EPA REGISTRATION DIVISION COMPANY NOTICE OF FILING FOR PESTICIDE 

PETITIONS PUBLISHED IN THE FEDERAL REGISTER 

Tolerance Petition for EPTC in Forage and Hay of Grass Grown for Seed

EPA Registration Division contact: Jim Tompkins,703-305-5697

Gowan Company

[9F7620]

EPA has received a pesticide petition ([9F7620]) from Gowan Company, 370 S. Main 

Street, Yuma, AZ 85364, proposing, pursuant to section 408(d) of the Federal Food, Drug, and 

Cosmetic Act (FFDCA), 21 U.S.C. 346a(d), to amend 40 CFR part 180 by establishing a 

tolerance for residues of S-Ethyl dipropylthiocarbamate in or on the raw agricultural commodity

grasses grown for seed at 0.1 parts per million (ppm) for hay and 0.2 parts per million (ppm) for 

forage. EPA has determined that the petition contains data or information regarding the elements 

set forth in section 408 (d)(2) of FDDCA; however, EPA has not fully evaluated the sufficiency 

of the submitted data at this time or whether the data supports granting of the petition. Additional 

data may be needed before EPA rules on the petition.

A. Residue Chemistry

1. Plant metabolism. EPTC is systemic and rapidly metabolized in plants. Based on 

results of acceptable plant metabolism studies, the Agency has determined that EPTC and 

three hydroxy metabolites, EPTC sulfoxide, EPTC sulfone, and glutathione conjugate of 

the sulfone metabolite will serve as markers to represent EPTC residues in plants.

2. Analytical method. Adequate methods are available for the determination of EPTC 

and three hydroxy metabolites in crops, including grass grown for seed. The EPA reviewed 

these methods and noted in the 1999 EPTC Reregistration Eligibility Decision (RED) that 

methods are available and adequate. The Limit of Quantitation of the methods is 0.05 ppm 

for EPTC and 0.01 ppm for each of the hydroxy metabolites. 

3. Magnitude of residues. Maximum residues of EPTC and metabolites in hay and 

forage in three applicable MOR trials were 0.0819 ppm for hay and 0.152 ppm for forage. 

A permanent tolerance of 0.1 ppm for hay and 0.2 for forage are proposed and adequately 

supported for use in cool season grasses grown for seed in the Pacific Northwest 

(Washington, Oregon and Idaho).

B. Toxicological Profile

1. Acute toxicity. EPTC is moderately toxic (Toxicity Category III) via the oral and 

dermal routes, and in a primary eye irritation study in rabbits, the technical was found to 

be slightly irritating (Toxicity Category III). EPTC is most toxic via the inhalation route 

(Toxicity Category II).

2. Genotoxicty. Testing of EPTC for genotoxicity through an in vivo micronucleus 
test and a Drosophila sex-linked recessive lethal mutation assay gave negative results.

3. Reproductive and developmental toxicity. There does not appear to be concern 

about the reproductive or developmental toxicity of EPTC. Studies in rats and rabbits 

showed developmental and reproductive toxicity only in the presence of maternal or 

parental toxicity. In a two generation reproduction test in rats, effects in the offspring 

were observed only at or above treatment levels which resulted in parental toxicity.

Although EPTC did not produce any significant reproductive or developmental toxicity, 

the Agency recommended a 10X safety factor be applied for potential exposure to infants 

and children in residential use.

4. Subchronic toxicity. An acceptable subchronic study was reviewed by EPA and 

established a NOAEL at 600ppm (15 mkg/kg/day) in male dogs and 1800 ppm (45 

mg/kg/day) in females. The LOAEL for In two chronic/oncogenicity feeding studies and 

in 90-day feeding and inhalation studies, all rats exhibited myocardial degeneration during 

the histopathology examination (Mackenzie, 1986; U.S. EPA, 1999). In dogs, two chronic 

oral dosing studies revealed degenerative changes in the cardiac muscle when EPTC was 

administered in a capsule, but not when it was administered at comparable doses in the 

diet. Electrocardiograms were performed in both dog studies; however, only one high-dose 

male in the capsule study exhibited changes which were described as "potentially" 

treatment-related (U.S. EPA, 1999)

5. Chronic toxicity. Cardiotoxicity and neurotoxicity were observed in subchronic 

studies in rats. Cardiotoxicity was attributed to myocardial degeneration by histological 

exam. However, the acute neurotoxicity study in the hen did not show neurotoxicity. The 

Agency’s FQPA Safety Factor Committee recommends that a 10X safety factor be retained 

for all population subgroups for acute, chronic and residential exposure assessments.

6. Animal metabolism. The metabolism of EPTC in rats was studied using 

radiolabeled EPTC. Most of the radioactivity was quickly excreted in the urine and there 

was little accumulation in tissues. Small amounts were excreted in the feces by exhalation. 

No sex-linked difference in metabolism or distribution of EPTC was noted.

7. Metabolite toxicology. The Agency has determined that metabolites incorporating 

the thiocarbamate moiety are of concern. These residues include various acid conjugates. 

Therefore, EPTC tolerances are based on residue data of EPTC and its hydroxylated 

metabolites. 

8. Endocrine disruption. There is no evidence of endocrine disruptor effects in the 

EPTC database.

C. Aggregate Exposure

1. Dietary exposure. Tolerances have been established in 40 CFR 180.117 for the 

residues of EPTC in or on a variety of raw agricultural commodities. The addition of the 

proposed use on cool season grasses grown for seed would not affect the current EPA risk 
assessment as no residues are expected in meat or milk. Risk assessments were performed 

to assess dietary exposures from EPTC in food as follows:

i. Food. Acute and chronic risk from food does not exceed the Agency's level of 

concern. In both assessments, exposure (consumption) was compared to a population

adjusted dose (PAD) reflecting retention of the FQPA 10x factor. The PAD is equal to the 

acute or chronic RfD divided by the FQPA Safety Factor. The Agency considers dietary 

residue contributions greater than 100% of the PAD to be of concern. Acute dietary 

exposure comprised 40.5% of the aPAD for the general population, and 87.5% of the aPAD 

for the most highly exposed subgroup, children (1-6 years). Chronic dietary exposure 

comprised 9.6% of the cPAD for the general population, and 17.4% of the cPAD for the 

most highly exposed subgroup, children (1-6 years). Acute dietary risk analysis 

demonstrates acceptable food risk to the US population and all dietary subgroups. The 

acute dietary Margin of Exposure for the general population remains approximately 9000

based on a Tier 1 DEEM-FCID analysis as the proposed use will not affect dietary risk. 

EPTC residues in milk and meat “represents a Category 3 situation under 40CFR 

§180.6(a): i.e., a situation in which it is not possible to establish with certainty whether 

finite residues will be incurred under reasonable worst-case exposure scenarios, but there 

is no reasonable expectations of the occurrence of finite residues in animal commodities.”

ii. Drinking water. Estimation of drinking water levels for EPTC did not result in 

levels of concern.

2. Non-dietary exposure. Exposures by non-dietary means were determined to be not 

of concern in the EPTC RED.

D. Cumulative Effects

The Agency has determined that thiocarbamates cannot be regulated as a single 

class due to differing neurotoxic activity patterns. Due to incomplete information regarding 

developmental neurotoxicity, EPA has retained the 10X FQPA Safety Factor.

E. Safety Determination

1. U.S. population. The proposed use of EPTC on cool season grasses grown for seed 

use results in exposures to the general population and all subpopulations that are within 

acceptable ranges.

2. Infants and children. Risk calculations for the proposed grass grown for seed use 

result in acceptable exposures. The Agency has retained a 10X FQPA safety factor in the 

toxicological endpoints for EPTC which was included in the calculation of exposures.

F. International Tolerances

There are no international MRLs currently established for EPTC.