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Diflubenzuron - Pesticide Tolerances 4/99

[Federal Register: April 19, 1999 (Volume 64, Number 74)]
[Rules and Regulations]
[Page 19050-19057]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr19ap99-8]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 180
[OPP-300844; FRL-6075-4]
RIN 2070-AB78
Diflubenzuron; Pesticide Tolerances
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: This regulation establishes tolerances for residues of the
insecticide diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-2,6-
difluorobenzamide) and its metabolites, 4-chlorophenylurea (CPU) and 4-
chloroaniline (PCA) in/on rice grain at 0.02 ppm and rice straw at 0.8
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 these tolerances.

DATES: This regulation is effective April 19, 1999. Objections and
requests for hearings must be received by EPA on or before June 18,
1999.

ADDRESSES: Written objections and hearing requests, identified by the
docket control number, [OPP-300844], 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-300844], 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, 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-300844]. 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: Rita Kumar, 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) 308-8291, e-mail:
kumar.rita@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 Experimental Use Permit, and 8F4925, to
amend 40 CFR 180.377 to include a permanent 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. Background 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

[[Page 19051]]

exposure to the pesticide chemical residue. . . ."
    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 its metabolites, 4-chlorophenylurea (CPU)
and 4-chloroaniline (PCA) on rice grain at 0.02 parts per million (ppm)
and rice straw at 0.8 ppm, 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 its metabolites, 4-
chlorophenylurea (CPU) and 4-chloroaniline (PCA) on rice grain at 0.02
ppm and rice straw at 0.8 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 diflubenzuron (N-
[[4-chlorophenyl)amino]-carbonyl]-2,6-difluorobenzamide) and its
metabolites, 4-chlorophenylurea (CPU) and 4-chloroaniline (PCA) on rice
grain at 0.02 ppm and rice straw at 0.8 ppm 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.
    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. Since an oral NOAEL was selected
for a dermal endpoint, a dermal absorption factor of 0.5% should be
used for this risk assessment when converting dermal exposure to oral
equivalents. Therefore, the dermal equivalent dose producing a NOAEL by
the oral route is 400.0 mg/kg/day (i.e., 2.0 mg/kg/day divided by 0.005
= 400.0 mg/kg/day).
    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 1 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.

[[Page 19052]]

    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.
    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
NOEL 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 [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. Based on the developmental
and reproductive toxicity studies discussed above, for diflubenzuron
there does not appear to be an extra sensitivity for pre- or post-natal
effects. Based on the above, EPA concludes that reliable data support
use of a 100-fold margin of exposure/uncertainty factor, rather than
the 1,000-fold margin/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 were
calculated in livestock, citrus and mushroom commodities. Anticipated
residue estimates for diflubenzuron were not calculated for other 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.

    Dietary exposure estimates were based on the following percent crop
treated estimates: grass/rangeland, 1%; cottonseed, 3%; grapefruit, 8%;
mushrooms, 3.1%; oranges, 2%; tangerines, 4%; soybean, 1%; cattle
bolus, 5%. Other commodities were assumed to be 100% treated. The
Agency believes that the three conditions listed above have been met.
With respect to (1), EPA finds that the percent crop treated
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.
    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 chronic DEEM
analysis used mean consumption (3-day average). Anticipated residues
and percent crop treated information for select commodities were used.
Since EPA determined to reduce the 10x factor to 1x, the Population
Adjusted Dose (PAD) and the RfD are the same. Therefore, EPA's level of
concern are values >100% RfD. Dietary exposures for the U.S. general
population and other subgroups at percentage of RfD are presented
below. The other subgroups included represent the highest dietary

[[Page 19053]]

exposures for their respective subgroups (i.e., children, females, and
the other general population subgroup higher than U.S. population).

------------------------------------------------------------------------
                                                       Exposure (mg/kg/
            Subgroups                    %RfD                day)
------------------------------------------------------------------------
U.S. population (48 states)       <1%                 0.000027
Non-hispanic others               <1%                 0.000102
Non-nursing infants (<1 year      <1%                 0.000031
 old)
Females (20+ years, not           <1%                 0.000032
 pregnant, not nursing)
------------------------------------------------------------------------

    The U.S. population and all the DEEM subgroups have ARCs for
chronic dietary (non-cancer) risk from diflubenzuron well below the RfD
when all uses are considered.
    c. Cancer risk from consumption of PCA and related metabolites. The
Agency has determined that there are three possible sources for dietary
exposure to PCA and related compounds (CPU and PCAA): residues in
plants/fungi (mushrooms), residues in animal commodities (milk and
liver) and in vivo conversion of diflubenzuron.
    i. Mushrooms/milk/liver. The Agency used results from metabolism
studies to determine the percent of the total radioactive residue (TRR)
present as PCA and related compounds in mushrooms, milk and liver. For
milk and liver, anticipated residues were calculated from the results
of the ruminant feeding study using tolerance level residues in animal
feed items and adjusting for percent crop treated. The total levels of
PCA and related compounds were estimated by multiplying the ratio of
PCA/DFB by the diflubenzuron consumption (from DEEM). The PCA
consumption values were calculated as follows:
    Mushrooms = 0.0000062 mg/kg/day
    Milk = 0.0000004 mg/kg/day
    Liver = 0.00000002 mg/kg/day
    Total = 0.00000066 mg/kg/day
    Overall U.S.: 0.0000066 mg/kg/day (4.2 x 10-7
Carcinogenic Risk)

    ii.In vivo. Based on the results of a rat metabolism study, an
assumption of a 2.0% conversion of diflubenzuron to PCA in humans is
assumed for PCA risk assessment. Using the above exposure estimate for
rice and published uses (0.000027 mg/kg/day) the carcinogenic risk
estimate (overall U.S. population) is 3.4 x 10-8 (0.000027
mg/kg/day x 0.02 x 0.0638 (mg/kg/day)-1).
    Total cancer risk estimate for PCA and related metabolites:
    Overall U.S.: 4.5 x 10-7
    This cancer risk does not exceed the level of concern.
    2. From drinking water. EPA 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 0.30 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 DEEM) 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 = 0.02 mg/kg/day. Maximum
H2O = 0.02 - Food Exposure.

------------------------------------------------------------------
                             Food Exposure to
                               Diflubenzuron        Maximum H2O
      Subgroup               (from DEEM mg/kg/   Exposure (mg/kg/
                                   day)                day)
------------------------------------------------------------------
U.S. population                   0.000027            0.01997
------------------------------------------------------------------
Children (1-6 years)              0.00031             0.01997
------------------------------------------------------------------
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

------------------------------------------------------------------
                             Food Exposure to
                              PCA and Related       Maximum H2O
      Subgroup               Compounds (mg/kg/   Exposure (mg/kg/
                                   day)                day)
------------------------------------------------------------------
U.S. population                   0.0000071           0.0000089
------------------------------------------------------------------
U.S. population: DWLOC = 0.30 ppb

[[Page 19054]]

    The PCA and related compounds value is a total of residues in food
(0.0000066 mg/kg/day) + residues formed in vivo (0.000027 mg/kg/day DFB
x 2% conversion).
    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 0.73 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 (0.73 ppb) of CPU in surface water exceeds EPA's levels
of concern for CPU in drinking water (0.30 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 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 risks.
    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
food exposure. The estimated average concentrations of diflubenzuron in
surface and ground water are less than EPA'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 food exposure is 4.5 x 10-
7. The estimated average concentration (0.73 ppb) of CPU in
surface water exceeds EPA's levels of concern for CPU in drinking water
(0.30 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 0.73 ppb of CPU in
drinking water is 1.30 x 10-6. The aggregate cancer risk is
thus 1.8 x 10-6 (4.5 x 10-7 for food + 1.3 x
10-6 for water).
    4. Determination of safety. EPA believes that the total risk
estimate for CPU in food and drinking water of 1.8 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.

[[Page 19055]]

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.
    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. 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.

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).
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.
Individual analytical methods for rice commodities have been submitted
for CPU (LOQ of 0.001 ppm in grain, 0.01 ppm in straw) and PCA (LOQ of
0.005 ppm in grain and straw). The methods and ILVs have been sent to
Beltsville for Petition Method Validation. EPA will withhold a final
conclusion on the adequacy of these method as analytical enforcement
methods pending receipt of the PMV reports. However, these methods are
based on Method II. EPA thus has no objections to a conditional
registration while the PMV of the methods for PCA and CPU in rice
commodities is performed.

C. Multiresidue Methods

    The FDA PESTDATA data base dated January 1, 1994 (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 Multiresidue testing data that the Agency
has forwarded to the Food and Drug Administration (FDA). Also, the
results of Multiresidue Method testing of PCA and CPU have been
submitted and will be forwarded to FDA.

D. Storage Stability Data

    Data from a 12-month storage stability study were submitted
depicting the magnitude of residue of diflubenzuron (DFB) and its
metabolites CPU and PCA in/on rice grain, straw, bran and hulls (MRID #
44699202). Diflubenzuron was determined to be stable over a 12-month
period with average recoveries of 78% (grain), 99% (bran), 89% (straw),
and 78% (hulls). CPU exhibited the following average recoveries of a
12-month period: 76% (grain), 99% (bran), 89% (straw), and 78% (hulls).
Significant declines in the PCA concentration were observed, decreasing
rapidly to 56% (average) after 1 month and to 30% (average) after 12
months. The storage stability of diflubenzuron and CPU in/on rice
commodities have been adequately demonstrated. PCA is unstable,
degrading significantly after 1 month. Therefore, for magnitude of
residue samples with storage periods greater than 1 month, correction
factors must be used in order to determine the residue levels that were
present at the time of sample collection.

E. Magnitude of Residues

    A total of 14 acceptable field trials have been conducted: Region
IV (9 trials), Region VI (2 trials), and Region X (3 trials). EPA
requires that a minimum of 16 field trials be performed. The Agency
suggests the following distribution for the field trials: Region IV (11
trials), Region V (1 trial), Region VI (2 trials), and Region X (2
trials) (Residue Chemistry Test Guidelines, OPPTS 860.1500 Crop Field
Trials Tables 1 and 6). Additional field trials are thus required in
Regions IV (1 trial) and V (1 trial). EPA has decided to issue a
conditional registration for the use of diflubenzuron on rice until the
necessary field trials are performed.
    Residues of diflubenzuron, CPU and PCA in/on treated rice grain
were <0.01 ppm, <0.001 - 0.002 ppm and <0.005 ppm, respectively, and
the combined residues were <0.016 - <0.017 ppm. Residues of
diflubenzuron, CPU and PCA in treated straw samples were <0.01 - 0.57
ppm, <0.01 - 0.02 ppm and <0.005 - 0.021 ppm, respectively, and the
combined residues were <0.025 - <0.607 ppm. The residue data support
the proposed tolerance of 0.02 ppm for diflubenzuron in/on rice grain
and 0.8 ppm in/on rice straw.

F. 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, 82-85
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. 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.

G. 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 use on rice.

H. Magnitude of Residues in Water, Fish, and Irrigated Crops

    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), 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 - 0.04 ppm, 0.0007-

[[Page 19056]]

0.027 ppm, <0.0003 - 0.020 ppm, and <0.0003 - 0.0014 ppm; residues were
<LOQ for all samples collected 14 or more days after treatment.
    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.

I. 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 tolerance.

J. 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 on diflubenzuron end-use product labels.
    Uniroyal has submitted data depicting diflubenzuron residues in
representative rotational crops from two limited field trials. Provided
the petitioner explains the discrepancy in the 0.10 ppm residue value
reported for diflubenzuron in one of the wheat forage samples from CA,
the limited field rotational crop study is adequate. The available data
indicate that tolerances for diflubenzuron residues in rotational crops
will not be required provided the diflubenzuron labels specify a
restriction for the planting of rotation crops of at least 30 days.

IV. Conclusion

    Therefore, tolerances are established for residues of the
insecticide diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-2,6-
difluorobenzamide) and its metabolites, 4-chlorophenylurea (CPU) and 4-
chloroaniline (PCA) on rice grain at 0.02 ppm and rice straw at 0.8
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 June 18, 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 under the "ADDRESSES" section (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
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-300844] (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. 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 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 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 0.02 ppm and rice straw at
0.8 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

[[Page 19057]]

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 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 0.02 ppm and rice straw at 0.8 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 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 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: April 7, 1999.
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. 321(q), 346a and 371.

    2. In Sec. 180.377, by revising paragraph (a)(2) to read as
follows:

Sec. 180.377   Diflubenzuron; tolerances for residues.

    (a)  *  *  *
    (2) Tolerances are established for residues of the insecticide
diflubenzuron (N-[[4-chlorophenyl)amino]-carbonyl]-2,6-
difluorobenzamide) and its metabolites 4-chlorophenylurea and 4-
chloroaniline on rice grain at 0.02 ppm and rice straw at 0.8 ppm.
*    *    *    *    *

[FR Doc. 99-9711 Filed 4-16-99; 8:45 am]
BILLING CODE 6560-50-F