	UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

Date: April 16, 2007

MEMORANDUM

SUBJECT:	Naphthenate Salts (zinc/copper)- Endpoint Selection Report.   

FROM:	Timothy F. McMahon, Ph.D 

		Senior Toxicologist

Antimicrobials  Division (7510C)

 

TO:		Kathryn Jakob, Chemical Review Manager 

		Mark Hartman, Branch Chief

		Regulatory Management Branch II

		Antimicrobials Division (7510C)

		

		         And

		Timothy F. McMahon, Ph.D., Risk Assessor

		Antimicrobials Division  (7510C)

 		PC Code:  024002

   Toxicity endpoints of concern were selected by the Antimicrobials
Division for naphthenate salts. Scientists from the Antimicrobials
Division as well as from the Registration Division, Health Effects
Division, and Biopesticides Division participated in the endpoint
selection.     Potential enhanced sensitivity of infants and children
from exposure to naphthenate salts was not assessed as there are no food
uses for these chemicals.    The conclusions of this meeting are
presented in this report.



  In Attendance

Stephen Dapson, Ph.D.; Jonathan Chen, Ph.D.; Steve Malish, Ph.D.; Jenny
Tao; Timothy F. McMahon, Ph.D.

 

 

 



		

INTRODUCTION

The naphthenate salts (copper and zinc naphthenate) are both salts of
naphthenic acid, which is essentially a mixture of cyclic carboxylic
acids, predominantly cyclopentane derivatives with an average molecular
weight of 200-300 (BIBRA, 1999).  The mixture may also contain some
cyclic hydrocarbons (BIBRA, 1999).  The naphthenate salts are considered
together for hazard characterization.  The presence of a zinc or copper
ion does not have a significant influence on the mammalian toxicity of
naphthenic acid. 

Both   SEQ CHAPTER \h \r 1 copper and zinc naphthenate are
microbiocide/microbiostat, miticide, fungicide, insecticide, algaecide
and herbicide/terrestrial chemicals. Use sites for copper naphthenate
include pressure treatment and non –pressure treatment of wood for
exterior uses (residential and non-residential), wood used in contact
with fresh or salt water, and exterior wood exposed to moisture or
weather. Copper naphthenate is also used in brush, dip, roller, and low
pressure spray applications for the same uses listed above, and in
addition is used for greenhouse and horticultural uses (non-food
applications including wooden seedling trays, plant and flower boxes for
ornamental plantings, trellises, arbors, greenhouse benches, and nursery
flats).  Application by occupational applicators only includes  brush,
dip, roller, and low pressure spray to beverage cases, baskets, tents,
awnings, tarpaulins, canvas products, nets [except fishnets], ropes,
cordage, lumber for ammunition boxes, other boxes, crates, and
miscellaneous non –food contact containers, truck and boat covers,
non-rubber fabrics, and burlap. Copper naphthenate is also used as a
remedial treatment for standing wood utility poles, mine timbers, bridge
timbers, and cross-ties and stakes.  

Zinc naphthenate use sites are the same as for copper naphthenate but do
not include remedial treatments  or to beverage cases, etc. as listed
for copper naphthenate. 

There is also one tolerance exemption for residues of copper naphthenate
when used in accordance with good agricultural practice as an inert
ingredient in pesticide formulations applied to growing crops only (40
CFR 180.920). No more than 2.5% copper naphthenate can be present, and
products containing copper naphthenate can only be applied before the
edible portions of plants begin to form.



HAZARD IDENTIFICATION

A. Acute Reference Dose (aRfD) 

The committee agreed that there were no use sites that involve direct or
indirect food use of naphthenate salts.  Therefore, an acute  reference
dose is not required. 

B. Chronic Reference Dose (cPAD)

The committee agreed that there were no use sites that involve direct or
indirect food use of naphthenate salts.  Therefore, a chronic reference
dose is not required. 

C. Incidental Oral Exposure (short-term [1-30 days] and
intermediate-term [30 days-6months])

Study Selected: Developmental toxicity study in rats   (OPPTS 870.3700)

MRID Number: 41615101	

Executive Summary:  In a developmental toxicity study (MRID 41615101), 
copper naphthenate (purity assumed to be 100%) in corn oil, was
administered by gastric intubation to 4 groups of 25 rats/dose by
gastric intubation at dose levels of 0, 30, 100, or 300 mg/kg/day,
respectively, from gestation days (GD) 6 to 15.  The animals were
checked daily from gestation day 6 for indications of toxicity.  Body
weights were recorded daily from gestation days 6 through 15 and on
gestation days 16 and 21.  Food and water consumption were measured at 3
day intervals beginning on gestation day 6.  Examinations at sacrifice
consisted of a determination of the number and position of live, dead,
and resorbed fetuses and staining of apparent nonpregnant uteri along
with liver weights.

Maternal toxicity was noted in the 100 and 300 mg/kg/day groups in the
form of decreases in body weight and food consumption.  Evaluation of
developmental toxicity revealed an increase in the mean number of early
resorptions only, however the mean litter size of the treated and
control groups was comparable.  Therefore, these increases were
considered to be of no biological significance.  The maternal NOAEL is
30 mg/kg/day and the maternal LOAEL is 100 mg/kg/day.  The
developmental; toxicity NOAEL was determined to be greater than or equal
to 300 mg/kg/day and the developmental toxicity LOAEL was greater than
300 mg/kg/day. 

Dose Selected for Risk Assessment:  Maternal NOAEL of 30 mg/kg/day  was
selected based on  decreases in body weight gain and food consumption
observed at 100 mg/kg/day. 

Uncertainty factors:  A 10x uncertainty factor is applied for
interspecies extrapolation, and a 10x uncertainty factor is applied for
intraspecies variation. These are standard uncertainty factors applied
by the Agency when citing results from animal studies for purposes of
human risk assessment. 



D.  Dermal Absorption						

Dermal Absorption Factor:   Dermal absorption data are not available for
naphthenate salts.  However, a route-specific study is available for
dermal risk assessments.    

 

D1. Short-term (1-30 days) Dermal  

Study Selected:   90 day dermal toxicity in rabbits  (OPPTS 870.3200)

MRID Number: 41615001

						               

Executive Summary:   In a 90-day dermal toxicity test (MRID 41615001)
designed to determine the subchronic toxicity effects of repeated dermal
exposure to zinc naphthenate (14.5% purity) in New Zealand white
rabbits,  rabbits were dermally exposed to 0, 100, 300, or 1000
mg/kg/day of zinc naphthenate 6 hours a day, 5 days a week for 13 weeks.
 Animals were observed twice daily for signs of mortality and
moribundity and daily for signs of toxicity.  

Systemic toxicity was observed in the form of significantly  reduced
body weight gain in the high dose group throughout the study.  In male
rabbits, body weight gain decrement was also seen in the mid dose group
throughout the study.  No treatment related clinical signs of systemic
toxicity were noted (hematology, clinical chemistry or histopathology). 
In terms of dermal effects there were apparent dose related increases in
macroscopic and microscopic lesions related to dermal irritation.

The systemic  toxicity NOAEL is (100 mg/kg/day, M/F).  The systemic
toxicity LOAEL is (300 mg/kg/day, M/F), based on reductions in body
weight gain.  The dermal toxicity NOAEL is less than (100 mg/kg/day). 
The dermal toxicity LOAEL is less than or equal to (100 mg/kg/day).

This study is classified as Core-Minimum - Guideline.

Dose and Endpoint selected for Risk Assessment:   LOAEL of 100 mg/kg/day
based on moderate to severe dermal irritation observed during the first
4 weeks of the study.  It should be noted that in this study, a
tolerance developed to the dermal irritating effects of zinc naphthenate
during the final weeks of the study.  Therefore, the use of dermal
irritation for the short-term dermal endpoint is supported.    

Uncertainty factors:  A 10x uncertainty factor is applied for
interspecies extrapolation, and a 10x uncertainty factor is applied for
intraspecies variation.  A 3x factor is applied additionally for the use
of a LOAEL value.  These are standard uncertainty factors applied by the
Agency when citing results from animal studies for purposes of human
risk assessment. 

 

 D2. Intermediate-term (30 days- 6months) Dermal  

Study Selected:   90 day dermal toxicity in rabbits  (OPPTS 870.3200)

MRID Number: 41615001

						               

Executive Summary:   In a 90-day dermal toxicity test (MRID 41615001)
designed to determine the subchronic toxicity effects of repeated dermal
exposure to zinc naphthenate (14.5% purity) in New Zealand white
rabbits,  rabbits were dermally exposed to 0, 100, 300, or 1000
mg/kg/day of zinc naphthenate 6 hours a day, 5 days a week for 13 weeks.
 Animals were observed twice daily for signs of mortality and
moribundity and daily for signs of toxicity.  

Systemic toxicity was observed in the form of significantly  reduced
body weight gain in the high dose group throughout the study.  In male
rabbits, body weight gain decrement was also seen in the mid dose group
throughout the study.  No treatment related clinical signs of systemic
toxicity were noted (hematology, clinical chemistry or histopathology). 
In terms of dermal effects there were apparent dose related increases in
macroscopic and microscopic lesions related to dermal irritation.

The systemic  toxicity NOAEL is (100 mg/kg/day, M/F).  The systemic
toxicity LOAEL is (300 mg/kg/day, M/F), based on reductions in body
weight gain.  The dermal toxicity NOAEL is less than (100 mg/kg/day). 
The dermal toxicity LOAEL is less than or equal to (100 mg/kg/day).

This study is classified as Core-Minimum - Guideline.

Dose and Endpoint selected for Risk Assessment:   NOAEL of 100 mg/kg/day
based on significant reductions in body weight gain at 300 mg/kg/day.  

    

Uncertainty factors:  A 10x uncertainty factor is applied for
interspecies extrapolation, and a 10x uncertainty factor is applied for
intraspecies variation.   These are standard uncertainty factors applied
by the Agency when citing results from animal studies for purposes of
human risk assessment. 

E. Inhalation Exposure

E1. Inhalation- All Durations 

Study selected:   Developmental toxicity study in rats 						

MRID Number: 41615101	

Executive Summary:    In a developmental toxicity study (MRID 41615101),
 copper naphthenate (purity assumed to be 100%) in corn oil, was
administered by gastric intubation to 4 groups of 25 rats/dose by
gastric intubation at dose levels of 0, 30, 100, or 300 mg/kg/day,
respectively, from gestation days (GD) 6 to 15.  The animals were
checked daily from gestation day 6 for indications of toxicity.  Body
weights were recorded daily from gestation days 6 through 15 and on
gestation days 16 and 21.  Food and water consumption were measured at 3
day intervals beginning on gestation day 6.  Examinations at sacrifice
consisted of a determination of the number and position of live, dead,
and resorbed fetuses and staining of apparent nonpregnant uteri along
with liver weights.

Maternal toxicity was noted in the 100 and 300 mg/kg/day groups in the
form of decreases in body weight and food consumption.  Evaluation of
developmental toxicity revealed an increase in the mean number of early
resorptions only, however the mean litter size of the treated and
control groups was comparable.  Therefore, these increases were
considered to be of no biological significance.  The maternal NOAEL is
30 mg/kg/day and the maternal LOAEL is 100 mg/kg/day.  The
developmental; toxicity NOAEL was determined to be greater than or equal
to 300 mg/kg/day and the developmental toxicity LOAEL was greater than
300 mg/kg/day. 

Dose Selected for Risk Assessment:  Maternal NOAEL of 30 mg/kg/day was
selected based on  decreases in body weight gain and food consumption
observed at 100 mg/kg/day. 

Comments about Study/Margins of Exposure:   There are no repeated dose
inhalation toxicity studies available for naphthenate salts.  An oral
endpoint with an additional 10x uncertainty factor for route
extrapolation is selected.   

Uncertainty factors:  A 10x uncertainty factor is applied for
interspecies extrapolation, and a 10x uncertainty factor is applied for
intraspecies variation. An additional 10x uncertainty factor is applied
for route extrapolation from an oral study.   

						

F. Margins of Exposure for Occupational/Residential Exposure Risk
Assessments

Route	

Short-term (1-30 days)	

Intermediate-term (30 days- 6 months)	

Long-term (> 6 months)



Oral	

100	

100	

N/A



Dermal	

300	

100	

N/A



Inhalation	

1000	

1000	

1000





G. Recommendation for Aggregate Risk Assessments

To be determined on the basis of the exposure chapter. 

CLASSIFICATION OF CARCINOGENIC POTENTIAL

Naphthenate salts have not been formally classified as to
carcinogenicity.  There are no carcinogenicity studies available for
naphthenate salts.  

MUTAGENICITY

 Mutagenicity studies have been submitted and reviewed by the Office of
Pesticide Programs for  naphthenate salts.  These studies are considered
unacceptable/upgradable.  If information on test material purity is
provided these studies may be upgraded to acceptable. Summaries are
provided here for information purposes. 

870.5300	In vitro mammalian cell gene mutation test

There were two gene mutation assays.  In the first study , MRID
41402502, copper naphthenate, at concentrations of 0, 4.2, 5.6, 7.5, 10,
13, 24, 32, 42 and 56 ug/ml without metabolic activation and at 0, 3.2,
4.2, 5.6, 7.5, 10, 13, 18, 24, 32 and 42 ug/ml with metabolic activation
(S-9 Mix) was evaluated for mutagenic potential using the L5178Y TK+/-
mouse lymphoma mutagenesis assay.  A repeat test confirmed the increase
of mutant frequencies with copper naphthenate in the presence of
metabolic activation (+S9).  In another mouse lymphoma assay (MRID
41400701), zinc naphthenate was tested with mouse lymphoma L5178Y TK +/-
cells without and with rat liver activation (male Sprague-Dawley,
Aroclor 1254 induced) in two trials with duplicate cultures per
concentration for 4 hours of exposure. The concentrations used were,
without activation: Trial 1:  (ethanol), 3.2, 4.2, 5.6, 7.5, 10, 13, 18,
24, 32, 42, 56 and 75 ug/ml; trial 2 ) (ethanol), 7.5, 11, 15, 19, 23,
27, 30, 33, 36, 40, 44 and 48 ug/ml.  With activation, the
concentrations were: Trial 1: (ethanol), 4.2, 5.6, 7.5, 10, 13, 18, 24,
32, 42, 56, 75 and 100 ug/ml; trial 2: 0 (ethanol), 23, 27, 30, 33, 36,
40, 44, 48, 52, 56, 65 and 75 ug/ml. Several of the higher
concentrations per trial were too toxic to process.  There was a
possible adverse effect due to the mutation frequency was increased in a
concentration-dependent response both without and with activation. 
There was also a greater increase in small colonies versus large
colonies with exposure to zinc naphthenate as opposed to copper
naphthenate exposure.  Although the Office of Pesticide Programs 
reported these two studies to be unacceptable, California Department of
Pesticide Regulation (CAL EPA) found the studies to be Acceptable.

870.5385	Mammalian bone marrow chromosomal aberration test

There were two chromosome aberration tests submitted to the Agency.  In
the first study (MRID 41402503), copper naphthenate , at concentrations
of 4, 8, 15, 30 and 60 ug/ml without metabolic activation at 2, 4, 8, 15
and 30 ug/ml with Aroclor-induced rat liver S-9 mix was tested in the
first trial in a chromosome aberration assay using Chinese hamster ovary
cells.  Concentrations in the repeat trial –S9 were 40, 80, 120 and
160 ug/ml and +S9 were 20, 30, 40, 50 or 60 ug/ml.  Total incubation was
16 hours –S9 and 12 hours (with a 2 hour exposure to treatment) +S9. 
The mitotic index decreased at 120 ug/ml with no mitotic cells and at
160 ug/ml without activation.  No effect on the mitotic index was seen
at any concentration with activation.  There were no significant
reproducible increases in CHO cells with aberrations for any of the
copper naphthenate doses.  In the other study (MRID 41400702),zinc
naphthenate was tested in two trials without metabolic activation at
concentrations   0, 5, 10, 20, 40 and 80 ug/ml (first trial) and  0, 80,
110, 140, 170 and 200 ug/ml (second trial). In the presence of metabolic
activation, two trials were also conducted, the first at   0, 10, 20,
40, 80 and 160 ug/ml and the second at 0, 60, 80, 100, 120 and 140
ug/ml.  Exposure without activation was 18 hours followed by an
additional 2 hours with colcemid.  With activation, exposure was 2 hours
followed by 18 hours, both for a total of 20 hours.  In the repeat trial
with results reported at 80, 110 and 140 ug/ml, positive results were
found at all three concentrations.  With activation, in the first trial,
positive results were found at 80 ug/ml  in the repeat +S9 trial,
positive results were reported at 60, 80 and 100 ug/ml..  In both repeat
trials, there was a concentration dependent increase.  There was a 
possible adverse effect of an  increase in chromosomal aberrations with
increasing concentrations of zinc naphthenate. Although the Agency
reported these two studies to be Unacceptable, the California Department
of Pesticide Regulation (CAL  EPA) found the studies to be Acceptable.

Unscheduled DNA synthesis in mammalian cells in culture

 Two Unscheduled DNA Synthesis  (UDS) studies were also reviewed by OPP.
 In the first study (MRID 41402504), copper naphthenate at
concentrations of 0, .15, 0.5, 1.5, 5.0 and 15 ug/ml was evaluated in
the unscheduled DNA synthesis test using rat primary hepatocytes and
autoradiography.  The mean number of net nuclear grains did not increase
significantly at any dose level over the solvent control.  It was
concluded, therefore, that copper napthenate was tested over an
appropriate range of concentrations and failed to induce a genotoxic
response.  In the other UDS study (MRID 41400703), primary rat
hepatocytes, isolated from male livers, were treated with zinc
naphthenate at concentrations of  0, .15, 0.5, 1.5, 5.0 , 15 or 35 ug/ml
for 18-20 hours in the presence of  10 uCi/ml 3H-thymidine.   At
concentrations of 35 ug/ml and higher, the zinc naphthenate apparently
interfered with the LDH assay as the release of LDH with 1% Triton was
less when zinc naphthenate was present.   There was no evidence for the
induction of UDS by zinc naphthenate to toxic doses.  Toxicity was also
evaluated microscopically by cellular morphology.  There was no adverse
effect under the conditions of the assay.  It was concluded, therefore,
that zinc naphthenate was tested over an appropriate range of
concentrations and failed to induce a genotoxic response.               
                                                 

FQPA CONSIDERATIONS		

There are no indirect or direct food uses for naphthenate salts.  Thus
an FQPA analysis is not necessary. 

DATA GAPS / REQUIREMENTS

 A repeated dose inhalation toxicity study with naphthenate saltes is
considered a data gap for adequate assessment of risk from inhalation
exposures arising from paint and wood preservative uses. 

Data on the test article characterization is needed to upgrade the
existing mutagenicity studies for the naphthenate salts.  VII. 	ACUTE
TOXICITY  

Acute Toxicity of  Naphthenate Salts

Table 3.  Acute Toxicity Profile for Copper/Zinc Naphthenate

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

Citation	Results	Toxicity Category

870.1100

(§81-1)	Acute Oral- Rat

purity 45.4% -copper naphthenate	00266172	LD50 > 501 mg/kg	III

870.1100

(§81-1)	Acute Oral- Rat

purity 58% -copper naphthenate	433342402	Not determined	N/A

870.1100

(§81-1)	Acute Oral- Rat

purity 60%- zinc naphthenate	00244277	LD50 > 2000 mg/kg	IV

870.1200

(§81-2)	Acute Dermal- Rabbit

purity not determined – copper naphthenate	41140710	LD50 > 2000 mg/kg
III

870.1200

(§81-2)	Acute Dermal- Rabbit

Purity 60%-zinc naphthenate	00244277	LD50 > 2000 mg/kg	III

870.1300

(§81-3)	Acute Inhalation- Rabbit

Purity technical- copper naphthenate	41486301	LC50 > 2.966 mg/L	III

870.1300

(§81-3)	Acute Inhalation- Rabbit

Purity 60%- zinc naphthenate	00244277	LC50 > 11.6 mg/L	IV

870.2400

(§81-4)	Primary Eye Irritation- Rabbit purity 80% -copper naphthenate
00260891	Redness cleared on day 4	III

870.2400

(§81-4)	Primary Eye Irritation- Guinea pig purity 60% -zinc naphthenate
00244277	Redness cleared on day 2	III

870.2500

(§81-5)	Primary Dermal Irritation- Rabbit

purity technical –copper naphthenate	41140710	Moderate Irritant	III

870.2500

(§81-5)	Primary Dermal Irritation- Rabbit

60% -zinc naphthenate	00244277	Moderate to severe Irritant	II

870.2600

(§81-6)	Dermal Sensitization - Guinea pig

purity 58 % - copper naphthenate	41140710	Not a sensitizer.	No

870.2600

(§81-6)	Dermal Sensitization - Guinea pig

purity 60 % - zinc naphthenate	00244277	Primary skin irritant/possible
sensitizing agent	No



VIII. 	  SEQ CHAPTER \h \r 1 SUMMARY OF TOXICOLOGY ENDPOINT SELECTION
FOR NAPHTHENATE SALTS

 TABLE 4: Naphthenate Salts (Copper/Zinc) Endpoints for use in Risk
Assessments

Exposure Scenario

	Dose Selected for Risk Assessment	Target MOE for Risk Assessments	Study
Selected and Toxicological Effects

Non-Dietary Risk Assessments

Incidental Oral

Short–Term 

(1 - 30 Days)

 	NOAEL = 30 mg/kg/day

 

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

	Developmental Toxicity – Rat (Copper Naphthenate) 

 MRID 41615101

Maternal NOAEL = 30 mg/kg/day, based on decreased body weight and food
consumption at 100 mg/kg/day

Incidental Oral

Intermediate-Term 

(1-6 months)

 	NOAEL = 30 mg/kg/day

 

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

	Developmental Toxicity – Rat (Copper Naphthenate) 

 MRID 41615101

Maternal NOAEL = 30 mg/kg/day, based on decreased body weight and food
consumption at 100 mg/kg/day

Short -Term Dermal 

(1 - 30 Days)	LOAEL=100 mg/kg/day	Target MOE=300 (10x inter-species
extrapolation, 10x intra-species variation, 3x for use of LOAEL)

	90-day dermal toxicity-rabbit MRID 41515001 (Zinc naphthenate)

LOAEL(dermal) = 100 mg/kg/day, based on erythema, edema, and
desquamation at 100 mg/kg/day

Intermediate -Term Dermal 

(30 Days- 6 months)	NOAEL = 100 mg/kg/day	Target MOE=100 (10x
inter-species extrapolation, 10x intra-species variation)

	90-day dermal toxicity-rabbit MRID 41515001 (Zinc naphthenate)

NOAEL = 100 mg/kg/day, based on reductions in body weight gain observed
at 300 mg/kg/day. 

Inhalationa

( all exposure durations)

	NOAEL= 100 mg/kg/day

MOE = 1000c	Target MOE = 1000 (10x inter-species extrapolation, 10x
intra-species variation, 10x route-extrapolation)	Developmental Toxicity
– Rat (Copper Naphthenate) MRID 41615101 

Maternal LOAEL = 30 mg/kg/day, based decreased body weight and food
consumption at 100 mg/kg/day.

Cancer	Not classified;  no cancer data available. 

 a an additional uncertainty factor of 10x is used for route
extrapolation from an oral endpoint.  

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