Oiethofencarb Human Health Risk Assessment 

UNITED ST A TES ENVIRONMENT AL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

0418227 

OFFICE OF 

CllEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: 27-AUG-2015 

SUBJECT: Diethofencarb. I Iuman Health Risk Assessment for the Proposed Tolerances 

without a U.S. Registration for Residues of Diethofencarb inion Bananas. 

PC Code: 112102 

Decision No.: 486694 

Petition No.: 4E8232 

DP Barcode: 0418227 

Registration No.: NA 

Regulatory Action: Tolerances Without U.S. 

Registration 

Risk Assessment Type: Single Chemical/Aggregate 

TXR No.: NA 

Case No.: NA 

CAS No.: 87130-20-9 

MRIO No.: NA 40 CFR: § 180.TBD 

FROM: Cass

Risk 

i 

Assessment 

L. Walls, Ph

Branch 

.D., Senior 

I (RAB 

Biologist 

l) 

~ 

-....Jt2-"'-

2. 

~ 

~ 

Myron Ottley, Toxicologist /'hr)d} f /...,- ~ 

William Wassell, Chemist 

Risk Assessment Branch 3 (RAB3) 

Health Effects Division (HED; 7509P) 

THROUGH: Christine Olinger, Branch Chief/} ;f /.JC------

RAB3, HED (7509P) if G r 

Charles AND Smith, Designated Reviewer ~ ~~ 

Donald Wilbur, Designated Reviewer ~(..,.£, 

Risk Assessment Review Committee (RARC/HED) 

TO: Rachel Holloman/Driss Benmhend 

Fungicide-Herbicide Branch 

Registration Division (RD) (7505P) 

The Health Effects Division (HED) of the Office of Pesticide Programs (OPP) is charged with 

estimating the risk to human health from exposure to pesticides. RD of OPP has requested that 

HED evaluate hazard and exposure data and conduct a dietary exposure assessment as needed, to 

estimate the risk to human health that will result from the proposed use of the new active 

ingredient, diethofencarb, 1-methylethyl N-(3,4-diethoxyphenyl)carbamate. 

A summary of the findings and an assessment of human risk resulting from the proposed uses are 

provided in this document. The risk assessment and dietary risk assessment were provided by 

Cassi Walls (RAB I), the hazard characterization was provided by Myron Ottley (RAB3) and the 

residue chemistry review was provided by William Wassell (RAB I). 

Page I of 49 
Diethofencarb Human Health Risk Assessment 0418227 

Table of Contents 

1.0 Executive Sumn1ary ................................. ............ ............ ................................... ............... 3 

2.0 HED Recommendations .................................................................................................... 4 

2.1 Data Deficiencies ....................................................................................................... ..... 4 

2.2 Tolerance Considerations ............................... ............ ....... .... ........... ........................ ..... 4 

2.2.1 Enforcement Analytical Method .... .... ....................................................................... 4 

2.2.2 Recommended Toler ances .............................................. ........................................... 4 

2.2.3 Revisions to Petitioned-For Tolerances .................................................................... 5 

2.2.4 International Harmonization .................................................................. ... ................ 5 

3.0 Introduction .................................................... .......................................... .. ........................ 5 

3.1 Chemical Identity .............. .................... ........ ......... .............. .... .... .................................. 5 

3.2 Physical/Chemical Properties ........................................................................................ 5 

3.3 Use Pattern ... ........................................................................ .............. ............................. 5 

3.4 Anticipated Exposure Pathways .................................................................... ............... 6 

4.0 Hazard Characterization and Dose-Response Assessment ...................... ...................... 6 

4.1 Toxicology Studies Available for Analysis ............................................. ...................... 6 

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME) ............................... 6 

4.3 Toxicological Effects ............................................................................................ ...... .... 7 

4.4 Safety Factor for Infants and Children (FQPA Safety Factor) ............. .................... 7 

4.4.1 Completeness of the Toxicology Database .... ........................................................ 8 

4.4.2 Evidence of Neurotoxicity ...................................................................................... 8 

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal ...... 8 

4.4.4 Residual Uncertainty in the Exposure Database .................................................. 8 

4.5 Toxicity Endpoint and Point of Departure Selections .................... ............................ 8 

4.5.1 Dose-Response Assessment .. ........ .... ...................................................................... 8 

4.5.2 Cancer Classification and Risk Assessment Recommendation .......................... 9 

4.5.3 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk 

Assessn1ent ....................................................................................................... ....... ............... 9 

5.0 Dietary Exposure and Risk Assessment.. ............................................ ........................... 10 

5.1 Metabolite/Degradate Residue Profile ............................................ ........................... 10 

5.1.1 Summary of Plant and Animal Metabolism Studies ......................................... 10 

5.1.2 Summary of Environmental Degradation .......................................................... 10 

5.1.3 Comparison of Metabolic Pathways .................................................................... 10 

5.1.4 Residues of Concern Summary and Rationale ................................................... 11 

5.2 Food Residue Profile .................................................................................................... 11 

5.3 Drinking Water Residue Profile ................................................................................. 12 

5.4 Dietary (Food Only) Risk Assessment ........................................................................ 12 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ............................. 12 

7.0 Aggregate Exposure/Risk Characterization ................................................................. . 12 

8.0 Cumulative Exposure!Risk Characterization ............................................................... 13 

9.0 Occupational Exposure/Risk Characterization ............................................................ 13 

Appendix A. Toxicology Profile and Executive Summaries .................................................. 14 

A.1 Toxicology Data Requirements ................. .... ............... .... ........................................... 14 

A.2 Toxicity Profiles .......................................................... ....... ........... ................................ 15 

Appendix B. Metabolism Considerations ................................................................................ 46 

B.1 . Metabolism Summary Table ..................................................................................... .. 46 

B.2. Metabolic Path\vays .................................................................................. .. ........ ................ 48 

Page 2 of 49 
Diethofencarb Human Health Risk Assessment D418227

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1.0 Executive Summary

The new active ingredient (ai) diethofencarb (1-methylethyl N-(3,4-diethoxyphenyl)carbamate) 

is an N-phenyl, O-alkylcarbamate fungicide. It is a broad spectrum foliar fungicide for use on a 

variety of fruits and vegetables. Diethofencarb is currently registered in the European Union and 

Japan. The registrant (Bryant Christie Inc. on behalf of Sumitomo Chemical Co.) submitted a 

petition for establishment of a tolerance for residues of diethofencarb in/on bananas. There are 

no proposed or established domestic uses. The proposed tolerance is expressed in terms of the 

parent only.

Exposure Profile: Based on the proposed uses of diethofencarb, dietary exposure (food only) is 

the only anticipated exposure pathway. As there are no domestic agricultural or residential uses 

registered or proposed for diethofencarb, there is no potential for drinking water, residential, or 

occupational exposure.

Hazard Assessment: The risk assessment for diethofencarb is based on a well-characterized and 

complete toxicology database. In repeated dose animal studies, the liver was a target organ in 

the rat, mouse and dog. The most common effects were increased liver weights, hypertrophy and 

increase cholesterol levels which were not considered adverse. However, increased liver 

pigmentation observed histologically in the dog, and foci of necrosis and hepatocellular 

hyperplasia in the mouse, were considered adverse and evidence of toxicity. Other target organs 

identified were the kidney (proteinaceous cast and regenerative epithelium), urinary bladder 

(submucosal lymphoid hyperplasia) and thyroid (follicular cell adenomas and carcinomas) in the 

mouse, and the nervous system (changes in functional observational battery parameters, 

decreased motor activity and decreased pupillary reflex) in the rat. Decreased body weight and 

food consumption and increased salivation were observed in the dog, and increased abortions 

were observed in the rabbit. Decreased body weight was also seen in F2 pups during lactation in 

the rat in the absence of parental toxicity, raising a concern for increased susceptibility in 

offspring. However, appropriate endpoints and points of departure were used to address the 

susceptibility issue and there are no residual pre- and/or post-natal uncertainties, so the Food 

Quality Protection Act (FQPA) Safety factor has been reduced to 1X. The level of concern 

(LOC) for all durations and routes of exposure is 100. Mutagenicity tests were negative and data 

were submitted suggesting a non-genotoxic mode of action for the thyroid tumors observed in 

male rats. Diethofencarb is classified as “suggestive evidence of carcinogenicity” with no 

quantification required. There was no evidence of immunotoxcity in the immunotoxcity study or 

any other studies in the database. 

Dietary Risk Estimates (Food Only): A chronic dietary (food only) exposure and risk 

assessment was conducted for the general U.S. population and various population subgroups 

using the Dietary Exposure Evaluation Model software with the Food Commodity Intake 

Database (DEEM-FCID) Version 3.16. This software uses 2003-2008 food consumption data 

from the U.S. Department of Agriculture’s (USDA’s) National Health and Nutrition 

Examination Survey, What We Eat in America, (NHANES/WWEIA). The unrefined chronic 

assessment assumed that diethofencarb residues are present in all commodities at tolerance levels 

and that 100% of all crops are treated. DEEM Version 7.81 default processing factors were used 

to estimate residues in processed commodities. Drinking water estimates were not incorporated 

into the chronic dietary assessment, as there are no domestic uses proposed or established. Using 

the DEEM-FCID software, dietary risk is estimated at <1% of the cPAD for the general U.S. 

population and children 1 to 2 years old, the population subgroup with the highest estimated 
Diethofencarb Human Health Risk Assessment D418227

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chronic dietary exposure to diethofencarb. The chronic dietary risk assessment shows that for all 

included commodities, the chronic dietary risk estimates are below HED’s level of concern (i.e., 

<100% cPAD). An endpoint of concern attributable to a single dose was not identified; 

therefore, an acute dietary assessment was not performed. 

Aggregate Exposure Assessment: Because this action is for a tolerance without U.S. 

registration and there are no proposed or existing uses of diethofencarb that would result in 

drinking water or residential exposures, the chronic dietary (food only) exposure estimates 

represent the aggregate exposure assessment.

2.0 HED Recommendations

There are no data gaps that would preclude establishing the recommended tolerances for residues 

of diethofencarb in/on the requested crop. The specific tolerance recommendation is discussed 

in Section 2.2.2.

2.1 Data Deficiencies

There are no data deficiencies at this time; however, a revised Section F is required to amend the 

proposed tolerance level. HED notes that additional plant metabolism, livestock metabolism, 

confined rotational crop, and livestock feeding studies may be necessary to support any future use 

proposed for the U.S.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

A high-performance liquid chromatography method with tandem mass spectrometry detection 

(HPLC/MS/MS), PTRL West Method No. 2348W is proposed for the determination of residues 

of diethofencarb in banana pulp and banana peel. The method is adequate for the determination 

of diethofencarb in banana peel and pulp with a validated LOQ of 0.01 ppm. The method was 

adequately validated using samples of banana peel and banana pulp fortified with diethofencarb 

at 0.01 ppm and 0.10 ppm. An adequate independent laboratory validation (ILV) was conducted.

QuEChERS-method DIN 15662:2009-02 and DFG-S19 have been successfully tested with 

diethofencarb. HED concludes adequate enforcement methodology are available to enforce the 

proposed tolerance. 

2.2.2 Recommended Tolerances

HED has reviewed the available residue data and has determined the appropriate tolerance levels 

for residues of diethofencarb (Table 2.2.2.1). The recommended tolerance expression is as 

follows:

(a) General. (1) Tolerances are established for residues of the fungicide diethofencarb, 

including its metabolites and degradates, in or on the commodities in the table below. 

Compliance with the tolerance levels specified below is to be determined by measuring 

only (1-methylethyl N-(3,4-diethoxyphenyl)carbamate).
Diethofencarb Human Health Risk Assessment D418227

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Table 2.2.2.1. Tolerance Summary for Diethofencarb.

Commodity Proposed Tolerance 

(ppm)

HED-Recommended 

Tolerance (ppm)

Comments 

(correct commodity definition)

Banana1 0.09 0.10

1

 No U.S. registration as of [publication date of the tolerances].

2.2.3 Revisions to Petitioned-For Tolerances

As per the Organization for Economic Co-operation and Development Maximum Residue Limit 

(OECD MRL) methodologies, the submitted residue data support a tolerance level slightly 

higher than what was proposed. A revised Section F is required.

2.2.4 International Harmonization

There are no Codex, Canadian, and Mexican MRLs established for diethofencarb in/on bananas. 

There are no harmonization issues. 

3.0 Introduction

3.1 Chemical Identity

The chemical structure and nomenclature of diethofencarb is presented in Table 3.1.1. 

Table 3.1.1. Diethofencarb Nomenclature.

Compound: ai Chemical Structure

Common name Diethofencarb

Company experimental name None

IUPAC name isopropyl 3,4-diethoxycarbanilate

CAS name 1-methylethyl N-(3,4-diethoxyphenyl)carbamate

CAS # 87130-20-9

End-use product/EP Powmyl 25 SC (250 g/kg diethofencarb, suspension concentrate). Not registered 

in the US.

3.2 Physical/Chemical Properties

Technical-grade diethofencarb is a solid at room temperature and all environmentally relevant 

temperatures. The compound is not volatile (i.e., vapor pressure is 9.44 x 10-6 Pa at 20° C). The 

technical-grade material has a log KOW of 2.89, indicating that the compound is fat-soluble. 

Appendix C presents the physical/chemical parameters for diethofencarb.

3.3 Use Pattern

The petitioner provided copies and English translations of the proposed POWMYL® 25 SC label. 

POWMYL® is a SC formulation containing 25% diethofencarb for ground or aerial applications 
Diethofencarb Human Health Risk Assessment D418227

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to bananas. The proposed use directions, as identified by the petitioner, are detailed in Table 

3.3.1.

Table 3.3.1 Summary of Directions for Use of Diethofencarb on Bananas1.

Applic. 

Timing, 

Type, and 

Equip.

Formulation Applic. 

Rate 

Max. No. 

Applic. 

per Season

Max. Seasonal 

Applic. Rate PHI

(days)

Use Directions and 

Limitations

Banana

Foliar 250 g/kg SC

0.15 -0.20

kg ai/ha;

(0.13-0.18

lb ai/A)

6

1.2 kg ai/ha

(1.1 lb ai/A) 0

Application interval 

is 5 – 8 days.

1No domestic registrations (uses) are requested. The proposed label is for Guatemala, Belize, El Salvador, Honduras, 

Nicaragua, Costa Rice, Panama, and Dominican Republic and does not contain use information. The information 

entered is taken from the European Import Tolerance Request Tier II, Document M (MRID #49267481), prepared 

by the applicant.

3.4 Anticipated Exposure Pathways

Based on the proposed diethofencarb application scenarios, dietary exposure (food only) is the 

only anticipated exposure pathway. As there are no domestic agricultural or residential uses 

registered or proposed for diethofencarb, there is no potential for drinking water, residential, or 

occupational exposure.

4.0 Hazard Characterization and Dose-Response Assessment

Diethofencarb, a FRAC 10 N-phenyl carbamate, is a new active ingredient (a.i.) fungicide with 

broad spectrum activity in fruits and vegetables. It is a systemic fungicide with protective and 

curative action. It is readily absorbed though the leaves and roots and translocated throughout the 

plant. It inhibits mitosis in grey mold germ tubes, and has secondary activity against powdery 

mildews. This mode of action has not been established in mammals.

4.1 Toxicology Studies Available for Analysis

All of the required toxicity studies have been submitted to support the proposed food-use 

tolerance for diethofencarb and the potential exposure scenarios associated with this action. The 

available toxicology database is sufficient to characterize the hazard of diethofencarb for 

tolerance in the absence of a U.S. registration. Available repeated dose studies include oral 

subchronic and chronic studies in rats, mice and dogs, oral carcinogenicity studies in the rats and 

mice, oral pre-natal developmental studies in rats and rabbits, a multi-generation reproduction 

study in rats, a mutagenicity battery, a neurotoxicity battery in rats, an immunotoxicity study in 

mice, and a dermal subchronic study in rats.

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME)

Data from the ADME tests indicate that there is quick and extensive absorption of diethofencarb, 

limited distribution in tissues, extensive metabolism into sulfate and glucuronide metabolites, 

and quick and extensive excretion with no bioaccumulation. In a standard series of ADME tests 

with single and multiple gavage dosing at various dose levels, metabolism of diethofencarb in 

rats was found to be independent of sex, dose level and pre-treatment. Oral absorption is quick 
Diethofencarb Human Health Risk Assessment D418227

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and extensive (> 87% of administered dose or AD by day 2). Organ/tissue radioactivity 

decreased rapidly and was mainly found in liver, adrenals, blood/blood cells, kidney and skin. 

Tmax was 0.5 to 1.0 hr in blood and tissue. A plasma T1/2 value was not included in the report. 

Diethofencarb was extensively biotransformed into several metabolites, mainly sulfate and 

glucuronide conjugates. Excretion was extensive and quick (> 93% of AD by day 2) and 

occurred in urine (> 61% of AD), expired air (> 21% of AD) and feces (> 13% of AD). This 

resulted in organ/tissue depuration t1/2 values of <35 hours based on data up to 72 hr post-dose 

and a low retained fraction (<2% of AD on day 7), and the deduction that there is no significant 

entero-hepatic recirculation. The quick and extensive excretion, as well as the rapid organ/tissue 

decrease in radioactivity suggested there is no bioaccumulation.

4.3 Toxicological Effects

In repeated dose animal studies, the liver was a target organ in the rat, mouse and dog. The most 

common effects were increased cholesterol levels, increased liver weights, and hypertrophy; foci 

of necrosis and hepatocellular hyperplasia were observed in the mouse. Other target organs 

identified in the database were the kidney (proteinaceous cast and regenerative epithelium), 

urinary bladder (submucosal lymphoid hyperplasia) and thyroid (follicular cell adenomas and 

carcinomas) in the mouse. Decreased body weight and food consumption and increased 

salivation and vomiting were observed in the dog. 

In developmental toxicity studies, no adverse effects were seen in rat dams or fetuses up to the 

limit dose. In rabbits, an increase in late-term abortions occurred only at dose levels approaching 

the limit dose. In the multi-generation reproduction study in rats, no parental or reproductive 

effects were observed at any dose level tested; however, decreased body weight was seen in pups

of the F2 generation during lactation in the absence of parental toxicity, suggesting increased 

quantitative susceptibility in offspring. 

There was no evidence of immunotoxicity in the database, including the immunotoxicity study. 

Mutagenicity tests were negative, but as mentioned above, thyroid follicular cell tumors were 

seen in the rat and HED has determined a cancer classification for diethofencarb as “suggestive 

evidence of carcinogencity to humans” with no quantification required based on evidence of 

adenomas and carcinomas in one species (rat). There was no evidence of tumors in the mouse.

In acute studies, diethofencarb is categorized as Toxicity Category IV following oral and dermal 

exposure, and Toxicity Category III following inhalation exposure; it caused slight irritation to 

the eye (Toxicity Category III), no irritation to the skin (Toxicity Category IV) and is not a 

dermal sensitizer.

4.4 Safety Factor for Infants and Children (FQPA Safety Factor)

Based on the currently available toxicity and exposure data, the risk assessment team 

recommends that the FQPA Safety Factor be reduced to 1X. The toxicity database for 

diethofencarb is considered adequate for risk assessment for the following reasons: 1) the dietary 

exposure assessment is based on reliable data and will not underestimate exposure; 2) there is 

evidence of reproductive susceptibility as shown in the multi-generation reproduction study, but 

the effect is well-characterized; and 3) there is a clear No Observed Adverse Effects Level 

(NOAEL) for this effect and there are no residual pre- or post-natal uncertainties. 
Diethofencarb Human Health Risk Assessment D418227

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4.4.1 Completeness of the Toxicology Database

The diethofencarb toxicology database for FQPA assessment is considered adequate for purposes 

of setting a tolerance in the absence of a U.S. registration. It includes developmental toxicity 

studies in rats and rabbits, a multi-generation reproduction study, an acute and subchronic 

neurotoxicity battery, and an immunotoxicity study. 

4.4.2 Evidence of Neurotoxicity

The available database did not show diethofencarb to be neurotoxic. In the available acute 

neurotoxicity study (MRID 49267464), transient changes (observed on day 0 only) in decreased 

forelimb grip strength, reduced body temperature, increased landing foot-splay, decreased 

muscle tone and pupillary reflex, and reductions in motor activity were observed at the LOAEL 

of 2000 mg/kg in males and/or females. The NOAEL was 600 mg/kg. In the subchronic 

neurotoxicity study (MRID 49267463), decreased pupillary reflex seen in males at 571 

mg/kg/day was not considered biologically relevant because the degree of decrease was rated as 

“slight” in all affected animals, with no other changes in neurobehavioral or neuropathological 

parameters noted. No adverse effects were seen in females in this study. Therefore, the 

NOAELs for the study were 571 and 654 mg/kg bw/day, in males and females, respectively, the 

highest dose level tested.

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal

In the rat developmental study (MRID 49267450), there were no indications of toxicity in the 

dams or fetuses up to the limit dose. An acceptable (non-guideline) rabbit developmental 

toxicity study showed late-term abortions (considered evidence of both maternal and fetal 

toxicity) at dose levels near the limit dose (800 mg/kg/day and above). In the rat reproduction 

study, offspring effects (decreased pup body weight in F2 males and females) were noted below 

the parental NOAEL, indicating increased quantitative susceptibility in offspring. However, 

clear NOAELs and LOAELs are available for all parental and offspring effects and endpoints 

and PODs are based on the effects in the offspring. 

4.4.4 Residual Uncertainty in the Exposure Database

There are no residual uncertainties in the exposure database. The exposure databases are sufficient 

to determine the nature/magnitude of the residue in food and dietary analyses are unlikely to 

underestimate risk of exposure from diethofencarb. In addition, there are no currently proposed 

residential uses.

4.5 Toxicity Endpoint and Point of Departure Selections

The toxicity endpoints and PODs are summarized in Table 4.5.3.

4.5.1 Dose-Response Assessment

For acute dietary exposure (all populations including Females 13+), an endpoint attributable to a 

single dose has not been identified in the database; therefore, there is no risk assessment for 

acute dietary exposure. The acute neurotoxicity study produced effects only at the limit dose of 
Diethofencarb Human Health Risk Assessment D418227

Page 9 of 49

2000 mg/kg which is not relevant for risk assessment purposes, and the developmental and other 

available studies produced no effects that could be attributed to a single dose.

The chronic dietary endpoint was chosen from the chronic dog study (MRID 49267452). The 

NOAEL was 50 mg/kg/day and the LOAEL was 250 mg/kg/day in males and females, based on 

decreased body weights and increased emesis. This endpoint is considered to be robust and 

appropriate for the duration and route of exposure. It is considered protective of effects seen in 

the database following chronic oral exposures in mice, rats, and dogs. Although the 2-generation 

reproduction study had a higher NOAEL and a similar LOAEL to the chronic dog study, it was 

not selected because the effects in the reproduction study were seen only the F2 pups and it is 

uncertain what duration of exposure is needed to elicit the pup effects, whereas, the duration to 

cause adverse effects in the chronic dog study is clear.

Application of a 100-fold uncertainty factor has been determined to be appropriate (10X interspecies extrapolation and 10X intra-species variation). The FQPA SF is 1X, the cRfD is 

equivalent to the cPAD.

cRfD = cPAD = (50 mg/kg/day) = 0.50 mg/kg/day

100

Additional oral endpoints, as well as dermal and inhalation endpoints, were not evaluated or 

selected because they are not required for this import tolerance registration action.

4.5.2 Cancer Classification and Risk Assessment Recommendation

Diethofencarb did not produce a significant increase in tumors in a 78-week mouse oncogenicity 

study at dosages up to 2108 mg/kg/day, twice the limit dose. In rats, thyroid follicular cell 

tumors (adenomas in females and carcinomas in males) were observed at 220.3 /288.19

mg/kg/day, respectively. Special studies are available which suggest that the mode of action for 

these thyroid tumors is not quantitatively relevant to humans and there is no risk to humans, but 

the CARC examined these data and found they were inadequate to establish a mode of action. 

Consequently the CARC has assigned the classification “suggestive evidence of carcinogenicity 

to humans” based on the rat thyroid tumors, but quantification is not required. In both the mouse 

and rat studies, dosing was considered adequate to assess carcinogenic potential.

4.5.3 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk 

Assessment

Table 4.5.3 Summary of Toxicological Doses and Endpoints for Diethofencarb for Use in NonOccupational/Residential Human Health Risk Assessmentsa

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, Level of 

Concern for Risk 

Assessment

Study and Toxicological 

Effects

Acute 

Dietary (All 

Populations 

including 

Females 13+)

An endpoint attributable to a single dose was not identified in the database.
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Table 4.5.3 Summary of Toxicological Doses and Endpoints for Diethofencarb for Use in NonOccupational/Residential Human Health Risk Assessmentsa

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, Level of 

Concern for Risk 

Assessment

Study and Toxicological 

Effects

Chronic 

Dietary (All 

Populations)

NOAEL = 50

mg/kg/day

UFA = 10X

UFH = 10X

FQPA SF = 1X

Chronic RfD = 0.50

mg/kg/day

cPAD = 0.50 mg/kg/day

Chronic Toxicity, Dog.

LOAEL = 250 mg/kg/day 

based on decreased body 

weights and emesis.

Cancer (oral, 

dermal, 

inhalation)

Classification: “suggestive evidence of carcinogenicity to humans” based on the rat thyroid 

follicular cell tumors; quantification is not required.

a Point of Departure (POD) = A data point or an estimated point that is derived from observed dose-response data and used to 

mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures. 

NOAEL = no observed adverse effect level. LOAEL = lowest observed adverse effect level. UF = uncertainty factor. UFA = 

extrapolation from animal to human (interspecies). UFH = potential variation in sensitivity among members of the human 

population (intraspecies). FQPA SF = FQPA Safety Factor. RfD = Reference Dose. cPAD = chronic Population Adjusted 

Dose.

5.0 Dietary Exposure and Risk Assessment 

D421677, W. Wassell, xx-AUG-2015 (residue chemistry chapter for the current action)

D428591, C. Walls, 18-AUG-2015 (dietary exposure analysis for the current action)

D428492, E. Holman, xx-AUG-2015 (ROCKS memo for the current action)

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Animal Metabolism Studies

The metabolism of radiolabeled diethofencarb was studied in grapes, tomatoes, and lettuce. 

Studies were performed with [14C-phenyl]- and [14C-isopropyl]-diethofencarb. No study was 

conducted with banana. The results showed that only parent was found as a surface residue. In 

the three plant metabolism studies, diethofencarb is a major portion of the residue (>20%), 

however, the parent concentration decreases with increasing pre-harvest interval (PHI). 

Residues in plants undergo hydroxylation and conjugation while maintaining the diethofencarb 

backbone. 

Livestock metabolism data is not required as there are no feed items associated with bananas.

5.1.2 Summary of Environmental Degradation

As there are no domestic agricultural or residential uses registered or proposed for diethofencarb, 

environmental degradation is not relevant for this petition.

5.1.3 Comparison of Metabolic Pathways

Plant metabolism studies indicate that unchanged parent is a major portion of the residue. The 

total amount of parent declined with increasing PHI. Parent was 70.6% and 48.0% Total 

Radioactive Residues (TRR) in tomato, and lettuce, respectively at short PHIs (7 – 10-days). At 

the longer PHI of 35 days for grapes, parent declined to 21.5% TRR. Identified metabolites 

represent hydrolysis and subsequent conjugation of the parent. All metabolites have the 
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backbone structure of diethofencarb. Significant amounts of the TRRs were unidentified and 

attributed to many minor metabolites of relatively low concentration (<10% TRR).

Rat metabolism studies have shown that there is quick and extensive absorption of diethofencarb, 

limited distribution in tissues, extensive metabolism into sulfate and glucuronide metabolites, and 

quick and extensive excretion with no bioaccumulation. Appendix B presents the chemical 

structures of parent and metabolites of diethofencarb. 

No confined rotational crop studies were submitted. Additionally, no livestock metabolism 

studies were provided. These studies are not relevant to a tolerance without U.S. registration on 

a crop with no livestock feed components. Additionally, residues in water are not a concern for a 

tolerance without U.S. registration. 

5.1.4 Residues of Concern Summary and Rationale

Upon examination of the available data, the HED Residues of Concern Knowledgebase 

Subcommittee (ROCKS) determined that the parent compound, diethofencarb, is a suitable 

residue definition for purposes of both tolerance enforcement and risk assessment in plants.

Table 5.1.4.1. Summary of Metabolites and Degradates to be included in the Risk Assessment and 

Tolerance Expression for Bananas

Matrix Residues included in Risk 

Assessment

Residues included in 

Tolerance Expression

Plants Primary Crop Diethofencarb Diethofencarb

Rotational Crop Not applicable1 Not applicable1

Livestock Ruminant Not applicable1 Not applicable1

Poultry Not applicable1 Not applicable1

Drinking Water Not applicable1 Not Applicable

1 Request is for a tolerance without U.S. registration on banana only. 

5.2 Food Residue Profile

Ten independent banana field trials were conducted during the 2012 growing season in Costa 

Rica (3 trials), Ecuador (2 trials), Guatemala (3 trials), and Honduras (2 trials). The number and 

distribution of trials are adequate to support a tolerance for diethofencarb without U.S. 

registration on banana. Guatemala, Ecuador, Costa Rica, Colombia, and Honduras account for 

about 94% of U.S. banana imports (University of Florida, IFAS Extension, 2012). The trials 

reflect the proposed use directions, and the analytical method is adequate for the analysis of 

banana samples. Samples were stored frozen for a period of demonstrated residue stability.

Peel and pulp samples were analyzed separately for parent only. Residues in the peel ranged 

from non-detectable to 0.15 ppm; residues in the pulp were non-detectable. Calculated residue 

levels in whole bananas (unbagged) ranged for <0.01 to 0.071 ppm in samples collected at PHI 

of 0-day. Decline studies were conducted in two trials and residues of parent were nondetectable within five days of the final application. In summary, the HED has concluded that 

due to the very short pre-harvest interval any exposure will be to the parent only, but exposure to 

diethofencarb will likely be minimal in the edible commodity.
Diethofencarb Human Health Risk Assessment D418227

Page 12 of 49

5.3 Drinking Water Residue Profile

As there are no domestic agricultural or residential uses registered or proposed for diethofencarb, 

a drinking water assessment is not relevant for this petition. 

5.4 Dietary (Food Only) Risk Assessment

A chronic (food only) analysis was performed using DEEM-FCID, ver. 3.16, which incorporates 

consumption data from the USDA NHANES/WWEIA; 2003-2008, to estimate the dietary 

exposure of the U.S. population and various population subgroups. The unrefined chronic 

assessment assumed that diethofencarb residues are present in all commodities at recommended 

tolerance levels and that 100% of all crops are treated. DEEM Version 7.81 default processing 

factors were used to estimate residues in processed commodities. Drinking water estimates were 

not incorporated into the chronic dietary assessment, as there are no domestic uses proposed or 

established. The results are summarized in Table 5.4.1. The resulting chronic food estimates are 

not of concern to HED (<100% cPAD) for U.S. general population and all population subgroups 

(≤ 1% cPAD); the most highly exposed population subgroup is children 1-2 years old. The 

chronic dietary exposure and risk estimates are highly conservative since they assume that all 

subject crops consumed in this country have been treated (but use is not registered not in the 

U.S.) and that residues are present at tolerance levels. Dietary exposure estimates could be 

refined using anticipated residues and percent crop imported data. However, since estimated 

exposures and risks using conservative assumptions are below HED’s level of concern, such 

refinement is not warranted.

Table 5.4.1. Summary of Dietary (Food Only) Exposure and Risk for Diethofencarb.*

Population Subgroup

Chronic Dietary

Dietary Exposure

(mg/kg/day) % cPAD*

General U.S. Population 0.000038 < 1

All Infants (<1 year old) 0.000185 < 1

Children 1-2 years old 0.000213 < 1

Children 3-5 years old 0.000104 < 1

Children 6-12 years old 0.000040 < 1

Youth 13-19 years old 0.000016 < 1

Adults 20-49 years old 0.000022 < 1

Adults 50-99 years old 0.000035 < 1

Females 13-49 years old 0.000022 < 1

*Population subgroup with the highest exposure and risk is in bold type. 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

As there are no domestic agricultural or residential uses registered or proposed for diethofencarb, 

a residential exposure assessment was not performed.

7.0 Aggregate Exposure/Risk Characterization

In accordance with the FQPA, HED must consider and aggregate (add) pesticide exposures and 

risks from three major sources: food, drinking water, and residential exposures. In an aggregate 

assessment, exposures from relevant sources are added together and compared to quantitative 
Diethofencarb Human Health Risk Assessment D418227

Page 13 of 49

estimates of hazard (e.g., a NOAEL or PAD), or the risks themselves can be aggregated. When 

aggregating exposures and risks from various sources, HED considers both the route and 

duration of exposure. Because this action is for tolerances without a U.S. registration and there 

are no proposed or existing uses of diethofencarb which would result in drinking water or 

residential exposures, the dietary (food only) exposure estimates provided in Table 5.4.1 

represent the aggregate exposure assessment.

8.0 Cumulative Exposure/Risk Characterization

Unlike other pesticides for which EPA has followed a cumulative risk approach based on a 

common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as 

to diethofencarb and any other substances and diethofencarb does not appear to produce a toxic 

metabolite produced by other substances. For the purposes of this tolerance action, therefore, 

EPA has not assumed that diethofencarb has a common mechanism of toxicity with other 

substances. For information regarding EPA’s efforts to determine which chemicals have a 

common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the 

policy statements released by EPA’s Office of Pesticide Programs concerning common 

mechanism determinations and procedures for cumulating effects from substances found to have 

a common mechanism on EPA’s website at http://www.epa.gov/pesticides/cumulative/.

9.0 Occupational Exposure/Risk Characterization

Since the proposed use is for a tolerance without an U.S. registration, an occupational exposure 

assessment is unnecessary. 

Appendix A. Toxicology Profile and Executive Summaries

Appendix B. Metabolism Considerations

Appendix C. Physical/Chemical Properties of Diethofencarb
Diethofencarb Human Health Risk Assessment D418227

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Appendix A. Toxicology Profile and Executive Summaries

A.1 Toxicology Data Requirements

The requirements (40 CFR 158.340) for a food use for diethofencarb are in Table A1. Use of the new guideline 

numbers does not imply that the new (1998) guideline protocols were used.

Table A1. Summary of Toxicology Data Requirements

Guideline No. / Study Type Technical MRID No. Required Submitted

870.3100 Subchronic (Oral) Toxicity - Rodent...........................................

870.3150 Subchronic (Oral) Toxicity - Non-Rodent...................................

870.3200 21/28-Day Dermal Toxicity ........................................................

870.3250 90-Day Dermal Toxicity .............................................................

870.3465 90-Day Inhalation Toxicity .........................................................

Y

Y

Y

N

Na

Y

Y

Y

N

N

49267444

49267445

49267447

--

--

870.3700a Prenatal Developmental Toxicity -Rodent ..................................

870.3700b Prenatal Developmental Toxicity - Non-Rodent .........................

870.3800 Reproduction and Fertility Effects ..............................................

Y

Y

Y

Y

Y

Y

49267448

49267449

49267451

870.4100a Chronic (Oral) Toxicity - Rodent ................................................

870.4100b Chronic (Oral) Toxicity - Non-Rodent........................................

870.4200a Carcinogenicity -Rat....................................................................

870.4200b Carcinogenicity - Mouse .............................................................

870.4300 Combined Chronic Toxicity /Carcinogenicity.............................

N

Y

N

Y

Y

Y

Y

Y

Y

Y

49267454b

49267452

49267454b

49267453

49267454b

870.6100a Neurotoxicity - Acute Delayed Neurotox.- Hen..........................

870.6100b Neurotoxicity - Subchronic - Hen ..............................................

870.6200a Neurotoxicity Screening Battery - Acute - Rat............................

870.6200b Neurotoxicity Screening Battery -Subchronic - Rat....................

870.6300 Developmental Neurotoxicity ....................................................

N

N

Y

Y

N

N

N

Y

Y

N

--

--

49267464

49267463

--

870.5100 Bacterial Reverse Mutation Test .................................................

870.5300 In Vitro Mammalian Gene Mutation Test – Mouse 

Lymphoma Cells...................................................

870.5375 In Vitro Mammalian Chromosome Aberration Test....................

870.5395 In Vivo Erythrocyte Micronucleus Test - Mice ...........................

870.5550 Unscheduled DNA Synthesis......................................................

870.5900 In Vitro Sister Chromatid Exchange ...........................................

Y

Y

N

Y

N

N

Y

Y

Y

Y

Y

Y

49267456

49267457

49267458

49267459

49267460

49267461

49267475

870.7485 Metabolism and Pharmacokinetics..............................................

870.7200 Companion Animal Safety ..........................................................

870.7600 Dermal Penetration - Rat.............................................................

870.7600 Dermal Penetration - Human.......................................................

870.7800 Immunotoxicity - Rat ..................................................................

Y

N

CRa

CRa

Y

Y

N

N

N

Y

49267467

49267468

49267469

49267470

49267471

--

--

--

49267472

a This study is not required for a tolerance on imported foodstuffs.

b The requirements for the chronic oral (rat) and carcinogenicity (rat) studies are satisfied by the combined chronic/oncogenicity 

(rat) study.
Diethofencarb Human Health Risk Assessment D418227

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A.2 Toxicity Profiles

Table A.2.1 Acute Toxicity Profile for Diethofencarb

Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral (rat) 49267431 LD50 > 5000 mg/kg IV

870.1100 Acute oral (mouse) 49267432 LD50 > 5000 mg/kg IV

870.1100 Acute oral (mouse) 49267433 LD50 > 5000 mg/kg IV

870.1200 Acute dermal (rat) 49267434 LD50 > 5000 mg/kg IV

870.1200 Acute dermal (mouse) 49267435 LD50 > 5000 mg/kg IV

870.1300 Acute inhalation (rat) 49267436 LC50 > 1.05 mg/L III

870.2400 Acute eye irritation (rabbit) 49267437 Slight irritation III

870.2500 Acute dermal irritation (rabbit) 49267437 Non-irritating IV

870.2600 Skin sensitization (mouse) 49267438 Not a dermal sensitizer N/A

Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

870.3050 28-day oral dietary, rat 49267440 (1986)

0, 100, 1000, 3000, and 

10,000 ppm 

M: 0, 9.02, 89.1, 276, 

878 mg/kg bw/day

F: 0, 9.94, 98.9, 300, 

1009 mg/kg bw/day

Acceptable/Guideline

NOAEL = 878 / 1009 mg/kg bw/day (M/F)

LOAEL = not established. Increased blood 

cholesterol, increased liver weight and 

swelling of centrilobular hepatocytes 

considered adaptive and not adverse.

870.3050 28-day oral dietary, 

mouse

49267442 (1986)

0, 100, 3000, 10,000, 

30,000 ppm

0, 18.7, 563, 1852, 6169 

mg/kg bw/day (M)

0, 4.4, 720, 2337, 8450 

mg/kg bw/day (F)

Acceptable / nonguideline

NOAEL = 563/720 mg/kg bw/day (M/F)

LOAEL = 1852/2337 mg/kg bw/day (M/F) 

based on higher platelet counts (increases of 

10% and 17% in males and females, 

respectively), higher total cholesterol 

concentrations in blood (increases of 26% 

in both sexes), higher absolute liver weights 

(increases of 14% and 23% in males and 

females, respectively), higher relative liver 

weights (increases of 17% and 20% in 

males and females, respectively), as well as 

foci of necrosis in livers. Males only had 

submucosal lymphoid hyperplasia in 

urinary bladders and hepatocellular 

hypertrophy

No analysis of dietary admixtures 

performed to investigate the homogeneity, 

stability, and achieved concentrations of the 

test substance.

Rangefinding28-day oral capsule, dog 49267443 (1986)

0, 10, 50, 250, 1000 

mg/kg/day

Acceptable / nonguideline

NOAEL and LOAEL are not determined 

because the inadequate number of animals 

used makes data interpretation difficult.

Salivation and emesis, and decreases in 

food consumption, body weight and fecal 

output were observed in males and females, 

with the female being the more sensitive 

sex. Increased liver weight and 

hypertrophy considered adaptive. 

Range-finding study 
Diethofencarb Human Health Risk Assessment D418227

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Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

870.3100 13-week oral dietary, rat 49267444 (1986)

0, 300, 1000, 3000, 

10,000 ppm

0, 21.3, 78.2, 232 752 

mg/kg/day (M)

0, 27.2, 90.8, 275 824 

mg/kg/day (F)

Acceptable / NonGuideline

NOAEL = 275 mg/kg bw/day (F)

LOAEL = 824 mg/kg bw/day (F) based on 

decreased body weight (-15%, p<0.01) and 

food consumption (-25%, p<0.01) in 

females. LOAEL not established in males

Study did not meet the GLP standards. 

Although the stability of the test compound 

was confirmed in a 28-day rat study (MRID 

49267440), no dietary analyses for the 

homogeneity and concentration analysis 

were provided

870.3150 13-week oral capsule, 

dog

49267445 (1986)

0, 10, 30, 100 300 mg/kg 

bw/day

Acceptable/Guideline

NOAEL = 300 mg/kg bw/day

LOAEL = not established.

Note: emesis was observed at 100 and 300 

mg/kg bw/day in males and females, with 

both the number of animals affected and the 

frequency of emesis increasing with dose. 

However, there were no changes in body 

weight or food consumption to suggest 

animal is compromised. 

870.3200 28-day dermal, rat 49267447 (2002)

0, 100, 300, 1000 mg/kg 

bw/day

Acceptable/Guideline

NOAEL=1000 mg/kg bw/day

LOAEL not established

No local or systemic effects were seen at 

any dose level.

870.3465 90/28-day inhalation, rat Study Not Available Study Not Available

870.3700a Developmental Toxicity, 

rat

49267450 (1987)

0, 100, 300, or 1000 

mg/kg bw/day

Acceptable/Guideline

Maternal NOAEL = 1000 mg/kg bw/day

Maternal LOAEL = not established 

Developmental NOAEL = 1000 mg/kg 

bw/day

Developmental LOAEL = not established

870.3700b Developmental Toxicity, 

rabbit

49267447 (1986)

0, 50, 125, 300, or 750 

mg/kg bw/day

Unacceptable/nonguideline

NOAEL = not identified

LOAEL = not identified

The non-treatment-related maternal wastage 

(deaths, abortions/early deliveries) and total 

litter resorptions resulted in fewer than 

twelve litters per group at caesarean in four 

of five groups, which decreased the study’s 

sensitivity. In addition, the total numbers 

of deaths, abortions/early deliveries, and 

total litter resorptions call into question 

whether there might have been a problem 

with laboratory technique, the 

environmental conditions, or animal health.
Diethofencarb Human Health Risk Assessment D418227

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Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

870.3700b Developmental Toxicity, 

rabbit

49267448 (1987)

0, 125, 300, or 750 

mg/kg bw/day

Unacceptable/nonguideline

NOAEL = not identified

LOAEL = not identified

20% frequency of implantation loss in 

controls suggests unknown factors at play 

that make data interpretation difficult. Low 

number of dams for evaluation in the high 

dose (just 9) is too much at variance with 

guideline minimums.

870.3700b Developmental Toxicity, 

rabbit

49267449 (1992)

0, 800, or 900 mg/kg 

bw/day

Acceptable/nonguideline

Maternal

NOAEL < 800 mg/kg/day, not established

LOAEL = 800 mg/kg/day based on lateterm abortions

Developmental

NOAEL < 800 mg/kg/day, not established

LOAEL = 800 mg/kg/day based on lateterm abortions

870.3800 Multi-generation 

reproduction, rat

49267451 (1988)

0, 200, 1000, or 5000 

ppm. Pre-mating doses: 

0, 13.1, 65.5, 328 mg/kg 

bw/day F0 (M); 

0, 16.0, 88.0, 427 mg/kg 

bw/day F0 (F); 

0, 16.6, 84.8, 420 mg/kg 

bw/day F1 (M) 

0, 19.4, 105, 510 mg/kg 

bw/day in F1 (F).

Acceptable/Guideline

Parental NOAEL = 328/347 mg/kg bw/day 

M/F

Parental LOAEL = not established

Reproductive NOAEL =328/347 mg/kg 

bw/day M/F

Reproductive LOAEL = not established

Offspring NOAEL =65.5/88.0 mg/kg 

bw/day M/F

Offspring LOAEL = 328/347 mg/kg 

bw/day M/F based on decreased absolute 

body weights (-11% to -15%, p<0.05) in F2 

offspring of both sexes during lactation 

(PNDs 4, 14, 21).

870.4100 Chronic Toxicity, dog 49267452 (1988)

10, 50, 250, and 1000 

mg/kg/day

Acceptable/Guideline

NOAEL (M) = 50 mg/kg/day

LOAEL (F) = 250 mg/kg/day based on 

decreased body weight and increased 

emesis.

NOAEL (F) = 250 mg/kg/day

LOAEL (F) = 1000 mg/kg/day based on 

decreased absolute and relative uterine 

weights.
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Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

870.4200 Oncogenicity, mouse 49267453 (1988)

0, 10, 100, 1000, 10,000 

ppm 0, 1.63, 16.47, 

163.8, 1682 mg/kg/day 

(M)

0, 2.03, 20.53, 202.9, 

2108 mg/kg/day (F)

Acceptable/Guideline

NOAEL = 163.8 / 202.9 mg/kg/day (M/F)

LOAEL = 1682 / 2108 mg/kg/day (M/F) 

based on a dose-related increased incidence 

of hepatocellular hyperplasia in males 

(18%, p<0.01), and decreased survival rates 

at 78 weeks (p<0.05; 32% vs. 66% in 

controls in females.

At 1682 mg/kg/day a 27% increase (p<0.05 

in testes weight was observed in males but 

there were no histopathological changes.

No increase in tumor incidence.

Dosing was considered adequate to assess 

carcinogenic potential.

870.4300 Chronic/ Oncogenicity 

Study, rat

49267454 (1989)

0, 40, 200, 1000, 5000 

ppm

0, 1.69, 8.42, 42.70, 

220.30 mg/kg/day (M)

0, 2.18, 10.90, 54.50, 

288.19 mg/kg/day (F)

Acceptable/Guideline

NOAEL = 220.3 / 288.2 (M/F)

LOAEL not established because no nonneoplastic effects seen at any dose level. 

Dosing was considered adequate based on a 

treatment-related increase in thyroid 

follicular cell tumor incidence (carcinomas 

in males, adenomas in females)

870.5100 In vitro Bacterial Gene 

Mutation

49267456 (1984)

0, 5, 10, 50, 100, 500, 

and 1000 μg/plate, with 

and without S9-mix

Acceptable/Guideline

Negative. 

There was no evidence of induced mutant 

colonies over background.

870.5100 In vitro Bacterial Gene 

Mutation

49267457 (1988)

of 0, 50, 100, 200, 500, 

1000 and 2000 μg/plate, 

with and without S9-mix

Acceptable/Guideline

Negative. 

There was no evidence of induced mutant 

colonies over background.

870.5300 In Vitro Mammalian 

Cells in Culture Gene 

Mutation Assay 

49267458 (1989)

0, 20, 50, 100, or 200 

μg/mL in three 

independent experiments 

in the absence of 

metabolic activation and 

in two independent 

experiments in the 

presence of metabolic 

activation

Acceptable/Guideline

Negative. 

There was no evidence of induced mutant 

colonies over background.
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Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

870.5375 In vitro Mammalian 

Cytogenetics

Chromosome Aberration 

Assay

49267459 (1989)

0, 13.37, 26.73, 53.46 

and 133.66 μg/mL 

without S9;

0, 26.73, 53.46, 133.66 

and 267.32 μg/mL in the 

presence of S9 

activation

Acceptable/Guideline

Negative. 

There was no evidence of chromosome 

aberrations induced over background.

870.5395 In vivo Mammalian 

Cytogenetics -

Erythrocyte 

Micronucleus assay in 

the mouse

49267460 (1987)

1250, 2500 or 5000 

mg/kg

Acceptable/nonguideline

Negative.

There were no significant increases in the 

frequencies of micronucleated 

polychromatic erythrocytes in bone marrow 

after any treatment time or dose level.

Test conducted in males only, females 

excluded without justification.

870.5550 Unscheduled DNA 

Synthesis in Primary Rat 

Hepatocytes/Mammalian 

Cell Cultures

49267461 (1989)

25.3, 202 μg/mL

Unacceptable/Guideline

Negative.

There was no evidence that unscheduled 

DNA synthesis, as determined by 

radioactive tracer procedures [nuclear silver 

grain counts], was induced.

The results of the two assays were radically 

different, with an approximately 8-fold 

difference in cytotoxicity levels. This 

apparent discrepancy brings into question 

the validity of the procedure and results.

870.5900 In Vitro Sister 

Chromatid Exchange 

Assay in CHO Cells

49267475 (1986)

First assay: 0, 0.27, 0.81, 

2.67, 8.01, 26.73, 80.19, 

267.32 μg/mL, without 

and with activation

Second Assay: 0, 26.73, 

53.46, 133.65 and 

267.32 μg/mL, without 

and with activation

Acceptable/Guideline

Negative

There was no evidence of an increase in 

sister chromatid exchanges in CHO-K1 

cells induced over background

870.6200a Acute Neurotoxicity, rat 49267464 (2013)

0, 200, 600, or 2000 

mg/kg bw

Acceptable/Guideline

NOAEL = 600 mg/kg bw (M/F)

LOAEL = 2000 mg/kg bw (M/F) based on 

decreased forelimb grip strength, reduced 

body temperature and decreased alertness 

(M) and decreased muscle tone and 

pupillary reflex, reduced body temperature 

and increased landing footsplay (F)
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Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

870.6200b Subchronic 

Neurotoxicity, rat

49267463 (2013)

0, 1000, 3000, or 10,000 

ppm 0, 56.7, 172, and 

571 mg/kg bw/day (M) 

0, 65.4, 194, 654 mg/kg 

bw/day (F)

Acceptable/Guideline

NOAEL = 571 / 654 mg/kg bw/day (M/F)

LOAEL Not established

870.7485 Absorption Distribution 

Metabolism Excretion

49267467, 49267468, 

49267469, 49267470, 

49267471

10 or 300 mg/kg bw as a 

single or two-day dose. 

In an addition, male rats 

were treated with a 10 

mg/kg bw/day unlabeled 

test material for 14 days 

followed by a single 

radiolabeled dose of the 

test material. 

Acceptable/Guideline 

Metabolism of diethofencarb in rats was 

found to be independent of sex, dose level 

and pre-treatment. Oral absorption is quick 

and extensive (> 87% of AD by day 2). 

Organ/tissue radioactivity decreases rapidly 

and is mainly found in lever, adrenals, 

blood/blood cells, kidney and skin. 

Diethofencarb has no bioaccumulation 

potential. It is extensively biotransformed 

into several metabolites, mainly sulfate and 

glucuronide conjugate. Excretion is 

extensive and quick extensive (> 93% of 

AD by day 2) and occurs in urine (> 61% of 

AD), expired air (> 21% of AD) and feces 

(> 13% of AD). This results in organ/tissue 

depuration t1/2 values of <35 hours based on 

data up to 72 hr pose-dose and a low 

retained fraction (<2% of AD on day 7), 

and the deduction that there is no 

significant entero-hepatic recirculation.

870.7800 Immunotoxicity, rat 

(female only)

49267472 (2012)

0, 1000, 3000, 10,000 

ppm

0, 79.6, 236, 764 mg/kg 

bw/day (F)

Acceptable/Guideline

Systemic NOAEL = 764 mg/kg bw/day

Systemic LOAEL = not established

Immunotoxicity 

NOAEL = 764 mg/kg bw/day

Immunotoxicity 

LOAEL = not established

Nonguideline14-day thyroid 

mechanistic study, rat

49267473 (1989)

0, 5000, 20,000 ppm

0, 430, 1720 mg/kg 

bw/day for 7-wk olds; 

0, 345, 1380 mg/kg 

bw/day for 37- and 66-

wk olds

Acceptable/nonguideline; 

Numerous procedural 

deficiencies found. 

However, data 

corroborated and found 

useful in conjunction 

with MRID 49267474

Treatment with 20,000 ppm for up to two 

weeks decreased serum T4 concentrations 

and induced slight increases in TSH 

concentrations with no effect on T3 

concentrations. In the bioaccumulation 

study, the kidney had the highest 14C 

concentrations followed by the liver, skin 

and hair following both 7- and 14-days of 

treatment. No indication of 

bioaccumulation of radiolabel was found in 

the thyroid. The data also suggested that 

increased T4 excretion in the bile arose 

through metabolic processes related to 

hepatic UDP-GT induction.
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Table A.2.2 Repeated-Dose Toxicity Profile for Diethofencarb

Guideline Study, Species MRID (Year), Dose 

Levels, Classification

Results

Nonguideline3-month thyroid 

mechanistic study, rat

49267474 (1989)

0, 5000, 20,000 ppm

0, 430, 1720 mg/kg 

bw/day

Acceptable/nonguideline

Decreased body weight and food 

consumption were observed at 5000 ppm 

and higher. Examinations at termination 

demonstrated a decrease in serum free T4

level and an increase in serum TSH level in 

the 20000 ppm group. However, no 

compound related effects were observed in 

the thyroid weight, the thyroid uptake of 

125I, autopsy and histopathological 

examination of the thyroid. Liver weight 

increase at and above 5000 ppm, and an 

increase of UDP-GT (UDPglucuronyltransferase) activity at 20000 

ppm, were observed.
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EXECUTIVE SUMMARIES

Subchronic Toxicity

870.3050 28-Day Oral Toxicity — Mouse

Repeated dose oral toxicity 28-day feeding study in rats (MRID 49267442).

This 28-day oral toxicity study in the rat is Acceptable/Non-Guideline and does not satisfy the 

guideline requirement for a 4-week toxicity study in rodents (OCSPP 870.3050; OECD 408). 

Groups of CD-1 (ICR) BR mice (10/sex/group) were administered diethofencarb (97.2% a.i., 

Batch PKG 84093) in the diet at the dietary concentrations of 0, 100, 3000, 10,000 or 30,000 

ppm for 28 days. No analyses of dietary admixtures were performed to investigate the 

homogeneity, stability, and achieved concentrations of the test substance. Mortality, clinical 

signs, body weight, and food consumption were recorded. Samples of blood and were collected 

for clinical pathology evaluation at the end of treatment. All surviving animals in all groups were 

then sacrificed and subjected to gross necropsy. Selected organs were weighed, and, in the 

control and 30,000 ppm groups, a standard range of organs and tissues was removed, fixed, and 

examined microscopically. Livers, kidneys, and urinary bladders of mice in all groups were 

examined microscopically. The 100, 3000, 10,000 and 30,000 ppm dietary levels corresponded 

to nominal dose-levels of 18.7, 563, 1852, and 6169 mg/kg bw/day in males and to 24.4, 720, 

2337, and 8450 mg/kg bw/day in females for the 28 days of feeding. 

No mortality occurred. Both sexes at the 30,000 ppm diet had higher platelet counts (increases of 

16% and 24% in males and females, respectively), higher albumin concentrations (increases of 

13% and 20% in males and females, respectively), higher protein concentrations (increases of 

15% and 17% in males and females, respectively), higher total cholesterol concentrations in 

blood (increases of 74% and 66% in males and females, respectively), higher alanine 

aminotransferase (ALT) activities (increases of 88% and 79% in males and females, 

respectively), higher absolute liver weights (increases of 34% and 53% in males and females, 

respectively), higher relative liver weights (increases of 63% and 61% in males and females, 

respectively), dark livers in 6/10 males and in all 10 females, as well as foci of necrosis in livers, 

hepatocellular hypertrophy, proteinaceous casts and regenerative epithelium in kidneys, and 

submucosal lymphoid hyperplasia in urinary bladders in both sexes. Males only at the 30,000 

ppm diet showed a reduction in body weight gain, which amounted to 49%. The LOAEL in 

CD-1 (ICR) BR mice of both sexes was the 10,000 ppm diet (corresponding to nominal dose 

levels of 1852 and 2337 mg/kg bw/day in males and females, respectively) based on higher 

platelet counts (increases of 10% and 17% in males and females, respectively), higher total 

cholesterol concentrations in blood (increases of 26% in both sexes), higher absolute liver 

weights (increases of 14% and 23% in males and females, respectively), higher relative 

liver weights (increases of 17% and 20% in males and females, respectively), as well as foci 

of necrosis in livers. Males only at the 10,000 ppm dietary level had submucosal lymphoid 

hyperplasia in urinary bladders and hepatocellular hypertrophy.

No treatment-related adverse effects were observed at the 100 or 3000 ppm dietary levels in 

either sex. The NOAEL in both sexes was the 3000 ppm diet (corresponding to nominal 

doses of 563 and 720 mg/ kg bw/day in males and females, respectively). The target organs 

were identified as the liver, kidneys, and urinary bladder. 
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This repeated dose 28-day oral toxicity study in mice is Acceptable / non-guideline and does 

not satisfy the requirements of Guideline OCSPP 870.3050 (OECD 407) because of analytical 

deficiencies (see Deficiencies section). However, it does provide data useful in characterizing the 

toxicity of diethofencarb in the mouse and serves as a range-finding study.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, pp. 248-251 

(2007). Portions of this document were altered by the EPA reviewer to reflect Agency policies 

and conclusions.

870.3050 28-Day Oral Toxicity — Rat 

Repeated dose oral toxicity 28-day feeding study in rats (MRID 49267440).

This 28-day oral toxicity study in the rat is Acceptable/Guideline and satisfies the guideline 

requirement for a 4-week toxicity study in rodents (OCSPP 870.3050; OECD 408). 

In a 28-day feeding study (MRID 49267440), groups of Sprague Dawley rats (10/sex/group) 

were administered diethofencarb (97.4% a.i., Batch PK 84042) in the diet at concentrations of 0, 

100, 1000, 3000, or 10,000 ppm for 4 weeks. Dietary admixtures were analyzed to investigate 

the homogeneity, stability (over 7 days), and achieved concentrations of the test substance. 

Mortality, clinical signs, body weight, and food consumption were recorded. Samples of blood 

and urine were collected for clinical pathology evaluation at the end of treatment. At study 

termination, all surviving animals from the two highest dose groups and the controls were 

examined ophthalmologically. All surviving animals in all groups were then sacrificed and 

subjected to gross necropsy. Selected organs were weighed, and, in the control and 10,000 ppm 

dose group, a standard range of organs and tissues were removed, fixed, and examined 

microscopically. Livers of rats in all groups were examined microscopically. The 100, 1000, 

3000, and 10,000 ppm concentrations corresponded to dose-levels of 9.02, 89.1, 276, and 878 

mg/kg bw/day in males and to 9.94, 98.9, 300, and 1009 mg/kg bw/day in females for the 28 

days of feeding. 

No mortality occurred. Both sexes at the 10,000 ppm dose level had higher blood cholesterol 

concentrations (increases of 43% and 22% in males and females, respectively), and swelling of 

centrilobular hepatocytes in all animals. Males only at 10,000 ppm dose level had lower food 

intake (a reduction of 11%), higher absolute liver weight (increase of 14%), and higher relative 

liver weight (increase of 25%). These increases in cholesterol and liver weights are considered 

adaptive responses that are not adverse. No treatment-related adverse effects were observed at 

10 or 1000 ppm dose levels in either sex. The NOAEL was 10,000 ppm (878 / 1009 mg/kg 

bw/day, respectively) in males and females and the LOAEL was not established. 

This repeated dose 28-day oral toxicity study in rats is acceptable/guideline and satisfies the 

requirements of Guideline OCSPP 870.3050 (OECD 407).

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, pp. 246-248 

(2007). Portions of this document were altered by the EPA reviewer to reflect EPA policies and 

conclusions.
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Non-guideline 28-day Oral Toxicity – Dog

28-Day feeding study the dog. MRID 49267443.

This 28-day range-finding oral toxicity study in the dog is Acceptable/Non-guideline and does 

not satisfy a guideline requirement. 

In a four-week toxicity study, groups of Beagle dogs (2/sex/group) were administered 

diethofencarb (97.2% a.i., Batch PKG 84093) in gelatin capsules at 0, 10, 50, 250, or 1000 

mg/kg bw/day for 28 days. Mortality, clinical signs, body weight, and food consumption were 

recorded. Samples of blood were collected for hematological and blood biochemistry 

investigations prior to treatment (at week -1) and at the end of the treatment. Urinalyses were 

performed at the same times. Plasma and red blood cell cholinesterase concentrations were 

investigated prior to treatment and at 1 and 3 hours after dosing on treatment weeks 2 and 4. 

Brain cholinesterase concentration was determined at the time of necropsy. Ophthalmological 

examinations were performed on all dogs prior to treatment and at study termination, at which 

time all surviving animals were sacrificed and subjected to gross necropsy. Selected organs were 

weighed, and the following organs and tissues were removed, fixed, and examined 

microscopically for all dogs: hearts, lungs, pancreases, livers, kidneys, testes with epididymides, 

ovaries, spleens, urinary bladders, and any gross lesions. 

No mortality occurred. Males and females at the 1000 mg/kg bw/day dose had few or no feces, 

emesis, salivation, weight loss over the time of study (-15 % to -18% over both sexes), lower 

food intake (of 30% through 61% in males and of 65% through 81% in females), increased 

absolute liver weights (37% and 76%, respectively, in males and females), and increased liver 

weights (64% and 113%, respectively, in males and females). At this same dose, one of two 

males had tremors and compound-colored stools, and one of two females showed thinness, 

dehydration, and ataxia. Since this study used just two animals/sex/dose group, the findings are 

difficult to interpret, and the NOAEL and LOAEL are not determined.

This repeated dose 28-day oral toxicity study in mice is acceptable/non-guideline. The number 

of animals used/group was not sufficient. Nonetheless, it provides useful information as a 

supportive range-finding study.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, pp. 252-254

(2007). Portions of this document were altered by the EPA reviewer to reflect Agency policies 

and conclusions.

870.3100 90-Day Oral Toxicity — Rat

90-day feeding study in rats. MRID 49267444

This study is classified as Acceptable / Non-Guideline and satisfies the guideline requirements 

for an oral 90-day subchronic Toxicity Study in the rat (OCSPP 870.3100; OECD 408). 

In a 13-week study (MRID 49267444), groups of 15 male and 15 female Sprague-Dawley rats 

were fed S-32165 (Diethofencarb, 97.4% a.i., Batch PK 84042) at dietary concentrations of 0, 

300, 1000, 3000 or 10,000 ppm, for a period of 90 days (corresponding to 0, 21.3, 78.2, 232 or 
Diethofencarb Human Health Risk Assessment D418227

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752 mg/kg/day in males, and 0, 27.2, 90.8, 275 or 824 mg/kg/day in females). Animals were 

observed for mortality and clinical signs daily and body weight, food and water consumption 

were recorded weekly. Opthalmoscopic examinations were performed. Blood samples were 

taken during Week 13 for hematology and blood biochemistry investigations. Cholinesterase 

activity in plasma, erythrocytes and brain was investigated. Following completion of the 

scheduled treatment period, a detailed necropsy was performed on all animals and various organs 

were weighed. A full set of tissues and organs were prepared and subjected to histopahtology.

Oral administration of S-32165 caused statistically significant (p<0.05, p<0.01) decreases in 

body weights in both sexes, which were marginal (<10% in males) ; and lower food consumption 

and water intake in females at 10,000 ppm. Increases in absolute and relative liver weights 

accompanied by centrilobular hepatocellular hypertrophy as well as hypertrophy of endoplasmic 

reticulum in males at 3000 ppm and both sexes at 10,000 ppm were considered as adaptive 

responses to S-32165-induced toxicity.

The LOAEL is 824 mg/kg bw/day based on decreased body weight in females. The female 

NOAEL was 275 mg/kg bw/day. The LOAEL in males was is not established, and the 

NOAEL is 752 mg/kg bw/day.

This study is classified as Acceptable / Non-Guideline and satisfies the guideline requirements 

for an oral 90-day subchronic Toxicity Study in the rat (OCSPP 870.3100; OECD 408). The 

study did not meet the GLP standards. The stability of the test compound was not provided, but 

was confirmed in a 28-day rat study (MRID 49267440); no dietary analyses for the homogeneity 

and concentration analysis were provided. 

This Data Evaluation Record is a modified version of the Draft Assessment Report (DAR) of the 

Initial Risk Assessment by the Reporter Member State: France (2007), Diethofencarb Vol.3. 

Annex B, part 2/A, B.6., pages 254-257. Portions of this document were altered by the EPA 

reviewer to reflect Agency policies and conclusions.

870.3150 90-Day Oral Toxicity — Dog

90-Day oral toxicity study in dogs. MRID 49267445.

This study can be classified as Acceptable / Guideline and satisfies the guideline requirement 

for a 90-day subchronic toxicity study in non-rodents [OCSPP 870.3150; OECD 409].

In a subchronic toxicity study (MRID 49267445), Diethofencarb (98.1%; Batch No. PEG 85045) 

was administered orally in gelatin capsules to groups of 4 Beagle dogs/sex at dose levels of 0, 

10, 30, 100 or 300 mg/kg bw/day for 13 weeks. The control group received empty gelatin 

capsules. The dogs were observed twice daily for mortality and once daily for clinical signs. 

Body weights and food consumption were recorded weekly. Blood samples were taken for 

hematology and blood biochemistry investigations and urine samples were collected. 

Ophthalmological examinations were performed. Following completion of the scheduled 

treatment period, a detailed necropsy was performed on all animals and various organs were 

weighed. A full set of tissues and organs were collected, processed and examined 

microscopically.
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The only treatment-related effect in male and female dogs was emesis seen at 100 and 300 mg/kg 

bw/day. However, this effect was not sufficiently severe to cause significant decreases in food 

consumption or body weight, and is not considered adverse in this study. A LOAEL was not 

established. The NOAEL was 300 mg/kg bw/day. 

This study can be classified as Acceptable / Guideline and satisfies the guideline requirement 

for a 90-day subchronic toxicity study in non-rodents [OCSPP 870.3150; OECD 409]. 

This Data Evaluation Record is a modified version of the Draft Assessment Report (DAR) of the 

Initial Risk Assessment by the Reporter Member State: France (2007), Diethofencarb Vol.3. 

Annex B, part 2/A, B.6., pages 257-259. Portions of this document were altered by the EPA 

reviewer to reflect Agency policies and conclusions. 

870.3200 Subchronic Dermal Toxicity — Rat

28-Day dermal toxicity study in rat. MRID 49267446.

This 28-day dermal toxicity study in the Sprague Dawley rat is Acceptable / Guideline and 

satisfies the guideline requirement for a 28-day dermal toxicity study (OCSPP 870.3200; OECD 

410) in the rat.

Diethofencarb was applied moistened to the moistened clipped dorsal skin to groups of 10 male 

and 10 female Sprague Dawley rats at dose-levels of 0, 100, 300, or 1000 mg/kg bw/day for a 

period of 28 days. Dose-levels were selected based on a 7-day repeated dose dermal toxicity 

study in rats. Observation for clinical signs and skin reactions were carried out daily. The body 

weight and food consumption were recorded once a week. Opthalmoscopic and veterinary 

examinations were done and blood and urine samples were collected for clinical investigations at 

weekly intervals during the study. Following completion of the scheduled treatment period, a 

detailed necropsy was done on all animals and various organs were weighed. A full set of tissues 

and organs were prepared and examined for histopathology.

Following dermal application of diethofencarb for 28 days there were no deaths and no 

treatment-related clinical signs, skin reactions or ophthalmologic lesions. There were no 

significant differences in body weight, weight gain, food intake, hematological and blood 

biochemistry parameters as well as organs weights, between treated and control groups. There 

were no treatment-related gross and microscopic findings. There were no local or systemic 

effects seen at any dose level.

The NOAEL for Sprague Dawley rats was 1000 mg/kg bw/day (Limit dose). A LOAEL 

was not identified. This study is classified Acceptable / Guideline.

This Data Evaluation Record is a modified version of the Draft Assessment Report of the Initial 

Risk Assessment by the Reporter Member State: France (2007), Diethofencarb Vol.3. Annex B, 

part 2/A, B.6., pages 262-263. The EPA reviewer may have altered portions of this document to 

reflect Agency policies and conclusions.

870.3700 Prenatal Developmental Toxicity

Developmental toxicity study in rats. MRID 49267450.
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The developmental toxicity study in the rat is classified acceptable / guideline and satisfies the 

guideline requirement for a developmental toxicity study [OCSPP 870.3700; OECD 414] in the 

rat.

In a developmental toxicity study (MRID 49267450) S-32165 (Diethofencarb; 98.2% a.i.; Lot 

no. PSG 86018) was administered to 25 mated female Sprague-Dawley rats/dose by gavage in 

0.5% aqueous methylcellulose at dose levels of 0, 100, 300, or 1000 mg/kg bw/day on gestation

days (GDs) 6-15. On GD 21, dams were sacrificed and subjected to necropsy and caesarean 

section. Gravid uterine weights and numbers of corpora lutea, live and dead fetuses, early and

late resorptions, and implantation sites were recorded. Fetuses were examined grossly for 

external malformations/variations, weighed, and sexed. One half were fixed in Bouin’s fluid and 

the remaining half in alcohol, to evaluate visceral and skeletal anomalies, respectively.

There were no deaths or treatment-related clinical signs. During GDs 6-8, the 1000 mg/kg 

bw/day dams had decreased food consumption (-17%; p<0.05), which was not considered 

treatment-related or adverse because there was not a corresponding decrease in absolute body 

weight. There were no treatment-related effects on maternal intrauterine parameters. The 

maternal NOAEL is 1000 mg/kg bw/day. The maternal LOAEL was not established.

No treatment-related effects were observed on mean implantation efficiency, fetal viability, fetal 

body weight, or fetal sex ratio. At 1000 mg/kg bw/day, moderately dilated ureters were observed 

in 5.8% of fetuses (and 25% of litters) compared to 2.3% (and 13%) of control fetuses (and 

litters). However, since these fetus and litter values are within historical control ranges, they are 

not considered biologically relevant. The developmental LOAEL is not identified. The 

developmental NOAEL is greater than or equal to 1000 mg/kg bw/day.

The developmental toxicity study in the rat is classified Acceptable/Guideline and satisfies the 

guideline requirement for a developmental toxicity study (OCSPP 870.3700; OECD 414) in the 

rat. 

This Data Evaluation Record is a modified version of the Rapporteur Member States (RMS) 

Summary, Evaluation and Assessment of the Data and Information, Ministère de l’Agriculture et 

de la Pêche, Direction Générale de l’Alimentation, France (2007) Draft Assessment Report 

(DAR), public version, Diethofencarb, Volume 3 – Annex B.6, pp. 307-309. Portions of this 

document were altered by the EPA reviewer to reflect Agency policies and conclusions.

Developmental toxicity study in rabbits. MRID 49267447.

This study is classified as Unacceptable/non-guideline) and does not satisfy the guideline 

requirement for a developmental toxicity study in non-rodents (OPPTS 870.3700; OECD 414).

In a developmental toxicity study (MRID 49267447) S-32165 (Diethofencarb; 98.1% a.i.; batch 

No.: PEG 85045) was administered to 18 presumed pregnant New Zealand white rabbits/dose by 

gavage in 0.5% aqueous methylcellulose solution, at dose levels of 0, 50, 125, 300, or 750 mg/kg

bw/day (dosing volume 3 mL/kg bw) on gestation days (GDs) 7 through 19, inclusive. On GD

29, does were sacrificed and subjected to caesarean section. Gravid uterine weights and numbers 

of corpora lutea, live and dead fetuses, early and late resorptions, and implantation sites were 

recorded. All fetuses were given a gross external examination, weighed, sexed, and subjected to 

visceral and skeletal examinations. Heads of one half of the live fetuses were cut for 

examination of eyes, ears, palate, nasal septum, and brain. 
Diethofencarb Human Health Risk Assessment D418227

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Deaths of one dam from each of the control and 125-mg/kg groups and abortions/early deliveries 

by 1, 2, 3, 0, and 3 animals from the 0-, 50-, 125-, 300-, and 750-mg/kg groups, respectively, 

were not considered treatment-related. Relative to controls, dams treated at 750 mg/kg bw/day 

had statistically significant decreases in body weights (-7% to -10%) during treatment, and this 

group also had a mean weight loss of 50 g (vs. a weight gain of 140 g for controls) during the 

treatment interval. In addition, the food consumption of the 750-mg/kg dams was 38% less than 

that of controls during treatment. 

 

In the 0-, 50-, 125-, 300-, and 750-mg/kg groups, there were respectively 15, 16, 12, 10, and 14 

pregnant females (out of 18 initially), i.e. pregnancy was achieved by 56-89% of the animals in 

each group or ~74% overall. Due to maternal deaths, abortions/early deliveries, and total litter 

resorptions of three control litters and one 50-mg/kg litter, at caesarean, there were respectively 

10, 13, 8, 10, and 11 litters with live fetuses in the 0-, 50-, 125-, 300-, and 750-mg/kg groups. 

Mean numbers of corpora lutea and implantations and the mean percentages implantation 

efficiency of the treated groups were similar to those of controls. There were no evident 

treatment-related effects on postimplantation loss, numbers of early/late resorptions or dead 

fetuses, live litter sizes, fetal weight, or fetal sex ratio. Neither the pattern nor frequency of fetal 

malformations or variations indicated a treatment-related effect. 

In four of the five groups there were twelve or more pregnant rabbits, which was the minimum 

required by the guidelines before January 2000. However, the non-treatment-related maternal 

wastage (deaths, abortions/early deliveries) and total litter resorptions resulted in fewer than 

twelve litters per group at caesarean in four of five groups, which decreased the study’s 

sensitivity. In addition, the total numbers of deaths, abortions/early deliveries, and total litter 

resorptions call into question whether there might have been a problem with laboratory 

technique, the environmental conditions, or animal health.

Under the conditions of this study, the maternal NOAEL and LOAEL could not be 

determined, and the developmental NOAEL and LOAEL cannot be identified.

The developmental toxicity study in the rabbit is classified Unacceptable/Non-guideline and 

does not satisfy the guideline requirement for a developmental toxicity study (OCSPP 870.3700; 

OECD 414) in the rabbit. 

This DER is a modified version of the Rapporteur Member States (RMS) Summary, Evaluation 

and Assessment of the Data and Information, Ministère de l’Agriculture et de la Pêche, Direction 

Générale de l’Alimentation, France (2007) Draft Assessment Report (DAR), public version, 

Diethofencarb, Volume 3 – Annex B.6, pp. 307-309. Portions of this document were altered by 

the EPA reviewer to reflect Agency policies and conclusions. 

Developmental toxicity study in rabbits. MRID 49267448.

This study is classified as Unacceptable/non-guideline and does not satisfy the guideline 

requirement for a developmental toxicity study in non-rodents (OPPTS 870.3700; OECD 414).

In a developmental toxicity study (MRID 49267448), S-32165 (Diethofencarb; 98.2% a.i.; Batch 

no. PSG 86018) was administered to 16 presumed pregnant New Zealand white rabbits/dose by 
Diethofencarb Human Health Risk Assessment D418227

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gavage in 0.5% aqueous methylcellulose solution, at dose levels of 0, 125, 300, or 750 mg/kg

bw/day (dosing volume 3 mL/kg bw) on gestation days (GDs) 7 through 19, inclusive. On GD

29, does were sacrificed and subjected to caesarean section. Gravid uterine weights and numbers 

of corpora lutea, live and dead fetuses, early and late resorptions, and implantation sites were 

recorded. All fetuses were given a gross external examination, weighed, sexed, and subjected to 

visceral and skeletal examinations. Heads of one half of the live fetuses were cut (mid-coronal 

slice) for examination of eyes, ears, palate, nasal septum, and brain. This study was a repeat of 

earlier study (MRID 49267447) in which the pregnancy rate was low. The two studies were 

discussed and interpreted together by the notifier (Laboratory report no. HHT-0112, 2001).

There were no treatment-related effects on clinical signs, body weight, or food consumption. 

Single deaths in each of the low- and high-dose groups were not clearly attributable to exposure 

to the test material or to gavage error. A treatment-related increased incidence of total litter 

resorptions in the high-dose group is considered both a maternal effect and a developmental 

effect; at caesarean section, total litter resorptions were seen in 1/14, 1/12, 2/14, and 6/15 of the 

pregnant does in the control, low-, mid-, and high-dose groups, respectively.

No dead fetuses were observed, and there were no treatment-related effects on fetal weight, fetal 

sex ratios, or live litter sizes in the litters that were not totally resorbed. The total litter 

resorptions of 6/15 high-dose litters resulted in increased mean post-implantation loss for this 

group (45% vs. 20% for controls). This reflected greater numbers of resorptions per dam in the 

dams with total litter resorptions: the six affected high-dose dams had an average of 3.3 

resorptions (range: 1-8) compared to 1, 2, and 1.5 in the control, low-, and high-dose groups, 

respectively. In the affected animals, all of the resorptions were early resorptions, and in one 

dam from each of the mid- and high-dose groups, the corpora lutea appeared to have completely 

regressed. A total of 82 (13), 56 (11), 77 (12), and 60 (9) fetuses (and litters) were evaluated in 

the control, low-, mid-, and high-dose groups, respectively. Fused frontal bones (an uncommon 

malformation) were observed in 0 (0), 0 (0), 1 (1), and 3 (3) fetuses (and litters) in these same 

respective groups. Because this finding is considered uncommon, it is considered treatmentrelated and adverse despite the low incidence. The overall incidence of external, visceral, and/or 

skeletal malformations and/or variations were not affected by treatment.

There was a 20% frequency in post-implantation loss in the controls, which is unacceptably high, 

suggesting other unknown factors are in play which make data evaluation and interpretation 

difficult. In addition, the number of litters drops to nine in the high-dose group, which is 

unacceptably low even for the guidelines extant in 1987 (when the study was conducted) which 

required a minimum of 12 animals.

Therefore, under the conditions of this study, the maternal NOAEL and LOAEL are not 

determined, and the developmental LOAEL and NOAEL are not determined.

This study is classified as Unacceptable/Non-guideline and does not satisfy the guideline 

requirement for a pre-natal development toxicity study OCSPP 870.3700b [§83-3b]; OECD 

414} in rabbits.

This Data Evaluation Record is a modified version of the Rapporteur Member States (RMS) 

Summary, Evaluation and Assessment of the Data and Information, Ministère de l’Agriculture et 

de la Pêche, Direction Générale de l’Alimentation, France (2007) Draft Assessment Report 
Diethofencarb Human Health Risk Assessment D418227

Page 30 of 49

(DAR), public version, Diethofencarb, Volume 3 – Annex B.6, pp. 309-312. The EPA reviewer 

may have altered portions of this document to reflect Agency policies and conclusions.

Developmental toxicity study in rabbits. MRID 49267449.

This study is classified as Acceptable/non-guideline and satisfies the guideline requirement for a 

developmental toxicity study in non-rodents (OPPTS 870.3700; OECD 414).

In a developmental toxicity study (MRID 49267449), S-32165 (98.7% a.i., Lot # S-7509-TG)

was administered to 25-26 New Zealand White rabbits/dose by gavage at dose levels of 0, 800, 

or 900 mg/kg bw/day from days 7 through 28 of gestation. On gestation day (GD) 29, the 

females were sacrificed and fetuses removed by cesarean section. The evaluated parameters 

included clinical signs, mortality, body weight, body weight gain, food consumption, embryofetal death, fetal growth, and fetal malformations.

One animal at 900 mg/kg bw/day died on GD 22 and another delivered a litter before GD 29. At 

800 and 900 mg/kg bw/day, two and seven females, respectively, aborted during GD 22-27. 

Decreased feces and/or urine were observed at a higher frequency in treated animals. Body 

weights in both treatment groups were significantly decreased by 3-8% (p<0.05, p<0.01), and 

food consumption decreased by 10-53% (p<0.05, p<0.01). No differences were observed in 

cesarean parameters. No gross lesions were observed in animals that survived to scheduled 

necropsy. While the decreases in body weight were minimal and are not normally considered 

adverse, the decreased food consumption is considered to have led to decreased body weights 

and malnutrition, in turn leading to an increased incidence of aborted litters. The maternal 

LOAEL was 800 mg/kg bw/day, increased late-term abortions. The maternal NOAEL was 

not established.

There were no treatment-related effects in developmental parameters such as growth, 

developmental variations or malformations. Late-term abortions were increased at 900 mg/kg 

bw/day. However, the two dose levels are close and considered NOT to be biologically 

different. The developmental LOAEL was 800 mg/kg bw/day based on increased late-term 

abortions. The developmental NOAEL not established.

The developmental toxicity study in the rabbit is classified Acceptable/non-guideline and 

nevertheless satisfies the guideline requirement for a developmental toxicity study (OCSPP 

870.3700; OECD 414) in rabbits.

This Data Evaluation Record is a modified version of the Rapporteur Member States (RMS) 

Summary, Evaluation and Assessment of the Data and Information, Ministère de l’Agriculture et 

de la Pêche, Direction Générale de l’Alimentation, France (2007) Draft Assessment Report 

(DAR), public version, Diethofencarb, Volume 3 – Annex B.6. Portions of this document were

altered by the EPA reviewer to reflect Agency policies and conclusions.

870.3800 Reproduction and Fertility Effects

2-Generation reproduction study in rats. MRID 49267451.

This study is classified as acceptable/guideline and satisfied the guideline requirements (OPPTS 

870.3800; OECD N0. 416) for a multi-generation reproduction and fertility study.
Diethofencarb Human Health Risk Assessment D418227

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In a two-generation reproduction study (MRID 49267451) S-32165 (Diethofencarb; batch No.: 

PKG 84093, purity: 97.2%; batch No.: PEG 85045, purity: 98.1%; and batch No.: PSG 86018, 

purity: 98.2%) was administered to groups of 26 CD rats/sex/dose in the diet at concentrations of 

0, 200, 1000, or 5000 ppm. Pre-mating doses were respectively as follows: 0, 13.1, 65.5, or 328 

mg/kg bw/day in F0 males; 0, 16.0, 88.0, or 427 mg/kg bw/day in F0 females; 0, 16.6, 84.8, or

420 mg/kg bw/day in F1 males; and 0, 19.4, 105, or 510 mg/kg bw/day in F1 females. F0 and F1 

parental animals were administered the treated or control diets for at least 14 weeks prior to 

mating, during mating, and either throughout gestation, and lactation, and until necropsy after 

weaning of litters (females) or until pups were born (males). One litter was produced by each 

generation.

F0 males treated at 5000 ppm had a small but statistically significant decrease in absolute body 

weight (-7% at week 10). In the 5000-ppm males and females of the F1 generation, statistically 

significant decreases in body weight were also seen during pre-mating weeks 0-10 and/or 0-14 

but were of biologically insignificant magnitude (males: -7%; females: -4% to -7%). At 5000 

ppm, relative and/or absolute liver weights were significantly increased in both sexes and 

generations, as follows (for absolute/relative weights): F0 males, +19%/+26%; F0 females, 

+7%/+13%; F1 males, +12%/+18%; and F1 females, +12%/+16%. However there were no 

histopathological lesions in the liver. Therefore, the parental systemic NOAEL is 5000 ppm 

(328 mg/kg bw/day in males and 427 mg/kg bw/day in females). The parental systemic 

LOAEL was not established. 

Statistically significant (p<0.05) lower body weights were recorded in F2 pups at 5000 ppm; 

absolute body weights were 10% / 15% lower in males / females at day 4, respectively, 11% 

lower in males / females at day 14, and 15% / 13% lower in males / females at day 21, 

respectively, compared with controls. Although this effect was only present in one generation, 

it was considered to be biologically relevant. The offspring LOAEL is 5000 ppm (328 mg/kg 

bw/day in males and 427 mg/kg bw/day in females), based on decreased absolute body 

weights in F2 offspring of both sexes during lactation. The offspring NOAEL is 1000 ppm 

(65.5 mg/kg bw/day in males and 88.0 mg/kg bw/day in females). 

No evidence of reproductive toxicity was observed. The reproductive LOAEL is therefore 

unidentified, and the reproductive NOAEL is greater than or equal to 5000 ppm (328 

mg/kg bw/day in males and 427 mg/kg bw/day in females). 

This study is Acceptable/Guideline and satisfies the guideline requirement for a two-generation 

reproductive study (OCSPP 870.3800; OECD 416) in the rat.

This Data Evaluation Record is a modified version of the Rapporteur Member States (RMS) 

Summary, Evaluation and Assessment of the Data and Information, Ministère de l’Agriculture et 

de la Pêche, Direction Générale de l’Alimentation, France (2007) Draft Assessment Report 

(DAR), public version, Diethofencarb, Volume 3 – Annex B.6, pp. 309-312. Portions of this 

document were altered by the EPA reviewer to reflect Agency policies and conclusions.

870.4100b Chronic Toxicity — Dog

One-year oral toxicity study in dogs. MRID 49267452.
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This chronic oral toxicity study in the dog is Acceptable/Guideline and satisfies the guideline 

requirement for a chronic oral toxicity study (OCSPP 870.4100b; OECD 452) in a non-rodent 

species.

In a chronic study (MRID 49267452), groups of Beagle dogs (6/sex/group) were administered 

Diethofencarb daily via capsule at dose levels of 0, 10, 50, 250, and 1000 mg/kg/day for 52 

weeks. Mortality, clinical signs, body weight, and food consumption were recorded. Samples of 

blood and urine were collected for clinical pathology evaluation prior to study initiation and on 

weeks 13, 26, 39, and 52. At study termination, all animals were sacrificed and subjected to 

gross necropsy. Selected organs were weighed and a standard range of organs and tissues were 

removed, fixed, and examined microscopically. 

Both sexes at 1000 mg/kg/day and 250 mg/kg/day had increased frequency of emesis, increased 

absolute and relative liver weights, dark livers (increased liver pigment observed histologically), 

and hepatocellular enlargement. In males, body weights were decreased >10% (up to 23%) 

beginning at week 13 in the 250 and 1000 mg/kg/day groups. While these decreases reached 

statistical significance only at 1000 mg/kg/day (p<0.05, on week 13), the decreases were 

considered treatment related and adverse. Increased salivation and emesis were observed in both 

sexes at 1000 mg/kg/day. A statistically significant decrease (p<0.05) in absolute and relative 

uterine weights was observed at 1000 mg/kg/day. While a clear dose-response relationship could 

not be established at lower dose levels, this finding is considered biologically relevant because it 

is more severe in magnitude than at any other dose level, and is statistically significant. No 

treatment-related biological effects were observed at 10 mg/kg/day or 50 mg/kg/day. The 

increased incidence of emesis in the presence of decreased body weights and food consumption 

in males was considered adverse. 

Therefore, the LOAEL in males for this study is 250 mg/kg/day based on increased emesis 

and decreased body weights; the NOAEL in males is 50 mg/kg/day. In females the LOAEL 

is 1000 mg/kg/day based on decreased absolute and relative uterine weights and the 

NOAEL is 250 mg/kg/day.

This chronic toxicity study in dogs is Acceptable/Guideline and satisfies the requirements of 

Guideline OCSPP 870.4100 (OECD 452). Disclaimer

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, p. 259 

(2007). Portions of this document were altered by the EPA reviewer to reflect EPA policies and 

conclusions.

870.4200b Carcinogenicity (feeding) — Mouse

Mouse carcinogenicity study. MRID 49267453

This study is classified as Acceptable/guideline, and satisfies the guideline requirements 

(OSCPP 870.4200b; OECD 451) for a carcinogenicity study in the mouse.

In a mouse carcinogenicity study (MRID 49267453) Five groups of 75 Crl:CD-1(ICR)BR 

mice/sex/group were administered Diethofencarb (98.1% a.i., Lot Numbers PEG 85045 and PEG 

86018) in the diet at 0, 10, 100, 1000, or 10,000 ppm (equivalent to 0, 1.63, 16.47, 163.8, or 

1682 mg/kg/day in males; 0, 2.03, 20.53, 202.9, or 2108 mg/kg/day in females) for 78 weeks 
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with interim sacrifices of 10/sex/group at 13 weeks and 15/sex/group at 52 weeks. Mortality, 

clinical signs, body weight, and food and water consumption were recorded. Differential 

leukocyte counts and cell morphology were conducted on blood from all surviving animals after 

52 and 78 weeks of treatment. Gross necropsies, organ weights, and microscopic examination of 

tissues were performed on decedents and on those sacrificed on schedule. 

Females at 10,000 ppm had a significantly lower survival rate relative to controls at 78 weeks (-

33%, p<0.05). The incidence of hepatocellular hyperplasia in high dose males was significantly 

higher (+18%, p<0.05) relative to controls. 

Under the conditions of this study, the systemic LOAEL for Diethofencarb in CD-1 mice was 

10000 ppm in the diet in males (1682 mg/kg/day) based on increased incidence of 

hepatocellular hyperplasia, and 10000 ppm in females (2108 mg/kg/day) based on reduced 

survival. The NOAEL was 1000 ppm in males and females (163.8 and 202.9 mg/kg/day, 

respectively).

At the doses tested, there was not a treatment-related increase in tumor incidence when 

compared to controls. Dosing was considered adequate to assess carcinogenicity based on 

hepatocellular hyperplasia observed in males at 1682 mg/kg/day), and reduced survival in 

females at 2108 mg/kg/day. Dosing was also considered adequate because administered dose 

levels exceeded the limit dose.

This carcinogenicity study in mice is Acceptable/Guideline and satisfies the guideline 

requirements for a cancer study (OCSPP 870.4200b [§83-2b]; OECD 451) in the mouse.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, p. 288 

(2007). Portions of this document were altered by the EPA reviewer to reflect EPA policies and 

conclusions.

870.4300 Combined Chronic Toxicity/Oncogenicity (feeding) — Rat

Rat chronic/oncogenicity study. MRID 49267454

This study is classified as Acceptable/guideline, and satisfies the guideline requirements 

(OSCPP 870.4300; OECD 453) for a chronic/oncogenicity study in the rat.

In a rat chronic/oncogenicity study (MRID 49267454) five groups of 80 Crl:CD®(SD)BR 

rats/sex/group were administered Diethofencarb (Batch Nos. PKG 84093, PEG 85045, PSG 

86018) in the diet at 0, 40, 200, 1000, or 5000 ppm (equivalent to 0, 1.69, 8.42, 42.70, or 220.30 

mg/kg/day in males; 0, 2.18, 10.90, 54.50, or 288.19 mg/kg/day in females) for 104 weeks with 

interim sacrifices of 10/sex/group at 52 weeks and 20/sex/group at 104 weeks. Mortality, clinical 

signs, body weight, and food and water consumption were recorded. Samples of blood and urine 

were collected for clinical pathology evaluation, including cholinesterase activities in plasma and 

red blood cells, at weeks 13, 26, 52, 78, and 104. Brain tissue for cholinesterase determination 

was collected at weeks 52 and 104. Gross necropsies, organ weights, and microscopic 

examination of tissues were performed on decedents and on those sacrificed on schedule. 

Food conversion efficiency was lower in both sexes at the high dose and water consumption was 

also lower for females. Platelet counts and cholesterol levels were elevated in high dose females. 
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However, the elevated platelet counts were within the range of historical control and are not 

considered adverse; the elevated cholesterol was not considered adverse in the absence of 

corroborating effects such as changes in liver weight or liver histopathology.

There was a significantly higher incidence of thyroid follicular tumors in both sexes at 5000 ppm 

relative to controls. (220.3 mg/kg/day and 288.19 mg/kg/day in males and females, respectively, 

as evidenced by a treatment-related increase in thyroid follicular cell tumor incidence 

(carcinomas in males, adenomas in females). The NOAEL for this study was 5000ppm (220 

mg/kg/day in males, 288 mg/kg/day in females), the highest dose level test. The LOAEL 

was not established because there were insufficient indicators of non-neoplastic toxicity at 

the dose levels tested.

Dosing was considered adequate to assess carcinogenic potential based on the presence of 

treatment-related thyroid tumors at 5000ppm (220 mg/kg/day in males, 288 mg/kg/day in 

females).

This study in rats is classified as Acceptable/Guideline and meets the guideline requirements for 

a combined chronic Toxicity/Oncogenicity study in the rat [OCSPP 870.4300; OECD 453].

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, p. 284 

(2007). Portions of this document were altered by the EPA reviewer to reflect EPA policies and 

conclusions.

870.5100 Bacterial reverse mutation test

In vitro Bacterial Gene Mutation (MRID 49067456)

This mutagenicity study is classified as acceptable/guideline and satisfies the requirement for 

Test Guideline OCSPP 870.51001; OECD 471 for in vitro mutagenicity (bacterial reverse gene 

mutation) data.

In a reverse gene mutation assay in bacteria (MRID 49267456), S. typhimurium strains TA98, 

TA100, TA1535, and TA1537, TA1538 and E. coli strain WP2 uvrA were exposed to 

diethofencarb (97.4% a.i., batch number PK-84042) dissolved in dimethylsulfoxide (DMSO) in 

two independent assays using the pre-incubation method and duplicate plating. These 

mutagenesis assays were preceded by a range-finding assay performed at concentrations ranging 

from 10 through 5000 μg/plate. Both mutagenesis assays tested concentrations of 0, 5, 10, 50, 

100, 500, and 1000 μg/plate, with and without S9-mix. The S9 fraction was obtained from 

polychlorinated biphenyl (PCB)-induced male Sprague-Dawley rat liver.

The test article, diethofencarb, was tested up to, but not exceeding, the limit at which the 

presence of precipitate was expected to seriously interfere with the counting of revertant 

colonies, both in the absence and presence of S9 mix, based on findings in the range-finding test. 

At higher concentrations the precipitate precluded the counting of revertant colonies. No 

cytotoxicity was seen in the range-finding assay. Also, no cytotoxicity was observed in the two 

mutagenesis assays. There was no mention of a precipitate in the mutagenesis assays. The 

number of revertants per plate was not increased over the concurrent solvent control value at any 

test material concentration, with or without S9-mix, in any tester strain. The solvent and positive 
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controls induced the appropriate responses in the corresponding strains. There was no evidence 

of induced mutant colonies over background.

This study is classified as acceptable/guideline and satisfies the requirement for Test Guideline 

OCSPP 870.51001; OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, pp. 267-269 

(2007). Portions of this document were altered by the EPA reviewer to reflect Agency policies 

and conclusions.

In vitro Bacterial Gene Mutation (MRID 49067457)

This mutagenicity study is classified as acceptable/guideline and satisfies the requirement for 

Test Guideline OCSPP 870.51001; OECD 471 for in vitro mutagenicity (bacterial reverse gene 

mutation) data.

In a reverse gene mutation assay in bacteria (MRID 49267457), S. typhimurium strains TA98, 

TA100, TA1535, and TA1537, TA1538 and E. coli strain WP2 uvrA were exposed to 

diethofencarb (98.2% a.i., batch number PSG-86018) dissolved in dimethylsulfoxide (DMSO) in 

two independent assays using the pre-incubation method and duplicate plating. These 

mutagenesis assays were preceded by a range-finding assay performed at concentrations ranging 

from 15 through 5000 μg/plate. Both mutagenesis assays tested concentrations of 0, 50, 100, 

200, 500, 1000 and 2000 μg/plate, with and without S9-mix. The S9 fraction was obtained from 

polychlorinated biphenyl (PCB)-induced male Sprague-Dawley rat liver.

Based on findings in the range-finding test, the test article, diethofencarb, was tested up to and, 

in some cases, beyond the limit at which the presence of precipitate was expected to seriously 

interfere with the counting of revertant colonies, both in the absence and presence of S9 mix. At 

higher concentrations, the precipitate precluded the counting of revertant colonies. No 

cytotoxicity was seen in the range-finding assay. Also, no cytotoxicity was observed in the two 

mutagenesis assays. In the mutagenesis assays, a precipitate was observed at 1000 and 2000 

μg/plate both in the presence and absence of S9-mix. The precipitate was so heavy at the 

concentration of 2000 μg/plate with S9-mix that it was impossible to count the colonies. The 

number of revertants per plate was not increased over the concurrent solvent control value at any 

test material concentration, with or without S9-mix, in any tester strain. The solvent and positive 

controls induced the appropriate responses in the corresponding strains. There was no evidence 

of induced mutant colonies over background.

This study is classified as acceptable/guideline and satisfies the requirement for Test Guideline 

OCSPP 870.51001; OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, pp. 269-271 

(2007). Portions of this document were altered by the EPA reviewer to reflect Agency policies 

and conclusions.

870.5300 In vitro mammalian cell gene mutation test
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In Vitro Mammalian Cells in Culture Gene Mutation Assay in Chinese Hamster V79 Lung Cells

(MRID 49067458)

This study is classified as acceptable/guideline and satisfies the guideline requirement for Test 

Guideline OCSPP 870.5300, OECD 476 for in vitro mutagenicity (mammalian forward gene 

mutation) data.

In a mammalian cell gene mutation assay at the hypoxanthine-guanine phosphoribosyl 

transferase (HGPRT) locus (MRID 49267458), Chinese hamster lung V79 cells cultured in vitro

were exposed to technical diethofencarb (98.2% a.i., batch PSG-86018) dissolved in dimethyl 

sulfoxide (DMSO) for 5 hours at concentrations of 0, 20, 50, 100, or 200 μg/mL in three 

independent experiments in the absence of metabolic activation and in two independent 

experiments in the presence of metabolic activation. These concentrations were chosen based on 

the results of a range-finding assay that tested concentrations of the test article of 0, 5, 10, 20, 50, 

100, 200, and 500 μg/mL in the absence and presence of metabolic activation in exposures that 

lasted 5 hours. Mammalian metabolic activation was achieved using the S9 fraction obtained 

from polychlorinated biphenyl (PCB)-induced male Sprague-Dawley rat liver.

In the range-finding assay, the test article induced only slight cytotoxicity, with relative survival 

ranging from 71 through 96% of that of the solvent control at the four highest concentrations 

tested without and with metabolic activation. A precipitate was observed at concentrations of 200 

and 500 μg/mL in the absence and presence of metabolic activation. In all mutagenesis assays, 

the test substance was tested to above the limit of solubility. The positive controls induced the 

appropriate responses. Although the first mutagenesis assay in the absence of S9-mix suggested 

that mutations were induced at the maximum concentration tested, two repeat experiments in the 

absence of S9-mix provided no indication of mutation induction. Neither mutagenesis assay in 

the presence of S9-mix provided any suggestion of mutation induction. There was no evidence 

of induced mutant colonies over background.

This study is classified as acceptable/guideline and satisfies the guideline requirement for Test 

Guideline OCSPP 870.5300, OECD 476 for in vitro mutagenicity (mammalian forward gene 

mutation) data.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, pp. 271-273 

(2007). Portions of this document were altered by the EPA reviewer to reflect Agency policies 

and conclusions.

870.5375 In vitro mammalian chromosome aberration test

In vitro Mammalian Cytogenetics: Chromosome Aberration Assay Using Chinese Hamster 

Ovary Cells (MRID 49267459)

This study is classified as Acceptable/guideline, and satisfies the guideline requirement for Test 

Guideline OCSPP 870.5375; OECD 473 for in vitro cytogenetic mutagenicity data.

In an in vitro mammalian cell chromosome aberration assay (MRID 49267459), Chinese hamster 

ovary cells were exposed to Diethofencarb, (97.4% a.i., Lot No. PK-84042) in a range-finding 

test, for 48 h without S9 activation and for 6 h with activation, at concentrations ranging from 
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10-6to 10-2 M (0.27-2673.20 μg/mL). Based on the range-finding test, in the definitive test, 

without S9, the concentrations were 5x10-5, 10-4, 2x10-4, and 5x10-4 M, i.e. respectively, 13.37, 

26.73, 53.46 or 133.66 μg/mL. The exposures were for 24 and 48 h with no recovery period. In 

the presence of S9 activation, the concentrations were 10-4, 2x10-4, 5x10-4, and 10-3 M, i.e.

respectively, 26.73, 53.46, 133.66 or 267.32 μg/mL. The exposures were for 6 h with an 18 h 

recovery period. S9 came from male Sprague-Dawley rats induced with polychlorinated 

biphenyls (PCB).

Diethofencarb was tested up to a maximum concentration of 133.66 μg/mL (limit of 

cytotoxicity) in the absence of S9 mix and up to 267.32 μg/mL (limit of solubility) in the

presence of S9 mix. No increase in the frequencies of polyploid metaphases was found after 

treatment with the test article, without or with activation. All of the positive controls gave 

appropriate responses, without and with activation, as did the concurrent negative controls. No

historical laboratory positive or negative control data were reported. There was no evidence of 

chromosome aberrations induced over background.

This study is classified as Acceptable/Guideline, and satisfies the guideline requirement for Test 

Guideline OCSPP 870.5375; OECD 473 for in vitro cytogenetic mutagenicity data. Only 100 

metaphases were scored instead of the required 200, but acceptable positive control data were 

available and the concentrations of test substance reached the limits of cytotoxicity and 

solubility, so the results of the tests are not considered to be compromised.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B, part B.6 

Toxicology and metabolism, pp. 273-276 (2007). Portions of this document were altered by the 

EPA reviewer to reflect Agency policies and conclusions.

870.5395 Mammalian erythrocyte micronucleus test

In vivo Mammalian Cytogenetics – Mouse Erythrocyte Micronucleus assay (MRID 49267460)

This study is classified as acceptable/non-guideline and does not satisfy the guideline 

requirement for Test Guideline OCSPP 870.5395; OECD 474 for in vivo cytogenetic 

mutagenicity data.

In an ICR mouse bone marrow micronucleus assay (MRID 49267460), 6 male mice/group were 

each given a single intraperitoneal (i.p.) injection of diethofencarb (test article S-32165, purity 

97.4 %, Lot No. PK84042) in corn oil. Two independent studies were conducted: a time-course 

study and a dose-response study. In the time-course study, three groups of mice received a dose 

of 5000 mg/kg (guideline limit dose is 2000 mg/kg). Six animals were sacrificed at 24, 48 and 72 

h after treatment. Two additional groups of 6 mice apiece were treated with the vehicle only (20 

mL/kg) as a negative control, or with cyclophosphamide as a positive control (80 mg/kg bw). In 

the dose-response study, three groups of mice were treated with diethofencarb at dose-levels of 

1250, 2500 or 5000 mg/kg. Two additional groups of 6 mice apiece were treated with the vehicle 

only (20 mL/kg) as a negative control, or with 9,10-dimethyl-1,2-benzanthracene (DMBA) at a 

dose of 50 mg/kg bw. All animals were sacrificed 48 h after treatment.

In the dose-response study, the test article produced small, but statistically significant, decreases 

in the polychromatic erythrocytes (PCEs), which were also dose-related. The time-course studies

at 48 and 72 h also showed reductions in the PCEs. This was an indication that these treatments
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caused moderate bone marrow cell toxicity. Administration of the positive control chemicals in 

both studies resulted in significantly higher numbers of micronucleated-PCEs compared with the 

corresponding vehicle controls, demonstrating the validity of the assay. At the doses tested, 

there were no significant increases in the frequencies of micronucleated polychromatic 

erythrocytes in bone marrow after any treatment time or dose level. Note: The guideline

calls for testing both male and female animals unless there is data that show no sex differences 

exist in toxicity to the test article. No data was presented in this study to justify the exclusion of 

female mice.

This study is classified as acceptable/non-guideline and does not satisfy the guideline 

requirement for Test Guideline OCSPP 870.5395; OECD 474 for in vivo cytogenetic 

mutagenicity data, because no data were presented to justify the exclusion of female mice. The 

study can be upgraded to guideline if data can be presented that show that no sex differences 

exist in the toxicity of diethofencarb in mice.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B, part B.6 

Toxicology and metabolism, pp. 280-282 (2007). Portions of this document were altered by the 

EPA reviewer to reflect Agency policies and conclusions.

870.5550 Unscheduled DNA synthesis in mammalian cells in culture

Unscheduled DNA Synthesis in Primary Rat Hepatocytes/Mammalian Cell Cultures (MRID 

49267461)

This study is classified as unacceptable/guideline and does not satisfy the guideline requirement 

for Test Guideline OCSPP 870.5550; OECD 482/486 for other genotoxic mutagenicity data.

In an unscheduled DNA synthesis (UDS) assay (MRID 49267461), primary hepatocyte cultures 

from male Fischer 344 rats were exposed in vitro to diethofencarb (98.2% a.i., Lot # PSG86018), dissolved in DMSO, at concentrations of 0, 0.507, 1.01, 2.53, 5.07, 10.1, or 25.3 μg/mL 

for 21.3 h in assay 1 and at concentrations of 0, 6.32, 12.6, 25.3, 50.6, 101, or 202 μg/mL for 

19.0 h in assay 2.

Diethofencarb was tested up to cytotoxic concentrations (64.5% survival at 25.3 μg/mL and 

67.7% survival at 202 μg/mL) in assays 1 and 2, respectively. In assay 2, the cytotoxicity was 

much weaker: at 50.6 μg/mL, the relative survival was unaffected (97%) while the same 

concentration was found to be highly cytotoxic in assay 1. In a similar manner, the cytotoxicity 

at 25.3 μg/mL was about 35% less in assay 2 (relative survival of 99.5%) than in assay 1 

(relative survival of 64.5 %). Overall, there was an approximately 8-fold difference in sensitivity 

to cytotoxicity between the cells used in assays 1 and 2, with the same relative survival being 

observed at 25.3 μg/mL in assay 1 and at 202 μg/mL in assay 2. None of the treatments with 

diethofencarb caused nuclear labeling to differ significantly from the solvent control. However, 

both assays showed a non-statistically-significant increase in the mean net nuclear grain counts 

at the highest concentration level and, for both assays, the average percent of nuclei having five 

or more net grains is two times higher at the highest concentration level than at the next lower 

concentration level (for assay 1, these concentrations were 25.3 μg/mL and 10.1 μg/mL, 

respectively, and for assay 2, they were 202 μg/mL and 101 μg/mL, respectively). These results 

are not considered reliable, and the suggested negative result must be confirmed by another study 

(preferably done in vivo). The positive control elicited the expected nuclear labeling. There was
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no evidence that unscheduled DNA synthesis, as determined by radioactive tracer 

procedures [nuclear silver grain counts], was induced.

This study is classified as unacceptable/guideline and does not satisfy the guideline requirement 

for Test Guideline OCSPP 870.5550; OECD 482/486 for other genotoxic mutagenicity data. 

Because of strong differences in the cytotoxicity seen in the two assays, because both assays 

showed non-statistically significant increases in the mean net nuclear grain counts at the highest 

concentrations tested, and because the average percentage of nuclei having five or more net 

grains is two times higher at the highest concentration level than the next lower concentration 

level in both assays, the suggested negative results must be confirmed by another study.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B, part B.6 

Toxicology and metabolism, pp. 278-280 (2007). Portions of this document were altered by the 

EPA reviewer to reflect Agency policies and conclusions.

870.5900 In Vitro Sister Chromatid Exchange Assay in mammalian cells in culture

In Vitro Sister Chromatid Exchange Assay in Chinese Hamster Ovary Cells (MRID 49267475)

In a Chinese hamster in vitro sister chromatid exchange (SCE) assay (MRID 49267475), CHOKl cells were exposed to diethofencarb (purity 97.4 %, Lot No. PK-84042) dissolved in DMSO 

and culture medium at concentrations of 0, 0.27, 0.81, 2.67, 8.01, 26.73, 80.19 and 267.32 

μg/mL, without and with activation in the first assay and at concentrations of 0, 26.73, 53.46, 

133.65 and 267.32 μg/mL, without and with activation in the second assay. Exposure was for 2 

hours followed by a 28-hour recovery period. The S9 came from PCB-treated male SpragueDawley rats.

Diethofencarb was tested up to cytotoxic and precipitating concentrations. The positive controls 

induced the appropriate response. There was no evidence of an increase in sister chromatid 

exchanges in CHO-K1 cells induced over background.

This study is classified as acceptable/guideline and satisfies the guideline requirement for Test 

Guideline OCSPP 870.5900; OECD 479 for in vitro cytogenetic mutagenicity data.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B, part B.6 

Toxicology and metabolism, pp. 276-278 (2007). Portions of this document were altered by the 

EPA reviewer to reflect Agency policies and conclusions.

870.6200 Neurotoxicity Battery

Acute Neurotoxicity study – Rat (MRID 49267464 )

This acute neurotoxicity study is classified acceptable/guideline and satisfies the guideline 

requirement for an immunotoxicity study (OCSPP 870.6200a) in the rat.

In an acute neurotoxicity study (MRID 49267464), groups of 10 non-fasted, ~ 6-week-old 

Crl:CD(SD) rats/sex/dose were given a single oral dose of Diethofencarb (99.5% a.i, batch/lot #

S-7509-TG) in 0.5% sodium methylcellulose at doses of 0, 200, 600, or 2000 mg/kg bw and 

observed for 14 days. Neurobehavioral assessment (functional observational battery and motor 
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activity testing) was performed on 10 animals/sex/group prior to initiation of treatment (-1 week) 

and at 6 hours (Day 0), 7 days, and 14 days post dosing. Cholinesterase activity was not 

determined. At study termination, 5 animals/sex/group were euthanized and perfused in situ for 

neuropathological examination. Of the perfused animals, rats from the control and high-dose 

groups were subjected to histopathological evaluation of brain and peripheral nervous system 

tissues. 

Treatment with up to 2000 mg/kg bw of Diethofencarb did not produce any changes in clinical 

signs, mortality, body weight or body weight gain, or gross and neuro-histological findings. 

Treatment with 600 and/or 2000 mg/kg bw produced neurological effects 6 hours post dosing on 

Day 0. In males at 600 and 2000 mg/kg bw, changes included decreased forelimb grip strength 

(474 and 449 g, respectively, vs. 527 g for controls) and reduced body temperature (37.4 and 

37.2°C, respectively, vs. 37.8°C for controls), with males at 2000 mg/kg bw additionally 

exhibiting decreased alertness (9/10 high-dose males affected vs. 1/10 controls). In females at 

2000 mg/kg bw, changes included a slight decrease in muscle tone (8/10 high-dose females 

affected vs. 0/10 for controls) and pupillary reflex (7/10 high-dose females affected vs. 0/10 for 

controls), reduced body temperature (35.8°C compared to 37.9°C for controls), and increased 

landing footsplay (101 mm in high-dose females vs. 86 mm for controls). Although not 

attaining statistical significance, a decrease in alertness was noted during handling in high dose 

females (4/10) compared to controls (1/10). Reductions in motor activity accompanied the 

changes in FOB parameters observed after dosing on Day 0. Overall mean motor activity was 

significantly decreased in males at 600 and 2000 mg/kg bw (532 and 492 counts, respectively, 

vs. 1190 for controls). When viewing the intersession data, males at 600 mg/kg bw had 

significantly reduced activity only over the first interval, while males at 2000 mg/kg bw had 

significantly decreases in motor activity over the first two intervals. In females, a decrease in 

mean motor activity was noted at 2000 mg/kg bw, but the decrease did not attain statistical 

significance. Examination of intersession data revealed a significant decrease in activity only 

over the first interval. 

Observed in this study is a suite of functional observational battery (FOB) effects. These 

included decreased forelimb grip strength, reduced body temperature, and decreased alertness in 

males and decrease in muscle tone and pupillary reflex, reduced body temperature, and increased 

landing footsplay in females. While the FOB effects are slight and individually would not have 

been considered adverse, the suite of effects as a whole are considered adverse and are consistent 

with the effects indicative of a sympathetic nervous system response. This is considered to be a 

conservative call.

The LOAEL in this study is 2000 mg/kg in males and females based on decreased forelimb 

grip strength, reduced body temperature and decreased alertness (M) and decreased 

muscle tone and pupillary reflex, reduced body temperature and increased landing 

footsplay (F). The NOAEL was in males and females is 600 mg/kg bw.

This neurotoxicity study is classified as Acceptable / Guideline and satisfies the guideline 

requirement for an acute neurotoxicity study in rats (OCSPP 870.6200; OECD 424). 

Subchronic Neurotoxicity study – Rat (MRID 49267463)

This subchronic neurotoxicity study is classified acceptable/guideline and satisfies the guideline 

requirement for an immunotoxicity study (OCSPP 870.6200b) in the rat.
Diethofencarb Human Health Risk Assessment D418227

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In a subchronic neurotoxicity study (MRID 49267463), Diethofencarb (99.5% a.i, batch/lot # S7509-TG) was administered daily to 10 Crl:CD(SD) rats/sex/dose in the diet at doses of 0, 1000, 

3000, or 10,000 ppm (equivalent to 0, 56.7, 172, or 571 mg/kg bw/day in males, respectively, 

and 0, 65.4, 194, or 654 mg/kg bw/day in females, respectively) for 13 weeks. Neurobehavioral 

assessment (functional observational battery [FOB] and motor activity testing) was performed on

10 animals/sex/group during pre-exposure and during Weeks 2, 4, 8, and 13. Cholinesterase 

activity was not measured. At study termination, five animals/sex/group were euthanized and 

perfused in situ for neuropathological examination. Of the perfused animals, rats from the 

control and high-dose groups were subjected to histopathological evaluation of brain and 

peripheral nervous system tissues. The rats not selected for neuropathological examination were 

sacrificed and discarded.

Treatment of rats with 1000 or 3000 ppm of Diethofencarb did not produce any changes in 

clinical signs, mortality, body weight or body weight gain, food consumption, FOB parameters, 

motor activity, or gross or neuro-histological findings. The only death occurred in one male 

from the 3000 ppm group before the commencement of dosing and therefore was not related to 

treatment. 

Treatment with 10,000 ppm Diethofencarb produced minimal changes. Females had reductions 

in body weight gain over the intervals assessed by the reviewer (Weeks 0-1 and 0-13; 83 and 

84% of controls, respectively) but absolute body weight remained comparable to controls. No 

significant changes in absolute body weight or body weight gain were noted in males. Food 

consumption was unaffected in males and females. No other changes in FOB parameters were 

observed in males or females at any other time point. No changes in motor activity or gross or 

neuropathological findings were noted. 

The NOAEL in males and females was 10,000ppm (571 and 654 mg/kg bw/day, 

respectively), and the LOAEL was not established.

This neurotoxicity study is classified as Acceptable / Guideline and satisfies the guideline 

requirement for a subchronic neurotoxicity study in rats (OCSPP 870.6200; OECD 424).

870.7485 Metabolism — Rat

Absorption, distribution, metabolism, and elimination study in rats. MRIDs 49267467 –

49267471. This metabolism study in the rat is classified Acceptable / Guideline and satisfies 

the guideline requirement for a metabolism study [OCSPP 870.7485, OECD 417] in the rat.

In a series of metabolism studies (MRIDs 49267467 – 49267471), [Phenyl14C] Diethofencarb

(Unlabeled Lot No. PK-84042, purity ~98%, Radiolabeled: [Phenyl14C]Diethofencarb, Batch 

No. C-84-127, radiochemical purity >99%, specific activity 30.1 mCi/mmol used in MRIDs 

49267467and 49267468). (Unlabeled Batch No. S0518G, purity 98.2%, Radiolabeled: [Phenyl14C]Diethofencarb, Batch No. CFQ12311, radiochemical purity >99.2%, specific activity 

9.6MBq/mg used in MRIDs 49267469, 49267470) was administered to groups of male or female 

rats at doses of 10 or 300 mg/kg bw as a single or two-day dose. In an addition, male rats were 

treated with a 10 mg/kg bw/day unlabeled test material for 14 days followed by a single 
Diethofencarb Human Health Risk Assessment D418227

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radiolabeled dose of the test material. Absorption, tissue distribution, metabolism and excretion 

of the test material were monitored. 

The studies indicate that oral absorption was rapid and extensive; with 87 – 95% being 

eliminated in the urine and feces, and absorption was not saturated at doses up to 300 mg/kg 

bw/day or by multiple low dose exposures. No sex-related effects on absorption were found. 

The blood and tissue Tmax was ~0.5 hours and was independent of sex or dose in one study and 

was ≤ 1 hour in another. 

Organ/tissue radioactivity was very low 7 days after treatment; the highest total radioactivity 

residue after a 10 mg/kg bw dose was in the liver (0.05-0.08 μg equivalent/g), adrenals (0.02-

0.04 μg equivalent/g), whole blood, blood cells and kidney (each 0.01-0.02 μg equivalent/g) and 

skin (0.01 μg equivalent/g). Based on these results and the rapidly decreasing fat/blood 

radioactivity ratio (1.07 at 1 hour down to 0.36 at 24 hours), Diethofencarb was not bioaccumulated. 

Diethofencarb was extensively bio-transformed into many metabolites, irrespective of dose or 

pretreatment, recovered in the urine. The primary metabolites were identified as: (4-OH-DFC 

sulfate (~49% administered dose); 4-OH-DFC glucuronide (6-16% administered dose); 3-OEt-4-

OH-AA sulfate (10-17% administered dose); 3-OEt-4-OH-AA glucuronide (2-3% administered 

dose); sulfate and/or glucuronide conjugates of 3-OEt-4-OACA-AA (3% administered dose), and 

an unknown metabolite that comprised 3% of the administered dose. Numerous minor metabolites were also present with each contributing <1% of the administered dose. In the feces, 

numerous metabolites were identified with the unconjugated metabolite 4-OH-DFC comprising 

2-4% of the administered dose being in the highest concentration. 

Based on these results, the major metabolic routes involved: 1) de-ethylation of the 4-ethoxy 

group; 2) cleavage of the carbamate linkage; 3) acetylation of the resultant amino group; and 4) 

conjugation of the resultant phenols with sulfuric acid and/or glucuronic acid. Additional minor 

metabolic routes were: 1) oxidation of the isopropyl group; 2) cyclization of the oxidized 

isopropyl carbamate group; 3) oxidation of the 4-ethoxy group; 4) conjugation of the phenols 

with glutathione; 5) γ-glutamyltranspeptidation and depeptidation of glutathione to form the

cysteine conjugate (4-OH-5-Cys-DFC was not detected); 6) N- acetylation of the cysteine; 7) 

cleavage of C-S linkage of the cysteine followed by methylation; and 8) oxidation of the Smethyl group. A minor metabolite, 3,4-OEt-6-OH-AA, was detected and may be produced by 

cleavage of the carbamate linkage followed by oxidation of C-6 position of the phenyl ring. 

Excretion was rapid; being 93-100% of the administered dose by day 2 and was independent of 

sex, dose, and pre-treatment. Most of the radiolabel was eliminated in the urine (≥80%) with the 

remainder eliminated in the feces. The short tissue distribution times and very short retained 

fractions on day 7 (<0.2% of the administered dose) do not suggest the metabolites undergo

extensive enterohepatic recirculation. 

This metabolism study in the rat is classified Acceptable/Guideline and satisfies the guideline 

requirements for a metabolism study [OCSPP 870.7485, OECD 417] in the rat. Biliary or IV 

studies should have been conducted to determine the contribution of liver or intestinal microflora 

metabolites recovered in the feces, as well as whether cleavage of the isopropyl linkage of the 

test material described in a report, but data not provided to the Reviewer, was the result of an 

isotopic effect or metabolism. 
Diethofencarb Human Health Risk Assessment D418227

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Portions of this Data Evaluation Record is a modified version of the Ministere de l’Agriculture et 

de la Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6, (2007). 

Portions of this document were altered by the EPA reviewer to reflect Agency policies and 

conclusions.

870.7800 Immunotoxicity

28-Day Immunotoxicity study – mouse (MRID 49267472 )

This immunotoxicity study is classified acceptable/guideline and satisfies the guideline 

requirement for an immunotoxicity study (OCSPP 870.7800) in mice. 

In an immunotoxicity study (MRID 49267472), Diethofencarb (99.5% a.i., Lot No. S-7509-TG)

was administered to groups of 10 female Sprague Dawley rats in the diet at concentrations of 0, 

1000, 3000, or 10,000 ppm (equivalent to 0, 79.6, 236, or 764 mg/kg bw/day) for 28 days. A 

concurrent positive control group of 8 female rats was fed the basal diet for 28 days, and received Cyclophosphamide (CPS), 10 mg/kg bw/day, on Days 23 – 27 by oral gavage. Six days 

before scheduled sacrifice, all rats were immunized with a single 0.5 mL IV injection of 2 × 108

sheep red blood cells (SRBC) into the tail vein. 

One rat in the low-dose group was found moribund unrelated to treatment and euthanized in 

extremis on study day 14. No clinical signs of toxicity were found from the remaining rats and 

all other rats survived to scheduled sacrifice. The body weight of high-dose rats was statistically 

decreased ~8% on study days 21 – 28, which was not sufficient to be to be considered 

biologically significant. In addition, food consumption was ≥ 1 g/rat/day lower for high-dose 

rats and was statistically decreased during Weeks 1 and 3. No decreases in body weight, or food 

consumption were found in lower dose rats or rats receiving the positive control. No effects on 

absolute or relative to body thymus and spleen weights were found in Diethofencarb-treated rats, 

however the absolute and relative to body thymus and spleen weights of CPS positive control 

rats was statistically decreased ~65% and 27%, respectively. The systemic Diethofencarb

LOAEL for female Sprague Dawley rats not established. The corresponding NOAEL was 

10,000 ppm (equivalent to 764 mg/kg bw/day). 

The anti-SRBC titer of Diethofencarb-treated rats was not decreased by treatment while the antiSRBC titer of CPS-treated rats was decreased 97%, indicating the validity of the study. The 

immunotoxicity LOAEL for Diethofencarb was not found. The NOAEL ≥ 10,000 ppm 

(≥ 764 mg/kg bw/day). 

This immunotoxicity study is classified Acceptable / Guideline and satisfies the guideline 

requirement for an immunotoxicity study (OCSPP 870.7800) in the rat.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6 (2007). 

Portions of this document were altered by the EPA reviewer to reflect Agency policies and 

conclusions.

Non-Guideline: Thyroid Mechanistic Studies

14-day Special Thyroid Mechanistic Study MRID 49267473.
Diethofencarb Human Health Risk Assessment D418227

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This special study is Acceptable / Non-guideline and does not satisfy a guideline requirement. 

The study has numerous deficiencies but when combined with the companion study (MRID 

49267474) provides data that can be considered reliable.

In a series of non-guideline studies to determine effects on the thyroid gland (MRID 49267473), 

Diethofencarb (purity 97.8% and 98.2% and Lot numbers PK-84042 and PSG-86018M, respectively, and/or radiochemical purity >98% uniformly labeled on phenyl ring) was administered to 

groups of 10 male Sprague Dawley rats 7-, 37-, and 66-weeks of age at concentrations of 0, 5000 

or 20,000 ppm for 2 weeks to determine effects on thyroid hormone concentration; to groups of 

ten 31-week male Sprague Dawley rats at concentrations of 20,000 ppm for 7 and 14 days to 

determine tissue distribution; and to groups of two to four 7- and 37-week male Sprague Dawley 

rats at concentrations of 0 or 20,000 ppm for 14 days for biliary excretion and metabolism 

studies. The study report does not make clear whether non-radiolabeled compound was 

administered to rats during the two-week and biliary excretion and metabolism studies. Rats in 

the biliary excretion/metabolism study received an IV injection of 2 μg/kg bw 125I-thyroxin in 

0.5 mL saline at the end of feeding period to determine radiolabeled excretion. Since individual 

animal body weights were not provided in the study reports, the estimated doses to animals in the 

two-week feeding study were approximately 0, 430, or 1720 mg/kg bw/day for 7-week animals, 

and 0, 345, or 1380 mg/kg bw/day for 37- and 66-week animals, respectively. These were 

calculated by the Reviewer using food conversion factors of 0.086 for 7 week and 0.069 for 37-

and 66-week animals, respectively. For the tissue distribution study, the rats received an 

estimated dose of approximately 1380 mg/kg bw/day (based on a food conversion factor of 0.069 

and assuming food consumption was similar to the 2-week study). Finally, the estimated doses 

for rats treated with the test material were approximately 430 and 1380 mg/kg bw/day for 7-

week and 37-week rats treated with 20,000 ppm, respectively (again assuming food consumption 

was similar to the 2-week study. Since body weights were not reported except terminal body 

weights in the 2-week study, these were not included in the assumptions for bioaccumulation and 

biliary excretion studies.). 

Summary data from these studies indicate treatment with 20,000 ppm Diethofencarb for up to 

two weeks decreased serum T4 concentrations and induced slight increases in TSH concentrations with no effect on T3 concentrations. In the bioaccumulation study, the kidney had the 

highest 14C concentrations followed by the liver, skin and hair following both 7- and 14-days of 

treatment. No indication of bioaccumulation of radiolabel was found in the thyroid. The data 

also suggested that increased T4 excretion in the bile arose through metabolic processes related 

to hepatic UDP-GT induction. 

This study is classified as Acceptable/non-guideline, and does not satisfy a guideline 

requirement. It has numerous deficiencies; however, but when evaluated in conjunction with 

MRID 49267474, which is a similar and better conducted study, and which produced similar, 

corroborating results, this study is considered useful in determining the effects of diethofencarb 

on thyroid tissue and function.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6 (2007). 

Portions of this document were altered by the EPA reviewer to reflect Agency policies and 

conclusions.

90-day Special Thyroid Mechanistic Study MRID 49267474.
Diethofencarb Human Health Risk Assessment D418227

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This special study is Acceptable / Non-guideline and does not fulfill a guideline requirement.

In a 90-day Non-guideline oral toxicity study to determine effects on thyroid function (MRID 

49267474), Diethofencarb (98.2% a.i., Lot No. PSG-86018-M) was administered to 20 male SD 

rats/sex/dose in the diet at levels of 0, 5000, or 20,000 ppm (equivalent to 0, 307.9, or 1277.9 

mg/kg bw/day). Twenty-four hours before scheduled sacrifice, half the rats in each group were 

given a single IP injection of 125I to determine uptake. Histological examinations were limited to 

the thyroid of rats not treated with 125I. 

Treatment of male rats with 20,000 ppm Diethofencarb for 90 days induced alopecia on 7-8/20 

rats during the first 8 days of treatment. Thereafter, alopecia was not increased through the 

remainder of the study. The body weight of 20,000 ppm male rats was statistically decreased 

from Day 5 through the remainder of the study and total weight gain was decreased 16%. Body 

weight of 5000 ppm rats was decreased 4 – 6% from Day 12 through study end, with total weight 

gain decreased 8%. Food consumption was slightly decreased (<10%) through week 10 of the 

study for both 5000 ppm and 20,000 ppm rats. Slight dose-related statistical decreases in 

circulating free T4 and increases in TSH (thyroid stimulating hormone) were found in 20,000 

ppm rats at study end; however, total T4 was not statistically different from control rats, though 

decreased 16%. No significant effects were found on total or free T3 in rats treated with 20,000 

ppm. There was a 16% increase in relative to body thyroid weight of 20,000 male rats, but no 

effects were found on absolute thyroid weight or 125I thyroid uptake, and no microscopic effects 

were found. Statistically significant increases in liver UDP-GT (UDP-glucuronyltransferase)

activities were found in 20,000 ppm rats with activity/kg bw (3.7 fold), activity/g liver weight 

(2.6 fold), and activity/mg protein (1.9 fold). Slight increases were also found in 5000 ppm rats 

for the same parameters, but were not statistically increased (1.3 fold for activity/kg bw, 1.4 fold 

for activity/g liver weight, and 1.4 fold for activity/mg protein). The absolute liver weight of 

20,000 ppm rats was statistically increased 25%, while the liver relative to body weight was 

increased 42%. The liver weight relative to body weight was statistically increased 13% in 5000 

ppm rats, while no significant increase in absolute liver weight was found.

These results suggest that Diethofencarb had no direct effect on the thyroid, but the effects were 

due to accelerated excretion of thyroid hormones from the liver as evidenced by the increase in 

liver UDP-GT activity. This resulted in a decrease in serum free T4 concentrations that likely 

triggered the feedback mechanism of the pituitary gland, and promotion of TSH release. 

The LOAEL for Diethofencarb in male SD rats was 20,000 ppm (equivalent to 1277.9 

mg/kg bw/day) based on decreased body weight and body weight gain, decreased serum 

free T4, increased TSH, and increased liver UDP-GT activities. The NOAEL was 5000 ppm 

(307.9 mg/kg bw/day).

This 90-day oral toxicity supplemental study in the male rat is Acceptable / Non-guideline and 

does not satisfy a guideline requirement.

This Data Evaluation Record is a modified version of the Ministere de l’Agriculture et de la 

Peche (France) Draft Assessment Report (DAR), Diethofencarb Vol. 3, Annex B6 (2007). 

Portions of this document were altered by the EPA reviewer to reflect Agency policies and 

conclusions.
Diethofencarb Human Health Risk Assessment D418227

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Appendix B. Metabolism Considerations

B.1. Metabolism Summary Table

Summary of Metabolites and Metabolism Studies 1

Name; Abbreviation; Structural formula Crop

Major 

Residue;

%TRR

Minor 

Residue; % 

TRR

Diethofencarb

1-methylethyl(3,4-diethoxyphenyl)carbamate Tomato 69; 72.9 ---

Lettuce 57.3; 52.0 ---

Grape 19.9; 23.1 ---

DFC-COOH

2-[(3,4-diethoxyphenylcarbamoyl)oxy]propionic acid

Lettuce --- ---

Tomato --- 2.6; 2.42

Grape --- ---

Rat Feces, 2-4% AD

4-OH-DFC

Isopropyl 3-ethoxy-4-hydroxycarbanilate

Tomato --- 2.6; 2.42

Lettuce --- 0.5; 0.3

Grape --- 0.4; 0.9

Rat Multiple conjugates were found 

in urine, individually up to 49%

DPO

3-(3,4-diethoxyphenyl)-5-methyloxazolidine-2,4-dione Lettuce --- ---

Tomato --- 0.9; 1.2

Grape --- ---

4-OH-5-TLA DFC; (OTD)

3-{3-ethoxy-2-hydroxy-5-[(isopropoxycarbonyl)amino] 

phenylthio}-2-hydroxypropionic acid

Lettuce --- 0.6; 0.6

Tomato --- ---

Grape --- 3.2; 2.0

NH

O

O

O

O

NH

O

O

O

O

HOOC

NH

O

O

HO

O

N

O

O

O

O

O

NH

O

O

HO

S

O

HO

COOH
Diethofencarb Human Health Risk Assessment D418227

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Summary of Metabolites and Metabolism Studies 1

Name; Abbreviation; Structural formula Crop

Major 

Residue;

%TRR

Minor 

Residue; % 

TRR

4-Glc-5-TLA DFC ; (GTD)

3-{3-ethoxy-2--glucopyranosyloxy-5-

[(isopropoxycarbonyl)amino] phenylthio-2-

hydroxypropionic acid

Lettuce --- 0.9; 1.93

Tomato --- 2.6; ND3

Grape --- 1.6; 1.9

4-Glc-DFC; (GD)

Isopropyl 3-ethoxy-4--glucopyranosyloxycarbanilate Lettuce --- 0.9; 1.93

Tomato --- 2.6; ND3

Grape 15.5; 14.6 ---

4-OH-5-(OGlc-TLA) DFC

3-{3-ethoxy-2-hydroxy-5-[(isopropoxycarbonyl)amino] 

phenylthio}-2--glucopyranosyloxypropionic acid

Tomato --- 1.7; 2.4

Lettuce --- ---

Grape 21.5; 20.7 ---

Unknown 1 4 Tomato 11.8 

(isopropyl) 6.9 (phenyl)

Tomato - [Phenyl-14C]; two applications; PHI = 3 days; TRR = 0.116 ppm; 2 x 375 g a.i./ha/application

Tomato - [Isopropyl14C]; two applications; PHI = 3 days; TRR = 0.085 ppm; 2 x 375 g a.i./ha/application

Lettuce - [Phenyl-14C]; five applications; PHI = 7 days; TRR = 2.02 ppm; 5 x 38 g ai./ha/application.

Lettuce - [Isopropyl14C]; five applications; PHI 7 Days; TRR = 1.76 ppm; 5 x 38 g ai./ha/application.

Grape - [Phenyl-14C]; one application; PHI = 35 days; TRR = 2.83 ppm; 1 x 500 g a.i./ha/application

Grape - [Isopropyl14C]; one application; PHI 35 Days; TRR = 5.46 ppm; 1 x 500 g a.i./ha/application

(Note that the current labels for bananas allow up to 6 applications at 150 g ai/ha with a 0 day PHI.)

1

If two values are listed, results from phenyl label study listed first. Summary at bottom of table. Three crop studies 

were conducted at different PHIs and are listed in increasing PHIs.

24-Glc-5-TLA DFC could not be distinguished from 4-Glc DFC (GTD or GD) using method employed so both 

analytes are reported in this table.

34-OH DFC could not be distinguished from DFC-COOH using method employed so both analytes are reported in 

this table.

4Although this unknown was >10% of the residue in tomatoes (isopropyl label only), the level was low, 0.01 ppm. 

It did not co-chromatograph with any reference standard and could not be identified.

NH

O

O

O

S

O

HO

COOH

O

HOH2C

HO

OH

OH

NH

O

O

O

O

O

HOH2C

HO

OH

OH

NH

O

O

HO

S

O

O

COOH

O

HOH2C

HO

OH

OH
Diethofencarb Human Health Risk Assessment D418227

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B.2. Metabolic Pathways

Proposed Metabolic Pathway in Plants

(Copied directly from EFSA Draft Assessment Report for Diethofencarb, Vol 3 – Annex B7).

a The metabolites 4-Glc-DFC and 4-Glc-5-TLA DFC could not be separated; the percentage of TRR given 

corresponds to the sum of the amount of both metabolites.

Diethofencarb

GSH

NH

O

O

O

S

O

HO

COOH

O

HOH2C

HO

OH

OH

NH

O

O

HO

S

O

O

COOH

O

HOH2C

HO

OH

OH NH

O

O

HO

S

O

HO

COOH

NH

O

O

HO

S

O

O

COOH

NH

O

O

HO

S

O

H2N

COOH

N

O

O

O

O

Benzoquinone form

4-OH-DFC

Cystein conj. form

NH

O

O

O

O

NH

O

O

HO

O

Pyruvate intermediate

4-OH-5-(OGlc-TLA) DFC

4-OH-5-TLA DFC 4-Glc-5-TLA DFC

NH

O

O

O

O

O

HOH2C

HO

OH

OH 4-Glc-DFC

O N

O

O

O

O

NH

O

O

O

O COOH

DFC-COOH DPO

Tomato: 73 %, Grape 23%,

Lettuce 55% TRR

Tomato: 2.6 % TRR Tomato: 1.2 % TRR

Tomato: 2.6 %, Grape 0.9%,

Lettuce 0.5% TRR

Grape: 3.2 % Lettuce 0.6% 

TRR T

Tomato: 2.6 % Grape 1.9% 

lettuce 1.5% TRRa

Tomato: 2.4 % Grape 

21%TRR

Tomato: 2.6 %, Grape 15%,

Lettuce 1.5% TRRa
Diethofencarb Human Health Risk Assessment D418227

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Appendix C. Physical/Chemical Properties

Physicochemical Properties of the Nominal 99% Diethofencarb

Parameter Value Reference

Molecular weight (g/mole) 267.32 g/mol MRID 49267477.

EFSA Journal 

2010:8(9):1721, Appendix 

A

Melting point/range (°C) 98.3-100.9 MRID 49267477.

EFSA Journal 

2010:8(9):1721, Appendix 

A

pH Does not dissociate MRID 49267477.

EFSA Journal 

2010:8(9):1721, Appendix 

A

Density (g/cm3) 1.206 at 25o C EC Draft Assessment 

Report, Vol3, Annex B, 

B.2.1.2

Water solubility ( mg/L at 20°C) 27.64 MRID 49267477.

EFSA Journal 

2010:8(9):1721, Appendix 

A

Solvent solubility (g/L at 25°C) Methanol 106.1

Acetone 207.4

n-Octanol >28.9

Xylene 29.9

Ethyl acetate 140.4

Dichloromethane413.2

n-Heptane 1.23

Vapor pressure at 25°C (Pa) 9.44 X 10-6

Dissociation constant (pKa) Does not dissociate between pH 2 

and pH 12

Octanol/water partition coefficient Log(KOW) 2.89 at 20oC