EPA REGISTRATION DIVISION COMPANY NOTICE OF FILING FOR 

PESTICIDE PETITIONS PUBLISHED IN THE FEDERAL REGISTER 

Interregional Research Project Number 4 (IR-4)

EPA Registration Division contact: Laura Nollen, (703) 305-7390

Petition Number 0F7796

EPA has received a pesticide petition, PP # 0F7796, from Interregional Research 

Project Number 4 (IR-4), 500 College Road East, Suite 201 W, Princeton, NJ 08540,

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 180.142 to establish tolerances for 

residues of 2,4-D (2,4-D dichlorophenoxyacetic acid), both free and conjugated, 

determined as the acid in or on the raw agricultural commodities teff, bran at 4.0 parts per 

million (ppm); teff, forage at 25.0 ppm; teff, grain at 2.0 ppm; and teff, straw at 50.0 

ppm. 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 This petition for teff (a minor crop grain) builds on the existing 

registration of 2,4-D for use in wheat.

1. Plant metabolism. Acceptable wheat, lemon, and potato metabolism studies 

have been submitted and reviewed as part of the 2005 EPA RED (EPA 738-R-05-002).

2. Analytical method. Per the 2005 EPA RED (EPA 738-R-05-002) page 98, the 

2,4-D Task Force II submitted an adequate GC/ECD enforcement method for plants 

(designated as EN-CAS Method No. ENC-2/93) which has been independently validated. 

Adequate radiovalidation data have been submitted and evaluated for the enforcement 

method using samples from the wheat metabolism study.

3. Magnitude of residues. IR-4 submitted a proposal to US EPA ChemSAC to 

extrapolate to teff from wheat. Teff and other cereal grains including corn (sweet and 

field), rice, sorghum, wheat, barley, pearl and proso millet, oats, popcorn, rye, teosinte, 

and triticale have similar morphological, cultural practices, taxonomical characteristics, 

and share similar pest problems. Teff is scheduled for inclusion in the revised Cereal 

Grains Crop Group 15 to be proposed by IR-4 and the International Crop Grouping 

Consulting Committee. IR-4 proposed that the 2,4-D tolerances for teff be based on the 

existing residue tolerances for 2,4-D (40 CFR 180.142) on wheat, barley, oats, rye, and 
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millet. US EPA ChemSAC in a meeting on October 29, 2008 agreed with the proposal, 

considering the low acreage of teff grown in the US and the similarity to other cereal 

grains.

B. Toxicological Profile Per the 2005 RED (EPA 738-R-05-002), the EPA stated that 

with very few exceptions, the effects and relative toxicities of the salt and ester forms of 

2,4-D are quite similar to those of the acid form. Thus, the acid form was selected as 

being representative of all members of the 2,4-D reregistration case. The toxicological 

profile was reviewed and selected endpoints for 2,4-D were previously published in the 

Federal Register of July 27, 2005 (Vol. 70, Number 143, 43302), per Table 2. At that

time, the EPA determined that the “toxicological database is sufficient for reregistration”

but included a 10X database uncertainty factor in lieu of a DNT study. The toxicity

database is now augmented by a new F1-extended one generation dietary toxicity study

in rats (MRID 47972101) which was recently submitted by the 2,4-D task force and is 

currently under review at the EPA. It is anticipated that the data base UF will be reduced 

in the future based on the new study.

1. Acute toxicity. Per Table 2 of Federal Register of July 27, 2005 (Vol. 70, 

Number 143, 43302), EPA has established acute endpoints from two different studies. 

For the general population including infants and children, the NOAEL of 67 mg/kg/day

from the acute neurotoxicity study in rats is currently used in conjunction with a 1,000 X 

UF to arrive at an aRfD = aPAD of 0.067 mg/kg/day. For females 13-50 years of age the 

NOAEL of 25 mg/kd/day from the rat developmental toxicity study is currently used with 

a UF of 1000 to establish an aRfD = aPAD of 0.025 mg/kg/day for this subpopulation.

2. Genotoxicty. Per the 2005 RED (EPA 738-R-05-002), based on the overall 

pattern of responses observed in both in vitro and in vivo genotoxicity tests, 2,4-D was 

not mutagenic, although some cytogenic effects were observed. Per Table 1 of Federal 

Register of July 27, 2005 (Vol. 70, Number 143, 43302), several genotoxicity studies 

have been conducted. In the Ames tests, no evidence of bacterial mutation in S

typhimurium. strains TA1535, TA1537, TA1538, TA98, TA100, with and without S9 

were observed. No significant increase in bone marrow polychromatic erythrocytes were 

found in the in vivo erythrocyte micro-nucleus assay. No evidence of increased 

chromosome aberrations in human lymphocytes in the in vitro chromosome aberration 

study with human lymphocytes. Equivocal results (+ at top 2 doses, with results similar 

to dimethyl sulfoxide (DMSO control) were noted in the cytogenetics in vivo

chromosome aberration study with rat bone marrow. No evidence of induction of 

unscheduled DNA synthesis has been noted. 2,4-D is considered “Not likely to pose a 

cancer risk” based on the lack of carcinogenicity in a rat carcinogenicity study and a 

mouse carcinogenicity study.

3. Reproductive and developmental toxicity. Per the 2005 RED (EPA 738-R-05-

002), the toxicity database for 2,4-D includes acceptable developmental and reproductive 

toxicity studies for use in risk assessment. However, the recently submitted F1-extended 

one generation dietary toxicity study in rats (MRID 47972101) provides a new and 

detailed evaluation of the potential effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on 

the reproductive function, as well as potential effects on numerous endpoints in the first 
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generation offspring, including survival, growth and the development of nervous, 

immune and reproductive systems. Across life stages, the 2,4-D extended one generation 

study has established a no-observed adverse effect level (NOAEL) based on systemic 

toxicity of 100 ppm in males (5.5 mg/kg/day) and 300 ppm in females (20.6 mg/kg/day in 

non-pregnant P1 adults).

Regarding reproductive effects, there was no indication of reproductive toxicity by 2,4-D 

in the new study. 2,4-D had no effects on estrous cyclicity or reproductive indices, 

including mating, fertility, time to mating, gestation length, pre- and post-implantation 

loss and corporalutea number. Litter sizes, pup survival, sperm parameters, ovarian 

follicle counts and reproductive organ histopathology were unaffected by 2,4-D. Pup 

growth was affected during lactation, but only at a dose causing parental toxicity and 

resulting in nonlinear renal clearance. Overall, 2,4-D is not a reproductive toxin. 

There was no evidence of developmental neurotoxicity related to 2,4-D exposure. There 

were no exposure-related effects on brain histopathology at any age. Functional 

observational battery (FOB) parameters (hand-held and open-field observations, grip 

performance, landing foot splay, rectal temperature), motor activity and acoustic startle 

response (ASR) were assessed in these animals on post natal date (PND) 54-59. The 

offspring adults were perfused for central and peripheral nervous system neuropathology. 

In addition, brain weights, gross brain measurements and morphometric measurements 

were evaluated. There were no exposure-related effects on FOB parameters, motor 

activity or ASR. Habituation (behavioral response to a stimulus) was not affected at any

dose of 2,4-D. Gross and morphometric brain measurements also were not affected. 

There was no exposure-related neuropathology in PND 22 or 60 animals, including no 

effects on brain myelin (assessed by special staining). Thus 2,4-D exposure shows no 

evidence of DNT.

4. Subchronic toxicity. Per Table 2 of Federal Register of July 27, 2005 (Vol. 70, 

Number 143, 43302), the short-term incidental oral and a short-term dermal endpoints are 

currently established based on the rat developmental toxicity NOAEL = 25 mg/day with 

an associated LOAEL of 75 based on decreased maternal body-weight gain and skeletal 

abnormalities. The intermediate-term incidental oral and dermal endpoints are 

established based on the subchronic rat oral toxicity NOAEL of 15 mg/kg/day with an 

associated LOAEL = 1000 mg/kd/day based on decreased body weight/body-weight gain, 

alterations in some hematology (decreased platelets (both sexes)) and clinical chemistry

(decreased T3 (females) and T4 (both sexes)) parameters, and cataract formation. The 

LOC for Residential MOEs is 1000.

5. Chronic toxicity. In the rat chronic toxicity study, a LOAEL of 75 mg/kg/day

was observed based on decreased body-weight gain (females) and food 

consumption(females), alterations in hematology(decreased RBC, HCT, and HGB 

(females),platelets (both sexes)) and clinical chemistry parameters (increased creatinine

(both sexes), alanine and aspartate aminotransferases (males), alkaline phosphatase (both 

sexes), decreased T4 (both sexes), glucose (females), cholesterol (both sexes), and 

triglycerides (females). Per Table 2 of Federal Register of July 27, 2005 (Vol. 70, 

Number 143, 43302), the NOAEL = 5 mg/kg/day from this study and a UF = 1000, EPA 

has currently established an cRfD = cPAD = 0.005 mg/kg/day for all populations. This 
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NOAEL is also used for the long-term inhalation and dermal endpoints with a “LOC for 

MOE” of 1000.

6. Animal metabolism. The absorption, distribution, metabolism and excretion of 

2,4-D has been studies in rats. Per Table 1 of Federal Register of July 27, 2005 (Vol. 70, 

Number 143, 43302), 2,4-D elimination (85.5%-93.7%) is primarily via urine with 3.6%-

10.5% of dose eliminated via the feces. At the high-dose level, it appears that a nonlinear 

region (decreased clearance) is being reached in the disposition of 2,4-D. Parent 2,4-D 

was the major metabolite found in urine (72.9%-90.5% of the oral dose), with small 

amounts of uncharacterized compounds (0.6%-1.3% and 0%-0.7%) being found in the 

urine. 

Per the 2005 RED (EPA 738-R-05-002), EPA has noted that the mechanisms responsible 

for renal clearance of 2,4-D have been investigated in several species. 2,4-D is actively

secreted by the proximal tubules. This mechanism of renal clearance is consistent with 

results seen with other phenoxy acids. It has been suggested that observed dose

dependent, non-linear, pharmacokinetics of 2,4-D are primarily due to the saturation of 

this renal secretory transport system. Due to a limited capacity to excrete organic acids, 

the dog is more sensitive to the effects of 2,4-D than the rat with respect to repeated 

dosing.

7. Metabolite toxicology. 2,4-dichlorophenol (2,4-DCP) is a known plant and 

animal metabolite is 2,4-D. However, per the EPA RED (EPA 738-R-05-002), EPA has 

concluded that 2,4-D alone is the residue of concern.

8. Endocrine disruption. The recently submitted F1-extended one generation 

dietary toxicity study in rats (MRID 47972101) included numerous endpoints to assess 

for endocrine effects. Endocrine-sensitive endpoints included estrous cyclicity, 

reproductive indices, organ weights/pathology, and sperm parameters. Anogenital 

distance, nipple retention, and puberty onset were assessed in offspring; quantitative 

ovarian follicle counts in a subset of offspring. 2,4-D did not alter estrogen- or androgensensitive endpoints. There were no effects on estrogen-sensitive endpoints including 

vaginal opening, estrous cyclicity, uterine weights or histopathology, or quantitative 

ovarian follicle counts. There were no significant, exposure-related changes in 

reproductive organ weights in offspring. Other androgen-sensitive endpoints, including 

anogenital distance (AGD) and nipple retention, which are considered very sensitive 

endpoints, sperm parameters and testicular and accessory sex gland histopathology, were 

not altered. Based on this data and other studies, 2,4-D shows no evidence of being an 

endocrine disruptor interacting with either estrogen or androgen at doses at or below 

those resulting in nonlinear renal clearance. 

There were no thyroid effects at low and mid dose levels and no biologically significant 

effects on thyroid endpoints at all life stages examined. There were no adverse 

pathological alterations, thus, slight thyroid changes seen in a satellite group of pregnant 

females were considered adaptive, non-adverse responses. The only altered thyroid 

endpoints occurred at an exposure level that clearly resulted in nonlinear renal clearance.
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C. Aggregate Exposure This proposal is based on bridging uses and tolerances from 

wheat to teff. Wheat use is covered by the exposure assessments within the EPA 2005 

RED. The proposed additional use of 2,4-D on teff would not have changed the results of 

those assessments.

1. Dietary exposure. Tolerances for: Wheat, bran at 4.0 ppm, Wheat, forage at 25 

ppm Wheat, grain at 2.0 ppm are included in the EPA Final Rule (72 52017, Sept. 12, 

2007). The exposure assessment supporting these tolerances values is found in the 2005 

RED. The existing exposure assessment for wheat is sufficient to cover any teff 

exposure, because the exposure from the proposed use on teff is already covered by the 

existing EPA dietary assessment for small grains. If the consumer switches to 

consumption of teff in place of traditional grains, the dietary exposure assessment is 

unchanged, hence the information from the 2005 RED is reiterated below.

i. Food. Per the 2005 Reregistration Eligibility Decision for 2,4-D (EPA738-R05-002) regarding acute food, exposure estimates to the general U.S. population were

18% and 17% of the aPAD using both DEEM and Lifeline, respectively. The most 

highly exposed population subgroup using both DEEM and Lifeline was children 1-2 

years of age; exposures were 33% and 32% of the aPAD, respectively. Calculated 

exposure to females 13-49 years of age was 31% of the aPAD using DEEM and 42% of 

the aPAD using Lifeline; these higher calculated percentages for women of child-bearing 

age are due to the 2.7x lower toxicological point of departure for developmental effects 

applicable to Females 13-49 years of age. These acute dietary (food) exposure estimates

are all less than the Agency’s level of concern (100% of aPAD).

For chronic exposure the EPA RED concludes that exposures to the general U.S. 

population were 4.1% and 3.8% of the cPAD, using DEEM and Lifeline, respectively. 

Calculated food exposures to children 1-2 years of age, the most highly exposed 

population subgroup, was 8.5% of the cPAD using DEEM and Lifeline.

ii. Drinking water. Drinking water estimates were included in the previous DEEM 

model estimates listed in Federal Register of July 27, 2005 (Vol. 70, Number 143, page 

43307). The resulting exposure estimates were 10% of the cPAD for the U.S. population, 

24% of the cPAD for all Infants (< 1 year old), and 18% of the cPAD for children 1–2 

years old.

2. Non-dietary exposure. Per Federal Register of July 27, 2005 (Vol. 70, Number 

143, 43302), there are no residential uses for 2,4-D that result in chronic residential 

exposure to2,4-D. 2,4-D is currently registered for uses that could result in short-term

residential exposure. Short-term turf exposures were calculated only for females 13–49 

and children 1–6, because these population subgroups have the highest exposure and are 

protective of the other subgroups. EPA published potential turf exposure values of 0.024 

mg/kg/day for females and 0.021 mg/kg/day for children 1-6, respectively.

D. Cumulative Effects. For the purposes of this tolerance action, it is not assumed that 
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2,4-D has a common mechanism of toxicity with other substances.

E. Safety Determination

1. U.S. population. Per the Federal Register of July 27, 2005 (Vol. 70, Number 

143, 43302) aggregate risk assessments for the general population were conservatively 

covered by calculations for females 13–49 and children 1–6, because these population 

subgroups have the highest exposure and are protective of the other subgroups. EPA 

determined, the short-term aggregate MOEs which include turf exposure are not of 

concern because the MOEs equal or exceed the target MOE of 1,000.

2. Infants and children. In the Federal Register of July 27, 2005 (Vol. 70, Number 

143, 43302) and after evaluating hazard and exposure data for 2,4-D, EPA removed the 

default 10X FQPA safety factor, but retained a database uncertainty factor (UFDB) of 

10X in lieu of a developmental neurotoxicity (DNT) study in rats for 2,4-D. This FQPA 

decision was based on the existing toxicity database for 2,4-D at that time which includes 

acceptable developmental and reproductive toxicity studies. The new extended F1-

generation study in rats is anticipated to result in the removal of the 10X UFDB in the 

future.

F. International Tolerances

There are no known tolerances specifically for teff elsewhere in the world. 

According to Homologa (www.homologa.com), there are many international MRLs 

established for wheat: Argentina, Australia and Brazil have established 0.2 ppm, Japan 

and Mexico list 0.5 ppm, CODEX and the US list 2 ppm and the EU, Russian Federation 

and Switzerland list 0.05 ppm.