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diflufenzopyr Pesticide Tolerance 1/99


[Federal Register: January 28, 1999 (Volume 64, Number 18)]
[Rules and Regulations]
[Page 4301-4308]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr28ja99-10]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 180

[OPP-300778; FRL 6053-8]
RIN 2070-AB78

Diflufenzopyr; Pesticide Tolerance

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This regulation establishes a tolerance for combined residues
of diflufenzopyr, 2-(1-[([3,5-difluorophenylamino]carbonyl)-
hydrazono]ethyl)-3-pyridinecarboxylic acid, and its metabolites
convertible to M1 (8-methylpyrido[2,3-d]pyridazin-5(6H)-one) in or on
field corn stover, forage and grain. BASF Corporation requested this
tolerance under the Federal Food, Drug, and Cosmetic Act (FFDCA), as
amended by the Food Quality Protection Act of 1996 (Pub. L. 104-170).

DATES: This regulation is effective January 28, 1999. Objections and
requests for hearings must be received by EPA on or before March 29,
1999.

ADDRESSES: Written objections and hearing requests, identified by the
docket control number, [OPP-300778], must be submitted to: Hearing
Clerk (1900), Environmental Protection Agency, Rm. M3708, 401 M St.,
SW., Washington, DC 20460. Fees accompanying objections and hearing
requests shall be labeled "Tolerance Petition Fees" and forwarded to:
EPA Headquarters Accounting Operations Branch, OPP (Tolerance Fees),
P.O. Box 360277M, Pittsburgh, PA 15251. A copy of any objections and
hearing requests filed with the Hearing Clerk identified by the docket
control number, [OPP-300778], must also be submitted to: Public
Information and Records Integrity Branch, Information Resources and
Services Division (7502C), Office of Pesticide Programs, Environmental
Protection Agency, 401 M St., SW., Washington, DC 20460. In person,
bring a copy of objections and hearing requests to Rm. 119, Crystal
Mall #2, 1921 Jefferson Davis Hwy., Arlington, VA.
    A copy of objections and hearing requests filed with the Hearing
Clerk may also be submitted electronically by sending electronic mail
(e-mail) to: opp-docket@epamail.epa.gov. Copies of objections and
hearing requests must be submitted as an ASCII file avoiding the use of
special characters and any form of encryption. Copies of objections and
hearing requests will also be accepted on disks in WordPerfect 5.1/6.1
or ASCII file format. All copies of objections and hearing requests in
electronic form must be identified by the docket control number [OPP-
300778]. No Confidential Business Information (CBI) should be submitted
through e-mail. Electronic copies of objections and hearing requests on
this rule may be filed online at many Federal Depository Libraries.

FOR FURTHER INFORMATION CONTACT: By mail: Joanne I. Miller,
Registration Division (7505C), Office of Pesticide Programs,
Environmental Protection Agency, 401 M St., SW., Washington, DC 20460.
Office location, telephone number, and e-mail address: Crystal Mall #2,
1921 Jefferson Davis Hwy., Arlington, VA, (703) 305-6224; e-mail:
miller.joanne@epamail.epa.gov.

SUPPLEMENTARY INFORMATION: In the Federal Register of November 21,
1997, (62 FR 62304) (FRL 5755-4), EPA, issued a notice pursuant to
section 408 of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21
U.S.C. 346a(e) announcing the filing of a pesticide petition (PP) for
tolerance by BASF Corporation, P.O. Box 13528, Research Triangle Park,
North Carolina 27709. This notice included a summary of the petition
prepared by BASF Corporation, the registrant. There were no comments
received in response to the notice of filing.
    The petition requested that 40 CFR part 180 be amended by
establishing tolerances for combined residues of the herbicide
diflufenzopyr, 2-(1-[([3,5-difluorophenylamino]carbonyl)-
hydrazono]ethyl)-3-pyridinecarboxylic acid, and its metabolites
convertible to M1, (8-methylpyrido[2,3-d]pyridazin-5(6H)-one), in or on
field corn fodder (stover), forage and grain at 0.05 part per million
(ppm). Note that the scientific assessments relevant to establishing
these tolerances for diflufenzopyr were conducted jointly between EPA
and the Pest Management Regulatory Agency (PMRA) of Canada as a project
under the North American Free Trade Agreement (NAFTA) and the Canadian
United States Trade Agreement (CUSTA). Diflufenzopyr qualified as a
candidate for such a program due to its classification as a reduced
risk pesticide.

I. Risk Assessment and Statutory Findings

    Section 408(b)(2)(A)(i) of the FFDCA allows EPA to establish a
tolerance (the legal limit for a pesticide chemical residue in or on a
food) only if EPA determines that the tolerance is "safe." Section
408(b)(2)(A)(ii) defines "safe" to mean that "there is a reasonable
certainty that no harm will result from aggregate exposure to the
pesticide chemical residue, including all anticipated dietary exposures
and all other exposures for which there is reliable information." This
includes exposure through drinking water and in residential settings,
but does not include occupational exposure. Section 408(b)(2)(C)
requires EPA to give special consideration to exposure of infants and
children to the pesticide chemical residue in establishing a tolerance
and to "ensure that there is a reasonable certainty that no harm will
result to infants and children from aggregate exposure to the pesticide
chemical residue."
    EPA performs a number of analyses to determine the risks from
aggregate exposure to pesticide residues. For further discussion of the
regulatory requirements of section 408 and a complete description of
the risk assessment process, see the Final Rule on Bifenthrin Pesticide
Tolerances, November 26, 1997, (62 FR 62961) (FRL 5754-7).

II. Aggregate Risk Assessment and Determination of Safety

    Consistent with section 408(b)(2)(D), EPA has reviewed the
available scientific data and other relevant information in support of
this action. EPA has sufficient data to assess the hazards of
diflufenzopyr and to make a determination on aggregate exposure,
consistent with section 408(b)(2), for tolerances for combined residues
of diflufenzopyr, 2-(1-[([3,5-difluorophenylamino]
carbonyl)hydrazono]ethyl)-3-pyridinecarboxylic acid, and its
metabolites convertible to M1, (8-methylpyrido[2,3-d]pyridazin-5(6H)-
one) on field corn stover, forage and grain at 0.05 ppm. EPA's
assessment of the dietary exposures and risks associated with
establishing the tolerance follows.

A. Toxicological Profile

    EPA has evaluated the available toxicity data and considered its
validity, completeness, and reliability as well as the relationship of
the results of the studies to human risk. EPA has also considered
available information concerning the variability of the sensitivities
of major identifiable subgroups of consumers, including infants and
children. The nature of the toxic effects caused by diflufenzopyr are
discussed below.
     1. Acute toxicology studies place technical-grade diflufenzopyr in
Toxicity Category III or IV for all routes of exposure. It is not a
dermal sensitizer.
     2. In a subchronic feeding study in rats, male and female Wistar
rats were fed test diets containing technical diflufenzopyr, purity
96%, at dose levels of 0, 1,000, 5,000, 10,000 and 20,000 ppm (equal to
0, 60.8, 352, 725 and 1,513 milligram/kilogram body weight/day (mg/kg
bw/day) for males, and 0, 72.8, 431, 890 and 1,750 mg/kg bw/day for
females) for a period of 13 weeks, 10 rats per sex per group. An
additional 10 rats per sex were assigned to the 0 and 20,000 ppm groups
for a 4-week recovery period following treatment. The no observed
adverse effect level (NOAEL) was set at 5,000 ppm (equal to 352 mg/kg
bw/day for males, and 431 mg/kg bw/day for females) based on lower mean
body weight gain and decreased food efficiency in the 10,000 and 20,000
ppm groups, both sexes. Additional findings were decreased food intake
(20,000 ppm, males only); slight increases in cholesterol (20,000 ppm,
both sexes, and 10,000 ppm, males only) and ALAT (10,000 and 20,000
ppm, both sexes); and slightly lower chloride (20,000 ppm, both sexes).
Histopathological findings were an increased incidence of foamy
macrophages in the lungs in the 10,000 and 20,000 ppm groups, both
sexes, and testicular atrophy in the 20,000 ppm group. Following the 4-
week recovery period, the only treatment-related effects which showed
partial or no evidence of recovery were foamy macrophages in the lungs
and testicular atrophy.
     3. In a 13-week feeding study, male and female CD-1 mice were fed
test diets containing technical diflufenzopyr, purity 97.1%, at dietary
concentrations of 0, 350, 1,750, 3,500 and 7,000 ppm (equal to 0, 58,
287, 613 and 1,225 mg/kg bw/day for males, and 0, 84, 369, 787 and
1,605 mg/kg bw/day for females) for a period of 13 weeks, 10 mice per
sex per group. The NOAEL was determined to be 7,000 ppm (equal to 1,225
mg/kg bw/day for males and 1,605 mg/kg bw/day for females) since there
were no treatment-related effects observed in male or female mice at
any dose level tested.
     4. In a subchronic toxicity study in dogs, diflufenzopyr (98%
a.i.) was administered to beagle dogs (4/sex/dose) by feeding at dose
levels of 0, 1,500, 10,000, or 30,000 ppm (0, 58, 403, or 1,131 mg/kg/
day for males; 0, 59, 424, or 1,172 mg/kg/day for females) for 13
weeks. The lowest adverse effect level (LOAEL) for this study is 10,000
ppm (403 mg/kg/day in males and 424 mg/kg/day in females), based on the
occurrence of erythroid hyperplasia in the bone marrow, extramedullary
hemopoiesis in the liver, and hemosiderin deposits in Kupffer cells.
The NOAEL is 1,500 ppm (58 mg/kg/day in males and 59 mg/kg/day in
females).
     5. In the subchronic dermal toxicity study, technical
diflufenzopyr, purity 96.4%, was moistened with distilled water and
administered by dermal application to male and female New Zealand White
rabbits, 5/sex/dose, at dose levels of 0, 100, 300 and 1,000 mg/kg bw
per application. Duration of application was 6 hours a day, daily for
21 to 24 consecutive days. The NOAEL for systemic toxicity was
determined to be 1,000 mg/kg bw/day, since there were no apparent signs
of treatment-related systemic effects observed in male or female
rabbits at any dose level tested. A NOAEL for dermal effects could not
be determined since local dermal irritation was observed at all dose
levels tested (there were no corresponding findings upon
histopathological examination).
     6. In a chronic toxicity study in dogs, diflufenzopyr (98.1% a.i.)
was administered to beagle dogs (4/sex/dose) by feeding at dose levels
of 0, 750, 7,500, or 15,000 ppm (0, 26, 299, or 529 mg/kg/day for
males; 0, 28, 301, or 538 mg/kg/day for females) for 52 weeks. The
LOAEL for this study is 7,500 ppm (299 mg/kg/day for males and 301 mg/
kg/day for females), based on erythroid hyperplasia in the bone marrow
in bone sections, reticulocytosis, and increased hemosiderin deposits
in the liver, kidneys, and spleen. The NOAEL is 750 ppm (26 mg/kg/day
for males and 28 mg/kg/day for females).
     7. In a mouse carcinogenicity study, male and female CD-1 mice
were fed test diets containing technical diflufenzopyr, purity 98.1%,
at dietary concentrations of 0, 700, 3,500 and 7,000 ppm (equal to 0,
100, 517 and 1,037 mg/kg bw/day for males, and 0, 98, 500 and 1,004 mg/
kg bw/day for females), 60 mice per sex per group, for a period of 78
weeks. The NOAEL for systemic toxicity was determined to be 7,000 ppm
(equal to 1,037 mg/kg bw/day for males and 1,004 mg/kg bw/day for
females). There were no treatment-related effects observed at any dose
level tested in male rats. There was a slight, but statistically
significantly lower mean overall body weight gain for females in the
7,000 ppm group, due primarily to decreased gain/increased weight loss
during the second year of the study. In the absence of any other treatment-
related findings, this was not considered to be an adverse, toxicologically
significant finding. There was no evidence of oncogenic potential of
diflufenzopyr for male or female mice at any dose level tested.
     8. In a combined chronic toxicity/carcinogenicity study, male and
female Wistar rats were fed test diets containing technical
diflufenzopyr, purity 97.1% to 99.6%, at dietary concentrations of 0,
500, 1,500, 5,000 and 10,000 ppm (equal to 0, 22, 69, 236 and 518 mg/kg
bw/day for males, and 0, 29, 93, 323 and 697 mg/kg bw/day for females),
72 rats per sex per group, for a period of 104 weeks. The NOAEL for
systemic toxicity was set at 5,000 ppm (equal to 236 mg/kg bw/day for
males and 323 mg/kg bw/day for females). Treatment-related effects in
the 10,000 ppm group were significantly lower body weight and body
weight gains throughout the study period and decreased food efficiency.
There was no evidence of oncogenic potential of diflufenzopyr at any
dose level tested. The incidences of benign and malignant tumors were
comparable between control and treated groups.
     9. In a developmental toxicity study, technical diflufenzopyr
(98.1% a.i.) in 0.5% aqueous methyl cellulose was administered by
gavage to 25 female Crl: CD BR VAF/Plus (Sprague Dawley) rats/dose at
dose levels of 0, 100, 300, or 1,000 mg/kg/day from days 6 through 15
of gestation. The maternal NOAEL is 300 mg/kg/day and the maternal
LOAEL is 1,000 mg/kg/day based on decreases in food consumption and
weight gain. Developmental effects, characterized as significantly
lower fetal body weights in males ( 5%) and skeletal variations,
exhibited as incompletely ossified and unossified sternal centra and
reduced fetal ossification sites for caudal vertebrae, were observed at
1,000 mg/kg/day. The developmental LOAEL is 1,000 mg/kg/day, based on
decreased fetal body weights and skeletal variations. The developmental
NOAEL is 300 mg/kg/day.
     10. In a developmental toxicity study, technical diflufenzopyr
(98.1% a.i.) in 0.5% aqueous methyl cellulose was administered by
gavage to 20 female New Zealand White Hra: (NZW)SPF rabbits/dose at
dose levels of 0, 30, 100, or 300 mg/kg/day from days 6 through 19 of
gestation. The maternal LOAEL is 100 mg/kg/day, based on minimal
reductions in body weight gain with no reduction in food consumption
and clinical signs of toxicity (abnormal feces). The maternal NOAEL is
30 mg/kg/day. Developmental effects, characterized as significant
increases (p≤0.01) in the incidence of supernumerary thoracic
rib pair ossification sites (12.74 vs. 12.54 for controls) occurred at
the 300 mg/kg/day dose. No treatment-related developmental effects were
noted at the low- or mid-doses. The developmental LOAEL is 300 mg/kg/
day based on increased skeletal variations (supernumerary rib
ossification sites). The developmental NOAEL is 100 mg/kg/day.
     11. In a 2-generation reproduction study, technical diflufenzopyr
(98.1% a.i.) was administered continuously in the diet to 26 Wistar
rats/sex/dose at dose levels of 0, 500, 2,000 or 8,000 ppm in the diet
(0, 27.3-42.2, 113.1-175.9, or 466.2-742.0 mg/kg/day). The systemic
LOAEL is 2,000 ppm (113.1-175.9 mg/kg/day) based on reduced body weight
gain, increased food consumption, and increased seminal vesicle
weights. The systemic NOAEL is 500 ppm (27.3-42.2 mg/kg/day). The
reproductive LOAEL is 8,000 ppm (466.2-742.0 mg/kg/day) based on lower
live birth and viability indices, total pre-perinatal loss, reduced
body weights and body weight gain during lactation, a higher proportion
of runts, and a higher percentage of offspring with no milk in the
stomach. The reproductive NOAEL is 2,000 ppm (113.1-175.9 mg/kg/day).
     12. In an acute neurotoxicity study, diflufenzopyr (96.4% a.i.)
was administered by gavage to Crl:CD BR rats (10/sex/group) at dose
levels of 0, 125, 500 or 2,000 mg/kg. The rats were evaluated for
reactions in functional observations and motor activity measurements at
3 hours, 7 days, and 14 days postdosing. Histopathological evaluation
on the brain and peripheral nerves was assessed after day 14.
Diflufenzopyr had no definite impact on neurotoxic responses, although
a few abnormalities were observed in the functional battery on the day
of dosing. A decrease in immediate righting responses that was observed
in several males in all treatment groups was not concentration-
dependent. Nasal staining was observed in more rats in the 2,000 mg/kg
treatment groups (6 males; 3 females), but was not considered a
definite or significant response to treatment. Lower mean brain weights
in all female treatment groups lacked associated macroscopic and
microscopic histopathological changes, and were only 4-5% lower than
the control brain weight. Mean locomotor activities for the 2,000 mg/kg
female treatment groups were decreased on Days 7 (difference 27%, p <
0.05) and 14 (difference 15%, not significant) after dosing, but the
pattern of activity for the individual animals was similar to the
individual controls over time. There were no definite treatment-related
differences in body weights or food consumption in any of the treatment
groups. There was no evidence of treatment-related neuropathology in
the 2,000 mg/kg treatment group. A LOAEL was not established. The NOAEL
for acute neurotoxicity is 2,000 mg/kg (the limit dose).
     13. In a subchronic neurotoxicity study, diflufenzopyr (96.4%
a.i.) was administered in the diet to Crl: CD BR rats (10/sex/group) at
dose levels of 0, 25, 75 or 1,000 mg/kg/day for 13 weeks. The rats were
evaluated for reactions in functional observations and motor activity
testing at 4 hours and during weeks 4, 8 and 13 of treatment. No
treatment-related neurotoxicological effects were observed at any
treatment level. A LOAEL for neurotoxicological effects was not
established; the NOAEL was 1,000 mg/kg/day for both sexes. Treatment-
related toxic effects were observed at the 1,000 mg/kg/day treatment
level. The toxicological LOAEL for this study is 1,000 mg/kg/day, based
on decreased body weight gains for both sexes. The toxicological NOAEL
is 75 mg/kg/day.
     14. In a microbial mutagenicity assay, Salmonella typhimurium
strains TA98, TA100, TA1535, TA1537, and TA1538 were exposed to
diflufenzopyr (97.1%) in DMSO at concentrations of 333, 667, 1,000,
3,330, 6,670 and 10,000 μg/plate in the presence and absence of
mammalian metabolic activation. Diflufenzopyr (97.1%) was tested to
twice the limit concentration of 5,000 μg/plate and
cytotoxicity was observed at 6,670 and 10,000 μg/plate in the
absence of activation (-S9) but not in its presence (+S9). The positive
controls induced the appropriate responses in the corresponding
strains. There was no evidence that the test article induced mutant
colonies over background.
     15. In a mammalian cell gene mutation assay at the thymidine
kinase locus, heterozygous L5178Y (TK +/-) mouse lymphoma cells
cultured in vitro were exposed in independent repeat assays to
diflufenzopyr technical (97.1% a.i.) in dimethyl sulfoxide at dose
levels ranging from 0.05 to 3.0 mg/mL (50 to 3,000 μg/mL) in
the presence and absence of S9 mammalian metabolic activation in the
first trial, and 0.05 to 2.0 mg/mL (50 to 2,000 μg/mL) in the
second. Diflufenzopyr was tested up to cytotoxic dose levels and
mutation frequencies were determined for dose levels selected on the
basis of relative growth. Although initially declared positive by the then
study director, application of more recent criteria for mutagenic responses
has rendered the test article negative for forward gene mutation at the
TK locus in mouse L5178Y cells in the presence and absence of S9
activation. The positive controls induced the appropriate responses.
     16. In an in vivo mouse bone marrow micronucleus assay, groups of
15 male and female ICR mice were dosed by oral gavage with
diflufenzopyr (technical, 97.1%) in corn oil at 500, 1,667, and 5,000
mg/kg. Bone marrow cells were harvested at 24, 48, or 72 hours and
scored for micronucleated polychromatic erythrocytes (MPCEs). No
mortalities or adverse clinical signs were observed at any dose
including the limit dose of 5,000 mg/kg, and there were no changes in
the PCE/NCE ratios (an indirect measure of cytotoxicity). The positive
control induced significant increases in MPCEs, also in the absence of
any target cell cytotoxicity. No significant increase in the frequency
of MPCEs in bone marrow cells after any treatment time were recorded;
therefore, the test article is considered negative in this micronucleus
assay.
     17. In an unscheduled DNA synthesis assay, primary rat hepatocyte
cultures were exposed to diflufenzopyr (97.1% a.i.) in
dimethylsulfoxide (DMSO) at 15 concentrations ranging from 0.0250 to
1,000 μg/mL in the presence of 10<greek-
m>Ci/ml3 HtdR (42 Ci/mmole) for approximately 19
hours. Mutagenicity, as measured by unscheduled DNA synthesis (UDS), was
determined for 6 concentrations selected on the basis of cytotoxicity. The
concentrations selected were 5.00, 10.0, 25.0, 50.0, 100, and 250
μg/mL. The highest concentration selected for UDS evaluation,
250 μg/mL, was moderately toxic (50.8% survival). There was no
evidence that unscheduled DNA synthesis, as determined by radioactive
tracer procedures (nuclear silver grain counts) was induced. The
positive control induced the appropriate response.
     18. In a rat metabolism study, (phenyl-U-14C) or
(pyridinyl-4,6-14C) diflufenzopyr was administered to
five Wistar rats/sex/dose group as a single intravenous dose at 1 mg/kg/day,
a single oral dose (gavage) at 10 or 1,000 mg/kg or a single dose at 10
mg/kg following a 14-day pretreatment with unlabeled diflufenzopyr at
10 mg/kg. Bile-duct cannulated rats from each dose group were
sacrificed at 48 hours post-dose (Subgroup 2). Non-cannulated rats from
each dose group were sacrificed at 72 hours (Subgroup 1) or 24 hours
(Subgroup 3) post-dose. (14C) Diflufenzopyr was only
partially absorbed from the GI tracts of orally dosed rats as indicated
by the levels of excretion in urine and bile. In all orally dosed
groups, 20-44% of the dose was excreted in the urine and 3-11% was
excreted in the bile. In contrast, intravenously dosed rats excreted
61-89% of the dose in urine and 4-19% of the dose in bile. For all
orally dosed groups, the level of absorption was similar between sexes.
Dose level and pretreatment had little effect on the proportion of the
dose excreted in urine following oral administration. Enterohepatic
circulation plays a role in the elimination of 14C
diflufenzopyr in rats. 3-19% of the dose was recovered in the bile of
all dose groups. Within 72 hours of dosing, intravenously-dosed rats
excreted the majority of radioactivity in urine (61-89%), whereas
orally-dosed rats excreted most of the radioactivity in feces (49-79%),
regardless of radiolabel or sex. Pretreatment did not appear to affect
the pattern of excretion. Bile-cannulated rats excreted lesser amounts
in feces compared to non-cannulated rats; 3-19% of the dose was
excreted in bile. The estimated half-lives of radiocarbon eliminated in
urine and feces was 5.3-6.9 hours for all single intravenous and oral
dose groups, and 7.7-10.8 hours for all repeat oral dose groups. Total
radioactive residues in tissues from rats in all dose groups were <3%
of the administered dose. Total tissue residue levels were highest in
rats sacrificed at 24 hours post-dose; residue levels were highest in
blood, blood cell, and serum for the phenyl label groups, and were
highest in liver and kidney for the pyridinyl label groups. Blood
residue levels for all dose groups were <1% of the administered dose at
all sampling intervals through 72 hours post-dose. TLC and HPLC
analyses were conducted on 0-72 and 0-48 urine and feces samples, and
on 0-48 hour bile samples from each treatment regimen. The structures
of the metabolites were confirmed using 2-D TLC, HPLC, LC/MS, DIP/MS,
FAB/MS, and proton NMR. For each dose group, the metabolic profile was
similar between sexes, except for differences in metabolite levels.
Unchanged diflufenzopyr was identified as the major component in urine,
feces, and bile from all dose groups using either radiolabel. Urinary
metabolites identified in the 14C-phenyl labeled dose
groups included: 3,5-difluoroaniline (M2; aniline) and 6-((3,5-difluorophenyl)
carbomyl)-8-methyl-pyrido (2,3-d)-5-pyridazinone (M5; carbamoyl
phthalazinone). Urinary metabolites identified in the
14C-pyridinyl labeled dose groups included: 8-methyl-5-
hydroxy-pyrido(2,3-d)-pyridazine (M1; phthalazinone); carbamoyl phthalazinone
(M5); 2-acetyl nicotinic acid (M6; 2-acetyl nicotinic acid); 8-
methylpyrido[2,3-d]pyridazine-2,5(1H, 6H)-dione (M9; 2-keto-M1); 8-
hydroxymethyl-5(6H)-pyrido[2,3-d]pyridazinone (M10; 8-hydroxymethyl-
M1); and, 8-hydroxymethylpyrido[2,3-d]pyridazine-2,5(1H,6H)-dione (M19;
2-keto-8-hydroxymethyl-M1 or Metabolite E). Fecal metabolites
identified in the phenyl label groups included: methyl N-(3,5-
difluorophenyl)carbamate (M8) and M5. Fecal metabolites identified in
the pyridinyl label groups included: M1, M5, M6, M9, and M10. Besides
parent, bile samples also contained minor amounts of M5 (both labels)
and M1 (pyridinyl label only). The data indicate that diflufenzopyr is
excreted primarily as unchanged parent in urine, feces, and bile. Minor
amounts of hydrolysis products (M1, M5, and M6) and hydroxylation
products (M9, M10, and M19) were identified in excreta.

B. Toxicological Endpoints

    1. Acute toxicity. For acute dietary risk assessment, an acute
Reference Dose (RfD) of 1.0 mg/kg/day has been selected, based on the
developmental NOAEL of 100 mg/kg/day from the Rabbit Developmental
Study and an uncertainty factor of 100 (10x for interspecies
differences and 10x for intraspecies variations). The endpoint is based
on developmental findings (increased skeletal variations) in rabbits
which can be attributed to a single gavage dose during gestation and
which occurred at a maternally toxic dose. The population subgroup at
risk for this developmental effect is females of child-bearing age (13+
years). No appropriate toxicological endpoint is available in the data
base for other subgroups of the population including infants and
children.
     2. Short - and intermediate - term toxicity. Since there was no
observed dermal or systemic toxicity in a rabbit 21-day dermal study
with diflufenzopyr, short- and intermediate-term toxicity endpoints are
not being established.
     3. Chronic toxicity. EPA has established the RfD for diflufenzopyr
at 0.26 milligrams/kilogram/day (mg/kg/day). This RfD is based on bone
marrow compensated hemolytic anemia observed in the 1-year dog feeding
study with a NOAEL of 26 mg/kg/day.
    4. Carcinogenicity. Based on the lack of evidence of
carcinogenicity in mice and rats at doses that were judged to be
adequate to assess the carcinogenic potential, diflufenzopyr has been
characterized as "not likely" to be a human carcinogen.

C. Exposures and Risks

    1. From food and feed uses. No previous tolerances have been
established for the combined residues of diflufenzopyr, 2-(1-[([3,5-
difluorophenylamino]carbonyl)-hydrazono]ethyl)-3-pyridinecarboxylic
acid, and its metabolites convertible to M1, (8-methylpyrido[2,3-
d]pyridazin-5(6H)-one). Risk assessments were conducted by EPA to
assess dietary exposures from diflufenzopyr as follows:
    i.  Acute exposure and risk. Acute dietary risk assessments are
performed for a food-use pesticide if a toxicological study has
indicated the possibility of an effect of concern occurring as a result
of a one day or single exposure. An acute dietary risk assessment was
performed for diflufenzopyr, its metabolites characterized as M1, and
M10. The analysis was conducted using the acute RfD of 1.0 mg/kg/day,
based on developmental findings (increased skeletal variations)
observed in the Rabbit Developmental Study. For the population subgroup
of concern, females 13 years and older, the estimated 95th percentile
of exposure is equal to 0.01% of the acute RfD. The analysis is
conservative since it assumes that 100% of corn-derived foods contain
residues at the tolerance level (0.05 ppm).
    ii. Chronic exposure and risk. A chronic dietary risk assessment
was performed for diflufenzopyr, its metabolites characterized as M1,
and M10. The analysis used the RfD of 0.26 mg/kg bwt/day and assumed
that 100% of corn-derived foods contain residues at the tolerance level
(0.05 ppm). These assumptions result in a Theoretical Maximum Residue
Contribution (TMRC) that is less than or equal to 0.1% of the RfD for
the overall U.S. population (48 states) and all population subgroups.
    2. From drinking water. There are no established Maximum
Contaminant Levels or health advisory levels for residues of
diflufenzopyr or its metabolites in drinking water. EPA used the SCI-
GROW (Screening Concentration in Ground Water) model to estimate
residues of diflufenzopyr in ground water and the GENEEC (Generic
Expected Environmental Concentration) model to estimate diflufenzopyr
residue levels in surface water. Estimated environmental concentrations
(EECs) in ground water reflecting an application rate of 0.12 pounds of
active ingredient per acre were 0.006 parts per billion (ppb) for acute
and chronic exposure scenarios. EECs in surface water were 3.8 ppb for
acute exposure scenarios and 1.95 ppb for chronic exposure scenarios.
The computer generated EECs represent conservative estimates and should
be used only for screening.
    i. Acute exposure and risk. EPA has calculated a drinking water
level of comparison (DWLOC) for acute exposure to diflufenzopyr in
drinking water for the relevant population subgroup, females 13 + years
of age. THE DWLOC is 29,970 ug/L.
     To calculate the DWLOCs for acute exposure relative to an acute
toxicity endpoint, the acute dietary food exposure from the DEEM
(Dietary Exposure Evaluation Model) analysis was subtracted from the
ratio of the acute NOAEL (used for acute dietary assessments) to the
acceptable margin of exposure (MOE) for aggregate exposure to obtain
the acceptable acute exposure to diflufenzopyr in drinking water.
DWLOCs were then calculated using default body weights and drinking
water consumption figures.
     Estimated maximum concentrations of diflufenzopyr in surface and
ground water are 3.80 ppb and 0.006 ppb, respectively. The estimated
maximum concentrations in water are less than EPA's level of comparison
(29,970 ppb) for diflufenzopyr residues in drinking water as a
contribution to acute aggregate exposure. Therefore, taking into
account the use proposed in this action, EPA concludes with reasonable
certainty that residues of diflufenzopyr in drinking water (when
considered along with other sources of exposure for which EPA has
reliable data) would not result in unacceptable levels of aggregate
human health risk at this time.
    ii. Chronic exposure and risk. EPA has calculated drinking water
levels of comparison (DWLOCs) for chronic exposure to diflufenzopyr in
drinking water. For chronic (non-cancer) exposure to diflufenzopyr in
surface and ground water, the drinking water levels of comparison are
9,100 ug/L and 2,600 ug/L for the U.S. population and the subgroup
children (1-6 years old), respectively.
     To calculate the DWLOCs for chronic (non-cancer) exposure relative
to a chronic toxicity endpoint, the chronic dietary food exposure (from
the DEEM analysis) and residential exposure were subtracted from the
RfD to obtain the acceptable chronic (non-cancer) exposure to
diflufenzopyr in drinking water. DWLOCs were then calculated using
default body weights and drinking water consumption figures.
     Estimated average concentrations of diflufenzopyr in surface and
ground water are 1.95 ppb and 0.006 ppb, respectively. The DWLOCs are
9,100 ppb for the U.S. population and 2,600 ppb for the subgroup,
children (1-6 years old). The estimated average concentrations of
diflufenzopyr in surface and ground water are less than EPA's levels of
comparison for diflufenzopyr in drinking water as a contribution to
chronic aggregate exposure.
    3. From non-dietary exposure. There are no registered or proposed
residential uses for diflufenzopyr.
    4. Cumulative exposure to substances with common mechanism of
toxicity. Section 408(b)(2)(D)(v) requires that, when considering
whether to establish, modify, or revoke a tolerance, the Agency
consider "available information" concerning the cumulative effects of
a particular pesticide's residues and "other substances that have a
common mechanism of toxicity."
    EPA does not have, at this time, available data to determine
whether diflufenzopyr has a common mechanism of toxicity with other
substances or how to include this pesticide in a cumulative risk
assessment. Unlike other pesticides for which EPA has followed a
cumulative risk approach based on a common mechanism of toxicity,
diflufenzopyr 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 diflufenzopyr 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 Final Rule
for Bifenthrin Pesticide Tolerances (62 FR 62961, November 26, 1997).

D. Aggregate Risks and Determination of Safety for U.S. Population

    1. Acute risk. For the population subgroup of concern, females 13+
years old, the acute dietary (food) exposure does not exceed 0.02% of
the acute RfD. The drinking water level of comparison (DWLOC) for acute
exposure to diflufenzopyr residues is 29,970 ug/L for females (13+
years). The maximum concentration of diflufenzopyr in drinking water
(3.80 ug/L) is less than EPA's level of comparison for diflufenzopyr in
drinking water as a contribution to acute aggregate exposure. EPA
concludes with reasonable certainty that residues of diflufenzopyr in
drinking water will not contribute significantly to the aggregate acute
human health risk and that the acute aggregate exposure from diflufenzopyr in
food and water will not exceed the Agency's level of concern for acute dietary
exposure.
    2. Chronic risk. Using the TMRC exposure assumptions described
above, EPA has concluded that aggregate exposure to diflufenzopyr from
food will utilize less than 0.1% of the RfD for the U.S. population.
The major identifiable subgroup with the highest aggregate exposure,
children 1-6 years old, is "discussed below." EPA generally has no
concern for exposures below 100% of the RfD because the RfD represents
the level at or below which daily aggregate dietary exposure over a
lifetime will not pose appreciable risks to human health. Despite the
potential for exposure to diflufenzopyr in drinking water and from non-
dietary, non-occupational exposure, EPA does not expect the aggregate
exposure to exceed 100% of the RfD. EPA concludes that there is a
reasonable certainty that no harm will result from aggregate exposure
to diflufenzopyr residues.
    3. Short- and intermediate-term risk. Short- and intermediate-term
aggregate exposure takes into account chronic dietary food and water
(considered to be a background exposure level) plus indoor and outdoor
residential exposure. There are no established or proposed residential
uses for diflufenzopyr. Therefore, the short and intermediate aggregate
risks are adequately addressed by the chronic aggregate dietary risk
assessment.
    4. Aggregate cancer risk for U.S. population. Diflufenzopyr has
been classifiedd as "not likely" to be a human carcinogen.
    5. Determination of safety. Based on these risk assessments, EPA
concludes that there is a reasonable certainty that no harm will result
from aggregate exposure to diflufenzopyr residues.

E. Aggregate Risks and Determination of Safety for Infants and Children

    1. Safety factor for infants and children-- i. In general. In
assessing the potential for additional sensitivity of infants and
children to residues of diflufenzopyr, EPA considered data from
developmental toxicity studies in the rat and rabbit and a two-
generation reproduction study in the rat. The developmental toxicity
studies are designed to evaluate adverse effects on the developing
organism resulting from maternal pesticide exposure gestation.
Reproduction studies provide information relating to effects from
exposure to the pesticide on the reproductive capability of mating
animals and data on systemic toxicity.
    FFDCA section 408 provides that EPA shall apply an additional
tenfold margin of safety for infants and children in the case of
threshold effects to account for pre-and post-natal toxicity and the
completeness of the database unless EPA determines that a different
margin of safety will be safe for infants and children. Margins of
safety are incorporated into EPA risk assessments either directly
through use of a margin of exposure (MOE) analysis or through using
uncertainty (safety) factors in calculating a dose level that poses no
appreciable risk to humans. EPA believes that reliable data support
using the standard uncertainty factor (usually 100 for combined inter-
and intra-species variability) and not the additional tenfold MOE/
uncertainty factor when EPA has a complete data base under existing
guidelines and when the severity of the effect in infants or children
or the potency or unusual toxic properties of a compound do not raise
concerns regarding the adequacy of the standard MOE/safety factor.
    ii. Pre- and post-natal sensitivity.  There is no indication of
increased sensitivity of rats or rabbits to in utero and/or early
postnatal exposure to diflufenzopyr in the developmental and
reproductive toxicity studies.
    iii. Conclusion. There is a complete toxicity database for
diflufenzopyr and exposure data is complete or is estimated based on
data that reasonably accounts for potential exposures. Taking into
account the completeness of the database and the toxicity data
regarding pre- and post-natal sensitivity, EPA concludes, based on
reliable data, that use of the standard margin of safety will be safe
for infants and children without addition of another tenfold factor.
    2. Acute risk. No appropriate acute toxicological endpoint has been
identified for infants and children.
    3. Chronic risk. Using the exposure assumptions described above,
EPA has concluded that aggregate exposure to diflufenzopyr from food
will utilize 0.1% of the RfD for infants and children. EPA generally
has no concern for exposures below 100% of the RfD because the RfD
represents the level at or below which daily aggregate dietary exposure
over a lifetime will not pose appreciable risks to human health.
Despite the potential for exposure to diflufenzopyr in drinking water,
EPA does not expect the aggregate exposure to exceed 100% of the RfD.
    4. Determination of safety. Based on these risk assessments, EPA
concludes that there is a reasonable certainty that no harm will result
to infants and children from aggregate exposure to diflufenzopyr
residues.

III. Other Considerations

A. Metabolism In Plants and Animals

    The nature of the residue in plants (field corn) and animals is
understood. In field corn, the urea bond is cleaved to yield
metabolites containing a new bicyclic ring system. No diflufenzopyr was
detected in any of the corn matrices; metabolites comprising >10% total
radioactive residue (TRR) include M1 (8-methylpyrido[2,3-d]pyridazin-
5(6H)-one), M10 (8-hydroxymethyl-5(6H)-pyrido[2,3-d]pyridazone) and its
glucose conjugate, and M9 (8-methylpyrido[2,3-d]pyridazine-2,5(1H,6H)-
dione in forage and fodder, and 6-14% TRR lignin was found in fodder.
Corn grain contained 3-4 discrete unknowns, all at <10% TRR or <0.05
ppm each. The residues of concern in plants are diflufenzopyr, 2-(1-
[([3,5-difluorophenylamino]carbonyl)-hydrazono]ethyl)-3-
pyridinecarboxylic acid, and its metabolites convertible to M1 (8-
methylpyrido[2,3-d]pyridazin-5(6H)-one).
     In livestock, the majority (≥90%) of diflufenzopyr was
excreted. In the ruminant, major metabolites include M1, M5 (6-((3,5-
difluorophenylcarbamoyl-8-methyl-pyrido[2,3-d]-5-pyridazinone) and M19
(8-hydroxymethylpyrido[2,3-d]pyridazine-2,5(1H,6H)-dione. A substantial
amount (8-50%) of diflufenzopyr was also found in milk, kidney, and
liver. In poultry, diflufenzopyr was not detected, and M1 was the only
significant metabolite identified, and in egg white only. Transfer of
secondary residues to livestock is not expected .

B. Analytical Enforcement Methodology

     Adequate enforcement methodology (gas chromatography) is available
to enforce the tolerance expression. The method may be requested from:
Calvin Furlow, PRRIB, IRSD (7502C), Office of Pesticide Programs,
Environmental Protection Agency, 401 M St., SW., Washington, DC 20460.
Office location and telephone number: Rm 101FF, Crystal Mall #2, 1921
Jefferson Davis Hwy., Arlington, VA 22202, (703-305-5229).

C. Magnitude of Residues

    Residues of diflufenzopyr, 2-(1-[([3,5-
difluorophenylamino]carbonyl)-hydrazono]ethyl)-3-pyridinecarboxylic
acid, and its metabolites convertible to M1 (8-methylpyrido[2,3-
d]pyridazin-5(6H)-one) are not expected to exceed 0.05 ppm in field
corn grain, forage and stover.

D. International Residue Limits

    There are no CODEX or Mexican residue limits established for
diflufenzopyr or its metabolites. As part of the joint review, Canada
will be setting an equivalent Maximum Residue Level (MRL) for corn
grain. Therefore, no compatibility problems exist for the proposed
tolerances.

E. Rotational Crop Restrictions

    The end-use product, which contains the active ingredients
diflufenzopyr and dicamba (sodium salts), will contain a statement
limiting the planting of rotational crops for a least 120 days after
application. This restriction is based on rotational crop data for
dicamba. The rotational crop study submitted for diflufenzopyr was not
conducted in accordance with EPA guidelines. However, based on the
results of this study, the low residues in the treated corn crop and
diflufenzopyr's lack of persistence in soil, EPA does not expect
residues of diflufenzopyr and its metabolites to occur in rotational
crops at the 120-day plant-back interval, when corn is treated at the
label rate of up to 0.125 pounds active ingredient per acre per season.

IV. Conclusion

    Therefore, tolerances are established for combined residues of
diflufenzopyr, 2-(1-[([3,5-difluorophenylamino]carbonyl)-
hydrazono]ethyl)-3-pyridinecarboxylic acid, and its metabolites
convertible to M1, (8-methylpyrido[2,3-d]pyridazin-5(6H)-one) in field
corn stover, forage and grain at 0.05 ppm ppm.

V. Objections and Hearing Requests

    The new FFDCA section 408(g) provides essentially the same process
for persons to "object" to a tolerance regulation as was provided in
the old section 408 and in section 409. However, the period for filing
objections is 60 days, rather than 30 days. EPA currently has
procedural regulations which govern the submission of objections and
hearing requests. These regulations will require some modification to
reflect the new law. However, until those modifications can be made,
EPA will continue to use those procedural regulations with appropriate
adjustments to reflect the new law.
    Any person may, by March 29, 1999, file written objections to any
aspect of this regulation and may also request a hearing on those
objections. Objections and hearing requests must be filed with the
Hearing Clerk, at the address given above (40 CFR 178.20). A copy of
the objections and/or hearing requests filed with the Hearing Clerk
should be submitted to the OPP docket for this rulemaking. 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 fee prescribed by 40
CFR 180.33. If a hearing is requested, the objections must include a
statement of the factual issues on which a hearing is requested, the
requestor's contentions on such issues, and a summary of any evidence
relied upon by the requestor (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 genuine and substantial issue
of fact; there is a reasonable possibility that available evidence
identified by the requestor would, if established, resolve one 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 issues in the manner sought by the requestor would be adequate
to justify the action requested (40 CFR 178.32). Information submitted
in connection with an objection or hearing request may be claimed
confidential by marking any part or all of that information as CBI.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2. A copy of the information that
does not contain CBI must be submitted for inclusion in the public
record. Information not marked confidential may be disclosed publicly
by EPA without prior notice.

VI. Public Record and Electronic Submissions

    EPA has established a record for this rulemaking under docket
control number [OPP-300778] (including any comments and data submitted
electronically). A public version of this record, including printed,
paper versions of electronic comments, which does not include any
information claimed as CBI, is available for inspection from 8:30 a.m.
to 4 p.m., Monday through Friday, excluding legal holidays. The public
record is located in Room 119 of the Public Information and Records
Integrity Branch, Information Resources and Services Division (7502C),
Office of Pesticide Programs, Environmental Protection Agency, Crystal
Mall #2, 1921 Jefferson Davis Hwy., Arlington, VA.
    The official record for this rulemaking, as well as the public
version, as described above will be kept in paper form. Accordingly,
EPA will transfer any copies of objections and hearing requests
received electronically into printed, paper form as they are received
and will place the paper copies in the official rulemaking record which
will also include all comments submitted directly in writing. The
official rulemaking record is the paper record maintained at the
Virginia address in "ADDRESSES" at the beginning of this document.

VII. Regulatory Assessment Requirements

A. Certain Acts and Executive Orders

    This final rule establishes tolerances under FFDCA section 408(d)
in response to a petition submitted to the Agency. The Office of
Management and Budget (OMB) has exempted these types of actions from
review under Executive Order 12866, entitled Regulatory Planning and
Review (58 FR 51735, October 4, 1993). This final rule does not contain
any information collections subject to OMB approval under the Paperwork
Reduction Act (PRA), 44 U.S.C. 3501 et seq., or impose any enforceable
duty or contain any unfunded mandate as described under Title II of the
Unfunded Mandates Reform Act of 1995 (UMRA) (Pub. L. 104-4). Nor does
it require any prior consultation as specified by Executive Order
12875, entitled Enhancing the Intergovernmental Partnership (58 FR
58093, October 28, 1993), or special considerations as required by
Executive Order 12898, entitled Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations (59 FR 7629, February 16, 1994), or require OMB review in
accordance with Executive Order 13045, entitled Protection of Children
from Environmental Health Risks and Safety Risks (62 FR 19885, April
23, 1997).
    In addition, since tolerances and exemptions that are established
on the basis of a petition under FFDCA section 408(d), such as the
tolerances in this final rule, do not require the issuance of a
proposed rule, the requirements of the Regulatory Flexibility Act (RFA)
(5 U.S.C. 601 et seq.) do not apply. Nevertheless, the Agency has
previously assessed whether establishing tolerances, exemptions from
tolerances, raising tolerance levels or expanding exemptions might
adversely impact small entities and concluded, as a generic matter,
that there is no adverse economic impact. The factual basis for the
Agency's generic certification for tolerance actions published on May
4, 1981 (46 FR 24950) and was provided to the Chief Counsel for
Advocacy of the Small Business Administration.

B. Executive Order 12875

    Under Executive Order 12875, entitled Enhancing the
Intergovernmental Partnership (58 FR 58093, October 28, 1993), EPA may
not issue a regulation that is not required by statute and that creates
a mandate upon a State, local, or tribal government, unless the Federal
government provides the funds necessary to pay the direct compliance
costs incurred by those governments. If the mandate is unfunded, EPA
must provide to OMB a description of the extent of EPA's prior
consultation with representatives of affected State, local, and tribal
governments, the nature of their concerns, copies of any written
communications from the governments, and a statement supporting the
need to issue the regulation. In addition, Executive Order 12875
requires EPA to develop an effective process permitting elected
officials and other representatives of State, local, and tribal
governments "to provide meaningful and timely input in the development
of regulatory proposals containing significant unfunded mandates."
    Today's rule does not create an unfunded Federal mandate on State,
local, or tribal governments. The rule does not impose any enforceable
duties on these entities. Accordingly, the requirements of section 1(a)
of Executive Order 12875 do not apply to this rule.

C. Executive Order 13084

    Under Executive Order 13084, entitled Consultation and Coordination
with Indian Tribal Governments (63 FR 27655, May 19, 1998), EPA may not
issue a regulation that is not required by statute, that significantly
or uniquely affects the communities of Indian tribal governments, and
that imposes substantial direct compliance costs on those communities,
unless the Federal government provides the funds necessary to pay the
direct compliance costs incurred by the tribal governments. If the
mandate is unfunded, EPA must provide to OMB, in a separately
identified section of the preamble to the rule, a description of the
extent of EPA's prior consultation with representatives of affected
tribal governments, a summary of the nature of their concerns, and a
statement supporting the need to issue the regulation. In addition,
Executive Order 13084 requires EPA to develop an effective process
permitting elected officials and other representatives of Indian tribal
governments "to provide meaningful and timely input in the development
of regulatory policies on matters that significantly or uniquely affect
their communities."
    Today's rule does not significantly or uniquely affect the
communities of Indian tribal governments. This action does not involve
or impose any requirements that affect Indian tribes. Accordingly, the
requirements of section 3(b) of Executive Order 13084 do not apply to

this rule.

VIII. Submission to Congress and the Comptroller General

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General of the
United States. EPA will submit a report containing this rule and other
required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register. This rule is not a
"major rule" as defined by 5 U.S.C. 804(2).

List of Subjects in 40 CFR Part 180

    Environmental protection, Administrative practice and procedure,
Agricultural commodities, Pesticides and pests, Reporting and
recordkeeping requirements.

    Dated: January 14, 1999.

Marcia E. Mulkey,
Director, Office of Pesticide Programs.
    Therefore, 40 CFR chapter I 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. By adding Sec. 180.549 to read as follows:

Sec. 180.549  Diflufenzopyr; tolerances for residues.

    (a) General. Tolerances are established for combined residues of
diflufenzopyr, 2-(1-[([3,5-difluorophenylamino]carbonyl)-
hydrazono]ethyl)-3-pyridinecarboxylic acid, and its metabolites
convertible to M1 (8-methylpyrido[2,3-d]pyridazin-5(6H)-one) in or on
the following raw agricultural commodities.

------------------------------------------------------------------------
                                                              Parts
     Commodity                                                 per
                                                             million
------------------------------------------------------------------------
Field corn, forage.........................................   0.05

Field corn, grain..........................................   0.05

Field corn, stover.........................................   0.05
------------------------------------------------------------------------

    (b) Section 18 emergency exemptions. [Reserved]
    (c)  Tolerances with regional registrations. [Reserved]
    (d)  Indirect or inadvertent residues. [Reserved]

[FR Doc. 99-1901 Filed 1-27-99; 8:45 am]
BILLING CODE 6560-50-F