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dimethenamid (Frontier) Pesticide Tolerances 3/93

Date="03/17/93"
Citation="58 FR 14316"
Group="environ"
Type="RULE"
Department="ENVIRONMENTAL PROTECTION AGENCY"
Agency="ENVIRONMENTAL PROTECTION AGENCY (EPA)"
Subject="Pesticide Tolerances for Dimethenamid"
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40 CFR Part 180

[PP 0F3918/R1184; FRL-4575-6]

RIN No. 2070-AB78

Pesticide Tolerances for Dimethenamid

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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40 CFR Part 180

[PP 0F3918/R1184; FRL-4575-6]

RIN No. 2070-AB78

Pesticide Tolerances for Dimethenamid

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This regulation establishes tolerances for residues
of the herbicide dimethenamid, 2-chloro-N-[(1-methyl-2-methoxy)ethyl]-
N-(2,4-dimethyl-thien-3-yl)-acetamide, in or on the raw agricultural
commodities (RAC) corn grain, corn fodder, and corn forage at
0.01 part per million (ppm). This regulation to establish the
maximum permissible level of residues of the herbicide in or
on these commodities was requested in a petition submitted by
Sandoz Agro, Inc.

EFFECTIVE DATE: This regulation becomes effective March 17,
1993.

ADDRESSES: Written objections, identified by the document control
number, [PP 0F3918/R1184], may be submitted to: Hearing Clerk
(A-110), Environmental Protection Agency, rm. 3708, 401 M St.,
SW., Washington, DC 20460.

FOR FURTHER INFORMATION CONTACT: By mail: Cynthia Giles-Parker,
Product Manager (PM) 22, Registration Division, Environmental
Protection Agency, 401 M St., SW., Washington, DC 20460. Office
location and telephone number: Rm. 229, CM #2, 1921 Jefferson
Davis Hwy., Arlington, VA 22202, (703-305-5540).

SUPPLEMENTARY INFORMATION: EPA issued a notice, published in
the Federal Register of April 3, 1991 (56 FR 13642), which announced
that Sandoz Agro, Inc., 1300 East Touhy Ave., Des Plaines, IL
60018, had submitted a pesticide petition (PP 0F3918) to EPA
requesting that the Administrator, pursuant to section 408(d)
of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C.
346a(d), establish tolerances for the residues of the herbicide
2-chloro-N-[(1-methyl-2-methoxy)ethyl]-N-(2,4-dimethyl-thien-
3-yl)-acetamide in or on the raw agricultural commodities (RACs)
corn forage, corn silage, corn grain, and corn stover at 0.01
ppm. Sandoz Agro, Inc., subsequently editorially amended PP
0F3918 to read dimethenamid, 2-chloro-N-[(1-methyl-2-methoxy)ethyl]-
N-(2,4-dimethyl-thien-3-yl)-acetamide in or on the raw agricultural
commodities corn grain, corn fodder, and corn forage at 0.01
ppm. There were no comments or requests for referral to an advisory
committee received in response to this notice of filing.

The data submitted in the petitions and all other relevant
material have been evaluated. The toxicology data considered
in support of the tolerances include:

1. A rat acute oral study with an LD50 of 2.14 grams (g)/kilogram
(kg), males, 1.30 g/kg females, and 1.57 g/kg combined.

2. A 13-week rat feeding study with a no-observed-effect
level (NOEL) of 500 ppm (33.5 milligrams (mg)/kg/day for males
and 40.1 mg/kg/day for females, based on food consumption).

3. A 13-week dog-feeding study with a NOEL of 100 ppm (2.5
mg/kg/day).

4. A 21-day rabbit dermal study with a NOEL of 50 mg/kg with
mild irritant effect at all dose levels.

5. A carcinogenicity study in mice with no carcinogenic effects
observed at any dose level under the conditions of the study,
and a systemic NOEL of 300 ppm (40.8 mg/kg/day for males and
40.1 mg/kg/day for females, based on food consumption), and
a systemic lowest effect level (LEL) of 1,500 ppm (205 mg/kg
day for males and 200 mg/kg/day for females due to food consumption)
due to elevated liver weights.

6. A rat chronic feeding/carcinogenicity study with a NOEL
of 100 ppm (5 mg/kg/day) and a LEL of 700 ppm (35 mg/kg/day)
due to decreased food consumption. Under the conditions of the
study, limited evidence of carcinogenicity was observed based
on the occurrence of increased benign liver cells in males and
ovarian tubular adenomas in females at the 1,500-ppm dose groups,
which are discussed further below.

7. A 1-year dog feeding study with a NOEL of 250 ppm (9.6
mg/kg/day) and with a LEL = 1,250 ppm (49 mg/kg/day for liver
changes).

8. A two-generation reproduction study in rats with a parental
and reproductive NOEL of 500 ppm (36 mg/kg/day for males and
40 mg/kg/day for females) and with a LEL of 2,000 ppm (150 mg/kg/day
for males and 160 mg/kg/day for females) due to reduction of
body weight and of food consumption, increases in liver weights,
and significant reductions in pup weight during lactation.

9. A rabbit developmental study with a maternal NOEL of 37.5
mg/kg/day and a LEL of 75 mg/kg/day due to decreased body weight
and food consumption and abortion/premature delivery, and with
a developmental NOEL of 75 mg/kg and a LEL of 150 mg/kg/day
due to a low incidence of abortion/premature delivery and hyoid
alae angulated changes.

10. A rat developmental study with a maternal NOEL of 50
mg/kg/day and a LEL of 215 mg/kg due to excess salivation, increased
liver weight, and reduced body weight gain and food consumption,
and with a developmental NOEL of 215 mg/kg/day and a LEL of
425 mg/kg due to increased resorptions.

11. An Ames mutagenicity assay negative with and without
activation, an in vitro chromosomal aberration using CHO cells
positive with and without activation, an unscheduled DNA synthesis
in rat hepatocytes unequivocally positive in one in vitro assay
and negative in another in vitro assay. A dominant-lethal study
to further evaluate the mutagenic mechanism is due 2 years after
the date of the conditional registration under the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA).

The Agency has concluded that the available data provide
limited evidence of the carcinogenicity of dimethenamid in rats
and has classified the pesticide as a Category C carcinogen
(possible human carcinogen with limited evidence of carcinogenicity
in animals) in accordance with Agency guidelines, published
in the Federal Register of September 24, 1986 (51 FR 33992).
Based on a review of the Health Effects Division Peer Review
Committee for Carcinogenicity of the Office of Pesticide Programs,
the Agency has determined that a quantitative risk assessment
is not appropriate for the following reasons:

1. The tumor response was primarily due to a significantly
increasing trend for benign and/or malignant liver tumors in
males and due to a significantly increasing trend for ovarian
tubular adenomas in female rats in the high dose only (1,500
ppm).

2. The chemical was not carcinogenic when administered in
the diet to mice at dose levels ranging from 30 to 3,000 ppm.

Based on this evidence, EPA concludes that dimethenamid poses
a negligible cancer risk to humans.

The standard risk assessment approach of using the Reference
Dose (RfD) based on systemic toxicity was applied to dimethenamid.
Using a 100-fold safety factor and the NOEL of 5 mg/kg bwt/day
determined by the most sensitive species from the 2-year rat
feeding study, the RfD is 0.05 mg/kg/day. The theoretical maximum
residue contribution (TMRC) from the proposed tolerances is
4 X 10-6 mg/kg bwt/day and utilizes 0.007 percent of the RfD
for the overall U. S. population. The exposure of the most highly
exposed subgroup in the population did not utilize a significantly
greater amount of the RfD. No previous tolerances have been
established for dimethenamid.

The metabolism of dimethenamid in plants is adequately understood.
There is no reasonable expectation of secondary residues occurring
in meat, milk, and eggs from tolerances associated with this
petition.

An adequate analytical method, gas chromatography, is available
for enforcement purposes. Because of the long lead time from
establishing these tolerances to publication of the enforcement
methodology in the Pesticide Analytical Manual, Vol. II, the
analytical methodology is being made available in the interim
to anyone interested in pesticide enforcement when requested
from: Calvin Furlow, Public Information Branch, Field Operations
Division (H7506C), Office of Pesticide Programs, Environmental
Protection Agency, 401 M St., SW., Washington, DC 20460. Office
location and telephone number: Rm. 242, CM #2, 1921 Jefferson
Davis Hwy., Arlington, VA 22202, (703-305-4432).

The pesticide is considered useful for the purposes for which
the tolerances are sought. Based on the information and data
considered, the Agency concludes that the establishment of the
tolerances will protect the public health. Therefore, the tolerances
are established as set forth below.

Any person adversely affected by this regulation may, within
30 days after publication of this document in the Federal Register,
file written objections with the Hearing Clerk, at the address
given above (40 CFR 178.20). The objections submitted must specify
the provisions of the regulation deemed objectionable and the
grounds for the objections (40 CFR 178.25). Each objection must
be accompanied by the fees provided by 40 CFR 180.33(i). If
a hearing is requested, the objections must include a statement
of the factual issue(s) on which a hearing is requested, and
the requestor's contentions on each such issue, and a summary
of the evidence relied upon by the objection (40 CFR 178.27).
A request for a hearing will be granted if the Administrator
determines that the material submitted shows the following:
there is a genuine and substantial issue of fact; there is a
reasonable possibility that available evidence identified by
the requestor would, if established, resolve on or more of such
issues in favor of the requestor, taking into account uncontested
claims or facts to the contrary; and resolution of the factual
issue(s) in the manner sought by the requestor would be adequate
to justify the action requested (40 CFR 178.32).

The Office of Management and Budget has exempted this rule
from the requirements of section 3 of Executive Order 12291.

Pursuant to the requirements of the Regulatory Flexibility
Act (Pub. L. 96-354, 94 Stat. 1164, 5 U.S.C. 601-612), the Administrator
has determined that regulations establishing new tolerances
or raising tolerance levels or establishing exemptions from
tolerance requirements do not have a significant economic impact
on a substantial number of small entities. A certification statement
to this effect was published in the Federal Register of May
4, 1981 (46 FR 24950).

List of Subjects in 40 CFR Part 180

Administrative practice and procedure, Agricultural commodities,
Pesticides and pests, Recording and recordkeeping requirements.

Dated: March 5, 1993.

Douglas D. Campt,
Director, Office of Pesticide Programs.
Therefore, 40 CFR part 180 is amended as follows:

PART 180-[AMENDED]

1. The authority citation for part 180 continues to read
as follows:

Authority: 21 U.S.C. 346a and 371.

2. In subpart C, by adding new 180.464, to read as follows:

180.464 Dimethenamid; tolerances for residues.

Tolerances are established for residues of the herbicide
dimethenamid, 2-chloro-N-[(1-methyl-2-methoxy)ethyl]-N-(2,4-
dimethyl-thien-3-yl)-acetamide, in or on the following raw agricultural
commodities:

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Commodity Parts per
million
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Corn, grain.................................................... 0.01
Corn, fodder................................................... 0.01
Corn, forage................................................... 0.01
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[FR Doc. 93-6147 Filed 3-16-93; 8:45 am]
BILLING CODE 6560-50-F