 

US ENVIRONMENTAL PROTECTION AGENCY

		WASHINGTON, D.C.  20460

OFFICE OF PREVENTION,

PESTICIDES AND

TOXIC SUBSTANCES

DATE: August 10, 2006

MEMORANDUM

SUBJECT:	Didecyl Dimethyl Ammonium Chloride (DDAC) - Report of the
Antimicrobials Division Toxicity Endpoint Committee (ADTC) and the
Hazard Identification Assessment Review Committee (HIARC). 

FROM:	Timothy F. McMahon, Ph.D.; Chair, ADTC

Michelle Centra, Pharmacologist;  Executive Secretary, ADTC

Antimicrobials Division (7510C)

TO:	Steve Malish, Ph.D., Toxicologist

Kathryn Montague, Team Leader	Risk Assessment and Science Support Branch
(RASSB)

Antimicrobials Division (7510C)

and

Tracy Lantz, Chemical Review Manager

Velma Noble, Team Leader

Regulatory Management Branch I

Antimicrobials Division (7510C)

PC Code: 069149

On  February 10, 2000, the Health Effects Division (HED)  HIARC
reviewed the recommendations of the toxicology reviewer for didecyl
dimethyl ammonium chloride (DDAC) with regard to the acute and chronic
Reference Doses (RfDs) and the toxicological endpoint selection for
occupational/residential exposure risk assessments.  The potential for
increased susceptibility of infants and children from exposure to DDAC
was also evaluated as required by the Food Quality Protection Act (FQPA)
of 1996.  In November of 2005, members of the ADTC met with the HED
Hazard Science Policy Council to discuss revision of the dermal
endpoints.  The conclusions drawn at this meeting are presented in this
report.

Committee Members in Attendance

HIARC members present: Willam Burnam, Vicki Dellarco, Elizabeth Doyle,
Pamela Hurley, Tina Levine, Elizabeth Mendez, David Nixon, Nicole
Paquette, Jess Rowland, and Brenda Tarplee.	

Also in attendance were:  Winston Dang (AD), Tim McMahon (AD)

HIARC Data Evaluation/Report Presentation:        
_______________________________

Jonathan Chen, Ph.D.

ADTC members: Michelle Centra,  Jonathan Chen, Ph.D., Stephen Dapson,
Ph.D.,  Roger Gardner,  Karen Hamernik, Ph.D., Timothy Leighton, Tim
McMahon, Ph.D., Melba Morrow, D.V.M., John Redden, Najm Shamim, Ph.D.,
Sanyvette Williams-Foy, D.V.M.

ADTC Data Evaluation/Report Presentation:	
___________________________________

Tim McMahon, Ph.D., Chair		

COMMITTEE MEMBERS  (Signature indicates concurrence unless otherwise
stated)   

Stephen Dapson 			_________________________________________			

Jonathan Chen			_________________________________________			

Roger Gardner			_________________________________________

Karen Hamernik			_________________________________________

Tim McMahon (Chair)		_________________________________________		

Melba Morrow			_________________________________________			

John Redden			_________________________________________			

SanYvette Williams		_________________________________________		

Michelle Centra 

(Executive Secretary)		 _________________________________________

Najm Shamim			_________________________________________

Timothy Leighton		    ________________________________________   
INTRODUCTION			

On February 10, 2000, the Health Effects Division (HED) Hazard
Identification Assessment Review Committee (HIARC) reviewed the
recommendations of the toxicology reviewer for didecyl dimethyl ammonium
chloride (DDAC) with regard to the acute and chronic Reference Doses
(RfDs) and the toxicological endpoint selection for
occupational/residential exposure risk assessments. The potential for
increased susceptibility of infants and children from exposure to DDAC
was also evaluated as required by the Food Quality Protection Act (FQPA)
of 1996. In December of 2005, the Antimicrobials Division(s ADTC updated
the dermal endpoints for DDAC  based on the recently adopted use of
dermal irritation as an endpoint for short-term dermal risk assessments.


HAZARD IDENTIFICATION

Acute Reference Dose (RfD)				Subpopulation Females 13+

Study Selected:   Developmental Toxicology - Rat, OPPTS 870.3700;  (
83-3

MRID No.: 	41886701

Executive Summary: In a prenatal developmental toxicity study (MRID
41886701), twenty five bred female CD( (Sprague-Dawley) rats per group
were administered DDAC (80.8% a.i.) in deionized water orally by gavage
at doses of 0, 1, 10, or 20 mg/kg/day on gestation days (GD) 6-15,
inclusive.  On GD 21, dams were sacrificed, subjected to gross necropsy,
and all fetuses examined externally, viscerally, and skeletally for
malformations/variations.   Maternal toxicity was observed at the mid
and high dose group in the form of audible respiration with the high
dose presenting with other observations.  Further, a treatment related
decrease in body weight gain was noted during the dosing period
(gestation day(s 6-15), the dosing period plus post dosing period
(gestation days 6-21) and for the corrected body weight gains for the
high dose.  There was also low food efficiency compared with controls
during the dosing period for the mid and high dose group.  The maternal
LOAEL is 10 mg/kg/day, based on reductions in body weight gain and
clinical signs of toxicity (audible respiration).  The maternal NOAEL is
1 mg/kg/day.   Developmental toxicity was noted at the high dose in the
form of increased incidences of skeletal variations.  Therefore, the
developmental toxicity LOAEL is 20 mg/kg/day based on an increased
incidence of skeletal variations, and the developmental toxicity NOAEL
is 10 mg/kg/day.

Dose and Endpoint for Establishing RfD: Developmental NOAEL of 10
mg/kg/day based on  increased incidences of skeletal variations at 20
mg/kg/day.

Uncertainty Factor (UF): 100X (10X for intraspecies extrapolation; and
10X for interspecies extrapolation)



Acute RfD (females 13+) =        10 mg/kg/day (NOAEL)    =     0.1
mg/kg/day

                                                               100 (UF) 

Comments about Study/Endpoint/Uncertainty Factor:  The developmental
endpoint is presumed to occur after a single exposure.  Since the effect
developed from in utero exposure, they are applicable for risk
assessment for female 13-50 subpopulation group only.

Acute Reference Dose (RfD)		General Population Including Infants and
Children+

Since the developmental endpoint selected is only applicable to Females
13+, another endpoint was considered for the general population
including infants and children.  However, an appropriate endpoint was
not identified for this population subgroup.  The maternal toxicity
(decreases in body weight gains) observed in maternal animals in the rat
and rabbit studies are NOT appropriate since the effects are not
attributable to a single exposure (dose).  Other oral studies did not
indicate endpoints that are appropriate for this exposure period.  

Study Selected:     	None

MRID No.: 	None

Executive Summary: 	None

Dose and Endpoint for Establishing RfD:	None

Uncertainty Factor (UF):	 None

Comments about Study/Endpoint/Uncertainty Factor:	This risk assessment
is NOT required for this subpopulation.    

Chronic Reference Dose (RfD)

Study Selected:  Chronic Oral Toxicity Study - Dog, OPPTS 870.4100; (
83-1b)			

MRID No.: 	41970401

Executive Summary: In a chronic one year oral toxicity study (MRID
41970401), male and female beagle dogs were given test compound at
dosages of 0, 3, 10, or 20/30 mg/kg/day (dosage at 30 mg/kg/day was not
tolerated well and was discontinued on day 31, dosing was resumed on day
36 at 20 mg/kg/day).  No treatment-related deaths occurred during the
study.  The treatment-related clinical signs (soft/mucoid feces, emesis)
were observed frequently in high-dose animals.  Hematology or urinalysis
results were normal.  Total cholesterol levels were significantly
decreased in the high-dose females.  Gross and histopathological
findings did not reveal any treatment-related effects. The LOAEL is 20
mg/kg/day based on increase incidence of clinical observations (emesis
and soft/mucoid feces) in males and females and decreased total
cholesterol levels in females.  The  NOAEL is 10 mg/kg/day.

Dose and Endpoint for Establishing RfD:   NOAEL of 10mg/kg/day based on
increased incidence of clinical observations (emesis and soft/mucoid
feces) in males and females and decreased total cholesterol levels in
females at 20 mg/kg/day (LOAEL)

Uncertainty Factor(s):	100X (10X for intraspecies extrapolation; and 10X
for interspecies extrapolation)

 

Comments about Study/Endpoint/Uncertainty Factor: The lowest NOAEL in
the most sensitive species following chronic exposure and is appropriate
for chronic dietary risk assessment.

Occupational/Residential Exposure

Dermal Absorption

The dermal absorption factor is not required since route-specific
studies are available to assess the need for endpoints.  

Dermal  Exposure

NOTE: studies are available for both the technical grade active
ingredient (80% a.i.) and two formulated products of DDAC (0.13% and 4%
a.i.).  Use of dermal irritation as an endpoint has recently been
adopted as a working policy measure for the Health Effects Division and
the Antimicrobials Division (meeting of the HED Hazard Science Policy
Council, November 30, 2005).  Therefore, endpoints for the technical and
formulated product are determined separately as needed. 

2.4.3	Short-term Incidental Oral Exposure   (1-30 days)

Study Selected:   Developmental Toxicology - Rat, OPPTS 870.3700;  (
83-3

MRID No.: 	41886701

Executive Summary: See summary under Acute RfD endpoint above. 

Endpoint selected: Developmental NOAEL of 10 mg/kg/day based on 
increased incidences of skeletal variations at 20 mg/kg/day.

Uncertainty Factor (UF): 100X (10X for intraspecies extrapolation; and
10X for interspecies extrapolation)

2.4.4	Intermediate-term Incidental Oral Exposure   (30 days- 6 months)

Study Selected:  Chronic Oral Toxicity Study - Dog, OPPTS 870.4100; (
83-1b)			

MRID No.: 	41970401

Executive Summary: See summary under Chronic RfD endpoint above. 

Endpoint selected:   NOAEL of 10mg/kg/day based on decreased total
cholesterol levels in females at 20 mg/kg/day (LOAEL)

Uncertainty Factor(s):	100X (10X for intraspecies extrapolation; and 10X
for interspecies extrapolation)

2.4.5	Short-term Dermal Exposure, technical grade a.i.  (1-30 days)

Study Selected: 90-Day Dermal Toxicity Study - Rat, 870.3250; ( 82-3				

MRID No.: 	41305901

Executive Summary: In a subchronic dermal toxicity study (MRID
41305901), fifteen Sprague-Dawley rats per sex per group received
repeated dermal dosing of test compound at 0, 2, 6, or 12 mg/kg/day
(concentrations of 0.1, 0.3, and 0.6%) for 6 hours/day, 5 days/week for
13 weeks.  No treatment-related effects were noticed in mortality,
weight gain, food consumption, or systemic toxicity.  Toxicity was
limited to treated skin of mid-dose females and high-dose males and
females.  The clinical and gross findings (erythema, edema, exfoliation,
excoriation and ulceration) were confirmed by histopathological
examination, where increased incidence of hyperkertosis, acanthosis,
epidermitis, dermatitis and ulceration were noted beginning after 5 days
of exposure.  The systemic NOAEL is grater than 12 mg/kg/day (highest
dose tested).  The dermal LOAEL for dermal toxicity is 6 mg/kg/day.  The
dermal NOAEL is 2 mg/kg/day.

Dose and Endpoint for Risk Assessment:   Dermal toxicity  NOAEL of 2
mg/kg/day based on increased clinical and gross findings at 6 mg/kg/day
(LOAEL).

Comments about Study/Endpoint:. The HIARC and ADTC selected irritation
as the short-term endpoint based on the policy adopted for use of dermal
irritation as a short-term endpoint. It is noted from the 90-day dermal
toxicity study that no systemic toxicity was seen at the highest dose
tested but dermal irritation was present after 5 days of exposure.  It
is further noted that a second dermal toxicity study is available (MRID
40565301 and 41105801) in which a dilution of a product containing 6%
DDAC and 4% ADBAC was studied for 21 daysin guinea pigs. However,  the
rat study was chosen for the short-term endpoint because between these
two studies, the concentration evoking the irritation response was lower
in the rat study (8 µg/cm2) than in the guinea pig study (500 µg/cm2)
and occurred within the same time frame (rat response observed after 5
days, guinea pig response observed after approximately 10 days). 

Short-term Dermal Exposure- formulated product, 0.13% a.i.

Study Selected: none 

Comments about Study/Endpoint: There is an available 21-day dermal
toxicity study for a formulation of DDAC at 0.13% (MRID 45656601).  This
study shows no dermal irritancy or systemic effects up to and including
a limit dose of 1000 mg/kg.  Thus, an endpoint for short-term dermal
exposure to 0.13% a.i. is not required. 

2.4.6	Intermediate (30 days-6 months) and Long-Term (> 6 months) Dermal
( Exposure

Study Selected: none 

Comments about Study/Endpoint:  The available data show no appropriate
endpoint for intermediate- and long-term dermal risk.  Use of irritation
as an endpoint for the short-term is protective of any dermal or
systemic effects from longer term exposures. 

 2.4.7   Inhalation Exposure (All Durations)	 

When DDAC is applied with a spraying system (e.g. sprayer), inhalation
may be a potential exposure route. Since no inhalation studies are
available, committee selected the oral NOAEL for this risk assessment. 
Since the dose identified for inhalation risk assessments are from oral
studies, route-to-route extrapolation should be as follows:

Step I:		The inhalation exposure component (i.e., μg a.i./day) using a
100% (default) absorption rate and application rate should be converted
to an equivalent oral dose (mg/kg/day)

Step II:		To calculate the MOE(s , the equivalent oral dose converted
from Step I should then be compared to the oral NOAEL of 10 mg/kg/day
for short term exposure study (MRID 418867-01), and  the oral NOAEL of
10 mg/kg/day for intermediate and chronic oral exposure based on chronic
dog study (MRID 419704-01).

3.0    Margins of Exposure for Occupational/Residential Risk Assessments

For acute and chronic dietary exposures, the standard UF of 100 is
applied. The special hazard-based FQPA safety factor is reduced to 1x. 

For incidental oral and dermal assessments, the MOE of 100 is applied
and for inhalation assessments, an MOE of 100 is applied.  An additional
database UF of 10x is applied for route-to-route extrapolation from an
oral endpoint.  

   

4	CLASSIFICATION OF CARCINOGENIC POTENTIAL

4.1	Combined Chronic Toxicity/Carcinogenicity Study in Rats

MRID No.	41965101

Discussion of Tumor Data: In a chronic/carcinogenicity study (MRID
41965101), 60 Sprague-Dawley CD rats per sex per group were fed diets
containing DDAC (Batch # B-1889,  80.8% a.i.)  At 0,300,750 or 1500 ppm
(mg/kg/day equivalents:0,13,32,or 64 for males and 0, 16, 41, or 83 for
females) for two years.  High-dose animals showed significant, but
slight (<10%) decreases in mean body weight during the study.  Treatment
related effects consisted of increased incidence of sinusoidal blood,
hemosiderosis and histiocytosis in the mesenteric lymph nodes of high
dose animals.  In addition, a treatment-related increase in the
incidence of interstitial cell adenomas in testes was reported.  In this
study, the incidences of this tumor for control and treated animals are
: Control 1 (5%, 3/60); Control 2 (5% 3/60), 300ppm (12.5%, 1/8), 750ppm
(17.9%, 5/28), and 1500ppm (11.7%, 6/60).   However, because the
incidence was within  historical incidence range, this chemical is not
considered carcinogenic in this study.  (See Table 1)

Adequacy of the Dose Levels Tested:The high dose tested (HDT)  in the
study is appropriate for carcinogenicity testing based on slight but
statistically significant decrease in mean body weight (<10%) and some
histopathological changes.

Table 1:	Incidence of Testicular Interstitial Adenomas in Male
Sprague-Dawley Rats for the Studies conducted at Bushy Run Research
Center since 1987 1,2

Study	

Dates of In-Life Phase	

Group3





C1	

C2	

L	

M	

H



DDAC	

06/13/88 to 06/19/90	

3/60	

3/60	

1/18	

5/28	

7/60



Historical Control #1	

03/22/88 to 03/27/90	

3/59	

1/60	

-	

-	

-



Historical Control #2	

03/08/89 to 03/13/91	

4/59	

7/60	

-	

-	

-



Historical Control #3	

04/29/91 to 05/04/93	

1/60	

6/60	

-	

-	

-

 	             1. 	Data provided by Bushy Run Research Center (1995,
MRID 436138-01).

                         2. 	All rats were from Charles River Breeding
Laboratories, Portage MI.

                         3.  	C1 - Control Group 1; C2 - Control Group
2; L - Low-dose Group; 

M - Mid -dose Group; and H- High-dose group.

4.2	Carcinogenicity Study in Mice

MRID No.	41802301

Discussion of Tumor Data: In a carcinogenicity study (MRID 41802301), 60
CD-1 mice per sex per group were fed diets containing DDAC (Batch #
B-1889,  80.8% a.i.) at levels of 0,100, 500 or 1000 ppm (mg/kg/day
equivalents:0, 15.0, 76.3, or 155.5 for males and 0, 18.6, 93.1,  or
193.1 for females) for 78 weeks. No treatment-related effects were noted
in the incidence of clinical signs, deaths, gross and histopathological
observations.  Hematological values were comparable among all study
groups.  The NOAEL for both male and females is 500 ppm (76.3 mg/kg/day
for males and 93.1 mg/kg/day for females), and the LOAEL is1500ppm
(155.5 mg/kg/day for males; 193.1 mg/kg/day for females).  The LOAEL is
based on decreases in mean body weights and body weight gains.  At the
level tested, the chemical is not carcinogenic.

Adequacy of the Dose Levels Tested: The HDT induce statistically
significant decreases ((10%) in mean body weight).

4.3  Mutagenicity

  SEQ CHAPTER \h \r 1 In an Ames test, with or without  microsomal
activation (S-9 fraction), DDAC was not mutagenic to Salmonella
typhimurium tester strains (MRID 40282201 and supplemental information
MRID 44005801).   

In  forward gene mutation assays (MRID 93014008, reformat of 40895202)
DDAC was negative for induction of gene mutations in CHO cells at the
HGPRT locus, with levels of DDAC ranging from 1-10 μg/ml without S9
induction and 1-26 μg/ml with S9 induction.  Severe toxicity was
demonstrated at doses of ≥10 μg/ml (-S9) and ≥ 25 μg/ml (+S9).

In an in vitro chromosome aberration test (MRID 41252601), DDAC failed
to induce chromosome aberrations in Chinese hamster ovary (CHO) cells
harvested 26 hours after exposure to DDAC at concentrations of 1-8
μg/ml without microsomal fraction (S9) induction or DDAC at
concentrations of 2-8 μg/ml with S9 induction.  Cytotoxic effects were
observed at DDAC concentrations 16 μg/ml (with or without S9).

In an in vitro mutagenicity test (MRID 93014007, reformat of 40895201),
DDAC did not induce unscheduled DNA Synthesis (UDS) in primary rat
hepatocytes treated with DDAC at doses up to 2.00 μg/ml.  Higher
concentrations (4.0 μg/mL) of DDAC were severely cytotoxic.

4.4	Classification of Carcinogenic Potential

The HIARC classified DDAC as not likely to be a human carcinogen based
on the lack of evidences of carcinogenicity in mice or rats.

FQPA CONSIDERATIONS

5.1	Adequacy of the Data Base

-- Acute delayed neurotoxicity study in hen (if applicable)?	No

-- Acute and subchronic neurotoxicity studies (if applicable)? No

-- Developmental toxicity studies in Rat & Rabbits	Yes

- Two-Generation Reproduction Study	Yes

-Developmental neurotoxicity study (if applicable)	No

5.2	Neurotoxicity 

Based on the available data, the committee concluded  that there is no
evidence DDAC will induce neurotoxic effects.

	5.3	Developmental Toxicity

In a developmental toxicity study in rabbits (MRID #: 410187-01), 16
female New Zealand White Rabbits per dose were administered  dose levels
of 0,1,3 or 10 mg/kg/day of DDAC (81% a.i.) by gavage on gestation days
6 - 18 inclusive.  The maternal toxicity NOAEL = 1 mg/kg/day; LOAEL = 3
mg/kg/day based on increased clinical signs (hypoactivity, labored
and/or audible respiration) and decreased body weight gain during the
dosing period.  The developmental toxicity NOAEL = 3  mg/kg/day; LOAEL =
10 mg/kg/day based on decreased fetal body weight and an increased
number of dead fetuses were reported.

In a developmental toxicity study in rats (MRID #: 418867-01), 25 female
 Sprague-Dawley  CD Rats were administered dose levels of 0,1,10 and 20
mg/kg/day DDAC (80.8% a.i.) by gavage on gestation days 6 - 15
inclusive.  The maternal toxicity NOAEL = 1 mg/kg/day; LOAEL = 10
mg/kg/day based on decreased body weight/weight gain.  The developmental
toxicity NOAEL = 10  mg/kg/day; LOAEL = 20 mg/kg/day based on skeletal
variations observed (split anterior archof the atlas, poorly ossified
thoracic centrum, bilobed thoracic centrum, unilateral short rib, poorly
ossified parietal, and poorly ossified sternebrae).

5.4	Reproductive Toxicity

In a two generation reproductive toxicity study in rats (MRID #:
418045-01), 28/sex/dose ( both F0 and F1) Sprague-Dawley  CD Rats were
fed a diet containing DDAC (80.8% a.i.) at dosage levels of 0, 300, 750,
or 1500ppm (during premating,  for both sexes = 22, 56, and 113
mg/kg/day;  for males  = 20, 50, or 103 mg/kg/day and for females =  24,
61, or 122 mg/kg/day).  Reproductive Toxicity NOAEL = 750ppm (56
mg/kg/day); LOAEL = 1500ppm (113 mg/kg/day) based on decreased pup body
weight/weight gain and food consumption were reported.

5.5	Determination of Susceptibility

There was no quantitative or qualitative evidence of increased
susceptibility to rat or rabbit fetus following in utero exposure in the
prenatal developmental toxicity studies or in the offspring when exposed
to adults in the two generation reproductive study.		

5.6	Recommendation for a Developmental Neurotoxicity Study

There was no evidence in the available database to support the need for
a Developmental Neurotoxicity study for DDAC.	

HAZARD CHARACTERIZATION

 DDAC was assigned Toxicity Category II in two acute oral toxicity
studies in rats, MRIDs 41394404 [65% a.i.; LD50 = 262 mg/kg (combined)]
and 42296101 [80% a.i.; LD50 = 238 mg/kg (combined)].  DDAC was assigned
Toxicity Category III in two acute dermal toxicity studies in rabbits,
MRIDs 42053801 [65% a.i.; LD50 = 2930 mg/kg (combined)] and 00071158
[50% a.i.; LD50 = 4350 mg/kg (combined)].  For acute inhalation toxicity
(MRID 00145074; TRID 455201010), the LC50 of DDAC (purity not reported)
was reported as 0.07 mg/L; Toxicity Category II was assigned.  For
primary eye irritation, DDAC was found to be corrosive (Toxicity
Category I) in two primary eye irritation studies in rabbits, MRIDs
41394404 [65% a.i.] and 42161602 [80% a.i].  For primary dermal
irritation, DDAC (80% a.i.) was found to be corrosive (Toxicity Category
I) in a primary dermal irritation study in rabbits (MRID 42161601).   A
dermal sensitization study in guinea pigs using BARDAC 2280 80% a.i.
(MRID 46367601) showed that DDAC is not a dermal sensitizer. 

For subchronic toxicity, the database includes a 90-day oral toxicity
test in rats (MRID 40966302), a 90-day oral study in dogs (MRID
40262901), two 21-day dermal toxicity studies with  product 
formulations (MRIDs 41105801 and 45656601), and a 90-day dermal toxicity
study in rats using the technical grade (MRID 41305901).  In the 90-day
rat oral feeding study (MRID 40966302), incidence of gross pathological
observations and non-neoplastic lesions, including a higher incidence of
glycogen depletion in the liver and contracted spleens were observed. 
In the 21-day dermal toxicity study in guinea pigs, MRIDs 40565301 and
41105801, a 1:5 dilution of HS sanitizing solution (containing 6% DDAC
and 4% alkyl dimethyl benzyl ammonium chloride) at the high dose (1000
mg/kg/day) resulted in skin irritation was observed in week 2 of the
study, body weights decreased in week 3 of the study, and a slight
elevation of basophils and eosinophils as well as a slight elevation of
SGPT and SGOT.  In a 21-day dermal toxicity study in rats using
SS0853-01 ( 0.13% a.i., MRID 45656601), no toxicity  was observed at any
dose level tested .  In the 90-day dog feeding study (MRID 40269201), no
treatment-related clinical chemistry, hematology, urinalysis, or
pathological findings were observed.

In the 90-day dermal toxicity test in rats (MRID 41305901), systemic
toxicity was not observed and clinical and gross findings (erythema,
edema, exfoliation, excoriation and ulceration) were limited to the
treated skins.

For developmental toxicity, the data from two developmental toxicity
studies, one in the rat (MRID 41886701, range-finder MRID 42746901) and
another in the rabbit (MRID 41018701), do not indicate   SEQ CHAPTER \h
\r 1 increased susceptibility in rats or rabbits from in utero and
postnatal exposure to DDAC.  In the rat developmental toxicity study
(MRID 41886701), developmental toxicity (skeleton variations) was
observed only at treatment levels which also resulted in maternal
toxicity (audible respiration).  In the rabbit developmental toxicity
study, developmental toxicity (decreased fetal body weight and increased
number of dead fetuses) occurred at levels which also resulted in
maternal toxicity (hypo activity, audible respiration, and decreased
body weight gain).  

For reproductive toxicity, the toxicity database for DDAC includes a
2-generational reproductive toxicity study in rats (MRID 41804501).  In
this study, 28/sex/dose (both F0 and F1) Sprague-Dawley CD rats were fed
a diet containing DDAC (80.8% a.i.) at dosage levels of 0, 300, 750, or
1500 ppm (during premating, for both sexes = 22, 56, and 133 mg/kg/day).
 The effects in offspring (decreased pup body weight/weight gain)
occurred at the same dose level as maternal effects (decreased maternal
body weight/weight gain and food consumption), 1500 ppm.  The NOAEL for
this study is 750 ppm (56 mg/kg/day) and the LOAEL for this study is
1500 ppm (113 mg/kg/day).

In a 1-year dog feeding study (MRID 41970401), beagle dogs were given
doses of 0, 3, 10, or 20/30 mg/kg/day in the diet.  Treatment-related
clinical signs (soft/mucoid feces, emesis) were observed frequently in
high-dose animals, and total cholesterol levels were significantly
decreased in high-dose females.

DDAC was not carcinogenic when administered in the diet in 2-year
chronic/ carcinogenicity studies in rats (MRID 41965101) and mice (MRID
41802301).  In the rat study, an increase in incidence of interstitial
cell adenomas in the tested were reported, but the incidence was with in
the range of historical controls.  In the mouse study, no
treatment-related effects were noted in the incidence of clinical signs,
deaths, and gross and histopathological observations.

For mutagenicity, DDAC was negative in a battery of tests.  In the Ames
test (MRID 40282201, supplemental information MRID 44005801), DDAC was
not mutagenic with or without metabolic activation.  In a forward gene
mutation test (MRID 93014008, reformat of 40895202), DDAC was negative
for induction of gene mutations in CHO cells at the HGPRT locus with and
without metabolic activation.  In an in vitro chromosome aberration test
(MRID 41252601),   SEQ CHAPTER \h \r 1 DDAC did not induce chromosome
aberration in the Chinese hamster ovary (CHO) cells with or without
metabolic activation.  In an unscheduled DNA synthesis (UDS) assay (MRID
93014007, reformat of 40895201), DDAC did not cause UDS in primary rat
hepatocytes.

Although there are no neurotoxicity studies available in the database,
the available toxicity for DDAC show no evidence for neurotoxic effects.

  SEQ CHAPTER \h \r 1 In a rat pharmacokinetics/ metabolism study (MRID
41617101 and addendum MRID 41385101), single oral doses of 14C-DDAC (5
or 50 mg/kg) or repeated dose (34 ppm of DDAC in the diet for 14 days
and then one single dose of 5 mg/kg of 14C-DDAC) were given to both male
and female rats.  DDAC was mostly excreted in the feces within 3 days
principally as parent compound and metabolites.  The elimination pattern
and metabolic profile was not substantially altered by the dose or
exposure duration.  Male and female rats showed similar elimination
patterns, but females metabolized DDAC more extensively than males. 
Four major metabolites were identified as oxidation products with
oxidation confined to the decyl side chains.

ACUTE TOXICITY of DDAC: 

Table 2.  Acute Toxicity Profile for DDAC

Guideline Number	Study Type/ Test substance (% a.i.)	MRID Number/
Citation	Results	Toxicity Category

870.1100

(§81-1)	Acute oral, rat

(Purity 65%)	MRID 41394404	  SEQ CHAPTER \h \r 1 LD50 =262 mg/kg
(combined)

  SEQ CHAPTER \h \r 1 LD50 =331 mg/kg (males)

  SEQ CHAPTER \h \r 1 LD50 =238 mg/kg (females)	II

870.1100

(§81-1)	Acute oral, rat

(Purity 80%)	MRID 42296101	  SEQ CHAPTER \h \r 1 LD50 =238 mg/kg
(combined)	II

870.1200

(§81-2)	Acute dermal, rabbit

(Purity 65%)	MRID 42053801	  SEQ CHAPTER \h \r 1 LD50 =2930 mg/kg
(combined)

  SEQ CHAPTER \h \r 1 LD50 =3140 mg/kg (males)

  SEQ CHAPTER \h \r 1 LD50 =2730 mg/kg (females)	III

870.1300

(§81-3)	Acute inhalation, rat

 (Purity not reported)	MRID 00145074

TRID 455201010	  SEQ CHAPTER \h \r 1 LC50 (combined) = 0.07 mg/L	II

870.2400

(§81-4)	Primary eye irritation, rabbit

(Purity 65% a.i.)	MRID 41394404	  SEQ CHAPTER \h \r 1 Corrosive.	I

870.2400

(§81-4)	Primary eye irritation, rabbit

(Purity 80% a.i.)	MRID 42161602	  SEQ CHAPTER \h \r 1 Corrosive.	I

870.2500

(§81-5)	Primary dermal irritation, rabbit

(Purity 80%)	MRID 42161601	Corrosive.	I

870.2600

(§81-6)	Dermal sensitization, guinea pigs

(Purity 80%)	MRID 46367601	Not a sensitizer.	NA



SUMMARY OF TOXICOLOGY ENDPOINT SELECTION-DDAC

The doses and toxicological endpoints selected for DDAC are summarized
below. 

Exposure

Scenario	

Dose Used in Risk Assessment

(mg/kg/day)	

Target MOE/UF,

Special FQPA SF

for Risk Assessment	

Study and Toxicological Effects



Acute Dietary

(Females 13+)	

NOAEL(developmental) = 10 mg/kg/day

	

FQPA SF = 1

UF = 100 (10x inter-species extrapolation, 10x intra-species variation)	

Prenatal Developmental Toxicity - Rat

MRID 41886701

LOAEL = 20 mg/kg/day based on increased incidence of skeletal
variations.

	

Acute RfD = 0.1 mg/kg/day (Females age 13+)



Acute dietary

(general pop.)

	

an acute dietary endpoint for the general population was not identified
in the database for DDAC.



Chronic Dietary

(general population)

	

NOAEL = 10

mg/kg/day	

FQPA SF = 1

UF = 100 (10x inter-species extrapolation, 10x intra-species variation	

Chronic Toxicity Study - Dog

MRID 41970401

LOAEL = 20 mg/kg/day based on increased incidence of clinical signs in
male and females and decreased total cholesterol levels in females. 

	

Chronic RfD = 0.1 mg/kg/day

Dermal, Short-Term (technical a.i.)

 

NOAEL = 2 

UF = 100Based on increased dermal clinical and gross findings

Rat 90-day Dermal Study

MRID 413059-01



Non-Dietary Exposures



Incidental Oral

Short-Term	

NOAEL(developmental) = 10 mg/kg/day

	

Target MOE = 100 (10x inter-species extrapolation, 10x intra-species
variation)

FQPA SF = 1

	

Prenatal Developmental Toxicity - Rat

MRID 41886701

LOAEL = 20 mg/kg/day based on increased incidence of skeletal
variations.



Incidental Oral

Intermediate-Term	

NOAEL  = 10 mg/kg/day

	

Target MOE = 100 (10x inter-species extrapolation, 10x intra-species
variation)

FQPA SF = 1	

Chronic Toxicity Study - Dog

MRID 41970401

LOAEL = 20 mg/kg/day based on decreased total cholesterol levels in
females. 



Dermal, Short-term (formulated product, 0.13% a.i.)	

No endpoint identified.  No dermal or systemic effects identified in the
21-day dermal toxicity study (MRID 45656601) up to and including the
limit dose of 1000 mg/kg/day





Dermal, Short-term (TGAI 80% diluted to 0.1%)	

NOAEL(dermal) = 2 mg/kg/day

(8 µg/cm2)c	

Target MOE = 10 (3x inter-species extrapolation, 3x intra-species
variation)

	

90-day Dermal Toxicity - Rat

MRID 41305901

LOAEL = 6 mg/kg/day based on increased clinical and gross findings
(erythema, edema, exfoliation, excoriation, and ulceration) beginning on
day 4-5 of treatment.



Dermal, Intermediate- and Long-term (formulated product)	

No appropriate endpoint identified. 





Inhalation, Short-Term

	

NOAEL   = 10 mg/kg/daya

	

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਀ = 100 (10x inter-species extrapolation, 10x intra-species variation,
10x route-extrapolation) 

DB UF- an additional 10x is necessary for route extrapolation.  If risk
estimates are below an MOE of 1000, a confirmatory inhalation toxicity
study may be required.	

Prenatal Developmental Toxicity - Rat

MRID 41886701

LOAEL = 20 mg/kg/day based on increased incidence of skeletal
variations.



 Inhalation, Intermediate- and Long-Term

	

NOAEL  = 10

mg/kg/daya	

 Target MOE = 100 (10x inter-species extrapolation, 10x intra-species
variation, 10x route-extrapolation) 

DB UF- an additional 10x is necessary for route extrapolation.  If risk
estimates are below an MOE of 1000, a confirmatory inhalation toxicity
study may be required.	

Chronic Toxicity Study - Dog

MRID 41970401

LOAEL = 20 mg/kg/day based on decreased total cholesterol levels in
females. 



     UF = uncertainty factor, FQPA SF = FQPA safety factor, NOAEL = no
observed adverse effect level, LOAEL = lowest observed adverse effect
level, RfD = reference dose, MOE = margin of exposure, LOC = Level of
concern, NA = Not Applicable.

  SEQ CHAPTER \h \r 1 aAn additional uncertainty factor of 10x is
applied for use of an oral endpoint for route-to-route extrapolation to
determine if a confirmatory inhalation toxicity study is warranted.

 

c  TGAI-based dermal endpoint = (2 mg/kg rat x 0.2 kg rat x 1000 ug/mg)
/ 50cm2  area of rat dosed = 8 µg/cm2  .

         

 PAGE  20 

