### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review)

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION 

### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460



## MEMORANDUM

DATE: February 20, 2013

SUBJECT : Toxicology Scoping Document for the Registration Review of 1,4

- Dimethylnap h thalene and 2,6

- Diisopropylnap h thalene.

Registration Review Case #: 6029

PC Code: 055802 and 05580 3

CAS #: 571

- 58

- 4 and 24157

- 81

- 1

Chemical Class: Biochemical s



## FROM: Angela L. Gonzales

, Biologist /s/

Biochemical Pesticides Branch Biopesticides & Poll ution Prevention Division (7511P )

TO: Colin Walsh, Regulatory Action Lead er Biochemical Pesticides Branch Biopesticides & Pollution Prevention Division (7511P)

ACTION REQUESTED

The following document contains a review of the mammalian toxicology data submitted as supplemental data

for the biopesticide 1,4

- dimethylnaphtha lene (1,4

- DMN) in support of the development of the Registration

Review Final Work Plan . The document also contains revised data table s for both 1,4

- DMN and 2,6

- DIP N which supersede the data tables in the preliminary work plan scoping document.

Executiv e Summary

In the previous sc oping document for 1,4

- DMN , a 90

- day oral toxicity study was identified that was submitted as supplemental data for which an Agency review could not be found

. The Agency has since conducted a review

of these data and det ermined that the data are acceptable; however, due to the toxic endpoints (kidney effects) identified in the study, the current risk assessment regarding the exemption from the requirement of a tolerance may need to be refined. R evised data tables for both 1,4

- DM N and 2,6

- DIPN have been included in this

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 2



## document which supersede the data tables in the preliminary work plan scoping document

.

I. Data Summary

A 90

- day oral toxicity study was conducted on 1,4

- DMN and submitted in MRID 46316806. The study was

conduc ted according to OCSPP Guideline 870.3100 , “90

- day Oral Toxicity in Rodents”

1,4

- dimethylnaphthalene was administered to groups of 10 female and 10 male Sprague

- Dawley rats in the diet at target doses of of 0, 50, 250 or 1,000 mg/kg/day (equivalent to 0, 500, 2,500 and 10,000 ppm, respectively) for 90 days

. Target doses were based on consumption of 25 g of food

- day by a 250 g rat. Twenty additional rats (10/sex) were included in the high

- dose and control group and were kept for 28 days after 90 days to det ermine the recovery potential from treatment

- induced effects

. The following evaluations were conducted: mortality,

food consumption and 1,4

- DMN intake, body weight

, functional observational battery and motor activity, clinical chemistry

, hematology, organ weight

, gross pathology and histopathology. No treatment

- related

mortal ity was observed

. Discolored inguinal fur was observed in 12/20 high

- dose males, 2/10 mid

- dose males and in one high

- dose female. Treatment

- related effects on food consumption were obs erved in a dose

- response manner throughout the study. A significant decrease in food consumption in the high dose group was observed, which resulted in reduced body weight gain compared to controls. A decrease in consumption was observed in

mid

- dose males for 7 weeks. Effects in the low

- dose group were minimal. No difference in food consumption was observed between the high

- dose and vehicle control groups during the recovery period. During the recovery period, high

- dose animal body weights remained signific antly lower than controls although total body weight gain was significantly higher in the high

- dose animals than in controls. Daily intakes of 1,4

- DMN ranged from

23

- 65, 119

- 315 and 367

- 1121 mg/kg/day for the target doses of 50, 250 and 1,000 mg/kg/day, re spectively. Daily food consumption remained steady while body weight increased (due to growth) which resulted in lower actual doses than targeted during the last few weeks, particularly in males. No significant differences in the

functional observational b attery or motor activity parameters were noted except for decreased forelimb strength in high

- dose males. This effect was most likely due to the decreased body weight in that group. Statistically significant differences between the treatment and control gr oups were observed with regard to clinical chemistry . Cholesterol levels were increased in the high

- and mid

- dose males. BUN levels were decreased in the high

- and mid

- dose females. Except for the differences in cholesterol and BUN levels, all other differ ences observed were considered unrelated to treatment because the values were considered within the normal range, were sporadic in nature and of low magnitude. Random differences in hematology were also noted which were

minor in nature and considered to be the result of biological variability rather than treatment

- related. Several statistically significant organ weight ratio differences were noted in the high

- dose group. In high

- and mid

- dose males, significantly increased kidney

- to

- body weight ratios were noted . I n high

- and mid

- dose females, the absolute liver, liver

- to

- body and liver to

- bra i n weight ratios were increased. No treatment

- related histopathological findings were noted in any of the organs (except for the kidneys ) that correlated with the

stati stically significant differences noted above. Gross necropsy findings were considered unrelated to treatment as they were sporadic, singular in occurrence and observed in all groups including controls

. Histopathology

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 3



## findings indicate that the kidney was t he target organ of 1,4

- DMN. An increase in incidence and severity of chronic progressive nephropathy (CPN) , a kidney anomaly that spontaneously occurs in aging rats , basophilic tubules and infiltration of mononuclear cells was observed in 5/10 high

- dose ma les and in 1/10 animals in each of the other groups including controls. After the recovery period, minimal CPN was observed in 6/10 high

- dose males and 1/10 control males. After the recovery period, CPN was noted in 3/10 high

- dose females. Effects

were mor e severe in males. Basophilic tubules were also noted in 6/10 mid

- dose males and 2/10 low

- dose and

control males ; these observations were considered to be treatment related. Infiltration of mononuclear cells was

observed in 3/10 mid

- dose males and 1/10 in each of the other groups. After the recovery period, there was no clear difference in the incidence of the changes between the high

- dose and control groups. All other histopathology findings were not considered to be related to treatment because they occur red sporadically, were low in severity and were observed in all groups including controls. Based on the findings in the study, the

lowest

- observed

- adverse

- effect

- level (LOAEL) is 250 mg/kg/day based on higher incidences of basophilic

tubules and mononuclea r cell infiltration in males. The no

- observed

- adverse

- effect

- level (NOAEL) is 50 mg/kg/day.

I I

. Toxicity Profile

1,4

- Dimethylnap h thalene

Sufficient data have been provided to fulfill the biochemical pesticide data requirements under 40 CFR

158.2050 for the current use patterns for 1,4

- DMN . The data available to the Agency are summarized in Table

1 below. The LD 50 

## value for the acute dermal toxicity data requirement has been revised subsequent to the review in the preliminary work plan.

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 4

Table 1 . Human Health Assessment Data Requirements for 1, 4

- DMN (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity Category/Description MRID

Acute oral toxicity (rat) (870.1100) LD 50 = 2,730 mg/kg for males and females I II 43082510

Acute dermal toxicity (rabbit ) (870.1200) LD 50 > 2,000 m g /kg for males and females I II 43082511

Acute inhalation toxicity (rat) (870.1300) LC 50 > 4.16 mg/L for males and females IV 43082512

Primary eye irritation (rabbit) (870.2400) Moderately irritating. Moderate ocular irritation was observed in all rabbits at 24 hours post

- treatment with clearance by day 21. II 43082513

Primary dermal irritation (rabbit) (870.2500) Slightly irritating. After treatment, very slight to slight erythema was observed in all males and femal es through 72 hours with persistence in females until day

7. Well

- defined to moderate edema was observed in all males and females within 24 hours post

- treatment. At 72 hours, slight edema was observed in one male and

one female. IV 1 43082514

Dermal sensit ization ( Buehler

- guinea pig) (870.2600) Not a sensitizer 43082515

Dermal sensitization (LLNA) (870.2600) Not a sensitizer 48590903

90

- Day oral toxicity (870.3100) LOAEL = 250 mg/kg/day based on kidney effects ( higher incidences of basophilic tubules a nd

mononuclear cell infiltration ) in male rats

. NOAEL = 50 mg/kg/day. 46316806

90

- Day dermal toxicity (870.3250) Waived. Prolonged dermal exposure is not expected based on the use pattern and appropriate PPE requirements and reentry restrictions on la bels of end

use products . Products are applied as aerosols in indoor potato storage facilities and applicators/handlers must vacate premises during treatment. Premises are ventilated prior to reentry. Applicators/handlers must wear long sleeved shirts,

lon g pants, socks, shoes, protective eyewear and

chemical

- resistant gloves. Should reentry occur after application and prior to ventilation, applicators must also wear coveralls, respirators and face

- sealing goggles (unless a full

- face respirator is used).

90

- Day inhalation toxicity (870.3465) Waived. Significant repeated inhalation exposure as a gas, vapor or aerosol is not expected based on the use pattern and appropriate PPE requirements and reentry

restrictions on labels of end

- use products . Products ar e applied as aerosols in indoor potato storage facilities and applicators/handlers must vacate premises during treatment. Premises are ventilated prior to reentry. Should reentry occur after application and prior to ventilation, applicators must wear respi rators to prevent inhalation exposure.

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 5

Table 1 . Human Health Assessment Data Requirements for 1, 4

- DMN (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity Category/Description MRID

Mutagenicity ( Bacterial reverse mutation test; 870.5100) Not mutagenic under the conditions of the study

. Mutagenicity was not observed with or without metabolic activation in any of the 5 strains of

Salmonella typhimurium tested. 43082516

Mutagenicity ( Unscheduled DNA synthesis in

mammalian cells; 870.555 0) ( In vitro ) Not genotoxic under the conditions of the study . No induction of nuclear grain counts in hepatocytes was observed at the tested concentration range of 0.25 μg/ml to 10 μg/ml. 43082517

( In vivo ) Not genotoxic under the conditions of the study . No induction of nuclear grain counts in hepatocytes was observed when rats were given a single dose of up to 1,000 mg/kg 1,4

- DMN. 48590901

Mutagenic ity ( In vivo m ammalian erythrocyte

micronucleus test; 870.5395 ) Not mutagenic under the conditions of the study . There was no increase in the number of micronuclei per 1,000 polychromatic erythrocytes in the bone marrow of mice at doses of 225 mg/kg, 450 mg/kg and 900 mg/kg 1,4

- DMN . A decrease in the polychromatic erythrocyte (PCE) and normochromatic erythrocyte (NCE) ratio was observed with increased doses of the

chemical. 43082518

Mutagenicity ( In vitro mammalian cell gene mutation test; 870.5300) Not mutagenic without metabolic activation in mouse lymphoma cells under the conditions of the study

. Dose

- dependent mutagenicity was observed however,

with metabolic activation. 2 46577001

Developmental toxicity (rabbits) (870.3700) Developmental toxicity w as not observed at the highest dose tested; therefore, the no

- observed

- adverse

- eff ect

level (NOAEL) was 250 mg/kg/ day. There were indications of maternal toxicity at 250 mg/kg

- day; reduced food consumption and reduced body weight gain were observed. The l owest

- observed

adverse

- eff ect

- level (LOAEL) was 250 mg/kg/day and the NOAEL was 80 mg/kg/ day for maternal toxicity. 48590904

Reproduction and fertility effects 3 (rats) (870.3800) Reproductive toxicity was not observed at the highest dose tested; there fore the NOAEL was 7,500 ppm.

There were indications of developmental toxicity at 7,500 ppm; delayed vaginal patency and preputial separation were observed, although these effects were considered secondary to body weight effects that were

attributed to a reduction in food consumption. The LOAEL was 7,500 ppm and the NOAEL was 2,000 ppm for developmental toxicity.

Based on a single histological change in the kidney observed in one rat at the 7,500 ppm dose, the LOAEL was 7,500 ppm and the NOAEL was 2,000 ppm for systemic toxicity. 48590905

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 6

Table 1 . Human Health Assessment Data Requirements for 1, 4

- DMN (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity Category/Description MRID

C arcinogenicity 3

(rats) (870.4300) Not carcinogenic under the conditions of the study . No carcinogenicity was observed when 1,4

- DMN was administered daily in the diet of rats for 52 or 104 weeks at doses of 0, 10, 33 and 250 mg/k g/ day. 48590906

Dermal absorption 3

(870.7600) The mean total percutaneous absorption of 1,4

- DMN when applied in vitro to human skin was 2.5% of the dose applied. 48590902

1 

### Originally classified as Toxicity Category III; however, the re sults of the study and the information provided under 40 CFR § 156.62 indicate that the chemical should be classified into Toxicity Category IV.

2 

### Although mutagenicity was observed with metabolic activation in this in vitro study, 1,4

- DMN is considered to not likely be mutagenic. This conclusion is based on the negative results observed in all of the four other mutagenicity studies, two of which were in

vivo studies.

3 This study was not required by the Agency but was submitted nonetheless.



## 2,6

- Diisopropy lnaphthalene

Sufficient data have been provided to fulfill the biochemical pesticide data requirements under 40 CFR 158.2050 for the current use patterns for 2,6

- DIPN . The data available to the Agency are summarized in Table

2 below. The LD 50 

## value for t he acute dermal toxicity data requirement has been revised subsequent to the review in the preliminary work plan.

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 7

Table 2 . Human Health Assessment Data Requirements for 2, 6

- DIPN (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity Category/Desc ription MRID

Acute oral toxicity (rat) (870.1100) LD 50 > 5,000 mg/kg for males and females I V 44641404

Acute dermal toxicity (rabbit ) (870.1200) LD 50 > 5 ,000 m g/kg for males and females IV 44614105

Acute inhalation toxicity (rat) (870.1300) LC 50 > 2.60 mg/L for males and females IV 4461410 6

Primary eye irritation (rabbit) (870.2400) Practically non

- irritating (24

- hour MMTS score of 0.7) 1

. No corneal opacity or iritis was noted during the study. One hour after test substance instillation, all

anim als exhibited conjunctivitis with clearance by 48

hours. III 1 44614107

Primary dermal irritation (rabbit) (870.2500) Slightly irritating. After treatment, very slight erythema

was observed in 4 animals, 2 of which exhibited very slight edema

. All animals were clear of irritation by 48

hours. IV 44614108

Dermal sensitization ( Buehler

- guinea pig) (870.2600) Not a sensitizer 44614109

90

- Day oral toxicity (870.3100) Rats were administered 2,6

- DIPN in the d iet at doses of 0, 53.9, 104 or 208 mg/kg/day in ma les a nd 0, 61.8,

121 or 245 mg/kg/day in females for 90 days. The

LOAEL was 208 mg/kg

- day for males and 245 mg/kg/day for females which was based on decreased body weight gains and food consumption, and adrenal and kidney effects. The NOAEL was 104 mg/kg/d ay for males and 121 mg/kg/day for females. 45049301

90

- Day dermal toxicity (870.3250) Waived. Prolonged dermal exposure is not expected based on the use pattern and appropriate PPE requirements and reentry restrictions on labels of end

use products. Pr oducts are applied as aerosols in indoor potato storage facilities and applicators/handlers must vacate premises during treatment. Premises are ventilated prior to reentry. Applicators/handlers must wear a respirator, long sleeved shirts, long pants, socks , shoes, and chemical

resistant gloves.

90

- Day inhalation toxicity (870.3465) Waived. Significant repeated inhalation exposure as a gas, vapor or aerosol is not expected based on the use pattern and appropriate PPE requirements and reentry

restrictions on labels of end

- use products. Products are applied as aerosols in indoor potato storage facilities and applicators/handlers must vacate premises during treatment. Premises are ventilated prior to reentry. Applicators/handlers must wear respirators to pre vent inhalation exposure.

Mutagenicity ( Bacterial reverse mutation test; 870.5100) Not mutagenic under the conditions of the study. Mutagenicity was not observed with or without metabolic activation in any of the 5 strains of Salmonella typhimurium t ested. 44614111

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 8

Table 2 . Human Health Assessment Data Requirements for 2, 6

- DIPN (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity Category/Desc ription MRID

Mutagenicity ( Unscheduled DNA synthesis in

mammalian cells; 870.555 0) Not genotoxic under the conditions of the study. No induction of nuclear grain counts in hepatocytes was observed when rats were given single doses of up to 2,000 mg /kg 2,6

- DIPN. 44614110

Mutagenicity ( In vivo mammalian erythrocyte

micronucleus test; 870.5395 ) Not mutagenic under the conditions of the study . There

was no increase in the number of micronuclei per approximately 2 ,000 polychromatic erythrocytes in the

bone marrow of mice at doses of 100, 200, 500, 800, 1,5 00 or 2,000 mg/kg 2,6

- DIPN . A decrease in the polychromatic erythrocyte (PCE) and normochromatic erythrocyte (NCE) ratio was observed at the highest

dose

. 44614112

Mutagenicity ( In vitro mammalian c ell gene mutation test; 870.5300) Under the conditions of the study, the test substance

was m utagenic without metabolic activation in mouse lymphoma cells. With metabolic activation, results were equivocal. 2 45438801

Developmental toxicity (rabbits) (87 0.3700) For developmental toxicity, the LOAEL was 500 mg/k g/ day based on reduced fetal body weights and a slightly increased incidence of skeletal malformations

. The NOAEL was 150 mg/kg/day. For maternal toxicity, the LOAEL was 150 mg/kg/day

based on reduc ed body weight gain and reduced food consumption

. The NOAEL is 50 mg/kg/day. 45000101

Metabolism Supplemental metabolism data were submitted from the open scientific literatures on 2,6

- DIPN in rats. In the first study, when rats were given a single dos e of 100 mg/kg of the chemical, residues were detectable in all tissues 2 hours after dosing . With the exception of body and subcutaneous fat, no residues were detected

after 48 hours. Similar results were observed in rats given daily doses of 100 mg/kg of the chemical for 30 days. The estimated half

- life of 2,6

- DIPN in fat was approximately 7 days. The second study suggested that the chemical is metabolized in rats primarily by way of an oxidative pathway involving the isopropyl groups. 45163201

1 

### In the study, t he severity of irritation score at 24

- hours (Maximum Mean Total Score [MMTS]) after dosing was calculated to be 0.7. Based on the interpretation of the score using this method, the test substance was classified as practically non

- irritating. The E PA, which uses a different method to classify a substance into a Toxicity Category, has classified the test substance into Toxici ty Category III because the minimal effects observed in the study did not clear in less than 24 hours.

2 

### Although mutagenicity w as observed in this in vitro study, 2,6

- DIPN is considered not likely to be mutagenic. This conclusion is based on the negative results observed in all of the three other mutagenicity studies, two of which were in vivo studies.



## cc: A. L. Gonzales

, C. W alsh , BPPD Science Review Fil e , IHAD/ARS

A. L. Gonzales

, FT, PY

- S: 02 /20 /13

### 1,4

- DMN and 2,6

- DIPN PC Code: 055802 and 055803 Type of Review: Toxicology (Registration Review) 9