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Diflubenzuron - Temporary Pesticide Tolerance 5/98

[Federal Register: May 13, 1998 (Volume 63, Number 92)]
[Rules and Regulations]
[Page 26481-26488]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr13my98-39]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 180
[OPP-300660; FRL-5790-5]
RIN 2070-AB78
Diflubenzuron; Temporary Pesticide Tolerance
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: This regulation establishes a temporary tolerance for residues
of the insecticide diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-
2,6-difluorobenzamide) and metabolites convertible to p-chloroaniline
expressed as diflubenzuron on rice grain at 0.01 ppm. Uniroyal Chemical
Company, Inc. submitted a petition to EPA under the Federal Food, Drug,
and Cosmetic Act (FFDCA), as amended by the Food Quality Protection Act
of 1996 requesting this temporary tolerance in association with an
Experimental Use Permit (EUP) under the Federal Insecticide, Fungicide,
and Rodenticide Act (FIFRA).

DATES: This regulation is effective May 13, 1998. Objections and
requests for hearings must be received by EPA on or before July 13,
1998.

ADDRESSES: Written objections and hearing requests, identified by the
docket control number, [OPP-300660], 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-300660], must also be submitted to: Public
Information and Records Integrity Branch, Information Resources and
Services Division (7506C), 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. 1132, CM #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 file
format or ASCII file format. All copies of objections and hearing
requests in electronic form must be identified by the docket control
number [OPP-300660]. 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: Paul Schroeder, 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) 305-6602, e-mail:
schroeder.paul@epamail.epa.gov.

SUPPLEMENTARY INFORMATION: In the Federal Register of February 25, 1998
(63 FR 9528) (FRL-5775-3), 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 6G4771) from Uniroyal
Chemical Company, Inc., Bethany, CT proposing to amend 40 CFR part 180
by establishing a tolerance for residues of the insect growth
regulator, diflubenzuron and metabolites convertible to p-
chloroaniline, expressed as diflubenzuron in or on rice at 0.02 parts
per million (ppm) and rice straw at 0.8 ppm. The notice included a
summary of the petition prepared by Uniroyal Chemical Company, Inc.,
the registrant. In the Federal Register of March 9, 1998 (63 FR 11445)
(FRL-5777-8), a clarification of the notice of filing was published
explaining that Uniroyal had submitted two petitions, 6G4771, for the
establishment of a temporary tolerance in or on rice at 0.01 ppm in
association with a 3,000 acre EUP, and 8F4925, to amend 40 CFR 180.377
to include a tolerance for residues of the insect growth regulator,
diflubenzuron and metabolites convertible to p-chloroaniline, expressed
as diflubenzuron in or on rice at 0.02 parts per million (ppm) and rice
straw at 0.8 ppm. There were no comments received in response to the
notice of filing or the clarification.

I. Risk Assessment and Statutory Findings

    EPA establishes maximum legal levels (tolerances) for pesticide
residues on food under section 408 of FFDCA. EPA performs a number of
analyses to determine the risk 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 (62 FR 62961,
November 26, 1997) (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 residues
of the insecticide diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-
2,6-difluorobenzamide) and metabolites convertible to p-chloroaniline
expressed as diflubenzuron on rice grain at 0.01, and to make a
determination on aggregate exposure, consistent with section 408(b)(2),
for a tolerance for residues of the insecticide diflubenzuron (N-[[4-
chlorophenyl)amino]-carbonyl]-2,6-difluorobenzamide) and metabolites
convertible to p-chloroaniline expressed as diflubenzuron on rice grain
at 0.01. EPA's assessment of the dietary exposures and risks associated
with establishing the tolerance follows.

[[Page 26482]]

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 diflubenzuron (N-
[[4-chlorophenyl)amino]-carbonyl]-2,6-difluorobenzamide) and
metabolites convertible to p-chloroaniline expressed as diflubenzuron
have been fully described in the Reregistration Eligibility Decision
(RED) document (EPA 738-R-97-008, August 1997), a copy of which is in
the public docket.

B. Toxicological Endpoints

    1. Acute toxicity. A risk assessment for acute dietary exposure (1
day) is not necessary. One day single dose oral studies in rats and
mice indicated only marginal effects on methemoglobin levels at a dose
level of 10,000 milligrams/kilograms (mg/kg) of diflubenzuron (25%
wettable powder formulation). Sulfhemoglobin levels and Heinz bodies
were not affected.
    2. Short- and intermediate-term toxicity. The toxicology endpoint
for short-term occupational or residential exposure (1 to 7 days) is
sulfhemoglobinemia observed in the 14-day subchronic oral study in mice
dosed with technical grade diflubenzuron. The no observed effect level
(NOEL) in this study was 40 mg/kg/day and the lowest effect level (LEL)
was 200 mg/kg/day.
    The toxicology endpoint for intermediate-term occupational or
residential exposure (1 week to several months) is methemoglobinemia
observed in the 13-week subchronic feeding study in dogs. For the
purpose of risk assessments, the NOEL of 1.64 mg/kg/day in this study
should be considered to be 2 mg/kg/day so as to be consistent with the
NOEL of 2 mg/kg/day in the chronic study used to calculate the RfD.
    The LEL in this study was 6.24 mg/kg/day. There were no acceptable
dermal absorption studies available. However, a dermal absorption rate
was selected from an acceptable dermal absorption submitted to the
Agency on June 25, 1996. From that study, a dermal absorption rate of
0.50% for exposures of 1 to 10 hours was determined for use in an
occupational exposure assessment.
    3. Chronic toxicity. The RfD was determined to be 0.02 mg/kg/day
and is based on the NOEL of 2.0 mg/kg/day in the 52-week chronic oral
study in dogs. Increases in methemoglobin and sulfhemoglobin were
observed at the next higher dose level of 10.0 mg/kg/day. An
uncertainty factor of 100 was applied to account for the interspecies
extrapolation and intraspecies variability. Diflubenzuron has been
reviewed by the FAO/WHO joint committee on pesticide residues and an
Acceptable Daily Intake (ADI) of 0.02 mg/kg/day was established in
1985. The ADI was based upon the one-year oral toxicity study in dogs
with a NOEL of 2.0 mg/kg/day. A safety factor of 100 was applied to
account for the interspecies extrapolation and intraspecies
variability.
    4. Carcinogenicity. Based on the available evidence, which included
adequate carcinogenicity studies in rats and mice and a battery of
negative mutagenicity studies, diflubenzuron per se has been classified
as Group E (evidence of non-carcinogenicity for humans). However, p-
chloroaniline (PCA), a metabolite of diflubenzuron, was classified as a
Group B2 carcinogen (probable human carcinogen). The classification for
PCA was based on the results of a National Toxicology Program (NTP)
study reported in July 1989 in which p-chloroaniline hydrochloride was
administered by gavage to rats and mice for 2 years. In rats, clearly
increased incidences of uncommon sarcomas (fibrosarcomas,
hemangiosarcomas and/or osteosarcomas) of the spleen were observed in
males. In females, two additional sarcomas of the spleen were also
found. Pheochromocytomas of the adrenal gland may also have been
associated with the test material in male and female rats. In mice,
increased incidences of hepatocellular neoplasms in the liver and of
hemangiosarcomas in the spleen and/or liver were observed in males. In
females, no evidence of carcinogenic activity was observed. The results
of several mutagenicity studies on PCA were also included in the same
NTP report. PCA was mutagenic in Salmonella strains TA98 and TA100 with
metabolic activation. Gene mutations were induced by PCA in cultured
mouse lymphoma cells with and without metabolic activation. In cultured
Chinese hamster ovary (CHO) cells, treatment with PCA produced
significant increases in sister chromatid exchanges (SCEs) with and
without metabolic activation. Chromosomal aberrations were also
significantly increased in CHO cells in the presence of metabolic
activation.
    For the purpose of calculating dietary risk assessments, the
following procedure was used:
    a. P-chlorophenylurea (CPU) and p-chloroacetanilide (PCAA),
additional metabolites of diflubenzuron that are closely related to PCA
and for which there are no adequate carcinogenicity data available,
should be considered to be potentially carcinogenic and to have the
same carcinogenic potency (Q1*) as PCA.
    b. The sum of PCA, CPU and PCAA residues in ingested food should be
used to estimate the dietary exposure of humans to the carcinogenic
metabolites of diflubenzuron.
    c. In addition to ingested residues of these three metabolites,
amounts of PCA, CPU, and/or PCAA formed in vivo following ingestion of
diflubenzuron should also be included when estimating the total
exposure of humans to the carcinogenic metabolites of diflubenzuron.
The in vivo conversion of ingested diflubenzuron to PCA and/or CPU was
estimated to be 2.0%, based on data in the rat metabolism study.
    The Q1* (estimated unit risk) for PCA, based upon spleen sarcoma
rates in male rats, was calculated to be 6.38 x 10-2 (mg/kg/
day)-1 in human equivalents.
    Where no PCA, CPU, and/or PCAA are present, the toxicological
endpoint for diflubenzuron per se should be used for risk assessments.
    Regarding potential carcinogenic risks to humans resulting from
dermal and/or inhalation exposures to PCA, CPU, and/or PCAA occurring
during occupational or residential exposures to diflubenzuron, it has
been determined that these risks are likely to be negligible since
exposure to these metabolites is not anticipated. Only in the event
that direct exposure to one or more of these metabolites of
diflubenzuron is demonstrated would it be necessary to perform such
risk assessments.
    It has been determined that PCAA does not occur in animal or plant
tissues in significant amounts.
    5. Special sensitivity to infants and children. In assessing the
potential for additional sensitivity of infants and children to
residues of diflubenzuron, EPA considered data from developmental
toxicity studies in the rat and rabbit and a 2-generation reproductive
toxicity study in the rat. Developmental toxicity studies are designed
to evaluate adverse effects on the developing fetus resulting from
maternal pesticide exposure during gestation. Reproductive toxicity
studies provide information relating to pre- and post-natal effects
from exposure to the pesticide, information on the reproductive
capability of mating animals, and data on systemic toxicity.

[[Page 26483]]

    FFDCA section 408 provides that EPA shall apply an additional 10-
fold 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 data base 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 analysis or through using
uncertainty (safety) factors in calculating a dose level that poses no
appreciable risk to humans. In either case, EPA generally defines the
level of appreciable risk as exposure that is greater than 1/100 of the
no observed effect level in the animal study appropriate to the
particular risk assessment. This 100-fold uncertainty (safety) factor/
margin of exposure (safety) is designed to account for inter-species
extrapolation and intra-species variability. EPA believes that reliable
data support using the 100-fold margin/factor, rather than the 1,000-
fold margin/factor, when EPA has a complete data base under existing
guidelines, and when the severity of the effect in infants or children,
the potency or unusual toxic properties of a compound, or the quality
of the exposure data do not raise concerns regarding the adequacy of
the standard margin/factor.
    a. Developmental toxicity studies--i. Rats. In the developmental
study in rats, the maternal (systemic) NOEL was 1,000.0 mg/kg/day
[HDT]. The developmental (fetal) NOEL was 1,000.0 mg/kg/day, [HDT].
    ii. Rabbits. In the developmental toxicity study in rabbits, the
maternal (systemic) NOEL was 1,000.0 mg/kg/day, [HDT]. The
developmental (pup) NOEL was 1,000.0 mg/kg/day, [HDT].
    b. Reproductive toxicity studies. In the 2-generation reproductive
toxicity study in rats, the maternal (systemic) NOEL was <36 males/<42
females mg/kg/day, [LDT] based on hematological effects at all dose
levels tested. The reproductive (pup) NOEL was 427.0 mg/kg/day, based
on decreases in the F-1 pup weight at the LEL of 2,454.0 mg/kg/day
[HDT].
    c. Pre- and post-natal sensitivity. The toxicological data base for
evaluating pre- and post-natal toxicity for diflubenzuron is complete
with respect to current data requirements. There is an ongoing review
of these data with respect to the requirements of the Food Quality
Protection Act. However, a preliminary decision, for purposes of this
temporary tolerance, is that there is no extra sensitivity for pre- or
post-natal effects and that there are reliable data to support use of a
100-fold margin of exposure/uncertainty factor, to protect infants and
children.

C. Exposures and Risks

    1. From food and feed uses. Tolerances have been established (40
CFR 180.377) for residues of diflubenzuron per se, in or on citrus,
artichokes, walnuts, mushrooms, cottonseed, soybean, and associated
livestock commodities. Existing tolerances range from 0.05 ppm in/on
soybeans to 6.0 ppm in/on artichokes. Tolerances of 0.05 ppm have also
been established for residues of diflubenzuron in animal commodities.
    For the dietary risk assessment, anticipated residues levels for
were calculated in livestock commodities. Anticipated residue estimates
for diflubenzuron were not calculated for raw agricultural commodities.
Percent crop treated data were utilized where available.
    Section 408(b)(2)(F) states that the Agency may use data on the
actual percent of food treated for assessing chronic dietary risk only
if the Agency can make the following findings: (1) That the data used
are reliable and provide a valid basis for showing the percentage of
food derived from a crop that is likely to contain residues; (2) that
the exposure estimate does not underestimate the exposure for any
significant subpopulation and; (3) where data on regional pesticide use
and food consumption are available, that the exposure estimate does not
understate exposure for any regional population. In addition, the
Agency must provide for periodic evaluation of any estimates used. To
provide for the periodic evaluation of these estimates of percent crop
treated as required by section 408(b)(2)(F), EPA may require
registrants to submit data on percent crop treated (PCT).
    Dietary exposure estimates were based on the following percent crop
treated estimates: grass/rangeland, 1%; cottonseed, 3%; soybean, 1%;
cattle bolus, 5%. Other commodities were assumed to be 100 percent
treated. The Agency believes that the three conditions listed above
have been met. With respect to (1), EPA finds that the PCT information
described above for diflubenzuron is reliable and has a valid basis.
The Agency has utilized statistical data from public and proprietary
sources, including DOANE, and checked these against data provided by
the registrant. These are the best available sources for such
information. Concerning (2) and (3), regional consumption information
and consumption information for significant subpopulations is taken
into account through EPA's computer-based model for evaluating the
exposure of significant subpopulations including several regional
groups. Use of this consumption information in EPA's risk assessment
process ensures that EPA's exposure estimate does not understate
exposure for any significant subpopulation group and allows the Agency
to be reasonably certain that no regional population is exposed to
residue levels higher than those estimated by the Agency. Other than
data available through national food consumption surveys, EPA does not
have available information on the consumption of food bearing
diflubenzuron in a particular area.
    Risk assessments were conducted as follows:
    a. Acute exposure and risk. A risk assessment for acute dietary
exposure (1 day) is not necessary. One day single dose oral studies in
rats and mice indicated only marginal effects on methemoglobin levels
at a dose level of 10,000 mg/kg of diflubenzuron (25% wettable powder
formulation). Sulfhemoglobin levels and Heinz bodies were not affected.
    b. Chronic exposure and risk. A chronic dietary risk assessment is
required for diflubenzuron. The RfD used for the chronic dietary
analysis for diflubenzuron is 0.02 mg/kg bwt/day. The DRES analysis
utilized anticipated residues and percent crop treated, where
available. The proposed diflubenzuron tolerance result in a dietary
exposure that is equivalent to the following percent of the RfD:

------------------------------------------------------------------------
                 Subgroups                          Diflubenzuron
------------------------------------------------------------------------
U.S. population (48 states)                 < 1%
Hispanics                                   < 1%
Non-hispanic others                         < 1%
Nursing Infants (< 1 year old)              < 1%
Non-nursing infants (<1 year old)           < 1%
Females (13+ years, pregnant)               < 1%
Females (13+ years, nursing)                < 1%
Children (1-6 years old)                    1%
Children (7-12 years old)                   < 1%
Females (20+ years, not pregnant, not       < 1%
 nursing)
------------------------------------------------------------------------

EPA does not consider the chronic dietary risk to exceed the level of
concern.

[[Page 26484]]

    c. Cancer risk from consumption of PCA and related metabolites. The
Agency has determined that there are three sources of carcinogenic
metabolites from the current uses of diflubenzuron and has added these
three sources together to estimate the total cancer risk for PCA and
related metabolites.
    The first source is mushrooms. The Agency used results from
mushroom metabolism studies to determine the percent of Total
Radioactive Residue (TRR) present as PCA or the related compound CPU in
mushrooms. The percent crop treated value for mushrooms, 30%, is an
upper bound estimate. The overall U.S. dietary exposure is 0.0000045
mg/kg/day for a risk estimate of 2.9 x 10-7.
    For the second source, animal commodities, tolerance levels for
diflubenzuron in animal commodities were used and, adjusting for
percent crop treated of feed items, total levels of PCA and related
compounds were estimated. The overall U.S. dietary exposure is 0.000004
mg/kg/day for a risk estimate of 2.7 x 10-7.
    Finally, based on the results of a rat metabolism study, assumption
of a 2.0% conversion of diflubenzuron to PCA in humans was assumed.
Using the above exposure estimate for rice and currently registered
uses of diflubenzuron, the calculated exposure is 0.00008 mg/kg/day for
a risk estimate of 1.0 x 10-7.
    The total of these three estimates gives a total cancer risk
estimate for PCA and related metabolites from all dietary sources of
diflubenzuron of 6.6 x 10-7.
    2. From drinking water. HED has calculated drinking water
levels of concern (DWLOCs) for chronic (non-cancer) exposure to
diflubenzuron in surface and ground water for the U.S. population and
children (1-6 yrs). They are 700 and 200 ppb, respectively. For chronic
(cancer) exposure to CPU in surface and ground water, the DWLOC is 0.21
ppb for the U.S. population. To calculate the DWLOC for chronic (non-
cancer) exposure relative to a chronic toxicity endpoint, the chronic
dietary food exposure (from DRES) was subtracted from the RfD to obtain
the acceptable chronic (non-cancer) exposure to diflubenzuron in
drinking water. To calculate the DWLOC for chronic exposures relative
to a carcinogenic toxicity endpoint, the chronic (cancer) dietary food
exposure was subtracted from the ratio of the negligible cancer risk to
the Q* to obtain the acceptable chronic (cancer) exposure to
diflubenzuron in drinking water. DWLOCs were then calculated using
default body weights and drinking water consumption figures.
    a. Chronic risk: Chronic RfD = 0.002 mg/kg/day. Maximum
H2O = 0.002 - Food Exposure.

------------------------------------------------------------------------
                                     Food Exposure        Maximum H2O
            Subgroup               (from DRES mg/kg/   Exposure (mg/kg/
                                         day)                day)
------------------------------------------------------------------------
U.S. population                   0.000080            0.01992
------------------------------------------------------------------------
Children (1-6 years)              0.00021             0.01980
------------------------------------------------------------------------

    U.S. Population: DWLOC = 700 ppb
    Children (1-6 years): DWLOC = 200 ppb

    b. Cancer risk: Q* = 6.38 x 10-2 (mg/kg/day) -- Maximum
H2O = 1.6 x 10-5 - Food Exposure

--------------------------------------------------------------------
                                                      Maximum H2O
        Subgroup              Food Exposure (mg/   Exposure (mg/kg/
                                    kg/day)              day)
--------------------------------------------------------------------
U.S. population                   0.0000101           0.0000059
--------------------------------------------------------------------

    U.S. population: DWLOC = 0.21 ppb

    The estimated average concentration of diflubenzuron in surface
water sources is not expected to exceed 0.05 ppb. Estimated average
concentrations of CPU in surface water sources is not expected to
exceed 0.85 ppb. The estimated average concentrations of diflubenzuron
in surface water are less than EPA's levels of concern for
diflubenzuron in drinking water as a contribution to chronic (non-
cancer) aggregate exposure. However, the estimated average
concentration (0.85 ppb) of CPU in surface water exceeds EPA's levels
of concern for CPU in drinking water (0.21 ppb) as a contribution to
chronic (cancer) aggregate exposure.
    EPA believes the estimates of CPU exposure in water derived from
the PRZM-EXAMS model, particularly the estimates pertaining to chronic
exposure, are significantly overstated for several reasons. The PRZM-
EXAMS model was designed to estimate exposure from ecological risk
assessments and thus uses a scenario of a body of water approximating
the size of a 1 hectare (2.5 acres) pond. This tends to overstate
chronic drinking water exposure levels for the following reasons.
First, surface water source drinking water generally comes from bodies
of water that are substantially larger than a 1 hectare (2.5 acres)
pond. Second, the modeled scenario also assumes that essentially the
whole basin receives an application of the pesticide. Yet in virtually
all cases, basins large enough to support a drinking water facility
will contain a substantial fraction of the area which does not receive
pesticide. Third, there is often at least some flow (in a river) or
turnover (in a reservoir or lake) of the water so the persistence of
the pesticide near the drinking water facility is usually
overestimated. Fourth, even assuming a reservoir is directly adjacent
to an agricultural field, the agricultural field may not be used to
grow a crop on which the pesticide in question is registered for use.
Fifth, the PRZM-EXAMS modeled scenario does not take into account
reductions in residue-loading due to applications of less than the
maximum application rate or no treatment of the crop at all (percent
crop treated data). Although there is a high degree of uncertainty to
this analysis, these are the best available estimates of concentrations
of CPU in drinking water. EPA believes that these numbers justify
asking for field runoff monitoring for CPU in conjunction with the
registered use on cotton.
    EPA bases this determination on a comparison of estimated
concentrations

[[Page 26485]]

of diflubenzuron and CPU in surface waters and ground waters to back-
calculated "levels of concern" for diflubenzuron and CPU in drinking
water. These levels of concern in drinking water were determined after
EPA has considered all other non-occupational human exposures for which
it has reliable data, including all current uses, and uses considered
in this action. The estimates of diflubenzuron and CPU in surface and
ground waters are derived from water quality models that use
conservative assumptions (health-protective) regarding the pesticide
transport from the point of application to surface and ground water.
Because EPA considers the aggregate risk resulting from multiple
exposure pathways associated with a pesticide's uses, levels of concern
in drinking water may vary as those uses change. If new uses are added
in the future, EPA will reassess the potential impacts of diflubenzuron
and CPU on drinking water as a part of the aggregate risk assessment
process.
    3. From non-occupational non-dietary exposure. Diflubenzuron is a
restricted use pesticide and therefore not available for use by
homeowners. However, non-agricultural uses of diflubenzuron may expose
people in residential locations. Based on the low dermal absorption
rate (0.5%), and the extremely low dermal and inhalation toxicity,
these uses are expected to result in insignificant risk.
    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." An explanation of the current Agency
approach to assessment of pesticides with a common mechanism of
toxicity may be found in the Final Rule on Bifenthrin Pesticide
Tolerances (62 FR 62961).
    Diflubenzuron is structurally similar to other substituted
benzoylurea insecticides including triflumuron and flucycloxuron. EPA
does not have, at this time, available data to determine whether
diflubenzuron 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, diflubenzuron 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 diflubenzuron has a common mechanism of toxicity with
other substances.

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

    1. Acute risk. There is no risk from acute dietary exposure (1 day)
to diflubenzuron as there is no toxic endpoint identified.
    2. Chronic. For the U.S. population, <1% of the RfD is occupied by
dietary (food) exposure. The estimated average concentrations of
diflubenzuron in surface and ground water are less than OPP's levels of
concern for diflubenzuron in drinking water. Therefore, EPA concludes
that there is a reasonable certainty that no harm will result to
infants, children, or adults from chronic aggregate (food plus water)
exposure to diflubenzuron residues.
    3. Carcinogenic aggregate exposure and risk. For the U.S.
population, cancer risk resulting from dietary (food) exposure is 6.6 x
10-7. The estimated average concentration (0.85 ppb) of CPU
in surface water exceeds EPA's levels of concern for CPU in drinking
water (0.21 ppb) as a contribution to chronic (cancer) aggregate
exposure. However, EPA believes that these PRZM-EXAMS model
overestimates exposures for the reasons given above. EPA does not
generally use surface water modeling values for quantitative risk
assessment. However, due to the statistical uncertainties regarding the
significance of cancer risks which are near 1 x 10-6, EPA
has calculated that the cancer risk resulting from 0.85 ppb of CPU in
drinking water is 1.55 x 10-6. The aggregate cancer risk is
thus 2.2 x 10-6 (6.6 x 10-7 for food + 1.55 x 10-6 for water).
    4. Determination of safety. EPA believes that the total risk
estimate for CPU in food and drinking water of 2.2 x 10-6
generally represents a negligible risk, as EPA has traditionally
applied that concept. EPA has commonly referred to a negligible risk as
one that is at or below 1 in 1 million (1 x 10-6).
Quantitative cancer risk assessment is not a precise science. There are
a significant number of uncertainties in both the toxicology used to
derive the cancer potency of a substance and in the data used to
measure and calculate exposure. The Agency does not attach great
significance to numerical estimates for carcinogenic risk that differ
by approximately a factor of 2.

III. Other Considerations

A. Metabolism in Plants and Animals

    The qualitative nature of the residue in plants is adequately
understood based on data from citrus, mushroom, and soybean metabolism
studies. The Agency has concluded that tolerances should be expressed
in terms of the combined residues of diflubenzuron and metabolites
convertible to PCA (CPU and PCAA) expressed as diflubenzuron. However,
for the purposes of this temporary tolerance petition, diflubenzuron
per se should be the regulated residue in plants.
    The nature of the residue in animals is adequately understood based
on acceptable poultry and ruminant metabolism studies reflecting oral
dosing. Terminal residues identified in animal tissues, milk, and eggs
include diflubenzuron, 2-hydroxy-diflubenzuron (2HDFB), 2,6-
difluorobenzamide (DFBAM), 2,6-difluorobenzoic acid (DFBA), N-(4-
chlorophenyl)urea (CPU), and PCA. For the purposes of this temporary
tolerance petition, diflubenzuron should be the regulated residue in
animals.

B. Analytical Enforcement Methodology

    Adequate methods are available for the analysis of Diflubenzuron in
rice grain (0.01 ppm), rice straw (0.01 ppm) and water (0.001 ppm). The
method for measuring PCA in rice grain recovers only about 50% at the
0.025 ppm level. As part of the reregistration of diflubenzuron, the
Agency concluded that tolerances should be expressed in terms of the
combined residues of diflubenzuron and metabolites. Until suitable
methodology is developed, regulation of diflubenzuron per se is an
acceptable alternative. Three enforcement methods for diflubenzuron are
published in PAM, Vol. II as Methods I, II, and III. Method II is a GC/
ECD method that can separately determine residues of diflubenzuron,
CPU, and PCA in eggs, milk, and animal tissues. All three methods have
undergone successful Agency validations and are acceptable for
enforcement purposes. The FDA PESTDATA data base dated 1/94 (PAM Vol.
I, Appendix II) contains no information on diflubenzuron recovery using
Multiresidue Methods PAM, Vol. I Sections 302, 303, and 304. However,
the registrant has submitted multi-residue testing data that the Agency
has forwarded to the FDA.

C. Magnitude of Residues

    Uniroyal Chemical Company submitted data from 10 tests depicting
residues of diflubenzuron in/on rice.

[[Page 26486]]

Ten trials were conducted in Arizona (2), California (2), Louisiana
(1), Mississippi (2), and Texas (3). At each site rice grain and straw
were harvested at normal maturity following one broadcast application
of diflubenzuron (25% WP, EPA Reg. No. 400-465; 2 lb/gal FlC, EPA Reg.
No. 400-461) at 0.25 lb. ai/A (1x the maximum proposed application
rate). A single application was made 10 days or 2 weeks following
permanent flood or rice emergence, respectively. Applications of the
WP/D and FlC formulation were made in 10 gal of water/A using ground
equipment. Aerial applications of the FlC formulation were made at 5-10
gal of water/A. Residues of diflubenzuron and PCA in/on treated rice
grain were <LOQ for all samples. The submitted field trial data
indicate that residues of diflubenzuron will not exceed the proposed
temporary tolerance of 0.01 ppm in/on rice grain. As an adjunct to the
magnitude of the residue study on rice, the petitioner also conducted
residue studies to determine the magnitude of the residue of
diflubenzuron in treated rice flood waters. Residue levels were
determined from samples taken from the treated and untreated plots of
the diflubenzuron crop field trials. Five trials were conducted in
California (2), Louisiana (1), and Texas (2). Following one broadcast
application of diflubenzuron as a 25% WP formulation or 2 lb/gal FlC
formulation at 0.25 lb. ai/A (1x the maximum proposed application rate)
as described in the crop field trial discussion, one control and
duplicate treated samples of water were collected from each plot at
each test site at intervals of 0, 1, 3, 7, 14, 21, and 28 days
following insecticide application. For the sampling intervals 0, 1, 3
and 7 days after application of diflubenzuron at 1x the maximum
proposed application rate (0.25 lb. ai/A), residues of diflubenzuron in
treated rice flood waters were 0.011 to 0.04 ppm, 0.0007 to 0.027 ppm,
<0.0003 to 0.020 ppm, and <0.0003 to 0.0014 ppm; residues were <LOQ for
all samples collected 14 or more days after treatment.
    There are several active SLNs [SLN Nos. AL930004, FL910004,
HI940003, CA850041, CA870049, and NV940003] which allow the application
of diflubenzuron to water at a maximum rate 0.25 lb. ai/A for mosquito
abatement. Labels prohibit the use of treated water for irrigation or
human consumption. The proposed label recommends the retention of flood
waters for 14 days to allow for the dissipation of diflubenzuron
residues. Residue data indicate that diflubenzuron residues >LOQ may be
present in rice flood waters <14 days after application of
diflubenzuron.

D. Magnitude of the Residue in Processed Commodities

    Uniroyal Chemical Company submitted data depicting the potential
for concentration of diflubenzuron residues in the processed
commodities of rice. Two tests were conducted in Mississippi (1) and
Texas (1). At each site, rice grain was harvested at maturity, 82 to 85
days following a post-permanent flood application of the 2 lb/gal FlC
formulation at 2 lb. ai/A (8x the proposed maximum application rate).
Samples were processed according to simulated commercial procedures
into hulls, bran, and polished rice. Residues of diflubenzuron were
non-detectable (LOQ <0.01 ppm) and 0.26 and 0.87 ppm in four treated
samples of the RAC, and did not concentrate in processed commodities of
rice harvested 82 to 85 days following a single 2 lb. ai/A (8x) of
diflubenzuron. As the residues of diflubenzuron did not concentrate in
the hull, bran, or whole rice fractions of processed rice grain, a
tolerance for residues in rice processed commodities is not required.

E. Magnitude of Secondary Residues in Meat/Milk/Poultry/Eggs

    Rice grain, straw, hulls and bran may be fed to livestock and/or
poultry. However, the incremental exposure of diflubenzuron residues to
livestock and poultry is minimal when compared to the existing
exposure. EPA concludes that the current tolerances on meat, milk,
poultry and eggs are adequate to cover the added residues resulting
from the experimental use on rice.

F. International Residue Limits

    There are no Codex proposals, Canadian, or Mexican limits for
residues of diflubenzuron on rice. A compatibility issue is not
relevant to the proposed temporary tolerance.

G. Rotational Crop Restrictions.

    The nature of the residue in rotational crops is adequately
understood for purposes of reregistration (residue chemistry chapters
for the Reregistration Eligibility Decision (RED) document, March 16,
1995). Although EPA concluded that the available confined rotational
crop study was inadequate to fully satisfy GLN 165-1 reregistration
requirements, another confined rotational crop study will not be
required because the study allowed EPA to make regulatory conclusions
regarding the need for limited rotational crop studies (GLN 165-2) and
to comment on the appropriateness of the currently established
plantback interval (PBI) on diflubenzuron end-use product labels.
    Residue data on field-grown rotational crops are not available.
Although the confined study was deemed inadequate, the available data
indicate that diflubenzuron and CPU may exceed 0.01 ppm in rotational
crops planted up to 4 months after a 1x application of diflubenzuron to
the primary crop and in cereal grains planted up to 12 months after a
1x application.

IV. Conclusion

    Therefore, the temporary tolerance is established for residues of
the insecticide diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-2,6-
difluorobenzamide) and metabolites convertible to p-chloroaniline
expressed as diflubenzuron on rice grain at 0.01 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 issued by EPA under
new section 408(e) and (l)(6) 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 July 13, 1998, 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(i). 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

[[Page 26487]]

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 Docket

    EPA has established a record for this rulemaking under docket
control number [OPP-300660] (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 Rm. 1119 of the Public Information and Records
Integrity Branch, Information Resources and Services Division (7506C),
Office of Pesticide Programs, Environmental Protection Agency, Crystal
Mall #2, 1921 Jefferson Davis Highway, Arlington, VA.
    Electronic comments may be sent directly to EPA at:
    opp-docket@epamail.epa.gov.
    Electronic comments must be submitted as an ASCII file avoiding the
use of special characters and any form of encryption.
    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

    This final rule establishes a temporary tolerance for the residues
of diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-2,6-
difluorobenzamide) and metabolites convertible to p-chloroaniline
expressed as diflubenzuron on rice grain at 0.01 ppm 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 these tolerances and exemptions that are
established on the basis of a petition under FFDCA section 408(d), such
as the tolerances for the residues of diflubenzuron (N-[[4-
chlorophenyl)amino]-carbonyl]-2,6-difluorobenzamide) and metabolites
convertible to p-chloroaniline expressed as diflubenzuron on rice grain
at 0.01 ppm 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.

VIII. Submission to Congress and the General Accounting Office

    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: May 7, 1998.
James Jones,
Director, Registration Division, 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 revising Sec. 180.377 to read as follows:

Sec. 180.377   Diflubenzuron; tolerances for residues.

    (a) General. (1) Tolerances are established for residues of the
insecticide diflubenzuron (N-[[(4-chlorophenyl)amino]carbonyl]-2,6-
difluorobenzamide) in or on the following raw agricultural commodities:

------------------------------------------------------------------------
                                                               Parts per
                          Commodity                             million
------------------------------------------------------------------------
Artichokes..................................................        6.0
Cattle, fat.................................................        0.05
Cattle, mbyp................................................        0.05
Cattle, meat................................................        0.05
Cottonseed..................................................        0.2
Eggs........................................................        0.05
Goats, fat..................................................        0.05
Goats, mbyp.................................................        0.05
Goats, meat.................................................        0.05
Grapefruit..................................................        0.5
Hogs, fat...................................................        0.05
Hogs, mbyp..................................................        0.05
Hogs, meat..................................................        0.05
Horses, fat.................................................        0.05

[[Page 26488]]

Horses, mbyp................................................        0.05
Horses, meat................................................        0.05
Milk........................................................        0.05
Mushrooms...................................................        0.2
Orange......................................................        0.5
Poultry, fat................................................        0.05
Poultry, mbyp...............................................        0.05
Poultry, meat...............................................        0.05
Sheep, fat..................................................        0.05
Sheep, mbyp.................................................        0.05
Sheep, meat.................................................        0.05
Soybeans....................................................        0.05
Tangerine...................................................        0.5
Walnuts.....................................................        0.1
------------------------------------------------------------------------

    (2) A temporary tolerance expiring June 30, 1999, is established
for residues of the insecticide diflubenzuron (N-[[4-
chlorophenyl)amino]-carbonyl]-2,6-difluorobenzamide) and metabolites
convertible to p-chloroaniline expressed as diflubenzuron on rice grain
at 0.01 ppm.
    (b) Section 18 emergency exemptions. [Reserved]
    (c) Tolerances with regional registrations. Tolerances with
regional registration, as defined in Sec. 180.1(n), are established for
residues of diflubenzuron in or on the following raw agricultural
commodities:

------------------------------------------------------------------------
                                                               Parts per
                          Commodity                             million
------------------------------------------------------------------------
Grass, pasture..............................................        1.0
Grass, range................................................        3.0
------------------------------------------------------------------------

    (d) Indirect or inadvertent residues. [Reserved]

[FR Doc. 98-12640 Filed 5-12-98; 8:45 am]
BILLING CODE 6560-50-F