortality (p<0.001) from the 12th month onward. Male rats in the
intermediate exposure groups showed a statistically-significant
concentration-dependent decrease in cumulative survival from 17 months
onward.  

In male mice, there were no differences in survival. The number of male
mice surviving a minimum of 18 months were 41, 33, 32, and 25 for the 0,
2.5, 6.9, and 18 mg/m3 exposure groups, respectively. There were no
differences in cumulative survival among the female mice.  

There were no alterations in the clinical pathology or ophthalmologic or
neurofunctional data that were considered related to formaldehyde
exposure.  

Exposure to formaldehyde produced a concentration-dependent increase in
yellow discoloration of the hair. Other significant macroscopic
observations (at the 18 mg/m3 group) included dypsnea, emaciation, and
large facial swellings that were proliferative lesions (carcinomas)
protruding from the nasal cavity. Neoplastic lesions were first observed
clinically at Day 358 in females and Day 432 in males.
Formaldehyde-induced microscopic lesions were confined to the nasal
cavity and the proximal trachea.  

Exposure to 18 mg/m3 formaldehyde for 24 months produced a high
incidence of nasal cancer in male and female rats. The tumors had a
sharp concentration-response relationship, with the 2 carcinomas in the
intermediate group identical to the 103 squamous cell carcinomas
observed in rats exposed to 18 mg/m3. Although the incidence of
polyploid adenomas in the nasal cavity was not statistically
significant, there was a positive concentration response for the
occurrence of benign neoplasms in male rats. There was no evidence of
progression of polyploid adenoma to squamous cell carcinoma.  

Two male mice exposed to 18 mg/m3 of formaldehyde developed squamous
cell carcinomas in the nasal cavity similar to the neoplasms in the
rats. Formaldehyde-induced lesions (squamous metaplasia and
inflammation) in mice were much less severe than similar lesions in
rats. The incidence of squamous cell carcinomas in mice exposed to 18
mg/m3 was similar to rats exposed to 6.9 mg/m3. 

Epidemiology Studies

The follow-up study by Hauptmann et al. (2003, 2004) of the National
Cancer Institute (NCI) retrospective cohort mortality study of U.S.
workers involved in the production or use of formaldehyde represents the
best available data set for quantitative cancer risk assessments of
lymphohematopoietic cancers and nasopharyngeal tumors based on human
data.   The NCI study is a large epidemiology study, and it provides
individual quantitative exposure estimates for the workers.

The NCI cohort consisted of 25,619 workers (88% male) employed in any of
the 10 plants prior to 1966; the current follow-up analyzes 8,486 deaths
(178 attributed to lymphohematopoietic malignancy and 9 to
nasopharyngeal cancer).  A detailed exposure assessment was conducted
for each worker based on exposure estimates for different jobs held and
tasks performed (Stewart et al., 1986).  Exposure estimates were made
using several different metrics - peak exposures, average intensity,
cumulative exposure, and duration of exposure.  Respirator use and
exposures to formaldehyde particles and other chemicals were also
considered.  Significant increases in relative risk for
lymphohematopoietic cancer were observed primarily for myeloid leukemia
and Hodgkin’s disease and for the peak exposure and average intensity
exposure metrics.  For the nasopharyngeal cancers, significant trends
were observed for the cumulative and peak exposure metrics.

With respect to the subtypes of lymphohematopoietic malignancy, the
strongest exposure-response relationships were observed for Hodgkin’s
disease and myeloid leukemia for both the peak exposure and average
intensity exposure metrics. The (all) lymphohematopoietic malignancies
category also showed a highly significant trend for the peak exposure
metric and a significant trend with the average intensity metric, and
this was the category selected for the cancer risk analyses presented
here.  While other lymphohematopoietic cancer subtypes did not exhibit
statistically significant increases, many did suggest increases in
relative risk with formaldehyde exposure, and the subtype analyses were
generally based on small numbers of cases (i.e., lower statistical
power).  Furthermore, as noted by the NCI investigators, “[a]lthough
the accuracy of death certificates for lymphohematopoietic malignancies
is generally high, classification of subtypes of leukemia and lymphoma
from death certificates is less accurate than from hospital records.” 
Finally, the all lymphohematopoietic cancer category contains the most
data, and the results are more stable.

4.8	Mutagenicity

Adequacy of database for Mutagenicity Toxicity: The database for
mutagenicity of formaldehyde is considered incomplete with the lack of a
bone marrow chromosome 

aberration test in the mouse.  

The mutagenicity data for Formaldehyde is summarized below in Table 3.

Table 3.  Mutagenicity data for Formaldehyde

Guideline No./

Study Type	MRID No./

Reference Information/

Study Classification	Dosing and Animal Information	Results

Mutagenicity



870.5100

Bacterial reverse mutation test

	

MRID 00132156

Jagannath, D. (1978) Mutagenicity Evaluation of Dantoin DMDMH-55 40-697
737543 in the Ames Salmonella/Microsome Plate Test: LBI Project No.
20838. Final rept. (Unpublished study received May 9, 1983 under
38906-5; prepared by Litton Bionetics, Inc., sub- mitted by Glyco, Inc.,
Greenwich, CT; CDL:250313-A)

Supplementary

	

0.001, 0.01, 0.10, 1.0, or 5.0 µL. 

Salmonella tester strains TA-98,

TA-100, TA-1535

TA-I 537 and TA-1538. Saccharamyces indicator organisms, strain 04.

	

Negative





870.5100

Bacterial reverse mutation test	

MRID 00132157

Haworth, S.; Lawlor, T.; Burke, P.; et al. (1982). Salmonella/

Mammalian-microsome Preincubation Mutagenicity Assay (Ames Test): Test
Article 447:34-3: Study No. T1804.502. (Unpublished study received May
9, 1983 under 38906-5; prepared by Microbiological Assoc., submitted by
Glyco, Inc., Greenwich, CT; CDL:250313-B).

Acceptable

	

Test material (447:34-3, MA #T1804) tested at concentrations of 3.0,
15.0, 75.0, 150, or 300 µg/plate. 

Tester strains TA98, TA100, TA1535, TA1357, TA1358 ± metabolic
activation with araclor induced rat liver microsomes.

	

Positive

Test article caused did cause a positive response (3.2-fold increase) on
tester strain TA98 without metabolic activation. A 1.9-fold increase was
observed on TA98 with metabolic activation. Also, increases of 2.2-fold
and 1.7-fold were observed on tester strain TA100 with and without
activation, respectively.



870.5100

Bacterial reverse mutation test

	

O'DONOVAN, MR AND MEE,CD; FORMALDEHYDE IS A BACTERIAL MUTAGEN IN A RANGE
OF SALMONELLA AND ESCHERICHIA INDICATOR STRAINS; MUTAGENESIS
8(6):577-581, 1993

(NCEA)

Open Literature

	

0-200 ug/plate, pre-incubation exposure and standard plate-
incorporation assays

S. typhimurium Strains TA1535, TA1537, TA1538, TA98, TA100, and TA102 
and E.coli Strains WP2(pKM101) and WP2uvrA(pKM101)  

Purity: 37%	

Pre-incubation exposure: positive for mutagenicity in TA98, TA100, and
TA102 and both E.coli strains.

Standard plate-incorporation assays:  

Consistent mutagenicity was seen only for TA100 and WP2uvrA (pKM101).

No evidence of mutagenicity was seen for TA1535, TA1537, or TA1538 using
either method of exposure.





870.5100

Bacterial reverse mutation test

	

Schmid, E., W. Goggelmann; and M. Bauchinger.  (1986)
Formaldehyde-induced Cytotoxic, Genotoxic, and Mutagenic Response in
Human Lymphocytes and Salmonella typhimurium.  Mutagenesis vol. 1 no. 6
p. 427-431. (NCEA)

Open Literature	

The tests were carried out using the plate incorporation assay and the
pre-incubation method +/- S9 activation at doses of 0-1.5mM and 0-0.3mM
formaldehyde, respectively.  

The incubation mixture consisted of 0.5 ml phosphate buffer or S9 mix
and10 ul of an appropriate concentration of formaldehyde in water. 

S. typhimurium Strain TA100 (0.1 ml bacterial suspension of about 10*8
cells were used in the pre-incubation method)

Purity: 37%

	

Plate Assay: weak positive response

Pre-Incubation Method: Without S9 mix, a1.6-fold increase of revertant
numbers over controls was induced.  With S9 mix, a 2.7-fold increase of
revertant numbers over controls was induced.



870.5100

Bacterial reverse mutation test	

Temcharoen, P; Thilly, WG.  (1983) Toxic and mutagenic effects of
formaldehyde in Salmonella typhimurium. Mutat Res 119:89-93. (NCEA)

Open Literature	

The capacity of formaldehyde to induce forward mutations to 8-azaguanine
resistance in was examined. Formaldehyde concentrations of 0.17 mM in
the absence of S9 and 0.33 mM in the presence of S9.  

S. typhimurium TM 677, a his+ revertant of TA 1535

Purity: 37%

	

Both toxicity and mutagenicity were obtained at formaldehyde
concentrations of 0.17 mM in the absence of S9 and 0.33 mM in the
presence of S9. The authors noted that, while the S9 might be enzyme
inactivating formaldehyde, the binding of formaldehyde to amino groups
of proteins in the S9 would effectively reduce the concentration of
formaldehyde entering the cells.  



870.5200

Mouse visible specific locus test	

Mouse Lymphoma L5178Y Cell TK Locus Assay for Mutagenicity; A Study with
Formaldehyde.  (DuPont, 7/28/80, Haskell Laboratory Report No. 581-80).

Open Literature 

	

Doses of 0, 0.1, 0.5, 1, 5, 10 or20 ug/ml without activation only, four
trials

Mouse Lymphoma L5178Y Cell 

Purity: 37%

	

An increase in mutation frequency was reported, especially at 10 and 20
ug/ml.





870.5275

Sex-linked recessive lethal test in Drosophila melanogaster	

Valencia, R., J.M. Mason, and S. Zimmering. (1989) Chemical Mutagenesis
Testing in Drosophila. VI. Interlaboratory Comparison of Mutagenicity
Tests After Treatment of Larvae. Environmental and Molecular
Mutagenesis, v. 14, p. 238-244.

Open Literature

	

Doses of 2,600 and 1,100 ppm  

D. melanogaster (Canton-S M and Basc F)  

Purity: 37%

	

Positive



870.5375

In vitro mammalian chromosome aberration test

	

MRID 00132168

Thilagar, A.; Kumaroo, P.; Pant, K. (1982) Cytogenicity Study: Chi- nese
Hamster Ovary (CHO) Cells in vitro: Test Article 447:34-1: Study No.
T1802.338. (Unpublished study received May 9, 1983 under 38906-5;
prepared by Microbiological Assoc., submitted by Glyco, Inc., Greenwich,
CT; CDL:250313-M)

Acceptable

	

Test material (447:34-1) was tested at concentrations of 28.43, 37.91,
or 50.55 nL/mL. 

Chinese hamster ovary cells (cell repository number CCL, 61)

Purity: 37% Formalin	

Positive

Test article caused a significant dose-dependant increase in the
frequencies of chromosome aberrations in the Chinese Hamster Ovary
cells, both with and without S-9 activation.





870.5375

In Vitro mammalian chromosome aberration test	

Natarajan, A.T. et al. (1983) Evaluation of the mutagenicity of
formaldehyde in mammalian cytogenics assays in vivo and vitro.  Mutation
Research 122: 355-360. (NCEA)

Open Literature	

In Vitro

CHO cells exposed to 0, 0.003, 0.006, 0.012, or 0.024 uL/mL
paraformaldehyde

In Vivo Mouse

0.4 mL paraformaldehyde injected intraperitoneally to achieve doses of
0, 6.25, 12.50, or 25.00 mg/kg

	

In Vitro: Positive

Frequencies of chromosomal aberrations and SCEs increased with
increasing dose. All classes of aberration, i.e. gaps, breaks, and
exchanges, were induced by formaldehyde. All the aberrations were
chromatid-type, indicating that formaldehyde acts as an S-dependent
agent. The addition of mammalian metabolic activation system reduced the
frequencies of formaldehyde-induced aberrations at all doses. 
Similarly, there was also a reduction in the frequencies of SCEs induced
by formaldehyde, if the treatment was done in the presence of S9.  

In Vivo: Negative 

None of the concentrations used increased the frequencies of micronuclei
over the control level.  Formaldehyde was not effective in inducing
chromosomal aberrations.





870.5380

Mammalian spermatogonial chromosomal aberration test	

Fontignie-Houbrechts, N. (1981) Genetic Effects of Formaldehyde in the
Mouse.  Mutation Research, v. 88, p. 109-114. (NCEA)

Open Literature

	

Mice received an i.p. injection of 50 mg/kg formaldehyde 

M Q Strain Mouse (200 spermatocytes/ animal)

Purity: 35%

	

Negative

No chromosomal lesions were revealed



870.5450

Rodent dominant lethal assay	

Fontignie-Houbrechts, N. (1981) Genetic Effects of Formaldehyde in the
Mouse.  Mutation Research, v. 88, p. 109-114. (as cited in Ma and
Harris) (NCEA)

Open Literature	

Mice received an i.p. injection of 50 mg/kg formaldehyde and 10 males
were caged with 2 virgin females each for one week.  The females were
renewed each week during 7 weeks.   

M Q Strain Mouse

Purity: 35%

	

Embryonic death or pre-post implantation death at 1 and 3 week periods



870.5450

Rodent dominant lethal assay	

Odeigah, P.G.C.  (1997) “Sperm Head Abnormalities and Dominant Lethal
Effects of Formaldehyde in Albino Rats.” Mutation Research 389:
141-148.

Open Literature   	

Five daily interperitonial injections of 0.125, 0.250, and 0.6 mg/kg
formaldehyde.  Males   were caged with 2 untreated virgin females which
were replaced weekly for 3 consecutive weeks giving a total of 24
females for the periods 1-7, 8-14, and 15-21 days post-injection,
respectively.  All females were sacrificed 13 days after the mid-week of
their caging.  At autopsy, each female was scored for total implants.   
 

Albino Rats (12 M/group)

Purity: 37% solution (stabilized with 10% methanol)

	

Positive

The frequency of dominant lethal mutations in female rats sired by males
exposed to formaldehyde was significantly higher than the control group.
 



870. 5550

Unscheduled DNA synthesis in mammalian cells in culture

	

MRID 00132169

Thilagar, A.; Pant, K. (1982) Unscheduled DNA Synthesis in Rat
Hepatocytes: Test Article 447:34-1: Study No. T1802.380002. (Un-
published study received May 9, 1983 under 38906-5; prepared by
Microbiological Assoc., submitted by Glyco, Inc., Greenwich, CT;
CDL:250313-N)

Acceptable

	

Test material (447:34-1) was tested at concentrations of 0.0005, 0.001,
0.005, 0.01, 0.02, or 0.04 µL/mL. 

Primary rat liver hepatocytes – Sprague-Dawley rats, 2.5 x 105
HPC/plate 

Purity: 37% a.i.	

Negative

The test article did not cause a significant increase in UDS in rat
hepatocytes. 





870.5900

In Vitro Sister Chromatid Exchange Assay	

A. Basler, W. v. d. Hude, and M. Scheutwinkel-Reich (1985)
“Formaldehyde-Induced Sister Chromatid Exchanges in vitro and the
Influence of the Exogenous Metabolizing Systems S9 Mix and Primary Rat
Hepatocytes.” Arch Toxicol 58: 10-13.  

Open Literature

	

The test compound was added to cell cultures 18 hours after seeding 5 x
105 cells per 25 cm2 flask.  The exposure time was 1, 2, 3, or 28 hours.
In the experiments with short-term exposure (1-3 hours), the medium was
removed after this treatment. The cells were restored in medium
supplemented with 5-bromo-2-deoxyuridine (BrdU).  The cells were
cultured in the presence of BrdU (10-5 M) for 28 h, with colcemide (0.1
µg/ml) for the last 4 h.  In the experiments with long-term exposure,
the cells were cultured in the presence of BrdU and the test compounds
for 28 hr. In tests with S9 mix, the cells were incubated with 0.5 ml S9
mix per 25 cm2 flask and 0.033, 0.067, 0.13, 0.2, 0.27, 0.4, and 0.54 mM
formaldehyde for 3 h, followed by incubation for 28 hr in the presence
of BrdU as described above. In tests with primary rat hepatocytes, 106
viable hepatocytes were added to the monolayer. After 2 hr, the
nonattached hepatocytes were sucked off and the different concentrations
of formaldehyde were added. The medium was complemented with BrdU and
incubated for 28 h as above. S9 fraction was prepared from Aroclor
1254-induced male Wistar rats.

Chinese Hamster V79 Cells

Purity: 37% Formaldehyde/10% Methanol 

	

There was a three- to four-fold increase in the SCE frequency at
non-toxic doses. However, in the presence of an exogenous metabolizing
system, the number of formaldehyde-induced SCE’s decreased. S9 mix as
well as hepatocytes reduced the SCE frequency to nearly that of the
control range. It could be demonstrated that the reduction was not due
to an unspecific binding of formaldehyde to macromolecules of the added
S9 mix. The decrease in genotoxic effects, due to rapid metabolisation
of formaldehyde in vitro and un vivo, explains the differences between
results obtained in the in vitro experiments – performed without
metabolizing systems – and in vivo results.   



870.5915

In Vivo Sister Chromatid Exchange Assay	

Kligerman,AD; Phelps, MC; Erexson, GL.  (1984) Cytogenetic analysis of
lymphocytes from rats following formaldehyde inhalation.  Toxicol Lett
21:241-246.

Open Literature	

Rats were exposed to 0.5, 6, or 15 ppm (0.6, 7.4, 18.5 mg/m3)
formaldehyde by inhalation for 6 hours/day for 5 days.   Blood was
obtained by cardiac puncture within 1 h of the last exposure and
cultured with BrdU for sister chromatid exchange (SCE) analysis.   

M and F Fischer F-344 Rat 

Purity: 95% a.i.? (Not reported in study) 

	

There were no increases in either SCE or chromosome aberrations at any
dose level.  



In vitro human lymphoblasts	

Craft, T.R., E. Bermudez, and T.R. Skopek (1987) Formaldehyde
mutagenesis and formation of DNA-protein crosslinks in human
lymphoblasts in vitro.  Mutation Research 176:  147-155. 

Open Literature	

0, 15, 30, 50, 125, or 150uM

Human Lymphoblasts (4x 10^5 cells/mL)

Formaldehyde (37% w/w 10-15% methanol)	

Positive

The 15, 30, and 50 uM treatments resulted in no significant difference
in growth rate compared to control values; the 125 uM and150 uM
treatments resulted in approximately 30% and 20% survival, respectively.
 Single treatments of various concentrations of formaldehyde resulted in
a nonlinear increase in induced mutant fraction at the thymidine kinase
locus with increasing slope above 125 uM.  Concentrations ≥ 30 uM
yielded statistically significant responses (p<0.05).  

Multiple treatments of 15, 30, and 50 uM also resulted in increases in
mutant fractions. Lymphoblasts exposed repeatedly to these lower
concentrations accumulate formaldehyde-induced mutations, but at a lower
rate than if a single 150uM treatment was given at one time.  





In vitro human lymphoblasts	

Liber, HL; Benforado, K; Crosby, RM; et al.  (1989) Formaldehyde-induced
and spontaneous alterations in human hprt DNA sequence and mRNA
expression.  Mutat Res 226:31-37. 

Open Literature

	

Liber et al. (1989) followed up the findings of Crosby et al. (1988) by
performing Northern blot and sequence analysis on the 16 induced and 10
spontaneous mutants not showing deletions. 

Human Lymphoblasts 

Purity: 37%	

Northern blot analysis showed that the point mutations fall into four
categories; normal size and amount of RNA, normal size but reduced
amounts of RNA, reduced size and amounts of RNA, and no RNA.  Sequence
analysis of recombinant DNAs from HRPT mRNA in compound-induced mutants
showed a preferential AT to CG transversion at a single site, with other
changes represented to a lesser degree.  





Other	

Graves, RJ; Trueman, P; Jones, S; Green, T.  (1996) DNA sequence
analysis of methylene chloride-induced HPRT mutations in Chinese hamster
ovary cells: Comparison with the mutation spectrum obtained for
1,2-dibromoethane and formaldehyde.  Mutagenesis 11:229-233. 

Open Literature

	

DNA sequence analysis of formaldehyde-induced HRPT mutations

Chinese Hamster Ovary Cell

Purity: 40%	

Single-base pair transversions, including three AT to TA at position 548
of exon 8, one GC to TA, and two AT to CG transversions at other sites. 




Other	

Blackburn, GR; Dooley, J, III; Schreiner, CA; et al.  (1991) Specific
identification of formaldehyde-mediated mutagenicity using the mouse
lymphoma L5178Y TK positive negative assay supplemented with
formaldehyde dehydrogenase.  In Vitro Toxicology 4:121-132. 

Open Literature

	

Forward mutation assay

Mouse lymphoma L5178Y tk+/- cells

Purity: 37% (w/w) aqueous solution (formalin)  	

Formaldehyde induced forward mutations to trifluorothymidine resistance
both in the absence and presence of rat liver S9 (higher concentrations
required for effect with S9). Both toxicity and mutagenicity were
abolished when formaldehyde dehydrogenase was incorporated in the
exposure medium.



	4.9	Neurotoxicity

Adequacy of database for Neurotoxicity: The database for neurotoxicity
consists of four open literature studies. 

870.6200	Neurotoxicity Screening Battery – Rat

Malek et al. (2003a) examined open field behavior of rats after acute
formaldehyde exposures.  Male and female LEW.1K rats (15/sex/group) were
exposed to 0, 1.0, 2.5, or 5.0 ppm (0, 1.23, 3.08, or 6.15 mg/m3)
formaldehyde for 2 hours. Formaldehyde was vaporized from aqueous
solutions directly below the exposure chamber. Formaldehyde levels were
checked 16 times throughout the 2-hour exposure periods. Mean
formaldehyde levels of 1.01 ± 0.29 ppm, 2.51 ppm (standard deviation is
missing) and 5.04 ± 0.27 ppm were achieved.  Locomotor activity was
assessed for 1 hour in an open field 2 and 24 hours after termination of
formaldehyde exposure using an automated device to count the number of
squares crossed.  Other behaviors were noted, including grooming (face
cleaning, fur licking, and scratching), rearing, sniffing (air and
floor), wall climbing, and defecation.

The authors reported no signs of irritation or changes in activity or
food or water intake during exposure (Malek et al., 2003a). In general,
sniffing was increased after formaldehyde exposure and movement was
decreased (crossed quadrants and climbing) in both male and female rats
(p<0.05). Significant reductions in horizontal movements (crossed
quadrants) were observed at all dose levels and were characterized by a
U-shaped dose response. The lowest dose tested (1 ppm) demonstrated
higher level of activity suppression than the two higher doses, but all
groups were still suppressed relative to controls. Although female rats
displayed a greater level of activity overall, a similar U-shaped
dose-response pattern was also observed.

Activity in the same apparatus was reassessed 24 hours later. As
expected, controls demonstrated habituation to the test apparatus
exhibiting only 20% of the motor activity observed on day 1. In
contrast, formaldehyde-treated animals failed to demonstrate the same
degree of habituation. Activity levels for males observed on day 2 were
60-80% of the activity levels seen on day 1. Formaldehyde-treated
females also failed to habituate and actually demonstrated increases in
activity on day 2 relative to day 1 at all formaldehyde exposure levels.

The neurotoxicity LOAEL was established to be 1.0 ppm, 2 hours

A follow-up study by Malek et al. (2003b) further expanded the
dose-response analysis for acute formaldehyde exposure. As described
above, male and female LEW.1K rats (10 per group) were exposed at 0,
0.1, 0.5, or 5.0 ppm (0, 0.123, 0.615, or 6.15 mg/m3) formaldehyde for 2
hours. Formaldehyde levels were checked 16 times throughout the 2-hour
exposure periods and mean values were found to be 0.13 ± 0.04, 0.48 ±
0.05, and 5.18 ± 0.66 ppm. Open field behavior tests were conducted on
each animal 2 hours after formaldehyde exposure. The number of crossed
quadrants for both controls and a 5 ppm group are comparable to those
observed in the first study. Horizontal movement was decreased by
formaldehyde exposure in a dose dependent manner with significant
reductions in motor activity as low as 0.1 ppm in males and 0.5 ppm in
females. The consistency of the data across studies and between genders
provides greater confidence in the effects of low level formaldehyde
exposure on this standard test of neurotoxicity.

The neurotoxicity LOAEL (Males) was established to be 0.1 ppm, 2 hours 

870.6500	Scheduled Control Operant Behavior – Rat

Pitten et al. (2000) evaluated the effects of very brief formaldehyde
exposures (10 minutes) but prolonged duration (90 days) on previously
learned performance in a land version of the labyrinth maze. Adult male
and female Wistar rats were acclimated to the task for 14 days, 2
trials/day.  Animals were required to make a series of five consecutive
turns from the entrance of the maze to retrieve a piece of cheese placed
in the goal box at the opposite end.  Animals were guided by the
experimenter through the maze during this acclimation phase until all
subjects were able to retrieve the food without aid. A pretraining phase
followed in which performance was assessed once daily for 11 days, and
the latency to complete the maze, as well as the number of errors
committed when traversing from the entrance to the goal box, were
recorded. The maze was wiped clean between subjects to remove urine,
boli and olfactory stimuli from the previous subject. Animals were then
assigned to one of three dose groups (five to eight/sex/group) such that
task performance was equivalent across groups prior to commencement of
formaldehyde exposures. Animals were exposed to 0 ppm, 2.6 ppm (0.25%
formaldehyde solution to yield 3.06 ± 0.77 mg/m3), or 4.6 ppm (0.70%
formaldehyde solution to yield 5.55 ± 1.27 mg/m3) formaldehyde, 10
minutes/day, 7 days/week for 90 days. Animals were assessed for
performance in the maze every seventh day, at least 22 hours after the
exposure on the previous day. At the end of the 90-day exposure period,
monitoring of maze performance continued once every 10 days for an
additional 40 days. All rats were sacrificed at the end of the
post-exposure trials and tissue sections were prepared for histological
examination by light microscopy, including liver, trachea, lung, kidney,
heart, spleen, pancreas, testicle, and brain. No changes in food or
water consumption weight gain or in histological samples of lung and
liver obtained at the termination of the experiment were observed.

The authors reported that no gender differences existed as a function of
formaldehyde treatment; therefore, data were presented by combining
sexes. Control rats showed no change in error rate but a slight decrease
in running time through the maze during the course of the experiment.
The formaldehyde-exposed groups began with a similar performance level
and error rate as controls, but their performance degraded over the
course of formaldehyde exposure. By the fourth week of exposure,
increased numbers of errors were evident in both exposed groups relative
to controls. This trend reached statistical significance by the
thirteenth week for a greater than twofold increase in error rate
(p<0.05). Formaldehyde-treated rats also tended to have increased run
times through the maze (p=0.04), but no difference was seen by
formaldehyde concentration. By 4 weeks after termination of exposure, no
statistical differences among the three groups were evident, but the
tendency for the two exposed groups to make more errors and have longer
latencies remained. Since Pitten et al. (2000) tested animals after the
task was acquired, these results indicate deficits in the retention of a
previously learned task.

The neurotoxicity LOAEL was established to be 2.6 ppm, 10 min/90 days. 

Non-Guideline Neurotoxicity 

In a neurotoxicity study conducted by Boja (1985), male Sprague-Dawley
rats were exposed to either air or formaldehyde at concentrations of 5,
10, or 20 ppm (6.20, 12.39, or 24.79 mg/m3) via inhalation for 3 hours
on two days

Exposure to 6.20 mg/m3 formaldehyde resulted in statistically
significant decreased motor activity within 15 minutes. At the beginning
of day 2, all of the rats exposed to formaldehyde on day 1 displayed
lower activity levels. Similar effects on motor activity were seen at
the 12.39 mg/m3 formaldehyde exposure level, whereas effects seen after
24.79 mg/m3 exposure were reported to be “not readily interpretable”
and were not shown. Exposure to 6.20 mg/m3 formaldehyde statistically
significantly increased concentrations of 5-hydroxyindoleacetic acid,
3,4-dihydroxyphenylacetic acid, and dopamine in the hypothalamus.

	4.10	Metabolism and Pharmacokinetics

Adequacy of database for Metabolism and Pharmacokinetics: The database
for metabolism of formaldehyde is considered complete with one submitted
and two open literature studies in the rat. 

870.7485	General Metabolism

In a metabolism study conducted by Casanova et al. (1989), rats
(4/group) were exposed to formaldehyde (nose-only exposure) at
concentrations of 0, 0.3, 0.7, 2, 6, or 10 ppm (0.37, 0.87, 2.5, 7.4, or
12 mg/m3) for 6 hours.

DNA-protein crosslinking occurred at all concentrations. The formation
of crosslinks was interpreted in terms of a nonlinear pharmacokinetic
model incorporating oxidation of inhaled formaldehyde as a defense
mechanism. The slope of the fitted concentration-response curve at 12
mg/m3 is7.3-fold greater than at 0.37 mg/m3, and the detoxification
pathway is half-saturated at an airborne concentration of 3.2 mg/m3.

870.7485	General Metabolism

In a metabolism study (Casanova-Schmitz et al., 1984), 14C and
3H-formaldehyde was administered at doses of 0, 0.3, 2, 6, 10, or 15 ppm
(0, 0.37, 2.5, 7.4, 12, or 19 mg/m3) for 6 hours.

The major route of nucleic acid labeling at all concentrations and in
all tissues was metabolic incorporation; protein labeling in the
respiratory mucosa was mainly due to covalent binding at the higher
formaldehyde concentration. Incorporation of 14C- formaldehyde into DNA
in the respiratory mucosa was maximal at 7.4 mg/m3 but decreased at
higher concentrations, whereas labeling of DNA in the olfactory mucosa
and bone marrow increased monotonically with concentration. Evidence for
covalent binding of formaldehyde to respiratory mucosal DNA was obtained
at formaldehyde concentrations equal to or greater than 2.5 mg/m3. The 

concentration of formaldehyde covalently bound to DNA at 7.4 mg/m3 was
10.5-fold higher than at 2.5 mg/m3, indicating significant nonlinearity
of DNA binding with respect to the inhaled formaldehyde concentration
under these conditions. Covalent binding to proteins increased in an
essentially linear manner with increases in the airborne concentration.
No evidence was obtained for the formation of covalent adducts with
macromolecules in the olfactory mucosa or bone marrow. The nonlinear
increase in covalent binding to respiratory mucosal DNA with increasing
formaldehyde concentrations may be explained either by a decrease in the
efficiency of defense mechanisms or by an increase in the availability
of reaction sites on the DNA resulting from increased cell turnover.

	4.11	Special Studies

The special studies data for formaldehyde is summarized in Table 4
below:

Table 4. Special studies data for Formaldehyde

Guideline Number/

Study Type/

Test Substance (% a.i.)	MRID Number (Year)/

Citation/ Classification/ Doses	Results



Modeling

 

	

Conolly, R.B., et al. 2003. Biologically Motivated Computational
Modeling of Formaldehyde

Carcinogenicity in the F344 Rat. Toxicol. Sci. 75: 432–447.

Open Literature

3-D F344 Rat Model 

Biologically based quantitative modeling of the relationship between
formaldehyde inhalation and the development of nasal squamous cell
carcinoma on the basis of the Kerns et al. (1983) and Monticello et al.
(1996) data.  

	

The analysis suggested evidence of: 1) a cytolethality-regenerative
cellular proliferation (CRCP) mechanism with little or no involvement of
direct mutagenesis; and 2) a J-shaped dose-response relationship between
formaldehyde and squamous cell carcinoma.  



Sensitization

 	

Ohtsuka, R; Shuto, Y; Fujie, H; et al.  (1997) Response of respiratory
epithelium of BN and F344 rats to formaldehyde inhalation.  Exp Anim
46:279-286. (NCEA)

Ohtsuka, R; Shutoh, Y; Fujie, H; et al.  (2003) Rat strain difference in
histology and expression of Th1- and Th2-related cytokines in nasal
mucosa after short-term formaldehyde inhalation.  Exp Toxicol Pathol
54:287-291.

 

Open Literature

18 F344 and 18 Brown Norway (BN) Rats

Rats were exposed to formaldehyde aerosol for 3 hours/day, 5 days/week
for 2 weeks.  The aerosol was generated from a 1% formaldehyde solution
by a two-fluid atomizer and formaldehyde level maintained at 2 mg (1%
sol.)/L (approximately 16 ppm or 20 mg/m3), by adjusting the flow rate
for formaldehyde solution to the atomizer.

	

Although no pulmonary measurements were made, the authors observed fewer
clinical signs of respiratory irritation in the BN rats compared to F344
rats, such as abnormal respiration (three versus five) and nasal
discharge (three versus five). Formaldehyde-treated F344 rats showed
less body weight gain over the 2-week treatment, resulting in lower body
weight at week 1 and week 2 than F344 controls (p<0.05 and 0.01). BN
rats were more resistant to epithelial cell damage than F344 rats,
exhibiting milder lesions that impacted a smaller portion of the URT. 
Squamous metaplasias were present in the respiratory epithelium (Levels
1 and 2) in both strains in formaldehyde-treated rats. However, a
distinct keratinized layer was noted in Level 1 epithelium of F344 rats,
and the extent of lesions in Level 2 respiratory epithelium was much
greater than that seen in BN rats.  Additionally, the olfactory
epithelium (Level 2) in formaldehyde-exposed F344 rats exhibited
degeneration, necrosis, and desquamation not seen in BN rats.  Mild
squamous metaplasia was noted in Level 3 of the respiratory epithelium
in the treated F344 rats but not the BN rats. The authors note that
their earlier research indicated the BN rats have well-developed
submucosal glands and that greater mucus flow may be partly responsible
for the greater resistance of BN rats to the histological signs of
formaldehyde toxicity. 

In a subsequent study in the same laboratory, Ohtsuka et al. (2003)
compared cytokine profiles in the nasal mucosa of formaldehyde-treated
F344 and BN rats.  Formaldehyde aerosol was generated as above and rats
(nine per group) were exposed 3 hours/day for 5 days to approximately 16
ppm of formaldehyde (20 mg/m3). 

The incidence and severity of clinical signs in F344 rats was greater
than BN rats as previously observed (Ohtsuka et al., 1997).  Also,
lesions and neutrophil infiltrations were more severe in F344
formaldehyde-exposed rats compared to treated BN rats. F344 rats had
various lesions in all three levels of epithelium examined, which
impacted both respiratory and olfactory epithelium.  Mucosal lesions in
formaldehyde-treated BN rats only impacted the respiratory epithelium of
Levels 1 and 2. Although changes in cytokine mRNA expression were
modest, there was a depression of T-lymphocyte helper 1 (TH-1)-related
cytokines in formaldehyde-treated BN rats (INF-g, Il-2) and a similar,
although not statistically significant, decrease in TH-2 cytokines
(IL-4, IL-5) compared to unexposed BN rats.  There were no treatment
differences in cytokine expression in F344 rats.  Type 1
hypersensitivity reactions generally result in increased TH-2 cytokines.
Therefore, although modest changes in cytokine profile were seen in
formaldehyde-treated BN rats, they were not consistent with Type 1
hypersensitivity.





Sensitization

Purity: 37% formalin	

Biagini, RE; Moorman, WJ; Knecht, EA; et al.  (1989) Acute airway
narrowing in monkeys from challenge with 2.5 ppm formaldehyde generated
from formalin.  Arch Environ Health 44:12-17. (NCEA)

Open Literature

9 Cynomolgus Monkeys known to be hyperreactive to methacholine
(acetyl-β-methacholine chloride) 

ean aerodynamic diameter of 1.0-1.5 μm).  After a 2-week recovery
period, pulmonary mechanics were measured before and after a 10-minute
exposure to 2.5 ppm formaldehyde (2, 5, and 10 minutes post-exposure).

	

Methacholine challenge increased pulmonary flow resistance at increasing
levels of methacholine (0.125, 0.5, 2.0, and 8.0 mg/mL) to 196 ± 16,
285 ± 57, 317 ± 64, and 461 ± 120 % of baseline levels respectively. 
Similarly, formaldehyde exposure increased pulmonary flow resistance
from 11.3 ± 1.4 cm H2O prior to formaldehyde exposure, to 16.1 ± 2.1,
16.9 ± 2.8, and 20.0 ± 3.4 cm H2O, at 2, 5, and 10 minutes after
formaldehyde exposure (with 142, 150, and 177% change, respectively).
Although bronchial constriction, seen as increased pulmonary flow
resistance, was increased by both methacholine and formaldehyde, there
was not a correlation between methacholine responsiveness and the
magnitude of effect after formaldehyde exposure (p>0.1). Therefore
although formaldehyde exposure stimulated BC similarly to a known direct
stimulating agent, formaldehyde may not work through the same site of
action as methacholine.





Sensitization

 	

Fujimaki, H; Kurokawa, Y; Kunugita, N; et al.  (2004) Differential
immunogenic and neurogenic inflammatory responses in an allergic mouse
model exposed to low levels of formaldehyde.  Toxicology 197:1-13.
(NCEA)

Open Literature

 OVA (immunized mice only), and supernatants were collected for cytokine
analysis (IL-4, IL-5, and INF-γ). Splenocytes were cultured for 24
hours in the presence or absence of OVA to assess chemokine production
(MCP-1 and MIP1-α). Anti-OVA IgE, IgG1, IgG2, and IgG3 were quantified
in blood plasma.

	

In nonimmunized mice, spleen weights were reduced by formaldehyde
exposure from 152 mg in control to 128, 118, and 121 mg in mice exposed
to 0.08, 0.40, and 1.8 ppm formaldehyde, respectively.  However, spleen
weights were unchanged by formaldehyde exposure in OVA-immunized mice. 
In immunized mice exposed to 1.8 ppm formaldehyde, the total number of
BAL cells, MPs, and eosinophils were increased (9.65 versus 2.84, 7.22
versus 2.74, and 2.0 versus 0.02 ×104 cells, respectively).

Levels of IL-1β in BAL of immunized mice were decreased by formaldehyde
exposure (p<0.05 at 1.8 ppm formaldehyde).  Immunization with OVA
significantly increased the neuropeptide nerve growth factor (NGF) in
BAL. However, this increase with OVA immunization was attenuated by 0.08
and 0.40 ppm formaldehyde exposure. A similar response was seen in blood
plasma NGF levels, where the increase with OVA immunization was
attenuated in mice exposed to 0.08 and 0.40 but not to 1.8 ppm
formaldehyde.  Plasma level of Substance P (a mediator of neurogenic
inflammation) was increased by formaldehyde exposures in non-immunized
mice. Although Substance P was increased by OVA immunization, this again
seemed to be attenuated by formaldehyde exposure, reducing Substance P
levels to undetectable levels.

Formaldehyde exposure (1.8 ppm) increased INF-γ fourfold in LPS
stimulated cultured spleen cells from non-immunized mice. OVA in vitro
stimulation significantly increased the chemokines MIP-1 and MCP-1 for
control and formaldehyde-treated OVA-immunized mice. The OVA stimulated
release of MCP-1 in vitro was enhanced by formaldehyde exposure in a
concentration dependent manner, increasing threefold and fourfold at
0.40 and 1.8 ppm, respectively. 

Anti-OVA IgG1 was slightly depressed in immunized mice exposed to 0.40
ppm formaldehyde, and anti-OVA IgG3 was depressed in immunized mice
exposed to 0.08 and 0.40 ppm formaldehyde.  





Pulmonary Hypersensitivity

 

	

MRID 43167201

Burleigh- Flayer, H. D. and W.J. Kintigh (1992) Glutaraldehyde and
Formaldehyde:  Vapor Pulmonary Hypersensitivity Study in Guinea Pigs. 
Bushy Run Research Center (Export, PA), Union Carbide. Study ID 92U1123,
dated February 28, 1992, Unpublished. 

 acceptable

Guinea Pig (8/group)

Induction:  14 ppm (17 mg/m3), 60 minutes, 5 consecutive days Challenge:
5 ppm (6.2 mg/m3) for 60 minutes, at days 14, 21, and 35 following
induction

	

Formaldehyde did not cause increased respiratory rate or altered
respiratory waveform indicative of pulmonary hypersensitivity during the
challenge exposures. No mortality, clinical signs, body weight effects,
or gross lesions were observed



870.1300

Acute Inhalation Toxicity

Purity: 95%

	

Dean et al. (1984) Studies of Immune Function and Host Resistance in
B6C3F1 Mice Exposed to Formaldehyde.  Toxicology and Applied
Pharmacology, v.72, p. 519-529.   

Open Literature

255 Female (SPF) B6C3F1 Mice

21-Day (6 hr/day, 5 days/week) inhalation exposure to 18.59 mg/m3
formaldehyde to test a series of immune function and host resistance
parameters.

	

Decrease in the absolute number of monocytes. In the absence of a
difference in recovery of peritoneal cells, the change in monocyte
number may signal only a peripheral response to the local nasal
inflammation and healing which occurs following HCHO exposure.  





Inhalation

 	

Casanova, Mercedes, et al. (1991) Covalent Binding of Inhaled
Formaldehyde to DNA in the Respiratory Tract of Rhesus Monkeys: 
Pharmacokinetics, Rat- to-Monkey Interspecies Scaling, and Extrapolation
to Man.  Fundamental and Applied Toxicology 17: 409-428.   

Open Literature

9 Male Rhesus Monkey (Macaca mulatta)

14C-Formaldehyde was administered at 0, 0.7, 2, or 6 ppm (0, 0.87, 2.5,
or 7.4 mg/m3) for 6 hours

	

DNA protein cross-links were formed in the respiratory tract of rhesus
monkeys exposed to formaldehyde. Concentrations of cross-links (pmol/mg
DNA) were highest in the mucosa of the middle turbinates; lower
concentrations were produced in the anterior lateral wall/septum and
nasopharynx. Very low concentrations were found in the
larynx/trachea/carina and in the proximal portions of the major bronchi
of some monkeys exposed to 7.4 mg/m3 but not to 9.87 mg/m3.  No
cross-links were detected in the maxillary sinuses or lung parenchyma.
The pharmacokinetics of cross-link formation in the nose were
interpreted using a model in which the rate of formation is proportional
to the tissue concentration of formaldehyde.  Using this model, the
concentration of cross-links formed in corresponding tissues of
different species can be predicted by scaling the pharmacokinetic
parameter depending on minute volume and quantity of nasal mucosal DNA> 
The concentration-response curve for the average rate of cross-link
formation in the turbinates, lateral wall, and septum of rhesus monkeys
as predicted from that of F344 rats exposed to similar conditions. 
Concentrations of cross-links that may be produced in the nasal mucosa
of adult men were predicted based on experimental data in rats and
monkeys. The results suggest that formaldehyde would generate lower
concentrations of cross-links in the nasal mucosa of humans than of
monkeys, and much lower concentrations in humans than in rats. The rate
of formation of DNA-protein cross-links can be regarded as a surrogate
for the delivered concentration of formaldehyde.





Inhalation

 	

D'A. Heck, Henry, and Merccedes Casanova (1987) Isotope Effects and
Their Implications for the Covalent Binding of Inhaled (3H) and (14C)
Formaldehyde in the Rat Nasal Mucosa.  Toxicology and Applied
Pharmacology 89: 122-134.  

Open Literature

Male F-344 (CDF/ CrIBR) rats

Isotopic effect on DNA-protein crosslinking by 3HCHO and H-14-CHO: Rat
hepatic nuclei incubated with 3H and 14C formaldehyde

Isotopic effect on the oxidation of 3HCHO and H14-CHO: homogenates of
the rat nasal mucosa incubated with 3H and14C formaldehyde at total
formaldehyde concentrations ranging from 0.1 to 11 uM, NAD+ (1 mM), GSH
(15 mM), and pyrazole (1mM)	

Isotopic effect on DNA-protein crosslinking by 3HCHO and H-14-CHO:

A small (3.4 +- 0.9%) isotope effect was detected on this reaction,
which slightly favored 3HCHO over H14CHO in binding to DNA.  The
magnitude of this isotope effect cannot account for the high isotope
ratio observed in the crosslinked DNA in vivo.

Isotopic effect on the oxidation of 3HCHO and H14-CHO:

3HCHO is oxidized significantly more slowly than H14CHO under these
conditions. A similar isotope effect was observed in the absence of GSH,
presumably due to the oxidation of 3HCHO and H14CHO, which can bind to
DNA resulting in an isotope ratio higher than that of inhaled gas. The
isotope effect on the oxidation of 3HCHO and H14CHO suggests that
previous estimates of the amount of formaldehyde covalently bound to
nasal mucosal DNA may have been too large; especially at low airborne
concentrations and that the shape of the concentration-response curve
for DNA-protein cross linking is more nonlinear than reported
previously.





Inhalation

 	

Morgan, K. et al. (1986) Responses of the Nasal Mucociliary Apparatus of
F-344 Rats to Formaldehyde Gas.  Toxicology and Applied Pharmacology 82:
1-13.  

Open Literature

Rat

0, 0.7, 2, 6, or 15 ppm (0, 0.62, 2.5, 7.4, or 19 mg/m3) 6 hour
exposures for up to 3 week duration

	

NOAEL: 2.5 mg/m3

LOAEL: 7.4 mg/m3

Rats exposed to 2.5, 7.4, or 19 mg/m3 exhibited concentration-related
evidence of eye and nose irritation, including ocular and nasal
discharge, and reddish exudate in the nasal passages.  

Defects in mucociliary function in specific regions of the nose, such as
cessation or severe slowing of mucus flow (mucostasis), loss of ciliary
activity (ciliastasis), or altered mucus flow patterns, were readily
detected.  These changes were clearly related to formaldehyde
concentration and duration exposure, and only minimal variation was
observed between animals within each exposure group.  Mucostasis was
usually more extensive than ciliastatsis, but in some areas mucus was
flowing over areas of inactivated cilia. Inhibition of
mucociliaryfuction by 19 mg/m3 formaldehyde was most frequently observed
on the dorsal and medial aspects of the maxilloturbinate, especially the
hook-like scroll of this turbinate (lateral scroll), the ridge dorsal to
this scroll (lateral ridge), and the lateral wall. These changes were
progressively more extensive with increasing number of days of exposure
and showed little or no evidence of recovery 18 hours after the last
exposure. At 7.4 mg/m3, the effects were much less extensive and they
were minimal or absent at 2.5 mg/m3.  Localized inhibition of ciliary
activity on the ventral margin of the nasoturbinate was observed in a
few animals exposed to 2.5 mg/m3 for 9 days.

Slowing or cessation of mucus flow was detected in the more anterior
regions of the maxilloturbinate following exposure for 1 day to 19
mg/m3, and more posterior regions were affected after 9 days. In rats
exposed to 7.4 mg/m3 formaldehyde, no consistent effects on the mucus
flow rate were observed except in areas exhibiting mucostasis. At 2.5
mg/m3, there was no evidence of reduced mucus flow rate.

In rats exposed to 19 mg/m3 formaldehyde, there were lesions in the
respiratory epithelium which became more extensive with increasing
number of days of exposure. Lesions were most severe in the anterior
nasal passages on the lateral, dorsal, and medial aspects of the
maxilloturbinate, the lateral and ventral surfaces of the nasoturbinate,
and the lateral wall. Exposure to 19 mg/m3 for 6 hours produced minimal
effects, characterized by separation of epithelial cells and
intravascular margination and local tissue infiltration by neutrophils
and monocytes in the regions which later exhibited severe, degenerative
changes. Over affected areas, a layer of floccular material was covered
by a continuous membrane. These layers were presumed to be coagulated
mucus and were not present elsewhere in the nose. The surface coagulum
was absent in animals killed 18 hours after a single 6-hour exposure,
and cilliated cells in affected areas were variably disintegrated while
infiltrating phagocytes were more numerous.  Following 2 days exposure
to 19 mg/m3, epithelial damage and inflammation were more severe and
extensive with a serofibrinous exudate present over damaged areas. 
These changes were even more advanced after 4 days. Epithelial lesions
had extended posteriorly along the lateral wall where exfoliating
ciliated and non-ciliated cells were located frequently over areas of
cellular proliferation and early squamous metaplasia. The distribution
of epithelial lesions correlated with the areas of inhibition of the
mucociliary function. No epithelial lesions were detected in areas
exhibiting mucostasis without ciliastasis. Similar, but less severe
changes were found in rats exposed to 7.4 mg/m3. There was a good
correlation between the distribution of epithelial lesions and
inhibition of ciliary activity. No epithelial lesions were detected in
rats exposed to 0.62 or 2.5 mg/m3.





Inhalation Short and Intermediate term

 	

Monticello, et al. (1991) Regional Increases in Rat Nasal Epithelial
Cell Proliferation following Acute and Subchronic Inhalation of
Formaldehyde.  Toxicology and Applied Pharmacology 111:  409-421.

Open Literature

Rats (36/group)

0, 0.7, 2, 6, 10, or 15 ppm (0, 0.87, 2.5, 7.4, 12, or 19 mg/m3), 6
hr/day for 1, 4, or 9 days, or 6 weeks (5 days/week)

	

NOAEL: 2.5 mg/m3 

LOAEL: 7.4 mg/m3

Animals exposed to 2.5 mg/m3 or less had no microscopic evidence of
formaldehyde-induced lesions.  Formaldehyde-induced lesions at higher
doses were confined to nasal passages primarily involving the
cuboidal-transitional and respiratory epithelium. Light microscopic
lesions were not observed in the trachea, carina, or more distal
conducting airways. Lesions exhibiting an anterior-posterior severity
gradient varied over exposure time and were concentration-dependent.  

For acute exposure (1 to 9 days), rats exposed to 12 or 19 mg/m3
formaldehyde had nasal lesions which became more severe and extensive
with increasing exposure time. Formaldehyde-induced lesions were more
severe in the anterior nasal passages on the lateral aspect of the
nasoturbinate, the lateral wall, and the lateral, dorsal, and
dorsomedial aspects of the maxilloturbinates. Less severe
formaldehyde-induced lesions were present on the midseptum at Levels II
and III and the midlateral wall at Level III. More severe effects were
observed at the higher dose.  

Following one 6-hour exposure to 10 or 15 ppm (12 or 19 mg/m3)
formaldehyde, lesions were characterized by epithelial cell vacuolar
degeneration, individual cell necrosis, epithelial exfoliation, and
multifocal erosions. There was also a mild mixed inflammatory cell
infiltrate consisting primarily of neutrophils with fewer numbers of
lymphocytes and plasma cells.  Formaldehyde-induced lesions progressed
by day 4 to erosions, locally extensive ulceration, and an increased
neutrophilic infiltrate.  There was evidence of early epithelial
hyperplasia with karyomegaly. Following 9 days of exposure, epithelial
hyperplasia and squamous metaplasia were also evident. These lesions
extended 

posteriorly to include the midlateral walls and the midventral septum at
Level III, and occasionally they included the ventral floor of the
nasopharynx.  

Lesions induced by exposure to 7.4 mg/m3 formaldehyde were much less
severe than at higher concentrations, primarily confined to Site 1 of
Level II. They were characterized by mild, multifocal, individual cell
necrosis, a very mild neutrophilic infiltrate, mild, patchy, epithelial
cell hyperplasia, and squamous metaplasia observed only after 9 days of
exposure.

For subchronic exposure (6 weeks), lesions in the 12 and 19 mg/m3 groups
consisted of epithelial hyperplasia, squamous metaplasia, and a mild
neutrophilic cellular infiltrate. These lesions were located on the
lateral wall, the midventral septum of Level II, and the lateral walls
of Level III. Lesions were also present in the nasopharynx,
characterized by mild epithelial hyperplasia and squamous metaplasia.
For animals exposed to 7.4 mg/m3, lesions were present at Level II,
characterized by mild hyperplasia and squamous metaplasia of the lateral
wall epithelium.

There were no detected treatment-induced responses in cell proliferation
indices in the two lowest formaldehyde concentration groups. Elevations
in cell proliferation were first detected following 1 day of
formaldehyde exposure in the 7.4, 12, and 19 mg/m3 groups. Increases in
the ULLI were present in every site except the nasal septum.
Statistically significant elevations in cell proliferation following 6
weeks of exposure to 7.4 mg/m3 were confined to the lateral wall and the
maxilloturbinate of Level II only. The levels of cell proliferation at
the lateral wall site decreased significantly (p<0.05) from Level II to
Level III, demonstrating a clear anterior-posterior response gradient.
Statistically significant increases in the ULLI at Level III were
present at Days 1, 4, and 9 for the lateral wall and at Days 4 and 9 for
the septum, even though epithelial lesions were not observed by light
microscopy in these locations.  

For the 12 and 19 mg/m3 dose groups, statistically significant increases
in the ULLI were observed at each site at days 1, 4, 6, 9, and 6 weeks,
with the exception of the maxilloturbinate at day 1. At Level III
following 6 weeks of exposure, the lateral wall site in both the 12 and
19 mg/m3 groups had a greater magnitude increase in cell proliferation
over controls, as compared to the Level II nasal spetal site. The
anterior-posterior gradient of the cell proliferation response observed
at 7.4 g/m3, was not apparent at these higher concentrations.





Other – Sensory Irritation

Purity: 37%

	

Kane, Laurel E.; and Alarie, Yves.  (1977)  Sensory Irritation to
Formaldehyde and Acrolein During Single and Repeated Exposures in Mice. 
American Industrial Hygiene Association Journal, v.38, p. 509-522.  

Open Literature

M SPF Swiss Webster Mouse (4/group)

Mice were exposed via inhalation for 3 hours/day for 4 days to a
concentration of formaldehyde that would be expected to produce a 30%
decrease in respiratory rate within the first 10 minutes of

exposure (as predicted by the 

concentration-response relationship) or to an atmosphere containing a
concentration equal to 1/10 the RD50 for formaldehyde for 3 hr/day for 3
days.  

	

RD50: 3.84 mg/m3





Other - Sensory Irritation

 	

Steinhagen, WH; Barrow, CS.  (1984) Sensory irritation
structure-activity study of inhaled aldehydes in B6C3F1 and
Swiss-Webster mice.  Toxicol Appl Pharmacol 72:495-503. (NCEA)

Open Literature

M Swiss Webster and B6C3F1 mice (3-4/dose)

10 minute head-only exposure to formaldehyde and other aldehydes

	

RD50: 3.2 ppm  (2.1–4.7 ppm) (Swiss Webster)

RD50: 4.90 ppm (3.9–6.4 ppm) (B6C3F1)

The difference in results between strains was not statistically
significant. On the average, α, β unsaturated aliphatic aldehydes and
formaldehyde were approximately 2 orders of magnitude more potent than
cyclic aldehydes and about 3 orders of magnitude more potent than
acetaldehdye and other saturated aliphatic aldehydes. The authors
hypothesized that the difference might be due to differences in the
degree to which a particular aldehyde undergoes hydration and its
subsequent hydrate dissociation constant (Khyd). This proposed mechanism
could account for the difference in RD50 between acetaldehyde with a
hydration of 49.7% and a Khyd value of 0.99 compared to formaldehyde
with a hydration of >99.8% and a Khyd value of >100 (Schauenstein et
al., 1977).





870.1300

Other - Sensory Irritation

Purity: 5% 

	

Gardner, RJ; Burgess, BA; Kennedy, GL, Jr.  (1985) Sensory irritation
potential of selected nasal tumorigens in the rat.  Food Chem Toxicol
23:87-92.  

Open Literature

8-week-old Crl-CD male rats (4/group)

The RD50 of eight chemicals was determined to determine whether there
was a correlation between the ability of a chemical to produce sensory
irritation and tumorigenic potency.  Groups of rats were exposed for 15
minutes to various concentrations of formaldehyde ranging from 0.77 to
24.9 ppm after a 5-minute pretest exposure to control air.  

	

RD50: 13.8 ppm

Estimate was about threefold less than the 31.7 ppm reported for male
F344 rats (Barrow et al., 1983).  This may indicate differences in
responsiveness to formaldehyde among different strains of rat. 
Concentrations of 5.5 ppm or more produced considerable depression in
respiratory rate. The decrease was observed during the first minute of
exposure and achieved a maximum at about 3 minutes. Some recovery was
observed during exposure from 3 to 10 minutes after the start but was
incomplete during the first 5 minutes after exposure. Taking the results
of the eight chemicals together, sensory irritation potency did not
correlate with the carcinogenic potency indicated by long-term
inhalation experiments.





870.1300

Other - Sensory Irritation

Purity: 95% paraformaldehyde	

Chang, JC; Barrow, CS.  (1984) Sensory irritation tolerance and
cross-tolerance in F-344 rats exposed to chlorine or formaldehyde gas. 
Toxicol Appl Pharmacol 76:319-327.  

Open Literature

M Fischer 344 (CDF[F 344]Crl/Br) rats (4/group)

Chang and Barrow (1984) determined whether tolerance would develop in
rats exposed to formaldehyde.  Tolerance was defined as return of
respiratory rate to baseline levels following an initial decrease
induced by test gas exposure.  Groups of rats were exposed in
double-chamber plethysmographs for 10 minutes after a 20-minute
acclimation and a 5-minute baseline period.  This measurement was
performed 18 to 24 hours after any pretreatment.  Pretreatment exposures
were carried out in a glass chamber for 6 hours/day, 5 days/week, for
various durations.

	

Exposure to formaldehyde at 15 ppm for 6 hours/day, 5 days/week failed
to induce tolerance. However, tolerance was observed following exposure
to 28 ppm formaldehyde for 4 days. The concentration-response curve in
these animals was significantly different than that of naïve animals,
with an increase in RD50 estimate for this exposure duration from 31.7
to 70.2 ppm.



870.1300

Other - Sensory Irritation

Purity: 90%-92% Paraformaldehyde

	

Cassee, FR; Arts, JH; Groten, JP; et al.  (1996) Sensory irritation to
mixtures of formaldehyde, acrolein, and acetaldehyde in rats.  Arch
Toxicol 70:329-337. (NCEA)

Open Literature

M Wistar rats (4/dose)

Cassee et al. (1996) determined the RD50 values for formaldehyde,
acetaldehyde, and acrolein as a result of a 30-minute nose-only
exposure.

	

RD50: 10.0 (95% CI 4.7–13.7)



870.1300

Other - Sensory Irritation

Purity: 95% Paraformaldehyde

	

Kulle, TJ; Cooper, GP.  (1975) Effects of formaldehyde and ozone on the
trigeminal nasal sensory system.  Arch Environ Health 30:237-243. (NCEA)

Open Literature

Adult M Sprague-Dawley rats (5/experiment)

The effects of formaldehyde on trigeminal nerve afferent activity in
rats was investigated.  Electrodes were implanted through a dissection
in the right eye orbit. The authors state that because the ethmoid nerve
and trigeminal nerve responded similarly the experiments were performed
with the nasopalatine nerve to eliminate potential contribution from the
mechanoreceptor fibers in the ethmoid nerve.  The sensory threshold was
determined by extrapolation from the measured nerve response to a range
of formaldehyde concentrations (0.5–2.5 ppm) or ozone (5.0–29 ppm)
for an exposure duration of 2 minutes. Amyl alcohol exposure (0.3–10.0
ppm) was for 25 seconds.  

Kulle and Cooper (1975) also investigated the effects of prolonged
exposure on trigeminal nerve activity using the in situ preparation
described above.  Formaldehyde (0, 0.5, 1.0, 1.5, or 2.0 ppm) was
presented continuously for 1 hour. Pre-exposure responsiveness was
determined to a test series of amyl alcohol (0.3, 0.7, 1.0, 3.3, 6.7, or
10.0 ppm).  After exposure to formaldehyde and a 10-minute recovery
period of exposure to control air, the amyl alcohol series was repeated
to evaluate reversibility.  If formaldehyde produced any depression or
enhancement of nerve activity as evidenced by the amyl alcohol test
series, another recovery period of control air ensued and the test was
repeated. Control tests with amyl alcohol were run for 8 hours to
establish that there were no significant changes in response to
prolonged exposures to the referent gas.  It was also determined if
there was a difference when the formaldehyde concentration was
progressively increased to 2.0 ppm in a series of exposures at the
concentrations above or presented separately at 2.0 ppm.

	

The mean thresholds were 0.25 ppm for formaldehyde, 5.0 ppm for ozone,
and 0.30 ppm for amyl alcohol.

There was a progressive depression in response to amyl alcohol with
increasing stimulus of formaldehyde concentration [p < 0.01, analysis of
variance (ANOVA)]. The effects of exposure to 2.0 ppm were similar
regardless of whether it was presented immediately as a separate
exposure or as the final concentration of a progressively increasing
series.  The response to amyl alcohol did not fully recover within the
1-hour extended recovery period. Thus it appeared that the afferent
function depression was not due to receptor adaptation or insufficient
time for formaldehyde diffusion away from receptor sites.





870.1300

Other - Sensory Irritation

 

	

Tsubone, H; Kawata, M.  (1991) Stimulation to the trigeminal afferent
nerve of the nose by formaldehyde, acrolein, and acetaldehyde gases. 
Inhal Toxicol 3:211-222.  

Open Literature

M Wistar Rat (6/group)

The afferent activity of the surgically isolated ethmoidal nerve (a
branch of the trigeminal nerve) during delivery of formaldehyde
(0.32–4.7 ppm) into the cannulated URT of rats at a flow rate of 200
mL/minutes for 22 seconds was recorded. Each exposure was repeated two
to four times at different concentrations.

	

The vapor concentration associated with a 50% increase in nerve activity
over the level of control gas was calculated as approximately 1.8 ppm
for formaldehyde.



Sensory Irritation

Formaldehyde, Lot No. 420807, 10 %a.i. (methanol free)

	

MRID No. 43170601

Werley et al. (1994). Glutardehyde and Formaldehyde: Sensory Irritation
Study in Swiss-Webster Mice.  Union Carbide Lab Project No. 91U0123.

Supplementary

Male Swiss-Webster ND4 mice (40-55 days old at start of study), 4
animals/dose

0, 0.34, 1.4, 6.9, 18.8, or 80.0 ppm (0, 0.42, 1.73, 8.55, 23.3, or 99.1
mg/m3), 30 min, head-only chambers

	

No treatment related mortality was observed. Mice exposed to
formaldehyde showed no treatment-related clinical findings. All mice
exposed to formaldehyde at 99.1mg/m3 showed increased lacrimation and
periocular wetness.  Slight reductions in body weight were observed in
some of the mice at the highest exposure doses for formaldehyde.





Immunologic Sensitization

 	

Tarkowski, M. and Gorski, P. 1995. Increased IgE antiovalbumin level in
mice exposed to formaldehyde. Int. Arch. Allergy Immunol. 106:
422–424.

Open Literature

F Balb/c Mouse

Groups were exposed to 2 mg/m3 formaldehyde either 6 hours/day for 10
days, or to 6 hours/day once a week for 7 weeks.  Then all mice were
sensitized intranasally with ovalbumin.  

	

Following sensitization, titer of serum anti-ovalbumin IgE antibodies
were significantly higher in mice exposed to formaldehyde 6 hours/day
for 10 days, compared to mice exposed 6 hours/week for 7 weeks or
untreated. The authors concluded that formaldehyde facilitates animal
sensitization to ovalbumin through histological changes occurring in the
upper respiratory tract.  





Immunologic Sensitization

 

	

Riedel, F., et al. C.H.L. 1996. Formaldehyde Exposure Enhances
Sensitization in the Guinea Pig. Allergy 51: 94–99.

Open Literature

Guinea Pig (12/group)

Animals were exposed to formaldehyde concentrations of 0 (controls), 160
or 310 ug/m3 (0.13 and 0.25 ppm) for 5 days, followed by sensitization
to inhaled ovalbumin at days 5 and 19.  On day 26, a bronchial
provocation test with ovalbumin was performed, followed by repeated lung
function measurements to monitor bronchial obstruction.  Also, blood
samples were taken on day 0 (before formaldehyde exposure) and day 25
(before bronchial provocation test) and tested for anti-ovalbumin IgG1
antibodies.  

	

Following ovalbumin challenge, 10/12 animals exposed to 310 ug/m3 showed
bronchial obstruction, compared with 3/12 control animals (p<0.01);
animals exposed to 160 ug/m3 were not significantly different from
controls. Anti-ovalbumin IgG antibodies were not detectable (<10 ELISA
units or EU) in any animal at day 0, but were detectable in 0/12
controls, 3/12 animals exposed to 160 ug/m3, and 6/12 animals exposed to
310 ug/m3 at day 25.   



Immunological

 

	

Jakab, GJ.  (1992) Relationship between carbon black particulate-bound
formaldehyde, pulmonary antibacterial defenses, and alveolar macrophage
phagocytosis.  Inhal Toxicol 4:325-342.  

Open Literature

White Female Swiss Mouse

Mice were exposed to formaldehyde after bacterial infection (Regimens A
and C), before bacterial infection (Regimen B), or before and after
infection (Regimen D).  In the first trial mice were exposed to 0, 1.0,
5.0, 10.0, or 15.0 ppm formaldehyde (0, 1.2, 6.2, 12.3, or 18.5 mg/m3). 
The remaining mice were exposed to 0, 0.5, or 1.0 ppm formaldehyde (0,
6.2, or 1.2 mg/m3).  A 30-minute exposure to an infectious aerosol of S.
aureus deposited 2x105 staphylococci in the lungs.  Bacterial loading
was determined in homogenized lung tissue by culturing diluted aliquots
for an estimate of bacteria present immediately after loading and 4
hours later.  

	

Mice exposed to 15 ppm formaldehyde for the 4 hours following bacterial
infection (Regimen A) had approximately an 8% increase in bacteria,
indicating decreased host resistance (p=0.006).  Pre-infection exposure
to 0.5 or 1.0 ppm did not change bacterial loading 4 hours after
infection (Regimen B).  However, combining an 18-hour pre-infection
formaldehyde exposure with a 4-hour post-infection 1 ppm formaldehyde
exposure increased pulmonary bacterial loading by approximately 6.5%
(p<0.05).  Increased bacterial loading indicates that formaldehyde
exposure (Regimens A and D) reduced pulmonary bacterial resistance. 
This is in apparent contradiction to the findings of increased host
resistance by Dean et al. (1984).  However, there are important
differences between the studies. The studies by Jakab (1992) are acute
studies examining effects at the respiratory tract where direct effects
are possible. Additionally, in some cases, the exposures were concurrent
with bacterial infection, and it is difficult to distinguish the
potential for formaldehyde effects directly on the mucociliary apparatus
as a barrier to infection.





Other

 	

Adams, D.O. et al. (1987) The Effect of Formaldehyde Exposure upon the
Mononuclear Phagocyte System of Mice. Toxicology and Applied
Pharmacology 88: 165-174.   

Open Literature

Female Mouse

15 ppm (19 mg/m3), 6 hr/day, 5 days/week. 3 weeks

	

Exposure of mice to 19 mg/m3, 6 hr/day, 5 days/week for 3 weeks did not
appreciably alter the number of resident macrophages in the peritoneal
cavit+y or that elicited in response to MVE-2.





Other

 	

Bartnik, F.G., Gloxhuber Chr., and Zimmermann V.  (1985)  Percutaneous
Absorption of Formaldehyde in Rats.  Toxicology Letters. v. 25. p. 167 -
172.   

Open Literature

10 Male/4 Female Rat

[14C] Formaldehyde as a tracer and non-labeled formaldehyde were
incorporated into a cream and dermally applied at 200 mg to occluded and
nonocclusive dosing areas for 48 hours

	

 Under non –occlusive conditions, absorption of radiolabeled
formaldehyde in the cosmetic cream preparation was published as 6.1% in
males and 9.2% in females. Occlusive conditions reported absorption as
3.4% in males.



Other

 	

Hester, et al. (2003) Formaldehyde-Induced Gene Expression in F344 Rat
Nasal Respiratory Epithelium.  Toxicology 187: 13-24. (NCEA)

Open Literature

8 F344 Male Rats 

40 ul aliquots of water or formaldehyde (400 mM) were instillled into
nostrils using a pipette.  Twenty-four hours after treatment, nasal
epithelium was recovered from which total RNA was used to generate cDNA
probes.

	

Siginificance analysis of microarrays (SAM) hybridization data revealed
that 24 of the 1185 genes queried were significantly up-regulated and 22
genes were significantly downregulated. The identified genes with
FA-induced change in expression belong to the functional gene categories
xenobiotic metabolism, cell cycle, apoptosis, and DNA repair. These data
suggest that multiple pathways are dysregulated by formaldehyde
exposure, including those involved in DNA synthesis/repair and
regulation of cell proliferation.





870.3100

Other

 Purity: 28.44%

	

Vargova M, Wagnerova J, Liskova A, et al. (1993) Subacute immunotoxicity
study of formaldehyde in male rats. Drug Chem Toxicol 16:255-275.

Open Literature

Male Wistar Rat

Formaldehyde was administered by gavage at doses of 0, 20, 40, and 80
mg/kg/day for 4 weeks, 5 days/week, 1x/day

	

NOAEL: 40 mg/kg/day

LOAEL: 80 mg/kg/day for an increase in the incidence of hepatocelluar
vacuolization



870.3465

Other

Purity: 14-C Paraformaldehyde (97.3-99%),

 Unlabeled paraformaldehyde (95%)	

Casanova, Mercedes, et al. (1994) DNA-Protein Cross-links and Cell
Replication at Specific Sites in the Nose of F344 Rats Exposed
Subchronically to Formaldehyde.  Fundamental and Applied Toxicology 23: 
525-536.  

Open Literature

Rats inhalation (20 rats/group, 10 of which are preexposed (PE), 10 not
(N))

0.7, 2, 6, 10, or 15 ppm (0, 0.87, 2.5, 7.4, 12.4, or 18.6 mg/m3)
Preexposed animals whole-body exposed 6 hr/day, 11 weeks +4 days) On the
5th day of the 12th week, animals exposed once nose-only for 3 hours
H14-CHO using nominal concentrations DPX estimation: 6 ppm or 10 ppm
(7.4 or 12.4 mg/m3) On 5th day of 12th week, exposed to unlabeled
formaldehyde once nose-only for 3 hours using nominal concentration 

	

NOAEL: 2.5 mg/m3

LOAEL: 7.4 mg/m3

Visible lesions were only observed in animals exposed to 18.6 mg/m3 for
12 weeks. No formaldehyde-induced lesions were observed in the squamous
and olfactory regions of the nose. Rats exposed to 0.87 or 2.5 mg/m3
were indistinguishable from controls. At 7.4 mg/m3, lesions were
confined to multifocal epithelial hypertrophy, hyperplasia, and squamous
metaplasia of the lM, while the rest of the nose was unaffected. At
12.39 mg/m3, the most characteristic response was squamous metaplasia of
the transitional epithelial lining of the LM and medial
maxilloturbinate, and mild epithelial hyperplasia of the midseptum with
generally mild inflammatory cell infiltration.

At 18.6 mg/m3, formaldehyde-induced lesions were more severe than all
other exposure groups. Rats exposed for 12 weeks exhibited extensive
damage to the lining of the LM (high tumor site) with epithelial
erosions, transitional epithelial hyperplasia, squamous 

metaplasia, intraluminal and mucosal infiltration by inflammatory cells,
and keratinizing epithelial plaques associated with subepithelial
inflammation. Animals exposed to 18.6 mg/m3 also exhibited thickening of
the periosteum of bones adjacent to severe epithelial damage, and
moderate degrees of edema and hyperemia of the lamina propria in these
regions. At 7.4 and 18.6 mg/m3, significantly (p<0.01) greater
incorporation of 14C into DNA occurred in the lateral meatus of
preexposed rats. Significantly (p<0.01) greater incorporation also
occurred in the medial and posterior meatuses of preexposed rats at 18.6
mg/m3.





5.0	Toxicity Endpoint Selection

	5.1	 See Section 7.1, Summary of Toxicological Doses and Endpoint
Selection

5.2	Dermal Absorption

Only two studies from the open literature were located that examined
dermal absorption of formaldehyde (Jeffcoat et al., 1983;  Bartnik et
al., 1985). In the Bartnik et al. study, a cosmetic cream containing
0.1% formaldehyde was applied an 8 cm2 area of the shaved dorsal skin of
male and female rats under non-occlusive and occlusive conditions. Urine
and feces were collected up to 48 hours post-dose. Under non
–occlusive conditions, absorption of radiolabeled formaldehyde in the
cosmetic cream preparation was published as 6.1% in males and 9.2% in
females.  Occlusive conditions reported absorption as 3.4% in males. 

In the study be Jeffcoat et al., rats, guinea pigs, and monkeys were
used in experiments to determine dermal absorption of  0.1 and 2.0 mg
doses of radiolabelled formaldehyde from application to a 2 cm2 area for
24 hours.  In rats, between 6-9% of a dose of 0.1 or 2.0 mg formaldehyde
was absorbed, while in guinea pigs results were similar.  In monkeys,
less than 1% was absorbed. 

5.3	Classification of Carcinogenic Potential

The Agency is currently reevaluating the carcinogenic potential of
formaldehyde. The historical and ongoing development of an inhalation
unit risk value to assess the carcinogenic potential of formaldehyde is
briefly summarized below. Contributors to this summary included
scientists from several EPA program offices (Office of Pesticide
Programs [OPP], Office of Pollution, Prevention, and Toxics [OPPT],
Office of Research and Development,/National Center for Environmental 
Assessment [ORD/NCEA], Office of Research and Development/National
Health Effects Exposure Research Laboratory [ORD/NHEERL], and Office of
Air and Radiation [OAR] ). 

:

otency factor of 1.3 E-5 per (μg/m3) on the basis of squamous cell
nasal tumors observed in a two-year study in rats (Kerns et al., 1983). 


In 1999 the Chemical Industry Institute of Toxicology (CIIT) developed a
health risk assessment for formaldehyde based upon  animal toxicity data
(CIIT, 1999).  This document presented the dose-response modeling of
these data in two distinct parts: 1). based upon a biologically-based
dose response (BBDR) model , 2) benchmark dose models that were based
upon point of departures at various response levels of the tumor and
precursor data.  Both these approaches made extensive use of the
available time-to-tumor and mechanistic information. The 1999 assessment
was subsequently published in various articles in peer-reviewed journals
(Kimbell et al., 2001; Schlosser et al., 2003; Conolly et al., 2002,
2003, 2004).

In 1999, the U.S. EPA’s Office of Air and Radiation and Office of
Research and Development, in conjunction with Health Canada, conducted
an external peer review workshop for the CIIT BDDR model as well as an
external written peer review and public comment period for their
assessments. While the review was largely positive on the overall
approach in the assessment, reviewers also pointed to the potential for
significant uncertainty due to model mis-specification and uncertainties
in key parameters involved in the BBDR model

Based on the peer review of the CIIT model, OAR determined in 2004 that
the CIIT model was the most appropriate tool for risk assessment for
formaldehyde.   OAR has subsequently used the the CIIT model for a
number of risk assessments involving formaldehyde emissions to the
atmosphere such as the Plywood and Composite Wood Products National
Emission Standard for Hazardous Air Pollutants (final rule 2004,
reconsidered final rule 2006, remanded to EPA by court 2007); Control of
Hazardous Air Pollutants from Mobile Sources (Final Rule 2007); and
Proposed Rule for National Emission Standard for Combustion Turbines
(2004). Health Canada, Australia, the World Health Organization, and the
German MAK Commission have also used the CIIT model. Model strengths
include consideration of the mode of action data for formaldehyde and an
approach to account for potential direct DNA interaction and mutation
induction.  Model uncertainties include variability for some of the
parameters of the model (e.g., cell proliferation) which can affect
predictions of risk (Subramanian et al 2007;   2008 [in press]).

In 2004, NCEA convened a panel of experts, including scientists from
CIIT, to provide advice on these and other critical biological and
statistical uncertainties. The strength of the CIIT model is its
consideration of mode of action and extensive mechanistic information.  

Although current OAR assessments still use the CIIT model, these
assessments now acknowledge previously unknown uncertainties with the
CIIT model when characterizing the risk results.   

In 2004, the International Agency for Research on Cancer (IARC)
characterized formaldehyde as a human carcinogen based on their review
of the current literature (IARC, 2004), including data in humans on 
nasopharyngeal cancer,  cancer of the nasal cavity and paranasal
sinuses, and  leukemia (Hauptmann et al., 2003, 2004).  It should be
noted that some epidemiology studies did not find a reported association
between formaldehyde exposure and carcinogenicity. For example, Coggon
et al, 2003 studied over 14,000 workers exposed to formaldehyde in
industrial workplaces and reported no excesses of either leukemia or
nasal and nasopharyngeal cancer.

In 2005, the Scientific Review Panel (SRP) of the California Office of
Environmental Health Hazard Assessment (OEHHA) responded to the CA Air
Resources Board request to reevaluate the carcinogenic potential of
formaldehyde.  The SRP noted in this 2005 review that OEHHA’s November
2002 evaluation of a petition had included the 1999 report on the CIIT
model and other information, and that California’s OEHHA had concluded
that “the evidence…(1) did not change the determination that
formaldehyde is a carcinogen; (2) presented information that considered
the possibility of non-linear dose response relationships, but presented
no clear grounds to review the original “no threshold”
determination; and (3) did not provide any new epidemiology or bioassays
supporting a change in potency.   In addition, there was insufficient
information to fully evaluate the CIIT model, issues such as model
uncertainty were not adequately addressed….”   The Scientific Review
Panel’s overall conclusion in 2005 was,  “there was not sufficient
new data to support the petition to review the [OEHHA’s earlier 1992]
formaldehyde risk assessment.  In addition, the newly published studies
represented relevant new information, but they did not allow
determination of a causal relationship between formaldehyde exposure and
leukemia.  These studies deserve further evaluation over time given
their potential importance.”  Froines (2005).

 

EPA is currently completing a new IRIS assessment that will include a
cancer unit risk value for formaldehyde; the reassessment is scheduled
to start internal peer review in May 2008 and begin independent external
peer review in January 2009
(http://cfpub.epa.gov/ncea/iristrac/index.cfm?fuseaction=viewChemical.sh
owChemical&sw_id=1031).  EPA anticipates that the peer review of the
formaldehyde assessment will not be finished before   EPA completes the 
reregistration process for formaldehyde pesticidal uses, scheduled to
conclude in September 2008. 

	

Based on the on going re-evaluation of the science  to predict
carcinogenic potential of formaldehyde, OPP has decided to present the
formaldehyde cancer risks for the pesticidal uses using both the
existing 1991 IRIS cancer unit risk of 1.3 E-5 per (µg/m3) and the CIIT
BBDR model until any new cancer estimates are fully peer reviewed.  OPP
also acknowledges the wide range in cancer risks using these approaches
and will coordinate with other offices in EPA on the outcome of the
upcoming peer review process on the carcinogenicity of formaldehyde.
Because formaldehyde air concentrations approach those associated with
ocular and respiratory tract irritation, the risk mitigation measures to
be implemented in the meantime for the pesticidal uses will be based on
mitigating the non-cancer effects at a limit of 0.01 ppm.  It is
believed that this level will reduce exposures sufficiently such that
the cancer risks would not be of concern.  The EPA  process of
regulating pesticides allows for reevaluation at any time if new
information from the peer review process of the carcinogenic potential
of formaldehyde warrants.

FQPA Considerations

Under the Food Quality Protection Act (FQPA), P.L. 104-170, which was
promulgated in 1996 as an amendment to the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, Drug and
Cosmetic Act (FFDCA), the Agency was directed to "ensure that there is a
reasonable certainty that no harm will result to infants and children"
from aggregate exposure to a pesticide chemical residue.  The law
further states that in the case of threshold effects, for purposes of
providing this reasonable certainty of no harm, "an additional tenfold
margin of safety for the pesticide chemical residue and other sources of
exposure shall be applied for infants and children to take into account
potential pre- and post-natal toxicity and completeness of the data with
respect to exposure and toxicity to infants and children. 
Notwithstanding such requirement for an additional margin of safety, the
Administrator may use a different margin of safety for the pesticide
residue only if, on the basis of reliable data, such margin will be safe
for infants and children."

Although formaldehyde has no food tolerances and the registered
antimicrobial uses do not involve dietary exposure, the database with
respect to determining susceptibility to infants and children shows no
increased susceptibility, based on results of developmental and
reproductive toxicity testing. Assessments of the reproductive and
developmental toxicity of formaldehyde conducted by the Australian
government (  HYPERLINK "http://www.nicnas.gov.au"  www.nicnas.gov.au )
as well as the Agency for Toxic Substances and Disease Registry (ATSDR,
1999)_support this conclusion. 

7.0	Summary of Toxicological Doses and Endpoints for Formaldehyde for
use in    Risk Assessment

	

Table 5 Summary of Toxicological Doses and Endpoints for Formaldehyde

  SEQ CHAPTER \h \r 1 Exposure

Scenario	Dose Used in Risk Assessment

(mg/kg/day) 	Target MOE, UF, 

Special FQPA SF* for Risk Assessment	Study and Toxicological Effects

Dietary Risk Assessments

Acute Dietary

(general population including infants and children) 	An acute dietary
assessment is not needed for the registered antimicrobial uses of
formaldehyde. 

Chronic Dietary

(all populations)	 A chronic dietary assessment is not needed for the
registered antimicrobial uses of formaldehyde. 

Non-Dietary Risk Assessments

Incidental Oral  

	 An incidental oral risk assessment is not required for the registered
antimicrobial uses of formaldehyde. 

Dermal (all durations)	A dermal risk assessment is not required for the
registered antimicrobial uses of formaldehyde. 

Inhalation

(all durations) 

	NOAEL (human) = 0.1 ppm 

 

	UF = 1 (occupational)

UF = 10 (residential)

 	ACGIH 2001 publication on formaldehyde

Horvath, E.P. et al. (1986): JAMA 259(5): 701-707.  Based on complaints
of eye, nose, and throat irritation in particle board workers at
concentrations of formaldehyde from 0.4 – 1.0 ppm.  

Redden, J. (2005): Section 18 Emergency Exemption for the use of
Paraformaldehyde: U.S. Army Medical Research Institute of Infectious
Diseases.

Cancer	Formaldehyde is currently classified as a  B1 (probable human
carcinogen) in EPA’s IRIS assessment. IARC has classified formaldehyde
as “carcinogenic to humans.” The Agency has decided to present the
formaldehyde cancer risks for the pesticidal uses using both the
existing 1991 IRIS cancer unit risk of 1.3 E-5 per (µg/m3) and the CIIT
BBDR model until any new cancer estimates are fully peer reviewed





8.0	Toxicity Profile Tables 

8.1	Acute Toxicity Profile Table - (See Section 4.1, Acute Toxicity,
Table 2).

8.2	Subchronic, Chronic and Other Toxicity Profiles Table (Table 6)

Table 6. Subchronic, Chronic and Other Toxicity Profiles for
Formaldehyde

Guideline Number/

Study Type/

Test Substance (% a.i.)	MRID Number (Year)/

Citation/ Classification/ Doses	Results

Subchronic Toxicity



870.3100

90-Day oral toxicity in rodents

Purity: 37% a.i.

	

MRID 00124677

Driedger, A.; Walker, J.; Galloway, F. (1973) Letter sent to C. Smart
dated Oct 1, 1973: “Rat tolerance to Dietary Formaldehyde: Reference
No. AD-114-73, JRW-341-73.” (Unpublished study; submitted by Celanese
Chemical Co., Dallas, TX; CDL:094622-H)  

 

10 male Holtzman rats/dose  

0, 0.3, 0.6, 1.2, or 2.4 % formaldehyde

	

NOAEL:  0.3% formaldehyde

LOAEL: 0.6% formaldehyde, based on irritability, weight loss, hair loss,
yellowing of teeth, and decreased food consumption 

Rats exposed to concentrations of 0.6% formaldehyde and higher exhibited
dose-related increases in irritability, disability, hair loss, and
yellowing of teeth and dose-related decreased food consumption.  Growth
rates significantly different from controls are expected at formaldehyde
concentrations ≥ 0.50 %, believed due to decreased food consumption.





870.3100

28-Day oral toxicity in rodents

Purity: 60% a.i.

	

MRID 00134114

Viguera, C.; Kundzins, M. (1960) “28-Day Oral Administration--Rats:
U.F. Concentrate-85|.” (Unpublished study; prepared by Hazleton
Laboratories, Inc.; CDL: 105284-C)  

 

10 Male Sprague-Dawley rats/dose

0, 79, 158, or 316 uL/kg/day, once daily, 5 days/ week, 20 doses

	

Statistical evaluation of overall body weight gains and total food
consumption revealed no significant differences between the control
group and test groups. The appearance and behavior of the test rats were
comparable to those of the control rats. No pathological findings
associated with the oral administration of the test substance were
observed.

One rat exposed to 158 uL/kg/day died during the 4th week. Autopsy
revealed a pale, mottled liver. Three rats receiving the high dose of
formaldehyde showed slight salivation during the 4th week of the study.





870.3100

90-Day oral toxicity in rodents

Purity: 95% a.i., aqueous paraformaldehyde

	

Johannsen, F.R., G.J. Levinskas A.S. Tegris (1986) Effects of
Formaldehyde in the Rat and Dog following Oral Exposure.  Toxicology
Letters 30:  1-6.  (NCEA)

Open Literature

Sprague-Dawley Albino Rat  

(15/sex/dose)

Formaldehyde was administered in the drinking-water at target doses of
0, 50, 100, or 150 mg/kg bw/d for 13 weeks (91 consecutive days)

	

NOAEL: 50 mg/kg/day (M), 100 mg/kg/day (F)

LOAEL: 100 mg/kg/day (M), 150 mg/kg/day (F), based on decreased body
weight gain

No deaths or abnormal reactions were observed in rats administered
formaldehyde for 90 days.  Significant reductions in weight gain were
observed in both sexes at 150 mg/kg and in male rats given 100 mg/kg.
There was a dose-related decrease in liquid consumption in both male
rats (9%, 18%, and 31%) and females (13%, 22%, and 30%) administered
formaldehyde in their drinking water. There were no overall differences
in mean food intake or feed efficiency in rats at any test level, thus
reductions in body weight gain are considered to be a reflection of
systemic effects of formaldehyde. No statistically-significant
differences were observed in hematologic parameters in any treated rats.
No specific treatment-related effects were observed on any organ or
tissue, including possible target organs like the kidney, liver, and
lung. Clinical chemistry and urinalysis studies failed to indicate any
necrotic effects on muscle, kidney, liver, or heart. No differences were
apparent between absolute or relative organ weights of treated rats. No
treatment-related pathological changes were observed microscopically.





870.3100

28-Day oral toxicity in rodents

Paraformaldehyde (95% a.i., aqueous)

	

Til, H.P., et al. (1988) Evaluation of the Oral Toxicity of Acetaldehyde
and Formaldehyde in a 4-week Drinking Water Study in Rats.  Fd. Chem.
Toxic. 26(5):  447-452. (NCEA)

Open Literature

Rat (10/sex/dose)

0, 5, 25, or 125 mg/kg/day; a water-restricted group (10/sex) received
the same amount of water as liquid consumed by the high-dose groups

	

NOAEL= 25 mg/kg/day

LOAEL = 125 mg/kg/day, based on yellowish fur from week 3 onward,
decreased food intake, decreased protein and albumin levels in blood
plasma, and histologic changes.

There were no deaths and the rats appeared healthy throughout the study.
 

The fur of the rats receiving 125 mg/kg/day showed a yellowish
discoloration from week 3 

onwards. Food intake of animals receiving the high dose was
significantly lower, whereas females receiving the low- and mid- dose
groups had increased food intake.  There were no significant changes in
hematology among the test groups.  Total protein and albumin levels in
the blood plasma were decreased in males in the high dose. Relative
kidney weights were increased at 125 mg/kg/day (p>0.05). Histologic
examination of test groups revealed: focal hyperkeratosis of the
forestomach (20/20); Focal gastritis (3/10 males, 3/10 females);
submucosal mononuclear-cell infiltrate (1/10 males); focal papillomatous
hyperplasia (1/10 females); and polymorphonuclear leukocytic
infiltration (1/10 females).  

The water- restricted group had slightly higher blood cell values in
males. Clinical chemistry and blood plasma changes observed include:
increased urea in males and females; decreased bilirubin levels and
increased chloride and sodium levels in males and decreased sodium,
calcium, and phosphorus in females.  Increased relative organ weights
were observed in male gonads (p<0.01), brains (males: p<0.05, females: 
p<0.01), male hearts (p<0.01), kidneys (p<0.01), and in the liver
(males:  p<0.01, females:  p<0.05). Histopath examination revealed
dilated fundic glands (2/10) in males.





870.3150

90-Day oral toxicity in nonrodents

Purity: Paraformaldehyde (95% a.i., aqueous)	

Johannsen, F.R., G.J. Levinskas, A.S. Tegris. (1986). Effects of
Formaldehyde in the Rat and Dog following Oral Exposure.  Toxicology
Letters 30:  1-6. (NCEA)

Open Literature

Beagle Dog (4/sex/dose)

0, 50, 75, or 100 mg/kg/day in drinking water for 90 days

	

NOAEL: 75 mg/kg/day (M/F)

LOAEL: 100 mg/kg/day (M/F), based on reduced weight gain

No deaths or abnormal reactions were observed. Significant reductions in
weight gain were observed in both sexes at 100 mg/kg/day. Treated
animals had reduced food consumption and feed efficiency even at the
lower dosages (50 and 75 mg/kg/day) which did not depress weight gain.
Hematological values from treated dogs fell within normal limits.No
specific treatment-related effects were observed on any organ or tissue,
including possible target organs like the kidney, liver, and lung. 





870.3465

90-Day inhalation toxicity

 

	

MRID 00082134

Coon, R.A. et al. (1970) Animal Inhalation Studies on Ammonia, Ethylene
Glycol, Formaldehyde, Dimethylamine, and Ethanol. Toxicology and Applied
Pharmacology 16:  646-655. (NCEA)

 

15 Sprague-Dawley  and Long-Evans rats (M/F), 15 Princeton-derived
guinea pigs (M/F), 3 New Zealand rabbits (M), 3 squirrel monkeys (M), 2
Beagle dogs (M)

Formaldehyde Continuous exposure to 4.6 mg/m3, 8 hours/day, 5 days/week,
6 weeks

	

One of the 15 rats died; none of the other animals showed signs of
illness or toxicity. Hematologic values were normal. On histopathologic
examination, the lungs of all species consistently showed varying
degrees of interstitial inflammation. The hearts and kidneys from guinea
pigs and rats showed focal chronic inflammatory changes.





870.3465

6-Week inhalation toxicity

Purity = 4.96%

	

MRID 00149755

Rusch, G.; Rinehart, W. (1980) A 26 Week Inhalation Toxicity Study of
Formaldehyde in Monkey, Rat, and Hamster: Project No. 79- 7259.
Unpublished study prepared by Bio/dynamics Inc. 184 p.

 

Fisher 344 rats – 10/sex/dose; Syrian golden hamsters –
10/sex/doseand Cynomolgous monkeys – 6 males/dose

Test material (Formaldehyde, Lot #0611N-79) was administered at 0, 0,
0.20, 1.00, or 3.00 ppm equivalent to 0, 0, 0.19, 0.98 and 2.95 ppm,
respectively, for 26 weeks. 

	

Treatment-related effects during the study were not seen. Compared to
controls, monkeys receiving 1.00 ppm showed increased incidence of dried
material around the nose, increased incidences of hoarseness and
congestion. 

Body weight

Compared to controls, no significant body weight changes were seen for
monkeys and hamsters throughout the study. The 3 ppm male and female
rats showed significant differences (p ≤ 0.01) from week 2-26 compared
to controls. 

Organ weight

Organ weights for monkeys and hamsters were not significantly different
compared to controls. Male and female rats in the 0.2 ppm group had
significant mean heart weight depression (p ≤ 0.01) compared to the
control. Males in the 3.0 ppm test group had significantly (p ≤ 0.01)
depressed mea absolute heart and kidney weights compared to the
controls, but the relative weights of these same tissues were
significantly increased for these same rats. Females in the 3.0 ppm test
group had significantly (p ≤ 0.01) depressed absolute heart weights
with the mean relative heart weight significantly increased (p ≤
0.01). For the 3 ppm group, the mean absolute and relative liver weights
were significantly depressed (p ≤ 0.01) compared to the controls. 

Gross and Microscopic Pathology

In monkeys, hamsters and rats, no abnormalities were seen in or
attributable to formaldehyde vapors. 





870.3465

90-Day inhalation toxicity

Purity: 97-99% a.i.	 

Woutersen, R.A. et al. (1987) Subchronic (13-week) Inhalation Toxicity
Study of Formaldehyde in Rats.  Journal of Applied Toxicology, 7(1):
43-49.  

Open Literature

Rats (10/sex/dose)

0, 1.0, 10, or 20 ppm (0, 1.2, 12, or 24 mg/m3), 6 hr/day, 5 days/week

	

NOAEL: 1.2 mg/m3

LOAEL: 12 mg/m3

In the high-dose group, uncoordinated locomotion, and climbing of the
cage walls were observed only during the 1st 30 minutes of each exposure
period.  Statistically-significant growth retardation occurred in males
and females of the high-dose group. Treatment-related changes were not
observed in the autopsy, except for a yellowish fur of mid- and
high-dose animals. No relevant differences were found in the
hematological and urinary parameters measured. Dose-related
histopathologic changes in the nose were observed in the mid- and
high-dose groups. Half of the 24 mg/m3 male rats showed squamous
metaplasia, occasionally accompanied by keratinization, of the
epithelium lining the vocal cord region of the larynx. The nasal
turbinates of rats exposed to12 or 24 mg/m3 formaldehyde exhibited a
marked increase in the number of labeled cells, practically all of which
were present in areas of the epithelium showing clear squamous
metaplasia and hyperplasia.





870.3465

90-Day inhalation toxicity

 	

Appelman, L.M. et al. (1988)  One-year Inhalation Toxicity Study of
Formaldehyde in Male Rats with a Damaged or Undamaged Nasal Mucosa. 
Journal of Applied Toxicology, 8(2):  85-90.

Open Literature

Male albino Wistar rats  (Cpb:WU) -40/dose

Formaldehyde exposure via inhalation route for 6 hr/day, 5 days/week, 13
or 52 weeks at concentrations of  0.1, 1, or 10 ppm (0, 0.12, 1.24, or
12.4 mg/m3), 1/2 with bilaterally damaged nasal mucosa

	

NOAEL = 1.24 mg/m3

LOAEL = 12.4 mg/m3, based on body weight retardation, incidence of
oliguria, and incidence of lesions of the respiratory and olfactory
epitheliums for damaged and undamaged animals

The nose damaged by electrocoagulation is more susceptible to cytotoxic
action of formaldehyde than the undamaged nose.  

8 animals (7 with damaged and 1 with undamaged nose) randomly
distributed among control and test groups, had to be killed in extremis
or were found dead. Growth retardation was observed in animals with or
without a damaged nose after 2 weeks exposure to 12.4 mg/m3
formaldehyde.

No relative differences were found between the hematological and urinary
parameters, with the exception of frequent oliguria (p<0.05) in the
high-dose group without nasal coagulation killed in week 53.

13 weeks: Histopathologic examination revealed focal squamous metaplasia
and focal basal cell hyperplasia (p<0.01) and focal rhinitis (p<0.05) in
the respiratory epithelium of the undamaged 12.4 mg/m3 dose group. In
the damaged 12.4 mg/m3 dose group, focal thinning/ disarrangement of the
olfactory epithelium was identified (p<0.05).

52 weeks: The undamaged 0.12 mg/m3 and 1.24 mg/m3 dose groups displayed
squamous metaplasia of the respiratory epithelium (p<0.05).  At 12.4
mg/m3, the undamaged group had squamous metaplasia, basal cell
hyperplasia, and focal rhinitis (p<0.05) of the respiratory epithelium.
The 12.4 mg/m3 damaged dose group displayed thinning/disarrangement and
loosely arranged submucosal connective tissue (p<0.01) in the olfactory
epithelium and squamous metaplasia (p<0.05) of the respiratory
epithelium.





870.3465

90-Day inhalation toxicity

	

Chemical Industry Institute of Technology 

20 Mice and Rats

Test material administered at concentrations of 4, 12.7, or 38.6 ppm for
6 hours each day, five days a week for 13 weeks. 

	

NOAEL = 4 ppm (LDT)

Systemic LOAEL = 12.7 ppm, based on body weight decrease and nasal
erosion. 

No adverse effects observed in the 4 ppm group. At 12.7 ppm, a decrease
in body weight and evidence of nasal erosion in two exposed rats was
observed. Ulceration and necrosis of the nasal mucosa seen at 38.6 ppm
resulted in termination of exposure after 2 weeks.  





870.3465

90-Day inhalation toxicity

Purity 

	

Test material administered at concentrations of 0.0098, 0.028, 0.82, or
2.4 ppm for 3 months. 

25 Rats

	

Systemic NOAEL = 0.028 ppm

Systemic LOAEL = 0.82 ppm, base don proliferation of lymphocytes,
histiocytes in the lungs, perivascular hyperemia. 

ChE NOAEL = 0.82 ppm

ChE LOAEL = 2.4 ppm

At 2.4 ppm there was a significant decrease in cholinesterase activity;
at 2.4 and 0.82 ppm, there was proliferation of lymphocytes and
histiocytes in the lungs and some peribronchial and perivascular
hyperemia. There were no significant findings at the two lower
concentrations. 





870.3465

90-Day inhalation toxicity

	

Dubreuil, A., G. Bouley, J. Godin, and C. Boudène. (1976). Continuous
inhalation of low-level doses of formaldehyde: Experimental study on the
rat. Eur. J. Toxicol. 9:245-250. 

Open Literature

25 rats

Test material administered at concentrations of 1.6, 4.55, or 8.07 ppm
for 45-90 days. 

	

NOAEL = 1.6 ppm 

The only adverse effect seen at 1.6 ppm was discoloration of hair. The
4.55 ppm group was exposed for 45 days and had a decrease in rate of
weight gain. The 8.07 ppm was exposed for 60 days and has respiratory
and eye irritation, a decrease in food consumption, and a decease in
liver weight. 

Developmental Toxicity



870.3700a 

Prenatal Developmental Toxicity 

Purity: 35% a.i.

	

MRID 00082136, 00123770

Schnurer, Lars- Bentil (1963) Maternal and Fetal Responses to Chronic
Stress in Pregnancy:  A Study in Albino Rats. Acta Endocrinologica,
Supplement 80:  1-96. 

Rats (56, 67, 50, 44/group, respectively)

Subcutaneous injection, Pregnant rats exposed to 0.25 mL of 2% solution,
pregnant control rats, non-pregnant rats exposed to 0.25 mL of 2%,
control non- pregnant rats; 2x/day, GD 2-19 to 22

	

Formalin exposure resulted in small, subcutaneous necroses. No
differences in smear cytology were noted between the pregnant treated
and pregnant control rats.

No stress-induced changes of the gastric mucosa were seen. The following
treatment- related organ weight changes were observed:  thyroid weight
was significantly lower in formaldehyde-exposed non-pregnant rats;
adrenal weights increased significantly in exposed non-pregnant rats.  

Formaldehyde- exposed pregnant rats yielded 56 litters, totaling 551
fetuses. Pregnant controls yielded 67 litters, 662 fetuses.
Formaldehyde-exposed rats had heavier fetuses than controls. No
instances of malformed limbs or cleft palate were observed.  Fetal
thyroid and adrenal weight reductions may be due to passage of
corticosteroids from exposed mothers to fetuses.  





870.3700a

Prenatal

Developmental

Toxicity (rodent)

Purity: Fischer certified ACS solution, contains 12-15% methanol

	

MRID 00164652

Marks, Thomas A. et al. (1980) Influence of Formaldehyde and Sonacide
(Potentiated Acid Glutaraldehyde) on Embryo and Fetal Development in
Mice.  Teratology 22:  51-58. 

Oral gavage (76/29/35/34 animals/dose) 0, 74, 148, or 185 mg/kg/day, GD
6-15

Female CD-1 Mice

	

Maternal Toxicity:

NOAEL = 0 mg/kg/day

LOAEL = 74 mg/kg/day, based on decreased body weight gain.

The 185 mg/kg/day dose of formaldehyde was clearly toxic; 22 of the 34
pregnant mice died before day 18. Methanol, 12-15% of the original
solution, may have contributed to this toxicity. There was also a
significant decrease in average weight gain during pregnancy at 74
mg/kg/day. The test solution did not have a significant effect in the
incidence of malformed mouse fetuses. Doses of 148 and 74 mg/kg/day had
no significant effect on the unborn offspring or on the pregnant dam.





870.3700a

Prenatal

Developmental

Toxicity 

Purity: 37% a.i.	

Saillenfait, A.M., et al (1989) The effects of maternally inhaled
formaldehyde on embryonal and foetal development in rats.  Fd. Chem.
Toxic. 27(8):  545-548. (NCEA)

Open Literature

Female Sprague-Dawley rats (25/dose)

0, 5, 10, 20, or 40 ppm (0, 6.2, 12.4, 24.8, or 49.6 mg/m3) for 6
hr/day, GD 6-20	

	

Maternal Toxicity:  

NOAEL = 24.8 mg/m3

LOAEL = 49.6 mg/m3, based on decreased body weight gain         

Offspring Toxicity:

NOAEL = 12.4 mg/m3

LOAEL = 24.8 mg/m3, based on reduced fetal 

weight gain  

Not teratogenic, slightly fetotoxic without overt signs of maternal
toxicity.  

There were no significant differences between groups in the numbers of
implantations, number of resorptions and the stage of gestation at which
they occurred, or the numbers of dead or live fetuses. Exposure to
formaldehyde had no detectable adverse influence on the incidence of
pregnancy or the fetal sex ratio.  

External, visceral and skeletal examination of the fetuses did not
reveal any major abnormalities. The only outward sign of a fetal
response was a significant concentration-related reduced in fetal body
weight gain (fetal body weight was 5% less at 24.8 mg/m3 and 21% less at
49.6 mg/m3).    

               



870.3700a

Prenatal

Developmental

Toxicity (rodent)

Purity: 37% a.i.	

Overman, D.O. (1984) Absence of Embryotoxic Effects of Formaldehyde
after Percutaneous Exposure in Hamsters.  Toxicology Letters 24:
107-110. 

Open Literature

Pregnant Charles river Lak:LVG (SYR) Golden strain hamsters – Number
of animals not reported

0.5 mL, 2 hours/day, GD 8-11

	

Treatment had no effect on maternal weight gain. The treatment did not
influence fetal C- R length. Mean fetal weight was slightly increased in
experimental animals, but the difference was not
statistically-significant. Two fetuses from the same litter after
treatment on day 8 were significantly smaller than their litter mates
(>3 SD below mean).  The same was true for 2 fetuses from different
litters after treatment on day 10. One fetus of normal size treated on
day 10 had a subcutaneous hemorrhage in the dorsal cervical region. No
skeletal malformations were found and no other malformations were
observed.



Reproductive Toxicity



870.3800

Reproduction and fertility effects

Purity: 40% a.i.

	

MRID 00143291

Hurni, H. and H. Odher (1972) Reproduction Study with Formaldehyde and
Hexamethylenetetr-amine in Beagle Dogs.  Fd. Cosmet. Toxicol. 11: 
459-462. 

51 female Beagle dogs

0, 3.1, or 9.4 mg/kg/day

	

The study revealed no teratogenic action.

The treatments did not affect the pregnancy rate. The body weight
increased regularly during pregnancy in all groups and the duration of
gestation was unaffected by the treatments. The mean litter size was
within the normal range for all groups, demonstrating that fecundity was
not affected by treatment. Neither the adult dogs nor their litters
showed any signs of physiological or skeletal abnormalities or disorders
of reproduction.





870.3800

Reproduction and fertility effects

Purity: 40% a.i.

	

Cassidy, S.L., K.M. Dix, and T. Jenkins (1983) Evaluation of a
testicular sperm head counting technique using rats exposed to
dimethoxyethyl phthalate (DMEP), glycerol a-monochlorohydrin (GMCH),
epichlorohydrin (ECH), formaldehyde (FA), or methyl methanesulphonate
(MMS). Arch. Toxicol. 53:71-78.

Open Literature

Male Wistar rats (5/group for treatment, 20 controls)

Treatment groups  were dosed once orally with 100 or 200 mg/kg
formaldehyde and killed 11 days after dosing

	

200 mg/kg: A statistically significant increase in total sperm heads per
gram testis, as well as an increase in percentage of abnormal sperm
heads. Data indicated that "the induction of increased levels of
abnormal sperm may be a measurable index of the mutagenic potential of a
chemical for mammalian germ cells”.



Chronic Toxicity



870.4100a

Chronic Toxicity

Purity: 9.20%	

Battelle, Pacific Northwest Laboratories.  (1980) 

"Tracor Jitco Inhalation Carcinogenesis Bioassay: Repeated Dose Study
Report on Formaldehyde."

Open Literature

B6C3F1 Mouse (5/sex/group)

Mice were exposed to one of five concentrations of vaporized
formaldehyde for a period of 6 hours per day for a total of ten
exposures.  The target concentrations were 15, 25, 50, 100, and 200 ppm
(18.59, 30.98, 61.96, 123.93, and 247.85 mg/m3).  

	

Concentrations of 123.93 mg/m3 or greater produced 100% mortality.  The
highly irritating nature of this chemical was evident microscopically in
all dose levels examined, ranging from minimal to mild supportive
rhinitis in the 18.59 mg/m3 dose level dose level, to necrosis and
sloughing of the mucosa in the turbinates, trachea, and proximal bronchi
in the 61.96 mg/m3 animals.  

Differential weight gains of both male and female mice at 18.59, 30.98,
and 61.96 mg/m3 was significant as compared to the controls. At 123.93
and 247.85 mg/m3, only female mice showed significant weight loss, as
the early mortality of the males precluded obtaining any meaningful
data.





870.4100a

Chronic Toxicity

Purity: 37% a.i.	

Kamata, Eiichi et al. (1997) Results of a 28-month Chronic Inhalation
Toxicity Study of Formaldehyde in Male Fischer-344 Rats.  The Journal of
Toxicological Sciences 22(3): 239-254.  

Open Literature

Male Fischer 344 rats (32/dose) 

0, 0.3, 2, or 15 ppm (0, 0.4, 2.5, or 19 mg/m3), 6hr/day, 5 days/week
via inhalation

	

NOAEL: 0.4 mg/m3

LOAEL: 2.5 mg/m3

Nasal tumors were macroscopically evident in the 19 mg/m3 group from the
14th month. Histopathological examination revealed squamous cell
papillomas and carcinomas. No nasal tumors were observed in the lower
exposure groups (0.4 and 2.5 mg/m3 groups). In the high-dose group,
frequent face washing, coughing and/or crouching position, lacrimation,
nasal discharge, and yellow discoloration of the haircoat were observed.
Significant decreased food consumption was observed and 20 rats died by
the 24th month.  Reduced triglyceride levels and liver weights,
presumably related to reduced food intake, were also seen in the 19
mg/m3 group. Epithelial cell hyperplasia, hyperkeratosis, and squamous
metaplasia were apparent in all exposure groups. Inflammatory cell
infiltration, erosion, or edema was apparent in all exposure groups,
including the controls. The benchmark dose for squamous metaplasia and
epithelial hyperplasia were 0.30 and 0.31 mg/m3, respectively.



Carcinogenicity



870.4200a

Oncogenicity (Rat)

	

MRID 00143288

Watanabe, F., et al. (1954) Study on the Carcinogenicity of Aldehyde.
1st Report.  Experimentally Produced Rat Sarcomas by Repeated Injections
of Aqueous Solution of Formaldehyde.  Two unpublished translations of
Japanese article published in Gann 45(2-3):451-452.

Rat

Repeated subcutaneous injections of 1 cc of an aqueous formaldehyde
solution at 0.6% to0.8%.  With 0.4% to 0.5% aqueous formaldehyde
solutions it was possible to inject subcutaneously once or twice a week.
Subcutaneous injections of 1 cc of a 0.4% aqueous formaldehyde solution
were continued on 10 rats once a week for about 1 year and three months.

	

0.6% to 0.8%: necrosis, the formation of an ulcer, while the area around
the injection spot formed a tuber which was very difficult to heal

0.4% - 0.5%: rare occurrence of an ulcer.  After two to five months
after having stopped the injections observations revealed the occurrence
of sarcomas either at the injection spot or in the internal organs of 4
out of 10 of the rats.  





870.4200a

Oncogenicity (Rat)

	

Tobe, M., T. Kaneko, Y. Uchida, et al. 1985. Studies of the inhalation
toxicity of formaldehyde. National Sanitary and Medical Laboratory
Service (Japan). p. 1-94.

Open Literature

32 Male Fischer 344 rats/dose

Test material was administered at concentrations of 0, 0.3, 2.0 or 15
ppm in aqueous solution methanol, 6 hours/day, 5 days/week for 28
months. The exposure at 15 ppm was tested for 24 months. A positive
control – 3.3 ppm methanol and a nonexposure (NE) control were also
used. 

	

During the exposure running noses, running tears and crouching were seen
in the 15 ppm dose group. These symptoms decreased as the number of
exposures increased. Hair around the abdominal region was observed to be
yellow in color and bleeding from the forelimbs was seen. Yellow
discoloration of abdominal hair was also seen in the 2.0 ppm dose group
although it was light. Significant suppression of weight gain and a
decrease in the amount of food gain were seen in the 15 ppm dose group.
20 of 24 animals in the 15 ppm dose group died in the 24 month dosing
period giving a high death rate of 88.3%. 

Recognizable tumors were observed in the 15 ppm group from the 420th day
onwards and tumors were recognized macroscopically in eight animals by
the 24th month. Squamous cell carcinoma was recognized in 14 rats and
pappiloma in 5 rats. Unclassified carcinoma was seen in 1 rat in the
nonexposure group which died on the 825th day. 

No neoplastic changes were seen in the 0.3 and 2.0 ppm and exposure
control dose groups. Excessive secretion was seen in the nasal cavity,
rhinitis accompanied by desquamation, squamous epithelial metaplasia and
epithelial cell hyperplasia were recognized in the 0.3 and 2.0 ppm dose
groups and these were significant in the 15 ppm dose group. 

A decrease in the T-GLY and a decrease in liver weight, assumed to be
changes accompanying decrease in food intake due to formaldehyde
exposure were seen in the 15 ppm dose group. However, these changes were
not accompanied by histological changes.  

 



870.4200a

Oncogenicity (Rat)

	

Takahashi et al. (1986) Effects of Ethanol, Potassium Metabisulfate,
Formaldehyde, and Hydrogen Peroxide on Gastric Carcinogenesis in Rats
after Initiation with N- methyl-N'nitro-N'nitrosoguanidine. Jap. J.
Cancer Res. 77: 118-124.

Open Literature

Male Wistar rats

A two-stage carcinogenesis bioassay was conducted in which
N-methyl-N'nitro- N'nitrosoguanidine was administered at 100 mg/l in the
drinking water for the first 8 weeks of the study, followed by
administration of formalin (dose not specified).  

	

Formalin did not produce malignant tumors when given alone.  Forestomach
papillomas occurred in 8/10 animals administered formalin alone.

In the group administered both MNG and formalin, forestomach papillomas
occurred in 15/17 animals, adenocarcinoma of the pylorus in 4/17,
preneoplastic hyperplasia of the pylorus in 7/17, and adenocarcinoma of
the duodenum in 1/17.





870.4200b

Oncogenicity

(Mouse)

Purity: 1% and 10%

	

Iversen, Olav Hilmar. (1986)  Formaldehyde and Skin Carcinogenesis.  
Environ Int 12:541-544. 

Open Literature

Hairless mice of the hr/hr Oslo Strain (16/sex)

Topical application of 200 ug formaldehyde in water on the back skin
twice a week for 60 weeks

	

Nonspecific granulomas in the lung; slight hyerplasia of the epidermis,
small skin ulcers





870.4200b

Oncogenicity

(Mouse)

Purity: 10%

	

Krivanek, N.D., N.C. Chromey and J.W. McAlack, "Skin initiation-
promotion study with formaldehyde in CD-1 mice", E.I. du Pont de Nemours
& Company, Inc. In: Formaldehyde: Toxicology, Epidemiology, and
Mechanisms, Clary, J.J., J.E. Gibson, and R.S. Waritz, Eds., N.Y.,
Marcel Dekker, Inc., 1983.

Open Literature

Female CD-1 Mouse

Mice were treated on shaved dorsal skin with up to 10 mg formaldehyde,
followed by repeated doses.  Formaldehyde was also applied once at 5
mg/mouse to assess initiation potential.  Promoter potential was tested
at 0.1, 0.5, and1.0 mg/mouse, applied 3 times/wk for 26 wk. Positive
controls [150 mg benzo(a)pyrene (BaP) as initiator, 2.5 mg 12-O-
tetradecanoylphorbol-13-acetate(TPA) as promoter], or negative control
(acetone) were used.

	

Repeated doses of 2-5 mg caused mild to moderate skin irritation,
whereas 1 mg caused only mild irritation.

As expected, BaP/TPA gave a high tumor yield (28/29 mice, 9 of which had
malignant tumors. Benign test site tumors were keratoacanthomas or
squamous papillomas. No other combinations gave yields significantly
different from controls. Thus the test is negative under study
conditions, with the caveat that one cannot be certain whether
formaldehyde underwent significant degradation to formic acid or other
products.





870.4200b

Oncogenicity

(Mouse)

Purity: 3.7%-4%

	

Spangler, F. and J.M. Ward, "Skin initiation/promotion study with
formaldehyde in Sencar mice". Study location: Microbiological Associates
(Bethesda, MD) in conjunction with NCI.  In: Formaldehyde: Toxicology,
Epidemiology, and Mechanisms, Clary, J.J., J.E. Gibson, and R.S. Waritz,
Eds., N.Y., Marcel Dekker, Inc., 1983.

Open Literature 

Female Sencar Mice (30/group)

Mice were treated in various combinations with or without an initiator
(DMBA) or promoter [12-O-tetradecanoylphorbol-13- acetate (TPA)]. All
test compounds were applied to back skin of mice with acetone, which was
used as a negative control in some treatment combinations Formaldehyde
was tested for initiating and promoting capability. In all cases,
formaldehyde was applied in acetone; however the amount of this solution
applied was not specified. All tests of initiators (including
formaldehyde, when tested for such potential) were as a single dose.
Promoters (including formaldehyde, when tested for such potential) were
applied once or twice a week. This is an interim report, relating counts
of skin papillomas as of the first 48 weeks of the study.

	

Study found no evidence of formaldehyde as an initiating agent, nor as a
complete carcinogen, however investigators considered there to be "a
slight possibility that formaldehyde may be a very, very weak promoting
agent", based on a very small tumor yield when formaldehyde was tested
as a promoter in mice treated with DMBA.





870.4200

Oncogenicity

Purity: Not reported

	

Dalbey, W.E. (1982). Formaldehyde and tumors in hamster respiratory
tract. Toxicology. 24: 9-14.

Open Literature

88 male Syrian golden hamsters

Test material was administered at a 10 ppm concentration 5 times/week
for lifetime. 

	

Lifetime exposure to formaldehyde reduced survival time (P < 0.05)
relative to unexposed controls. No tumors were observed in the
respiratory tract of non-exposed hamsters or of those exposed to
formaldehyde. There was, therefore, no evidence of carcinogenic activity
of formaldehyde under the given exposure conditions. 

Little evidence of toxicity from formaldehyde exposure was observed in
the nasal epithelium, expected to be a prime target issue. There was no
increase in the incidence of rhinitis related to exposure (observed in
31% of untreated animals and 24% of the formaldehyde-exposed hamsters).
Hyperplastic and metaplstic areas were each observed in the nasal
epithelium of 5% of hamsters exposed to formaldehyde while none were
observed in control animals. 





870.4300

Chronic/ Oncogenicity

Purity: Not Reported	

MRID 00143289

Kerns, W.D. et al. (1983) Carcinogenicity of Formaldehyde in Rats and
Mice after Long-Term Inhalation Exposure. Cancer Research 43: 4382-4392.


Rat (Fischer 344)  and Mice (B6C3F1) - approx 120/sex/dose

0, 2.0, 5.6, or 14.3 ppm (0, 2.5, 6.9, or 18 mg/m3), 6 hrs/day, 5
days/week, up to 24 months

	

From exposure weeks 3 to 103, mildly (15 to35 g) decreased body weights
(p<0.05) in male and female rats (6.9 and 18 mg/m3) were observed.
Animals in the 2.5 mg/m3 exposure group had sporadically reduced body
weights (p>0.05) throughout the exposure period.  Male and female rats
in the 18 mg/m3 exposure group exhibited significantly increased
mortality (p<0.001) from the 12th month onward. Male rats in the
intermediate exposure groups showed a statistically-significant
concentration-dependent decrease in cumulative survival from 17 months
onward.  

In male mice, there were no differences in survival. The number of male
mice surviving a minimum of 18 months were 41, 33, 32, and 25 for the 0,
2.5, 6.9, and 18 mg/m3 exposure groups, respectively. There were no
differences in cumulative survival among the female mice.  

There were no alterations in the clinical pathology or ophthalmologic or
neurofunctional data that were considered related to formaldehyde
exposure.  

Exposure to formaldehyde produced a concentration-dependent increase in
yellow discoloration of the hair.  Other significant macroscopic
observations (at the 18 mg/m3 group) included dypsnea, emaciation, and
large facial swellings that were proliferative lesions (carcinomas)
protruding from the nasal cavity.  Neoplastic lesions were first
observed clinically at Day 358 in females and Day 432 in males. 
Formaldehyde-induced microscopic lesions were confined to the nasal
cavity and the proximal trachea.  

Exposure to 18 mg/m3 formaldehyde for 24 months produced a high
incidence of nasal cancer in male and female rats. The tumors had a
sharp concentration-response relationship, with the 2 carcinomas in the
intermediate group identical to the 103 squamous cell carcinomas
observed in rats exposed to 18 mg/m3. Although the incidence of
polyploid adenomas in the nasal cavity was not statistically
significant, there was a positive concentration response for the
occurrence of benign neoplasms in male rats. There was no evidence of
progression of polyploid adenoma to squamous cell carcinoma.  

Two male mice exposed to 18 mg/m3 of formaldehyde developed squamous
cell carcinomas in the nasal cavity similar to the neoplasms in the
rats. Formaldehyde-induced lesions (squamous metaplasia and
inflammation) in mice were much less severe than similar lesions in
rats. The incidence of squamous cell carcinomas in mice exposed to 18
mg/m3 was similar to rats exposed to 6.9 mg/m3. 



Neurotoxicity



870.6200

Neurotoxicity screening battery

Purity:

(2003a) - 37% stock solution was used to prepare solutions of 0.5%, 1%,
and 2.5%

(2003b) – 0.1%, 0.2%, and 1%

	

Malek, FA; Moritz, KU; Fanghanel, J.  (2003a) Formaldehyde inhalation
and open field behaviour in rats.  Ind J Med Res 118:90-96. (NCEA)

Malek, FA; Moritz, K-U; Fanghaenel, J.  (2003b) A study on specific
behavioral effects of formaldehyde in the rat. J Exp Anim Sci
42:160-170. 

Open Literature

Male and Female LEW.1K Rat 

Malek et al. (2003a): Rats were exposed to 0, 1.0, 2.5, or 5.0 ppm (0,
1.23, 3.08, or 6.15 mg/m3) formaldehyde for 2 hours. Mean formaldehyde
levels of 1.01 ± 0.29 ppm, 2.51 ppm (standard deviation is missing) and
5.04 ± 0.27 ppm were achieved.  Locomotor activity was assessed for 1
hour in an open field 2 and 24 hours after termination of formaldehyde
exposure.  

Malek et al. (2003b):  Rats (10 per group) were exposed at 0, 0.1, 0.5,
or 5.0 ppm (0, 0.123, 0.615, or 6.15 mg/m3) formaldehyde for 2 hours.
Open field behavior tests were conducted on each animal 2 hours after
formaldehyde exposure.  

	

Malek et al. (2003a):

LOAEL = 1.0 ppm, 2 hours  

In general, sniffing was increased after formaldehyde exposure and
movement was decreased (crossed quadrants and climbing) in both male and
female rats (p<0.05). Significant reductions in horizontal movements
(crossed quadrants) were observed at all dose levels and were
characterized by a U-shaped dose response. The lowest dose tested (1
ppm) demonstrated higher level of activity suppression than the two
higher doses, but all groups were still suppressed relative to controls.
 Although female rats displayed a greater level of activity overall, a
similar U-shaped dose-response pattern was also observed.

After 24 hours, as expected, controls demonstrated habituation to the
test apparatus exhibiting only 20% of the motor activity observed on day
1. In contrast, formaldehyde-treated animals failed to demonstrate the
same degree of habituation. Activity levels for males observed on day 2
were 60-80% of the activity levels seen on day 1. Formaldehyde-treated
females also failed to habituate and actually demonstrated increases in
activity on day 2 relative to day 1 at all formaldehyde exposure levels.

Malek et al. (2003b):  

LOAEL (M) = 0.1 ppm, 2 hours 

The number of crossed quadrants for both controls and a 5 ppm group are
comparable to those observed in the first study. Horizontal movement was
decreased by formaldehyde exposure in a dose dependent manner with
significant reductions in motor activity as low as 0.1 ppm in males and
0.5 ppm in females. The consistency of the data across studies and
between genders provides greater confidence in the effects of low level
formaldehyde exposure on this standard test of neurotoxicity.





870.6500

Schedule-controlled operant behavior

Purity: Not reported

	

Pitten, FA; Kramer, A; Herrmann, K; et al.  (2000) Formaldehyde
neurotoxicity in animal experiments.  Pathol Res Pract 196:193-198. 

Open Literature

Adult Male and Female Wistar Rat (5 to 8/sex/group)

Pitten et al. (2000) evaluated the effects of very brief formaldehyde
exposures (10 minutes) but prolonged duration (90 days) on previously
learned performance in a land version of the labyrinth maze. Rats were
acclimated to the task for 14 days, 2 trials/day. Animals were required
to make a series of five consecutive turns from the entrance of the maze
to retrieve a piece of cheese placed in the goal box at the opposite
end. Animals were exposed to 0 ppm, 2.6 ppm (0.25% formaldehyde solution
to yield 3.06 ± 0.77 mg/m3 ), or 4.6 ppm (0.70% formaldehyde solution
to yield 5.55 ± 1.27 mg/m3) formaldehyde, 10 minutes/day, 7 days/week
for 90 days. Animals were assessed for performance in the maze every
seventh day, at least 22 hours after the exposure on the previous day. 
At the end of the 90-day exposure period, monitoring of maze performance
continued once every 10 days for an additional 40 days.

	

LOAEL: 2.6 ppm, 10 min/90 days

The authors reported that no gender differences existed as a function of
formaldehyde treatment; therefore, data were presented by combining
sexes. Control rats showed no change in error rate but a slight decrease
in running time through the maze during the course of the experiment. 
The formaldehyde-exposed groups began with a similar performance level
and error rate as controls, but their performance degraded over the
course of formaldehyde exposure.  By the fourth week of exposure,
increased numbers of errors were evident in both exposed groups relative
to controls. This trend reached statistical significance by the
thirteenth week for a greater than twofold increase in error rate
(p<0.05). Formaldehyde-treated rats also tended to have increased run
times through the maze (p=0.04), but no difference was seen by
formaldehyde concentration. By 4 weeks after termination of exposure, no
statistical differences among the three groups were evident, but the
tendency for the two exposed groups to make more errors and have longer
latencies remained. Since Pitten et al. (2000) tested animals after the
task was acquired, these results indicate deficits in the retention of a
previously learned task.





Other

Purity: 96%	

Boja JW, Nielsen JA, Foldvary E, et al. (1985) Acute Low-Level
Formaldehyde Behavioural and Neurochemical Toxicity in the Rat. Prog
Neuro-Psychopharmacol Biol Psychiat 9:671-674.

Open Literature

88 M Sprague-Dawley Rat

Rats were exposed to either air or formaldehyde at concentrations of 5,
10, or 20 ppm (6.20, 12.39, or 24.79 mg/m3) via inhalation for 3 hours
on two days

	

Exposure to 6.20 mg/m3 formaldehyde resulted in statistically
significant decreased motor activity within 15 minutes.  At the
beginning of day 2, all of the rats exposed to formaldehyde on day 1
displayed lower activity levels. Similar effects on motor activity were
seen at the 12.39 mg/m3 formaldehyde exposure level, whereas effects
seen after 24.79 mg/m3 exposure were reported to be “not readily
interpretable” and were not shown. Exposure to 6.20 mg/m3 formaldehyde
statistically significantly increased concentrations of 
5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid, and dopamine
in the hypothalamus.



Metabolism



870.7485

General Metabolism

	

Casanova, Mercedes, Donald F. Deyom and Henry D'A. Heck (1989) Covalent
Binding of Inhaled Formaldehyde to DNA in the Nasal Mucosa of Fischer
344 Rats:  Analysis of Formaldehyde and DNA by High-Performance Liquid
Chromatography and Provisional Pharmacokinetic Interpretation. 
Fundamental and Applied Toxicology 12: 397-417. 

Open Literature

	

Rat (4/group), nose-only exposure

0, 0.3, 0.7, 2, 6, or 10 ppm (0.37, 0.87, 2.5, 7.4, or 12 mg/m3) for 6
hours 	

DNA-protein crosslinking occurred at all concentrations. The formation
of crosslinks was interpreted in terms of a nonlinear pharmacokinetic
model incorporating oxidation of inhaled formaldehyde as a defense
mechanism. The slope of the fitted concentration-response curve at 12
mg/m3 is7.3-fold greater than at 0.37 mg/m3, and the detoxification
pathway is half-saturated at an airborne concentration of 3.2 mg/m3.





870.7485

General Metabolism

	

Casanova-Schmitz, Mercedes, Thomas B. Starr, and Henry D'A. Heck (1984)
Differentiation between Metabolic Incorporation and Covalent Binding in
the Labeling of Macromolecules in the Rat Nasal Mucosa and Bone Marrow
by Inhaled (14C)- and (3H) Formaldehyde.  Toxicology and Applied
Pharmacology 76: 26-44. 

Open Literature

Rats (4/group)

14C and 3H- formaldehyde was administered at doses of 0, 0.3, 2, 6, 10,
or 15 ppm (0, 0.37, 2.5, 7.4, 12, or 19 mg/m3) for 6 hours

	

The major route of nucleic acid labeling at all concentrations and in
all tissues was metabolic incorporation; protein labeling in the
respiratory mucosa was mainly due to covalent binding at the higher
formaldehyde concentration.  Incorporation of 14C- formaldehyde into DNA
in the respiratory mucosa was maximal at 7.4 mg/m3 but decreased at
higher concentrations, whereas labeling of DNA in the olfactory mucosa
and bone marrow increased monotonically with concentration. Evidence for
covalent binding of formaldehyde to respiratory mucosal DNA was obtained
at formaldehyde concentrations equal to or greater than 2.5 mg/m3. The
concentration of formaldehyde covalently bound to DNA at 7.4 mg/m3 was
10.5-fold higher than at 2.5 mg/m3, indicating significant nonlinearity
of DNA binding with respect to the inhaled formaldehyde concentration
under these conditions.  Covalent binding to proteins increased in an
essentially linear manner with increases in the airborne concentration.
No evidence was obtained for the formation of covalent adducts with
macromolecules in the olfactory mucosa or bone marrow. The nonlinear
increase in covalent binding to respiratory mucosal DNA with increasing
formaldehyde concentrations may be explained either by a decrease in the
efficiency of defense mechanisms or by an increase in the availability
of reaction sites on the DNA resulting from increased cell turnover.





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