[Federal Register Volume 63, Number 92 (Wednesday, May 13, 1998)]
[Rules and Regulations]
[Pages 26481-26488]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-12640]


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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: <a href="/cdn-cgi/l/email-protection#bcd3cccc91d8d3dfd7d9c8fcd9ccddd1ddd5d092d9ccdd92dbd3ca"><span class="__cf_email__" data-cfemail="f29d8282df969d91999786b29782939f939b9edc978293dc959d84">[email protected]</span></a>. 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: 
<a href="/cdn-cgi/l/email-protection#1d6e7e756f727879786f336d7c68715d786d7c707c747133786d7c337a726b"><span class="__cf_email__" data-cfemail="61120209130e040504134f1100140d210411000c00080d4f0411004f060e17">[email protected]</span></a>.

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<SUP>-2</SUP> (mg/kg/
day)<SUP>-1</SUP> 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<SUP>-7</SUP>.
    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<SUP>-7</SUP>.
    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<SUP>-7</SUP>.
    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<SUP>-7.
    </SUP>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 
H<INF>2</INF>O = 0.002 - Food Exposure.

                                                                        
------------------------------------------------------------------------
                                     Food Exposure        Maximum H<INF>2O   
            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<SUP>-2</SUP> (mg/kg/day) -- Maximum 
H<INF>2</INF>O = 1.6 x 10<SUP>-5</SUP> - Food Exposure

                                                                        
------------------------------------------------------------------------
                                                          Maximum H<INF>2O   
            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<SUP>-7</SUP>. 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<SUP>-6</SUP>, EPA 
has calculated that the cancer risk resulting from 0.85 ppb of CPU in 
drinking water is 1.55 x 10<SUP>-6</SUP>. The aggregate cancer risk is 
thus 2.2 x 10<SUP>-6</SUP> (6.6 x 10<SUP>-7</SUP> for food + 1.55 x 
10<SUP>-6</SUP> 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<SUP>-6</SUP> 
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<SUP>-6</SUP>). 
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:
    <a href="/cdn-cgi/l/email-protection#28475858054c474b434d5c684d584945494144064d5849064f475e"><span class="__cf_email__" data-cfemail="7e110e0e531a111d151b0a3e1b0e1f131f1712501b0e1f50191108">[email protected]</span></a>.
    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


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