Document ID: EPA-HQ-OPP-2006-0181-0004
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-11-29T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF

PREVENTION, PESTICIDES, AND

TOXIC SUBSTANCES

MEMORANDUM

DATE:		14-SEP-2006

SUBJECT:	Diflubenzuron on Barley, Oats, Wheat, Brassica Leafy Greens
(Crop Subgroup 5B), Turnip Greens, Eggplant, Okra, Peanut, and Pummelo
(PP#s 5E6965, 5E6966, and 5E6967).  Health Effects Division (HED) Risk
Assessment.  DP#s 321152, 321155, & 321158.  PC Code 108201.  Decision#s
359314, 359335, & 359336.

FROM:	George F. Kramer, Ph.D., Senior Chemist

Lisa Austin, Ph.D., Toxicologist

Mark I. Dow, Ph.D., Senior Biologist

Registration Action Branch 1 (RAB1)/HED (7509P)

THROUGH:	Dana Vogel, Acting Branch Chief

P.V. Shah, Ph.D., Branch Senior Scientist

RAB1/HED (7509P)

TO:		Barbara Madden/Dan Rosenblatt, PM Team 05

	Registration Division (RD; 7505P)

The HED of the Office of Pesticide Programs (OPP) is charged with
estimating the risk to human health from exposure to pesticides.  The RD
of OPP has requested that HED evaluate hazard and exposure data and
conduct dietary, occupational/residential, and aggregate exposure
assessments, as needed, to estimate the risk to human health that will
result from the registered and proposed uses of the
insecticide/acaricide diflubenzuron
(N-[((4-chlorophenyl)amino)carbonyl]-2,6-difluorobenzimide).

A summary of the findings and an assessment of human-health risk
resulting from the proposed uses of diflubenzuron are provided in this
document.  The risk assessment, dietary-exposure assessment, and the
residue chemistry data review were provided by George Kramer (RAB1); the
occupational/residential exposure assessment by Mark Dow (RAB1); the
hazard characterization by Lisa Austin (RAB1); and the drinking water
assessment by Amer Al-Mudallal of the Environmental Fate and Effects
Division (EFED).

NOTE:  HED completed a Section 3 risk assessment for the use of
diflubenzuron on peppers, stone fruits (except cherries), and tree nuts
(and pistachios) (DP# 277608, 3/21/02, G. Kramer et al.).  This document
contains only those aspects of the risk assessment which are affected by
the new tolerances for residues in/on barley, oats, wheat, Brassica
leafy greens (crop subgroup 5b), turnip greens, peanut, and pummelo.  

Table of Contents

  TOC \o "1-4" \h \z \u    HYPERLINK \l "_Toc145995572"  1.0 EXECUTIVE
SUMMARY	  PAGEREF _Toc145995572 \h  3  

  HYPERLINK \l "_Toc145995573"  2.0 PHYSICAL/CHEMICAL PROPERTIES
CHARACTERIZATION	  PAGEREF _Toc145995573 \h  8  

  HYPERLINK \l "_Toc145995574"  2.1 Identification of Active Ingredient	
 PAGEREF _Toc145995574 \h  8  

  HYPERLINK \l "_Toc145995575"  2.2 Physical and Chemical Properties	 
PAGEREF _Toc145995575 \h  9  

  HYPERLINK \l "_Toc145995576"  3.0 HAZARD CHARACTERIZATION	  PAGEREF
_Toc145995576 \h  9  

  HYPERLINK \l "_Toc145995577"  3.1 Dose-Response Assessment	  PAGEREF
_Toc145995577 \h  9  

  HYPERLINK \l "_Toc145995578"  3.2 Endocrine Disruption	  PAGEREF
_Toc145995578 \h  12  

  HYPERLINK \l "_Toc145995579"  4.0 EXPOSURE ASSESSMENT AND
CHARACTERIZATION	  PAGEREF _Toc145995579 \h  13  

  HYPERLINK \l "_Toc145995580"  4.1 Summary of Registered/Proposed Uses	
 PAGEREF _Toc145995580 \h  13  

  HYPERLINK \l "_Toc145995581"  4.2 Dietary Exposure/Risk Pathway	 
PAGEREF _Toc145995581 \h  14  

  HYPERLINK \l "_Toc145995582"  4.2.1 Residue Profile	  PAGEREF
_Toc145995582 \h  14  

  HYPERLINK \l "_Toc145995583"  4.2.2 Dietary-Exposure Analyses	 
PAGEREF _Toc145995583 \h  19  

  HYPERLINK \l "_Toc145995584"  4.2.2.1 Acute Dietary-Exposure Analysis	
 PAGEREF _Toc145995584 \h  20  

  HYPERLINK \l "_Toc145995585"  4.2.2.2 Chronic Dietary-Exposure
Analysis	  PAGEREF _Toc145995585 \h  20  

  HYPERLINK \l "_Toc145995586"  4.2.2.3 Cancer Dietary Exposure Analysis
  PAGEREF _Toc145995586 \h  20  

  HYPERLINK \l "_Toc145995587"  4.3 Water Exposure/Risk Pathway	 
PAGEREF _Toc145995587 \h  21  

  HYPERLINK \l "_Toc145995588"  4.4 Residential Exposure/Risk Pathway	 
PAGEREF _Toc145995588 \h  21  

  HYPERLINK \l "_Toc145995589"  5.0 AGGREGATE-RISK ASSESSMENTS AND RISK
CHARACTERIZATION	  PAGEREF _Toc145995589 \h  21  

  HYPERLINK \l "_Toc145995590"  6.0 CUMULATIVE RISK	  PAGEREF
_Toc145995590 \h  22  

  HYPERLINK \l "_Toc145995591"  7.0 OCCUPATIONAL EXPOSURE	  PAGEREF
_Toc145995591 \h  22  

  HYPERLINK \l "_Toc145995592"  7.1 Occupational Handler	  PAGEREF
_Toc145995592 \h  22  

  HYPERLINK \l "_Toc145995593"  7.2 Occupational Post-Application
Exposure	  PAGEREF _Toc145995593 \h  24  

  HYPERLINK \l "_Toc145995594"  8.0 DEFICIENCIES / DATA NEEDS	  PAGEREF
_Toc145995594 \h  25  

  HYPERLINK \l "_Toc145995595"  8.1 Chemistry	  PAGEREF _Toc145995595 \h
 25  

 

1.0 EXECUTIVE SUMMARY

Diflubenzuron
(N-[((4-chlorophenyl)amino)carbonyl]-2,6-difluorobenzimide), a member of
the urea-derivative chemical family, is an insecticide/acaricide (insect
growth regulator) that behaves as a chitin inhibitor to suppress the
growth of many leaf-eating larvae, mosquito larvae, aquatic midges, rust
mite, boll weevil, and flies.  Tolerances for residues of diflubenzuron
are established under 40 CFR §180.377.  Tolerances listed in 40 CFR
§180.377(a)(1) are expressed in terms of diflubenzuron per se.  Under
this section, tolerances of 0.05-6.0 ppm are established for residues
in/on eggs; milk; fat and meat of cattle, goat, hog, horse, poultry, and
sheep; poultry meat byproducts; cottonseed; mushroom; grapefruit, orange
(sweet); tangerine; soybean hulls; and globe artichoke.

Tolerances listed in 40 CFR §180.377(a)(2) are expressed in terms of
the combined residues of diflubenzuron and its metabolites
4-chlorophenylurea (CPU) and 4-chloroaniline (PCA).  Under this section,
tolerances of 0.02-6.0 ppm are established for residues in/on rice
grain; tree nuts (group 14); pistachios; fruit, stone (group 12) except
cherry; meat byproducts of cattle, goat, hog, horse, and sheep; pear;
rice straw; pepper; and almond hulls.

Time-limited tolerances listed in 40 CFR §180.377(b) are expressed in
terms of the combined residues of diflubenzuron and its metabolites CPU
and PCA, expressed as the parent diflubenzuron, in connection with use
of the pesticide under Section 18 Emergency Exemptions granted by EPA. 
Under this section, tolerances of 0.05-30 ppm are established for barley
grain, wheat grain, wheat milled byproducts, barley straw, wheat straw,
barley hay, wheat hay, alfalfa forage, alfalfa hay, and wheat aspirated
grain fractions. 

The Interregional Research Project No. 4 (IR-4), in cooperation with
Crompton Corporation, has submitted several petitions for the
establishment of permanent diflubenzuron tolerances on several raw
agricultural and processed commodities.  Under PP#5E6965, IR-4 requests
the establishment of tolerances for the combined residues of
diflubenzuron and its metabolites CPU and PCA in/on the following raw
agricultural commodities (RACs):

Barley, grain	0.06 ppm

Oat, grain	0.06 ppm

Wheat, grain	0.06 ppm

Barley, forage	5.0 ppm

Oat, forage	5.0 ppm

Wheat, forage	5.0 ppm

Barley, hay	2.0 ppm

Oat, hay	2.0 ppm

Wheat, hay	2.0 ppm

Barley, straw	2.0 ppm

Oat, straw	2.0 ppm

Wheat, straw	2.0 ppm

Grain, aspirated fractions	3.0 ppm

Pummelo	0.5 ppm

Under PP#5E6966, IR-4 requests the establishment of tolerances for the
combined residues of diflubenzuron and its metabolites CPU and PCA,
expressed as parent diflubenzuron, in/on the following RACs:

Brassica, leafy greens, subgroup 5B	8.0 ppm

Turnip greens	8.0 ppm

Eggplant	1.0 ppm

Okra	1.0 ppm

Lastly, under PP#5E6967, IR-4 requests the establishment of tolerances
for the combined residues of diflubenzuron and its metabolites CPU and
PCA, expressed as parent diflubenzuron, in/on the following raw
agricultural and processed commodities:

Peanut	0.2 ppm

Peanut, hay	20.0 ppm

Peanut, refined oil	0.2 ppm

Hazard Assessment

The acute oral, dermal and inhalation toxicity of diflubenzuron is low. 
It is a mild eye irritant and not a skin irritant in laboratory animals.
 It is negative for sensitization in the guinea pig.  In subchronic and
chronic feeding studies, the primary endpoint of concern, produced most
likely by PCA, was methemoglobinemia and/or sulfhemoglobinemia.  These
effects were evident in both sexes of mice, rats, and dogs and were
produced by more than one route of administration in rats [i.e., oral,
dermal and inhalation].  The general consequence of methemoglobinemia
and/or sulfhemoglobinemia is the impairment of the oxygen transportation
capacity of the blood, which is generally known to be caused by aromatic
amines in both humans and animals.

The overall toxicology database is sufficient for a determination of
potential hazard to infants and children.  The data provide no
indication of an increased susceptibility to rats or to rabbits from in
utero or post-natal exposure to diflubenzuron.  Developmental and
reproduction studies in rats and rabbits indicate a very low hazard
potential for adverse effects.  Developmental studies were tested at the
limit dose of 1000 mg/kg/day without apparent effects in both dams and
the fetuses.  The reproduction study indicated that effects in offspring
occurred at doses that were higher than the doses producing effects in
parents.  There was no indication of abnormalities in the development of
the fetal nervous system in the prenatal developmental toxicity studies
in either rats or rabbits at the maternal limit doses of 1000 mg/kg/day.
 In addition, there was no evidence of effects on the nervous system
following pre- and/or post-natal exposure in a two-generation
reproduction study in rats.  There were no reports of treatment-related
clinical observations indicative of central nervous system toxicity or
histopathological changes in the central nervous system [non-perfused
tissues] in the subchronic or the chronic studies.

Dose Response Assessment

On April 21, 1998 HED’s Hazard Identification Assessment Review
Committee (HIARC) evaluated the toxicology database, selected doses and
endpoints for chronic dietary exposures as well as occupational and
residential exposure scenarios [short-, intermediate-, and long-term
exposure (dermal and inhalation)], assessed the carcinogenic potential
and addressed the sensitivity of infants and children from exposure to
diflubenzuron as required by the Food Quality Protection Act (FQPA) of
1996.  On August 14, 2001, the HIARC revisited diflubenzuron and
selected the 21-day dermal toxicity study in rats for short-term dermal
exposure to be consistent with the current policy for 1- to 30-day
duration.  On February 12, 2002, the HIARC revisited diflubenzuron and
selected the 28-day inhalation toxicity study in rats for short-, and
intermediate-term inhalation exposure and reduced the uncertainty factor
(UFL) from 3x to 1x, since the selected study has a
no-observed-adverse-effect level (NOAEL).

The hemopoietic system is the target site with effects including
increased sulfhemoglobin and/or methemoglobin levels in rat and dog
studies.  No appropriate acute endpoint was identified in the hazard
database to quantitate the risk to the general population or to females
13-50 years old from single dose administration of diflubenzuron. 
Therefore, there is no acute reference dose (aRfD) or acute
population-adjusted dose (aPAD).  The short-term dermal endpoint was
selected from a 21-day rat dermal study with a NOAEL of 500 mg/kg/day
based on a significant increase in methemoglobinemia observed at the
lowest-observed-adverse-effect level (LOAEL) of 1000 mg/kg/day.  The
intermediate-term dermal endpoint was selected from a 13-week oral
(capsule) study in the dog with a NOAEL of 2 mg/kg/day based on
increased methemoglobinemia observed at the LOAEL 6.24 mg/kg/day.  The
short-, and intermediate-term inhalation endpoints were selected from a
28-day rat inhalation toxicity study with a NOAEL of 0.109 mg/L (highest
dose tested, HDT), based on a statistically significant increase in
methemoglobin levels observed at 0.12 mg/L (LOAEL) in a 21-day rat
inhalation toxicity study.  The chronic dietary, long-term dermal and
long-term inhalation endpoints were selected from a chronic dog study
with a NOAEL of 2 mg/kg/day based on increased methemoglobin levels
observed at 10 mg/kg/day (LOAEL).  The chronic RfD (cRfD) is 0.02
mg/kg/day and the chronic population-adjusted (cPAD) is 0.02 mg/kg/day. 
The HED RfD/Peer Review Committee classified diflubenzuron as “Group
E,” evidence of non-carcinogenicity for humans, based on lack of
evidence of carcinogenicity in rats and mice (April 27, 1995).  PCA, a
metabolite of diflubenzuron, tested positive for splenic tumors in male
rats and hepatocellular adenomas/carcinomas in male mice in a National
Toxicology Program (NTP) study.  Therefore, the RfD/Peer Review
Committee classified PCA as a “Group B2" probable human carcinogen. 
However, recently submitted acceptable rat metabolism studies show that
diflubenzuron was not metabolized to either PCA or CPU.  On May 8, 2001,
the MARC reviewed the recently submitted metabolism studies, accepted
the study findings, and concluded that cancer risks for CPU and PCA
should be assessed individually.  The non-carcinogenic risk assessment
should include diflubenzuron, CPU and CPA.

FQPA Decision

The FQPA Safety Factor Committee (SFC) recommended that the FQPA safety
factor used in human health risk assessments (as required by FQPA of
August 3, 1996) be reduced to 1x in assessing the risk posed by this
chemical (HED Document Number 012630, B. Tarplee, 06/14/1998). 
Consequently, the current cRfD and cPAD values are equivalent (0.02
mg/kg/day). This decision was based on the following:  1) there is no
indication of increased susceptibility of rats or rabbits to in utero or
postnatal exposure; 2) a developmental neurotoxicity study (DNT) with
diflubenzuron is not required; 3) food and drinking water exposure
assessments will not underestimate the potential exposure for infants
and children; and 4) there are currently no registered or proposed
residential (non-occupational) uses of diflubenzuron. 

Residential Exposure Estimates

Although there are no registered homeowner uses, there are registered
uses for professional applications to outdoor residential and
recreational areas to control mosquitoes, moths, and other insects. 
However, the potential for post-application residential exposure is
expected to be limited.  Due to the low dermal absorption rate (0.5%) of
diflubenzuron, and since it is only applied to the tree canopy, minimal
bystander contact is expected.

Occupational Exposure and Risk Assessment  

Based upon the proposed use patterns, short-term (1-30 days) dermal and
inhalation exposures are typically expected for commercial and private
(i.e., grower) pesticide mixers, loaders, and applicators.  The
toxicological endpoints for short-term dermal and short-term inhalation
effects were derived from two different studies; however, both studies
indicate similar toxicological effects (i.e., methemoglobinemia).  Since
the results of the two studies indicate similar toxicological effects,
the MOEs are shown as combined MOEs.  HED’s level of concern (LOC) is
a margin of exposure (MOE) <100.

No chemical-specific data were available with which to assess potential
exposure to pesticide handlers.  Therefore, the exposure and risk
estimates presented in this document are based upon surrogate data in
the Pesticide Handlers Exposure Database (PHED) Ver. 1.1, Surrogate
Exposure Guide (August 1998).  Occupational exposures are assessed for
pesticide handlers (i.e., mixers, loaders, applicators) and for
agricultural workers.  MOEs range from 15,000 for mixer/loaders using
protective gloves to 120,000 for aerial applicators.  A conservative,
screening-level assessment of post-application exposure to agricultural
workers yields MOEs of 2100 or more.  For occupational exposures, the
MOEs do not exceed HED’s LOC.  

Dietary Risk Estimates (Food + Water)

The Tier 1, chronic assessment assumed that diflubenzuron residues are
present in all commodities at established/recommended tolerance levels
and that 100% of all crops are treated. Drinking water was incorporated
directly into the dietary assessment using the estimated drinking water
concentration (EDWC) for surface water of 2.76 ppb generated by the
Pesticide Root Zone Model/Exposure Analysis Modeling System (PRZM/EXAMS)
with index reservoir (IR) scenarios and percent crop area (PCA)
adjustment factors.

 software, dietary exposure is estimated to be ≤37% of the cPAD for
the U.S. population and all population subgroups, including children 1
to 2 years old, the population subgroup with the highest estimated
exposure.

Aggregate-Risk Estimates

Aggregate exposure risk assessments were assessed by incorporating the
drinking water directly into the dietary-exposure assessment for the
following scenario:  chronic aggregate exposure (food + drinking water).
 Short-, intermediate-, and long-term aggregate-risk assessments were
not performed because there are no registered or proposed uses of
diflubenzuron which result in residential exposures.  Acute and cancer
aggregate-risk assessments were not performed because no appropriate
endpoint was available to determine the aRfD for the general population
or any population subgroup and diflubenzuron is not carcinogenic.  

Recommendations for Tolerances/Registration

PP#5E6965:  Provided revised Sections B and F are submitted,   SEQ
CHAPTER \h \r 1 HED concludes there are no residue chemistry or
toxicology data requirements that would preclude the establishment of
the HED-recommended tolerances for diflubenzuron in/on the relevant
commodities as specified below.  The proposed uses of Dimilin® 2L on
barley, oats, triticale, and wheat should be made conditional upon
resolving the storage stability deficiencies cited below.  The proposed
use of Micromite® 80WGS on pummelos can be unconditional.

PP#5E6966:  Provided revised Sections B and F are submitted,   SEQ
CHAPTER \h \r 1 HED concludes there are no residue chemistry or
toxicology data requirements that would preclude the establishment of
the HED-recommended tolerances as specified below and unconditional
registration for diflubenzuron on Brassica leafy greens (subgroup 5B)
and turnip greens.  

PP#5E6967:  Provided a revised Section F is submitted,   SEQ CHAPTER \h
\r 1 HED concludes there are no residue chemistry or toxicology data
requirements that would preclude the establishment of the
HED-recommended tolerances for diflubenzuron in/on the relevant
commodities as specified below.  The proposed use of Dimilin® 2L on
peanuts should be made conditional upon submission of additional field
trial and processing data as cited below.  

RESIDUE CHEMISTRY DEFICIENCIES

860.1200 Directions for Use

Barley, oats, and wheat:  The petitioner should delete the proposed
application method using ultra-low-volume (ULV; 24-32 fl. oz/A)
equipment.  Label revisions are requested to specify appropriate
preharvest intervals (PHIs) based on the reviewed data.  Labels should
be revised to specify PHIs of 50 days for grain and straw, 3 days for
forage, and 15 days for hay.  

Turnip greens:  The label should be amended to prohibit use on dual
purpose turnip cultivars or varieties which produce a harvestable root.

Okra and eggplant:  The use directions for okra and eggplant should be
removed from the label.

860.1380 Storage Stability

Barley, oats, and wheat:  Additional storage stability data for wheat
processed commodities (except bran) are requested to validate the
storage conditions and intervals of samples from the submitted wheat
processing study.  The available storage stability data for rice bran
may be translated to wheat bran; the petitioner is only requested to
generate storage stability data for wheat flour, middlings, shorts, and
germ.  The requested data should reflect the storage conditions and
intervals of samples from the wheat processing study.

860.1500 Crop Field Trials

≥3x, which is the maximum theoretical concentration factor (by crop)
for peanuts.  The meal samples from this study should be analyzed with a
method which has a LOQ for diflubenzuron which is comparable to that of
the RAC (0.05 ppm).

860.1550 Proposed Tolerances

Barley, oats, and wheat:  A revised Section F should be submitted to
reflect HED-recommended tolerance levels of 3.0 ppm for residues in/on
barley hay, 1.8 ppm for residues in/on barley straw, 7.0 ppm for
residues in/on wheat forage, 6.0 ppm for residues in/on wheat hay, 3.5
ppm for residues in/on wheat straw, and 11 ppm for residues in/on
aspirated grain fractions.  Barley forage is not listed in Table 1 of
OPPTS 860.1000; therefore, this entry should be removed from the
petitioner’s Section F.  The available data for wheat may be
translated to oats; the corresponding tolerances recommended for wheat
commodities also apply to oat commodities.

Brassica leafy greens:  A revised Section F should be submitted to
reflect HED-recommended tolerance level of 9.0 ppm for residues in/on
Brassica leafy greens, subgroup 5B.

Peanut:  A revised Section F should be submitted to reflect
HED-recommended tolerance levels of 0.10 ppm for residues in/on peanut,
55 ppm for residues in/on peanut hay, and 0.20 ppm for residues in/on
peanut oil.

Mustard greens:  A revised Section F should be submitted to reflect
HED-recommended tolerance level of 9.0 ppm.

Okra and eggplant:  The proposed tolerances for okra and eggplant should
be withdrawn.

2.0 PHYSICAL/CHEMICAL PROPERTIES CHARACTERIZATION

2.1 Identification of Active Ingredient

TABLE 2.1.1	Diflubenzuron Nomenclature.

Compound	

Common Name	Diflubenzuron

Trade and other Names	Dimilin, Vigilante, Micromite, Adept

IUPAC Name	1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea

CAS Name	N-[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide

CAS Registry Number	35367-38-5

End-Use Products (EP)	2 lb/gal FlC formulation; DIMILIN® 2L (EPA Reg.
No. 400-461);

25% WP formulation; DIMILIN® 25W (EPA Reg. No. 400-465);

80% G formulation; Micromite® 80WGS (EPA Reg. No. 400-487);

Regulated Metabolite	

Common name	4-chlorophenylurea (CPU)

Regulated Metabolite	

Common Name	4-chloroaniline (PCA)

2.2 Physical and Chemical Properties

TABLE 2.2.1  Physicochemical Properties of Diflubenzuron.

Parameter	Value	Reference

Melting range	230-232 °C	  HYPERLINK
"http://www.arsusda.gov/acsl/services/ppdb/textfiles/DIFLUBENZURON" 
http://www.arsusda.gov/acsl/services/ppdb/textfiles/DIFLUBENZURON 

pH	Not available

	Density	Not available

	Water solubility (25 °C)	0.08 ppm

	Solvent solubility (25 °C) (ppm)	6.5 x 103     Acetone             

2 x 103        Acetonitrile        

2.4 x 104     Dioxane             

1.04 x 105   Dimethylformamide    

1.2 x 105     Dimethylsulfoxide   

1 x 103        Methanol            

6 x 102        Dichloromethane     

	Vapor pressure (25 °C)	1.2 x 10- 4 mPa

	Dissociation constant, pKa	Not available

	Octanol/water partition coefficient, Log(KOW)	3.89

	

3.0 HAZARD CHARACTERIZATION

A complete hazard characterization is presented in the Section 3 risk
assessment for the use of diflubenzuron on rice (Memo, G. Kramer et al.,
3/30/99; D254693).  For purposes of clarity, the dose-response
assessment is summarized below.

3.1 Dose-Response Assessment

Acute Dietary Endpoint:  No appropriate toxicological endpoint
attributable to a single exposure was identified in the hazard database,
including oral developmental toxicity studies in rats and rabbits.

Chronic Dietary Endpoint:  The chronic dog study was used to select the
endpoint for establishing the cRfD of 0.02 mg/kg/day.  The standard 100x
UF was applied to account for interspecies extrapolation and
intraspecies variation.  The NOAEL of 2.0 mg/kg/day was based on
methemoglobinemia and sulfhemoglobinemia seen at 10 mg/kg/day (LOAEL). 
The FQPA SFC determined that a FQPA safety factor of 1x is applicable
for chronic dietary risk assessment. Thus, the cPAD is 0.02 mg/kg/day.

Carcinogenicity:  Based on the available evidence, which included
adequate carcinogenicity studies in rats and mice, and battery of
negative mutagenicity studies, diflubenzuron was classified as “Group
E,” evidence of non-carcinogenicity for humans, by the RfD Peer Review
Committee (4/27/95).  Rat metabolism data generated at this time also
indicated that diflubenzuron was metabolized to PCA and CPU and
estimated to be about 2% of in vivo conversion.

Recently submitted rat metabolism data (MRID#s 44875501 and 44875502)
indicate that diflubenzuron does not metabolize to PCA or CPU nor is CPU
converted to PCA.  The HED MARC met several times (2/20/01 and 5/8/01),
concurred with the study findings, and concluded that a 2% in vivo
conversion factor for diflubenzuron to PCA or CPU should be dropped
(MARC memo dated May 31, 2001).  In conclusion, the MARC recommended
that non-carcinogenic risk assessment should include parent, CPU and
PCA; and cancer risk for CPU and PCA should be assessed individually.

Short- and Intermediate-Term Incidental Oral Endpoint:  These endpoints
were not evaluated.  There are no registered or proposed uses of
diflubenzuron which result in significant residential exposure.

Dermal Penetration:  The HIARC recommended a dermal-absorption factor of
0.5% based on a 1- to 10-hour exposure from a rat study.

Short-Term Dermal Endpoint:  A short-term dermal endpoint was selected
from a 21-day rat dermal toxicity study.  The NOAEL of 500 mg/kg/day was
based on the significant increase in methemoglobinemia observed at 1000
mg/kg/day (limit dose).  This study is route-specific, is of appropriate
duration and measures the effects of concern; i.e., methemoglobin and/or
sulfhemoglobin.

Intermediate-Term Dermal Endpoint:  An intermediate-term dermal endpoint
was selected from a subchronic oral toxicity dog study.  The NOAEL of
2.0 mg/kg/day was based on increased methemoglobinemia at 6.24
mg/kg/day.  This endpoint (methemoglobinemia/ sulfhemoglobinemia) was
seen consistently in the 90-day dog study and chronic toxicity studies
in rats, mice and dogs at about similar ranges and it is appropriate for
this exposure period of concern.  Since an oral NOAEL was selected for a
dermal-exposure scenario, a dermal-absorption factor of 0.5% should be
used for this risk assessment when converting dermal exposure to oral
equivalents.

Long-Term Dermal Endpoint:  A long-term dermal endpoint was selected
from a chronic oral toxicity study in the dog.  The NOAEL of 2.0
mg/kg/day was based on increased methemoglobinemia and
sulfhemoglobinemia seen at 10.0 mg/kg/day.  An oral study was selected
since no appropriate long-term dermal study is available in the
database.  A 0.5% dermal-absorption factor should be used to convert to
oral equivalents.

Short-, and Intermediate-Term Inhalation Endpoint:  An inhalation
endpoint was selected from a 28-day rat inhalation toxicity study.  The
NOAEL of 0.109 mg/L (HDT) in this study was based on significant
increase in methemoglobinemia seen in a 21-day inhalation toxicity study
at 0.12 mg/L (LOAEL at LDT).

Long-Term Inhalation Endpoint:  A long-term inhalation endpoint was
selected from a chronic oral toxicity dog study.  The NOAEL of 2.0
mg/kg/day was based on increased methemoglobinemia and
sulfhemoglobinemia at 10.0 mg/kg/day.  An oral study was selected since
no appropriate long-term inhalation study is available in the database. 
A 100% inhalation-absorption factor should be used to convert to oral
equivalents.

MOE for Occupational Risk Assessment:  A MOE of 100 is adequate for
dermal and inhalation occupational exposure.

Table 3.1.1.  Summary of Toxicological Dose and Endpoints for
Diflubenzuron for Use in Human Risk Assessment1.

Exposure

Scenario	Dose Used in Risk Assessment, UF 	FQPA SF and LOC for Risk
Assessment	

Study and Toxicological Effects

Acute Dietary

all populations	Not Applicable	Not Applicable	No appropriate endpoint
attributable to single exposure was available in oral studies. 
Therefore, a risk assessment is not required.

Chronic Dietary

all populations	NOAEL= 2 mg/kg/day

UF = 100

Chronic RfD = 

0.02 mg/kg/day	FQPA SF = 1x

cPAD = 

chronic RfD

 FQPA SF

= 0.02 mg/kg/day	Chronic Toxicity Study - Dog

LOAEL = 10 mg/kg/day based on methemoglobinemia and sulfhemoglobinemia

Short- and Intermediate-Term Incidental Oral

(1 day - 6 months)

(Residential)	Not applicable	Not applicable	These endpoints were not
evaluated.    There are no registered uses of diflubenzuron which result
in significant residential exposure.

Short-Term Dermal (1 - 30 days)

(Occupational)	NOAEL = 500 mg/kg/day	LOC for MOE = 100	21-Day dermal rat

LOAEL = 1000 mg/kg/day based on methemoglobinemia

Intermediate-Term Dermal (1 - 6 months)

(Occupational)	NOAEL = 2 mg/kg/day	LOC for MOE = 100	13 - week oral dog 
                                   LOAEL = 6.4 mg/kg/day based on       
   methemoglobinemia 

Long-Term Dermal (Longer than 6 months)

(Occupational)	NOAEL = 2 mg/kg/day	LOC for MOE = 100	Chronic Toxicity
Study - Dog

LOAEL = 10 mg/kg/day based on methemoglobinemia and sulfhemoglobinemia

Short-Term Inhalation (1 - 30 days)

(Occupational)	NOAEL = 20.302 mg/kg/day	LOC for MOE = 100	28-day
Inhalation Toxicity Study - Rat/

21-day Inhalation Toxicity Study - Rat

LOAEL = 0.12 mg/L based on methemoglobinemia (21-day study)

Intermediate-Term Inhalation (1 - 6 months)

(Occupational)	NOAEL = 20.302 mg/kg/day	LOC for MOE = 100	28-day
Inhalation Toxicity Study - Rat/

21-day Inhalation Toxicity Study - Rat

LOAEL = 0.12 mg/L based on methemoglobinemia (21-day study)

Long -Term Inhalation (Longer than 6 months)

(Occupational)	NOAEL = 2  mg/kg/day	LOC for MOE = 100 (Occupational)
Chronic Toxicity Study - Dog

LOAEL = 10 mg/kg/day based on methemoglobinemia and sulfhemoglobinemia

Cancer (oral, dermal, inhalation)	Diflubenzuron

Not Required	Not Applicable	Acceptable oral rat and mouse
carcinogenicity studies; no evidence of carcinogenic or mutagenic
potential. “Group E” evidence of non- carcinogenicity for humans.

1.  UF = uncertainty factor, FQPA SF = FQPA safety factor, NOAEL =
no-observed-adverse-effect level, LOAEL = lowest-observed-adverse-effect
level, cPAD = chronic population-adjusted dose, RfD = reference dose,
MOE = margin of exposure, LOC = level of concern.

2.  Conversion from mg/L to oral dose (mg/kg/day)

3.2 Endocrine Disruption  TC \l2 "3.2	Endocrine Disruption 

EPA is required under the Federal Food Drug and Cosmetic Act (FFDCA), as
amended by FQPA, to develop a screening program to determine whether
certain substances (including all pesticide active and other
ingredients) "may have an effect in humans that is similar to an effect
produced by a naturally occurring estrogen, or other such endocrine
effects as the Administrator may designate."  Following the
recommendations of its Endocrine Disruptor Screening and Testing
Advisory Committee (EDSTAC), EPA determined that there was scientific
basis for including, as part of the program, the androgen and thyroid
hormone systems, in addition to the estrogen hormone system.  EPA also
adopted EDSTAC’s recommendation that the Program include evaluations
of potential effects in wildlife.  For pesticide chemicals, EPA will use
FIFRA and, to the extent that effects in wildlife may help determine
whether a substance may have an effect in humans, FFDCA has authority to
require the wildlife evaluations.  As the science develops and resources
allow, screening of additional hormone systems may be added to the
Endocrine Disruptor Screening Program (EDSP).

When the appropriate screening and/or testing protocols being considered
under the Agency’s EDSP have been developed, diflubenzuron may be
subjected to additional screening and/or testing to better characterize
effects related to endocrine disruption.

4.0 EXPOSURE ASSESSMENT AND CHARACTERIZATION

4.1 Summary of Registered/Proposed Uses

A summary of the proposed end-use products is presented in Table 4.1.1. 
Table 4.1.2 lists the summary of proposed use patterns.

Table 4.1.1.  Summary of Proposed End-Use Products.

Trade Name	

Reg. No.	% ai (formulation)	Formulation Type	

Target New Crops	

Target Pests	Label Date

Dimilin® 2L	400-461	22%

(2 lb ai/gal)	Flowable concentrate (FlC)	Barley, oats, triticale, and
wheat, peanut, leafy Brassica, and turnip greens	Grasshoppers, cereal
leaf beetle, velvet bean caterpillar, Mexican bean beetle, green clover
worm, armyworms, lesser cornstalk borer, soybean looper (suppression)
Undated specimen label

Dimilin® 25W	400-465	25%	Wettable powder (WP)	Eggplant and okra
Foliage-feeding Lepidopteran insects	Undated specimen label

Micromite® 80WGS	400-487	80%	Water-dispersible granule	Pummelos	Citrus
rust mite, Lepidopterous miners, and citrus root weevil complex	Undated
specimen label

Table 4.1.2.  Summary of Proposed Directions for Use of Diflubenzuron.

Applic. Timing, Type, 

Equipment.	Formulation

[EPA Reg. No.]	Applic. Rate 

(lb ai/A)	Max. No. Applic. per Season	Max. Seasonal Applic. Rate

(lb ai/A)	PHI

(days)

Barley, Oats, Triticale, and Wheat

Foliar prior to boot stage

ULV (24-32 fl. oz/A)

Aerial (3-5 GPA)

Ground (5-15 GPA)	Use Directions and Limitations:  Use limited to crops
grown in Alaska, Colorado, Idaho, Montana, Nevada, Oregon, Utah,
Washington, Wyoming, Western North and South Dakota, and Western
Nebraska (West of Route 281 in ND, SD, & NE).  Do not apply after boot
stage of growth.  For control of grasshoppers, apply when pests have
reached the 2nd to 3rd nymphal stage of development.  For control of
cereal leaf beetle, apply at first sign of egg laying.

	2 lb/gal FlC

[400-461]	0.0625	1	0.0625	45 for grain and straw

Brassica Leafy Greens including Mustard Greens; Turnip Greens

Foliar

Ground (Min 30 GPA)	Use Directions and Limitations:  For control of
grasshoppers, apply when pests have reached the 2nd to 3rd nymphal stage
of development.  Reapply in 7-10 day intervals if nymphal hatchout or
crop re-infestations continue.

	2 lb/gal FlC

[400-461]	0.0625	4	0.25	7

Eggplant

Foliar

Ground (Min 30 GPA)	Use Directions and Limitations:  Allow a minimum of
7 days between any 2 applications.

	25% WP

[400-465]	0.125	Up to 5 treatments may be made as long as the maximum
seasonal rate of 0.375 lb ai/A is not exceeded.	7

Okra

Foliar

Ground (Min 30 GPA)	Use Directions and Limitations:  Allow a minimum of
7 days between any 2 applications.

	25% WP

[400-465]	0.125	Up to 5 treatments may be made as long as the maximum
seasonal rate of 0.375 lb ai/A is not exceeded.	7

Peanut

Foliar 

Aerial (3-5 GPA)

Ground (10-20 GPA)	Use Directions and Limitations:  Allow at least 14
days between any two applications.  Repeat applications if the egg
laying period is lengthy and/or another pest infestation occurs.

	2 lb/gal FlC

[400-461]	0.125	3	0.375	28

Pummelo

Foliar

Aerial (5-20 GPA)

Ground (50-1,000 GPA)

	Use Directions and Limitations:  Maintain a minimum of 90 days between
applications.  Do not harvest cover crops for livestock feed or graze
livestock in treated groves.

	80% WGS

[400-487]	0.3125	3	0.9375

(max yearly rate)	21

The following rotational crop restriction is specified on the undated
draft specimen labels of the 2 lb/gal FlC (Dimilin® 2L; EPA Reg. No.
400-461) and 25% WP (Dimilin® 25W; EPA Reg. No. 460-465) formulations: 
“Do not plant food or feed crops in DIMILIN treated soils within 1
month following last application, unless DIMILIN is authorized for use
on these crops.”

Conclusions.  The submitted labels are adequate to allow evaluation of
the residue data relative to the proposed uses except:  Barley, oats,
and wheat:  The petitioner should delete the proposed application method
using ULV (24-32 fl. oz/A) equipment.  Label revisions are requested to
specify appropriate PHIs based on the reviewed data.  Labels should be
revised to specify PHIs of 50 days for grain and straw, 3 days for
forage, and 15 days for hay.  Turnip greens:  The label should be
amended to prohibit use on dual purpose turnip cultivars or varieties
which produce a harvestable root.  Okra and eggplant:  The use
directions for okra and eggplant should be removed from the label. 
Revised Section Bs should be submitted.

4.2 Dietary Exposure/Risk Pathway

The residue chemistry data submitted in support of the proposed
petitions were evaluated by HED on 14-SEP-2006 (Memo, G. Kramer,
D321623).  The drinking water assessment was completed by EFED on
25-AUG-2006 (Memo, A. Al-Mudallal, D321156).  The dietary-exposure
assessment was completed in a HED memorandum dated 14-SEP-2006 (G.
Kramer, D332081).

4.2.1 Residue Profile

Background

Diflubenzuron
(N-[((4-chlorophenyl)amino)carbonyl]-2,6-difluorobenzimide), a member of
the urea-derivative chemical family, is an insecticide/acaricide (insect
growth regulator) that behaves as a chitin inhibitor to suppress the
growth of many leaf-eating larvae, mosquito larvae, aquatic midges, rust
mite, boll weevil, and flies.

Tolerances for residues of diflubenzuron are established under 40 CFR
§180.377.  Tolerances listed in 40 CFR §180.377(a)(1) are expressed in
terms of diflubenzuron per se.  Under this section, the listed
tolerances are:  (i) 0.05 ppm for residues in/on eggs, milk, and the fat
and meat of cattle, goat, hog, horse, poultry, and sheep, and for the
meat byproducts of poultry; (ii) 0.2 ppm for residues in/on undelinted
cottonseed and mushroom; (iii) 0.5 ppm for residues in/on grapefruit,
orange (sweet), tangerine, and soybean hulls; and (iv) 6.0 ppm for
residues in/on globe artichoke.

Tolerances listed in 40 CFR §180.377(a)(2) are expressed in terms of
the combined residues of diflubenzuron and its metabolites CPU and PCA. 
Under this section, the listed tolerances are:  (i) 0.02 ppm for
residues in/on rice grain; (ii) 0.06 ppm for residues in/on tree nuts
(group 14) and pistachios; (iii) 0.07 ppm for residues in/on fruit,
stone (group 12) except cherry; (iv) 0.15 ppm for residues in/on the
meat byproducts of cattle, goat, hog, horse, and sheep; (v) 0.50 ppm for
residues in/on pear; (vi) 0.8 ppm for residues in/on rice straw; (vii)
1.0 ppm for residues in/on pepper; and (viii) 6.0 ppm for residues in/on
almond hulls.

Time-limited tolerances listed in 40 CFR §180.377(b) are expressed in
terms of the combined residues of diflubenzuron and its metabolites CPU
and PCA, expressed as the parent diflubenzuron, in connection with use
of the pesticide under Section 18 Emergency Exemptions granted by EPA. 
Under this section, the listed tolerances are:  (i) 0.05 ppm for
residues in/on barley grain and wheat grain; (ii) 0.10 ppm for residues
in/on wheat milled byproducts; (iii) 0.50 ppm for residues in/on barley
straw and wheat straw; (iv) 1.0 ppm for residues in/on barley hay and
wheat hay; (v) 6.0 ppm for residues in/on alfalfa forage and alfalfa
hay; and (vi) 30 ppm for residues in/on wheat aspirated grain fractions.
 Tolerances for alfalfa commodities will expire 6/30/2007 and tolerances
for barley and wheat commodities will expire 12/31/08.

The IR-4, in cooperation with Crompton Corporation, has submitted
several petitions for the establishment of permanent diflubenzuron
tolerances on several raw agricultural and processed commodities.

Under PP#5E6965, IR-4 requests the establishment of tolerances for the
combined residues of diflubenzuron and its metabolites CPU and PCA in/on
the following RACs:

Barley, grain	0.06 ppm

Oat, grain	0.06 ppm

Wheat, grain	0.06 ppm

Barley, forage	5.0 ppm

Oat, forage	5.0 ppm

Wheat, forage	5.0 ppm

Barley, hay	2.0 ppm

Oat, hay	2.0 ppm

Wheat, hay	2.0 ppm

Barley, straw	2.0 ppm

Oat, straw	2.0 ppm

Wheat, straw	2.0 ppm

Grain, aspirated fractions	3.0 ppm

Pummelo	0.5 ppm

Under PP#5E6966, IR-4 requests the establishment of tolerances for the
combined residues of diflubenzuron and its metabolites CPU and PCA,
expressed as parent diflubenzuron, in/on the following RACs:

Brassica, leafy greens, subgroup 5B	8.0 ppm

Turnip greens	8.0 ppm

Eggplant	1.0 ppm

Okra	1.0 ppm

Lastly, under PP#5E6967, IR-4 requests the establishment of tolerances
for the combined residues of diflubenzuron and its metabolites CPU and
PCA, expressed as parent diflubenzuron, in/on the following raw
agricultural and processed commodities:

Peanut	0.2 ppm

Peanut, hay	20.0 ppm

Peanut, refined oil	0.2 ppm

Nature of the Residue in Plants 

The qualitative nature of the residue in plants and fungi is adequately
understood based on data from citrus, mushroom, rice, and soybean
metabolism studies.  The metabolism of diflubenzuron in crops tested is
similar, and the radioactive components are also similar to those found
in soil.  The nature of the residue in livestock is also adequately
understood based on acceptable poultry and ruminant metabolism studies
reflecting oral dosing.  The HED Metabolism Assessment Review Committee
(MARC) has concluded that the residues of concern in plants, livestock,
and fungi, for the purpose of tolerance expression, are diflubenzuron
and its metabolites PCA and CPU.

Residue Analytical Methods

There are adequate enforcement methods, published in the Pesticide
Analytical Manual (PAM, Vol. II), for determining diflubenzuron residues
of concern.  In addition, a new analytical methodology for plant
commodities was successfully validated by an independent laboratory as
well as by Agency chemists at the Analytical Chemistry Branch
(ACB)/Biological and Economics Analysis Division (BEAD) in conjunction
with the approved rice petition (PP#8F4925).  The new methods were
forwarded to the Food and Drug Administration (FDA) for publication in
PAM Vol. II as Roman Numeral Methods.  T  SEQ CHAPTER \h \r 1 hese
methods can separately determine residues of diflubenzuron by gas
chromatography/electron-capture detection (GC/ECD), CPU by GC/ECD, and
PCA by GC/mass spectrometry (MS).  The reported limit of quantitation
(LOQ) for diflubenzuron in/on rice grain, straw, and bran is 0.01 ppm,
and is 0.05 ppm in/on rice hull.  In rice straw, the LOQ for CPU is 0.01
ppm and 0.005 ppm for PCA.

Samples of raw agricultural and processed commodities, collected from
the field, processing, and storage stability studies, were separately
analyzed for residues of diflubenzuron, CPU, and PCA using methods,
which are similar or based on method submissions previously deemed
acceptable by HED.  The data-collection methods were adequately
validated, and method recoveries were generally within the acceptable
range of 70-120%.

Magnitude of Residues in Plants

Adequate magnitude of the residue data have been submitted for barley
grain, barley hay, barley straw, wheat grain, wheat forage, wheat hay,
and wheat straw.  These data were generated from field trials using
spray volumes of 10-20 gallons per acre using ground equipment.  The
petitioner should delete the proposed application method using ULV
(24-32 fl. oz/A) equipment. Barley forage is not listed in Table 1 of
OPPTS 860.1000 and should be removed from the petitioner’s Section F. 
As the proposed use is geographically limited, the available data for
wheat may be translated to oats; the corresponding tolerances
recommended for wheat commodities also apply to oat commodities.  The
proposed use on triticale is supported by the submitted data for wheat
as per 40 CFR 180.1.

The established grapefruit tolerance may be used to support the
requested tolerance of 0.5 ppm on pummelos.

Adequate magnitude of the residue data have been submitted for mustard
greens, the representative commodity of the Brassica leafy greens
(subgroup 5B).

Turnip greens will be removed from Crop Group 2:  Leaves of root and
tuber vegetables group, and will become a member of Crop Subgroup 5B: 
Leafy Brassica greens (Reviewer’s Guide and Summary..., B. Schneider,
6/14/02).  Forage turnip varieties grown for livestock feed uses only
will remain in Crop Group 2:  Leaves of root and tuber vegetables group.
 As mustard greens are the representative commodity of the Brassica
leafy greens (subgroup 5B), the mustard green residue data can be
translated to turnip greens.  However, the label should be amended to
prohibit use on dual purpose turnip cultivars or varieties which produce
a harvestable root.

No residue data were submitted in support of the proposed uses on okra
or eggplant.  The petitioner requests translation of the available data
from pepper to okra and eggplant.  However, HED does not generally
translate residue data among members of a crop group unless a crop group
tolerance is established.  Thus, the proposed tolerances for okra and
eggplant should be withdrawn and the use directions for okra and
eggplant removed from the label until adequate okra and eggplant residue
data are available or a crop group tolerance for fruiting vegetables is
established.

The submitted data for peanut nutmeat and peanut hay are inadequate
because geographic representation of residue data is insufficient as the
results from three trials were invalidated because of possible sample
contamination.  Confirmatory residue data from an additional three
peanut field trials conducted in Zone 2 are requested.

Confined and Field Accumulation in Rotational Crops

  SEQ CHAPTER \h \r 1 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,
3/15/95).  The Residue Chapter concluded that although the available
confined rotational crop study was inadequate to fully satisfy
reregistration requirements, another confined rotational crop study will
not be requested because the study allowed HED to make regulatory
conclusions regarding the need for limited rotational-crop studies and
to comment on the appropriateness of the currently established plantback
interval (PBI) on diflubenzuron end-use product labels. 

An acceptable limited field rotational crop study has been submitted. 
HED’s review of the study concluded that   SEQ CHAPTER \h \r 1
quantifiable residues of diflubenzuron, CPU and PCA are unlikely to
occur in rotated crops planted at least 30 days following treatment at
the proposed rate.  The petitioner’s proposed PBI of 30 days is
appropriate.

Magnitude of Residues in Processed Commodities

The submitted peanut processing study is inadequate because the study
has not definitively proven that diflubenzuron residues of concern will
not concentrate in the processed commodities of peanuts as a result of
the proposed use.  A new processing study is requested.  Pending receipt
of these data, HED concludes that the proposed tolerance of 0.2 ppm for
residues in/on peanut oil is appropriate (HAFT residue (<0.06 ppm)
multiplied by the maximum theoretical concentration factor of 3x).

The submitted wheat processing study is not supported by adequate
storage stability data, and these data are requested.  Although
inadequate, the study indicates that the combined residues of
diflubenzuron and its CPU and PCA metabolites do not appear to
concentrate in shorts, middlings, flour, bran, and germ processed from
wheat grain treated at 1x and 10x the field rate.  The combined
residues, however, concentrated >35x and 180x in aspirated grain
fractions processed from wheat grain treated at 1x and 10x,
respectively.

Magnitude of Residues in Meat, Milk, Poultry and Eggs (MMPE)

There are ruminant and/or poultry feed items associated with the
proposed uses of diflubenzuron on barley, oats, wheat, and peanuts.  The
calculated maximum theoretical dietary burdens (22.2 ppm for beef
cattle, 34.8 ppm for dairy cattle, 0.052 ppm for poultry, and 0.058 ppm
for hog), resulting from the proposed/registered uses, are supported by
previously submitted livestock feeding studies.  HED concludes that the
current tolerances on meat, milk, poultry, and eggs are adequate to
cover the added residues resulting from the proposed uses.

Tolerance Summary

A summary of tolerance reassessment is presented in Table 4.2.1.1.  The
recommended tolerances for all commodities except barley grain, wheat
grain, and peanut nutmeat were derived with the aid of HED’s tolerance
spreadsheet.  The tolerance spreadsheet was not used for the
above-listed commodities because residues in/on treated samples were
mostly below the respective LOQs. 

  SEQ CHAPTER \h \r 1 The Codex Alimentarius has established maximum
residue limits (MRL), expressed in terms of diflubenzuron per se, for
many commodities including:  apple (5 ppm), citrus fruits (0.5 ppm),
edible offal (mammalian) (0.1 ppm), eggs (0.05 ppm), meat (from mammals
other than marine mammals) (0.1 ppm), milks (0.02 ppm), mushrooms (0.3
ppm), pear (5 ppm), pome fruits (5 ppm), poultry meat (0.05 ppm), rice
(0.01 ppm), and rice straw and fodder (dry) 0.7 ppm).  As the U.S.
residue definition includes CPU and PCA, compatibility is not possible
with the proposed tolerances.  

Table 4.2.1.1.  Tolerance Summary for Diflubenzuron.

Commodity	Proposed Tolerance (ppm)	Recommended Tolerance (ppm)	Comments;

[Correct Commodity Definition]

Tolerances Proposed in PP#5E6965

Barley, grain	0.06	0.06

	Barley, forage	5.0	Delete	Not a RAC of barley as per Table 1 of OPPTS
860.1000.

Barley, hay	2.0	3.0

	Barley, straw	2.0	1.8

	Oat, grain	0.06	0.06	The available data for wheat may be translated to
oat; the corresponding tolerances recommended for wheat commodities also
apply to oat commodities.

Oat, forage	5.0	7.0

	Oat, hay	2.0	6.0

	Oat, straw	2.0	3.5

	Wheat, grain	0.06	0.06

	Wheat, forage	5.0	7.0

	Wheat, hay 	2.0	6.0

	Wheat, straw	2.0	3.5

	Grain, aspirated fractions	3.0	11	The maximum diflubenzuron residues of
concern expected in wheat aspirated grain fractions is 6.42 ppm which is
derived by multiplying the HAFT residue (<0.06 ppm; see Table 7) with
the processing factor (180x).

Pummelo	0.5 	0.50	The available data for citrus fruits may be translated
to pummelo.

Tolerances Proposed in PP#5E6966

Brassica, leafy greens, subgroup 5B	8.0	9.0

	Turnip greens	8.0	9.0

	Eggplant	1.0	Delete	Residue data for eggplant are required to determine
appropriate tolerance.

Okra	1.0	Delete	Residue data for okra are required to determine
appropriate tolerance.

Tolerances Proposed in PP#5E6967

Peanut	0.2	0.10

	Peanut, hay	20.0	55

	Peanut, refined oil	0.2	0.20	Peanut, oil 

A new peanut processing study is requested.

4.2.2 Dietary-Exposure Analyses

™ Version 2.03, which incorporates consumption data from USDA’s
CSFII, 1994-1996 and 1998.  The 1994-96, 98 data are based on the
reported consumption of more than 20,000 individuals over two
non-consecutive survey days.  Foods “as consumed” (e.g., apple pie)
are linked to EPA-defined food commodities (e.g. apples, peeled fruit -
cooked; fresh or N/S; baked; or wheat flour - cooked; fresh or N/S,
baked) using publicly available recipe translation files developed
jointly by USDA/ARS and EPA.  For chronic exposure assessment,
consumption data are averaged for the entire U.S. population and within
population subgroups, but for acute exposure assessment are retained as
individual consumption events.  Based on analysis of the 1994-96, 98
CSFII consumption data, which took into account dietary patterns and
survey respondents, HED concluded that it is most appropriate to report
risk for the following population subgroups: the general U.S.
population, all infants (<1 year old), children 1-2, children 3-5,
children 6-12, youth 13-19, adults 20-49, females 13-49, and adults 50+
years old.

For chronic dietary-exposure assessments, an estimate of the residue
level in each food or food-form (e.g., orange or orange juice) on the
food commodity residue list is multiplied by the average daily
consumption estimate for that food/food form to produce a residue intake
estimate. The resulting residue intake estimate for each food/food form
is summed with the residue intake estimates for all other food/food
forms on the commodity residue list to arrive at the total average
estimated exposure.  Exposure is expressed in mg/kg body weight/day and
as a percent of the cPAD.  This procedure is performed for each
population subgroup.

4.2.2.1 Acute Dietary-Exposure Analysis

An acute dietary-exposure assessment was not performed because there
were no toxic effects attributable to a single dose.  Thus, an endpoint
of concern was not identified to quantitate acute dietary risk to the
general population or to any population subgroup.

4.2.2.2 Chronic Dietary-Exposure Analysis

™ Version 7.81 default processing factors for some processed
commodities.  Drinking water was incorporated directly into the dietary
assessment using the EDWC generated by PRZM/EXAMS with IR scenarios and
PCA adjustment factors.

Diflubenzuron chronic dietary (food + water) exposure estimates using
the DEEM-FCID™ software are below HED’s LOC for the U.S. population
and each of the population subgroups.  Using the DEEM-FCID™ software,
dietary exposure is estimated at 0.002285 mg/kg/day for the U.S.
population (11% of the cPAD) and 0.007404 mg/kg/day (37% of the cPAD)
for children 1 to 2 years old, the population subgroup with the highest
estimated chronic dietary exposure to diflubenzuron.  The estimated
exposures/risks for combined food and water are summarized in Table
4.2.2.2.1 for all populations.

Table 4.2.2.2.1.  Summary of Chronic Dietary Exposure and Risk for
Diflubenzuron.

Age Group	cPAD (mg/kg/day)	Exposure (mg/kg/day)	% cPAD

	General U.S. Population	0.02	0.002285	11

All Infants (<1 year old)	0.02	0.002299	12

Children 1-2 years old	0.02	0.007404	37

Children 3-5 years old	0.02	0.005714	29

Children 6-12 years old	0.02	0.003419	17

Youth 13-19 years old	0.02	0.002246	11

Adults 20-49 years old	0.02	0.001599	8

Adults 50+ years old	0.02	0.001784	9

Females 13-49 years old	0.02	0.001668	8

4.2.2.3 Cancer Dietary Exposure Analysis

Cancer risk from consumption of PCA and CPU:  Based on the submitted
metabolism studies, there are two possible sources for dietary exposure
to PCA and CPU- residues in fungi (mushrooms) and residues in livestock
commodities (milk and liver).  As human exposure to PCA and CPU is not
affected by the proposed new uses, the cancer dietary risk from PCA and
CPU will not be addressed in this document.

4.3 Water Exposure/Risk Pathway

EFED has provided (A. Al-Mudallal; 8/25/06, D321156) Tier II EDWCs for
use in drinking water assessments when diflubenzuron is used according
to proposed labeling.  Because monitoring data are unavailable,
estimates of diflubenzuron and the major degradate CPU concentrations
were made only with mathematical models.  The models PRZM/EXAMS with IR
scenarios and percent crop area adjustment factors were used to conduct
surface water exposure assessments.  Screening Concentration in Ground
Water (SCIGROW) was used for groundwater. EDWCs were generated for the
total toxic residue which includes parent diflubenzuron and the major
degradate CPU.  The highest estimated surface water concentrations
occurred with the PA pear scenario.  For chronic assessments the EDWC is
2.76 ppb; this was the value used in this assessment.  The groundwater
estimate from SCIGROW is 0.208 ppb.

4.4 Residential Exposure/Risk Pathway

Although there are no registered homeowner uses, there are registered
uses for professional applications to outdoor residential and
recreational areas to control mosquitoes, moths, and other insects. 
However, the potential for post-application residential exposure is
expected to be limited.  Due to the low dermal absorption rate (0.5%) of
diflubenzuron, and since it is only applied to the tree canopy, minimal
bystander contact is expected.

Spray drift is always a potential source of exposure to residents nearby
to spraying operations.  This is particularly the case with aerial
application, but, to a lesser extent, could also be a potential source
of exposure from groundboom application methods.  The Agency has been
working with the Spray Drift Task Force, EPA Regional Offices and State
Lead Agencies for pesticide regulation and other parties to develop the
best spray drift management practices.  The Agency is now requiring
interim mitigation measures for aerial applications that must be placed
on product labels/labeling.  The Agency has completed its evaluation of
the new data base submitted by the Spray Drift Task Force, a membership
of U.S. pesticide registrants, and is developing a policy on how to
appropriately apply the data and the AgDRIFT® computer model to its
risk assessments for pesticides applied by air, orchard airblast, and
ground hydraulic methods.  After the policy is in place, the Agency may
impose further refinements in spray drift management practices to reduce
off-target drift and risks associated with aerial as well as other
application types where appropriate. 

5.0 AGGREGATE-RISK ASSESSMENTS AND RISK CHARACTERIZATION

Aggregate exposure risk assessments were assessed by incorporating the
drinking water directly into the dietary-exposure assessment for the
following scenario:  chronic aggregate exposure (food + drinking water).
 Short-, intermediate-, and long-term aggregate-risk assessments were
not performed because there are no registered or proposed uses of
diflubenzuron which result in residential exposures.  Acute and cancer
aggregate-risk assessments were not performed because no appropriate
endpoint was available to determine the aRfD for the general population
or any population subgroup and diflubenzuron is not carcinogenic.  

6.0 CUMULATIVE RISK

Section 408(b)(2)(D)(v) of the FFDCA requires that, when considering
whether to establish, modify, or revoke a tolerance, the Agency consider
"available information” concerning the cumulative effects of a
particular pesticide's residues and "other substances that have a common
mechanism of toxicity.” 

EPA does not have, at this time, available data to determine whether
diflubenzuron has a common mechanism of toxicity with other substances. 
Unlike other pesticides for which EPA has followed a cumulative risk
approach based on a common mechanism of toxicity, EPA has not made a
common mechanism of toxicity finding as to diflubenzuron and any other
substances and 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.  For information
regarding EPA’s efforts to determine which chemicals have a common
mechanism of toxicity and to evaluate the cumulative effects of such
chemicals, see the policy statements released by EPA’s Office of
Pesticide Programs concerning common mechanism determinations and
procedures for cumulating effects from substances found to have a common
mechanism on EPA’s website at
http://www.epa.gov/pesticides/cumulative/.

7.0 OCCUPATIONAL EXPOSURE

An occupational exposure assessment for diflubenzuron was prepared in an
HED memorandum dated 08-MAR-2006 (M. Dow, DP# 321624).

7.1 Occupational Handler

Based upon the proposed new use patterns, HED believes the most highly
exposed occupational pesticide handlers will be:

1) mixer/loaders using open pour loading of liquids

2) mixer/loader using open pour of water-dispersible granules (i.e., dry
flowable)

3) applicator using open-cab ground-boom sprayer

4) applicator using open-cab airblast sprayer

5) applicator using fixed-wing aircraft

Micromite® 80 WGS is packaged in water-soluble packages.  HED
considers water-soluble packaging to be equivalent to a “closed
loading” system.  Exposure is negligible; therefore, mixer/loaders
handling the 80 WGS formulation are not assessed as their exposure will
be much less than those using open-pour loading practices.  

In some cases, HED believes that certain individuals (private growers
versus commercial applicators) may perform all three handler activities;
i.e., mix, load, and apply the material.  The available exposure data
for combined mixer/loader/applicator scenarios are limited in comparison
to the monitoring of these two activities separately.  These exposure
scenarios are outlined in the Pesticide Handlers Exposure Database
(PHED) Surrogate Exposure Guide (August 1998).  HED has adopted a
methodology to present the exposure and risk estimates separately for
the job functions in some scenarios and to present them as combined in
other cases.  Most exposure scenarios for hand-held equipment (such as
hand wands, backpack sprayers, and push-type granular spreaders) are
assessed as a combined job function.  With these types of hand held
operations, all handling activities are assumed to be conducted by the
same individual.  The available monitoring data support this and HED
presents them in this way.  Conversely, for equipment types such as
fixed-wing aircraft, groundboom tractors, or air-blast sprayers, the
applicator exposures are assessed and presented separately from those of
the mixers and loaders.  By separating the two job functions, HED
determines the most appropriate levels of personal protective equipment
(PPE) for each aspect of the job without requiring an applicator to wear
unnecessary PPE that may be required for a mixer/loader (e.g., chemical
resistant gloves may only be necessary during the pouring of a liquid
formulation).  

No chemical-specific data are available with which to assess potential
exposure to pesticide handlers.  The estimates of exposure to pesticide
handlers are based upon surrogate study data available in the PHED (v.
1.1, 1998).  For pesticide handlers, it is HED policy to present
estimates of dermal exposure for “baseline;” i.e., with a single
layer of work clothing consisting of a long-sleeved shirt, long pants,
shoes plus socks and no protective gloves and for “baseline” and the
use of  protective gloves or other Personal Protective Equipment (PPE)
as might be necessary. 

Table 7.1.1. Estimated Short-Term Handler Exposure and Risk from the Use
of  Diflubenzuron on the Proposed New Use Sites

Unit Exposure1

mg a.i./lb handled	Applic. Rate2	Units Treated3

Per Day	Average Daily

Dose4

mg a.i./kg bw/day	MOE5	COMBINED

MOE6

Mixer/Loader - Liquid - Open Pour - (Rate for peanuts)

Dermal:

SLNG       2.9    HC

SLWG      0.023 HC	

Inhal         0.0012 HC	0.125 lb a.i./A	350 A	Dermal:

No Gloves      1.81

With Gloves   0.0144

Inhal               0.00075	

No Glove        280

With Glove 35,000

Inhal            27,000	NG

270

WG

15,000

Applicator - Aerial (Pilots not required to wear protective gloves)

Dermal:

SLNG       0.0050 HC

Inhal         0.000068 MC	0.125 lb a.i./A	350	Dermal:

No Gloves      0.00313

Inhal               0.0000425	

No Glove   160,000

Inhal           480,000	NG	

120,000

Applicator - Air-blast - Open Cab (Rate for pummelo)

Dermal:

SLNG       0.36 HC

SLWG      0.24 HC

Inhal         0.0045 HC	0.3125 lb a.i./A	40 A	Dermal:

No Gloves      0.0643

With Gloves   0.0429

Inhal               0.000804	

No Gloves      7,800

With Gloves 12,000

Inhal             25,000	NG 

5,900

WG

8,000

Applicator -Ground-boom Open-cab (Rate for eggplant, okra & peanut)

Dermal

SLNG      0.014 HC

SLWG     0.014 MC

Inhal        0.00074 HC	0.125 lb a.i./A	200 A	Dermal:

No Gloves      0.005

Wit Gloves     0.005

Inhal               0.000264	

No Gloves 100,000

With Gloves 100,000

Inhal               77,000	NG 

43,000

WG

43,000

1.  Unit Exposures are taken from “PHED SURROGATE EXPOSURE GUIDE”,
Estimates of Worker Exposure from The Pesticide Handler Exposure
Database Version 1.1, August 1998.  SLNG = Dermal Single Layer Work
Clothing No Gloves; SLWG = Dermal Single Layer Work Clothing With
Gloves;  Inhal. = Inhalation.  Units = mg a.i./pound of active
ingredient handled.  Data Confidence:  LC = Low Confidence, MC = Medium
Confidence, HC = High Confidence.

2.  Applic. Rate = Taken from Sections A & B (proposed labeling) of IR-4
submission for each crop.

3.  Units Treated are taken from “Standard Values for Daily Acres
Treated in Agriculture”; SOP No. 9.1. ExpoSAC; Revised 5 July 2000;

Body Weight (70 kg).  

5.  MOE = NOAEL/ADD.  Dermal NOAEL = 500 mg a.i./kg bw/day; Inhalation
NOAEL = 20.3 mg a.i./kg bw/day

6.  The toxicological endpoints for short-term dermal effects and
short-term inhalation effects were derived from two different studies;
however, both studies indicate similar toxicological effects (i.e.,
methemoglobinemia).  Since the results of the two studies indicate
similar toxicological effects, the MOEs are shown as combined MOEs. 
Combined MOEs are expressed as:

                                   1                             (HED
SOP 97.2; 26 NOV 97).

	1/MOEDermal + 1/MOEInhalation  

A MOE of 100 is adequate to protect occupational pesticide handlers. 
All MOEs are >100; therefore, the proposed uses do not exceed HED’s
levels of concern.

7.2 Occupational Post-Application Exposure

Typically there is the possibility for agricultural workers to
experience post-application exposures to dislodgeable pesticide
residues.  There were no chemical-specific data with which to estimate
post-application exposure of agricultural workers to dislodgeable
residues of diflubenzuron.  Therefore, theoretical estimates of
exposure, based on surrogate studies, have been conducted.  The Science
Advisory Council for Exposure (ExpoSAC) (SOP 003.1, Rev. 7 Aug. 2000,
Regarding Agricultural Transfer Coefficients; Amended ExpoSAC Meeting
notes, 13-Sep-2001) lists a number of possible post-application
agricultural activities relative to the subject crops that might result
in pesticide exposure to agricultural workers.  Transfer coefficients
(TC) expressed as cm²/hr are identified for each of the
post-application, agricultural activities.  The TCs are derived from
data in surrogate exposure studies conducted during the various
activities listed.

The highest (i.e., most conservative) TCs relative to the subject crops
appear to be for activities related to pummelo.  The activity with the
highest TC is for hand harvesting with a TC of 3,000 cm²/hr.  For risk
assessment purposes, a TC of 3,000 cm²/hr is used in conjunction with
the maximum rate of application which is 0.3125 lb a.i./A.  

The TCs used in this assessment are from an interim TC SOP developed by
HED’s ExpoSAC using proprietary data from the Agricultural Re-Entry
Task Force (ARTF) database (policy # 3.1).  It is the intention of
HED’s ExpoSAC that this SOP will be periodically updated to
incorporate additional information about agricultural practices in crops
and new data on TCs.  Much of this information will originate from
exposure studies currently being conducted by the ARTF, from further
analysis of studies already submitted to the Agency, and from studies in
the published scientific literature.

Post-application worker exposure is estimated using HED procedure that
assumes 20% of the application rate is available as dislodgeable foliar
residue (DFR) on the day of treatment.  HED does not expect
post-application exposures to exceed short-term exposure.  Therefore,
only short term exposures are assessed.  The following convention is
used to estimate post-application exposures to agricultural workers. 

PDRt = DFRt * CF1 * TC * ET where:

PDRt = potential dose rate on day “t” (mg/day)

DFRt = dislodgeable foliar residue on day “t” (µg/cm2)

CF1 = weight unit conversion factor to convert µg units in DFR value to
mg for the daily dose (0.001 mg/µg)

TC = transfer coefficient (cm2/hr) (In this case 3,000 cm2/hr; ExpoSAC
Policy 003.1 Rev. 7 Aug. 2000; amended 13 Sept 01 ExpoSAC meeting
Notes). 

ET = Exposure Time (hrs) (8)

and

DFRt = AR * F * (1-D)t * CF2 * CF3 where:

AR = Application rate (lb a.i./A) (0.3125 lb a.i./A)

F = fraction of a.i. on foliage available as dislodgeable residue
(unitless)(20.0%)

D = fraction of residue that dissipates daily (unitless) (10.0%)

t = post-application day on which exposure is being assessed

CF2 = weight unit conversion factor to convert the lbs a.i. in the
application rate to µg for the DFR value (4.54E8 µg/lb)

CF3 = Area unit conversion factor to convert the surface area units
(ft2) in the application rate to cm2 for the DFR value (1.08E-3 ft2/cm2
or 2.47E-8 acre/cm2 if the application rate is per acre).

( DFR = 0.3125 lb a.i./A * 0.20 * (1-0)0 * 4.54E8 µg a.i./lb *
2.47E-8A/cm2 = 0.7 µg/cm2

PDR =0.7 µg/cm2 * 0.001 mg/µg * 3,000 cm2/hr * 8 hr/day = 16.8 mg
a.i./day ( 70 kg bw = 0.24 mg a.i./kg bw/day

MOE = NOAEL ( PDR 

( 500 mg a.i./kg bw/day ( 0.24 mg a.i./kg bw/day = 2,100

These estimates are considered to be screening-level estimates i.e.,
conservative (protective).  HED’s LOC for dermal exposure is for MOEs
<100.  In this case, MOEs are greater than 100 on day 0; therefore,
post-application dermal exposure is not of concern for agricultural
workers.  Post-application inhalation exposure is expected to be
negligible.

7.3 Restricted Entry Interval

Diflubenzuron is classified in acute toxicity category III for acute
dermal toxicity and primary eye irritation.  It is classified in
Category IV for acute inhalation toxicity and primary skin irritation. 
It is not a dermal sensitizer.  Therefore, the interim worker protection
standard (WPS) restricted entry interval of 12 hours is adequate to
protect agricultural workers from post-application exposures.  The
product labels list 12 hour restricted entry intervals.  

8.0 DEFICIENCIES / DATA NEEDS

8.1 Chemistry

860.1200 Directions for Use

Barley, oats, and wheat:  The petitioner should delete the proposed
application method using ULV (24-32 fl. oz/A) equipment.  Label
revisions are requested to specify appropriate PHIs based on the
reviewed data.  Labels should be revised to specify PHIs of 50 days for
grain and straw, 3 days for forage, and 15 days for hay.  



Turnip greens:  The label should be amended to prohibit use on dual
purpose turnip cultivars or varieties which produce a harvestable root.

Okra and eggplant:  The use directions for okra and eggplant should be
removed from the label.

860.1380 Storage Stability

Barley, oats, and wheat:  Additional storage stability data for wheat
processed commodities (except bran) are requested to validate the
storage conditions and intervals of samples from the submitted wheat
processing study.  The available storage stability data for rice bran
may be translated to wheat bran; the petitioner is only requested to
generate storage stability data for wheat flour, middlings, shorts, and
germ.  The requested data should reflect the storage conditions and
intervals of samples from the wheat processing study.

860.1500 Crop Field Trials

Peanut:  Confirmatory residue data on peanut nutmeat and peanut hay are
requested from three additional field trials conducted in Zone 2.

860.1520 Processed Food/Feed

 

 

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态ú摧̣îᜀusing a minimum seasonal rate of ≥3x, which is the
maximum theoretical concentration factor (by crop) for peanuts.  The
meal samples from this study should be analyzed with a method which has
a LOQ for diflubenzuron which is comparable to that of the RAC (0.05
ppm).

860.1550 Proposed Tolerances

Barley, oats, and wheat:  A revised Section F should be submitted to
reflect HED-recommended tolerance levels of 3.0 ppm for residues in/on
barley hay, 1.8 ppm for residues in/on barley straw, 7.0 ppm for
residues in/on wheat forage, 6.0 ppm for residues in/on wheat hay, 3.5
ppm for residues in/on wheat straw, and 11 ppm for residues in/on
aspirated grain fractions.  Barley forage is not listed in Table 1 of
OPPTS 860.1000; therefore, this entry should be removed from the
petitioner’s Section F.  The available data for wheat may be
translated to oats; the corresponding tolerances recommended for wheat
commodities also apply to oat commodities.

Brassica leafy greens:  A revised Section F should be submitted to
reflect HED-recommended tolerance level of 9.0 ppm for residues in/on
Brassica leafy greens, subgroup 5B.

Peanut:  A revised Section F should be submitted to reflect
HED-recommended tolerance levels of 0.10 ppm for residues in/on peanut,
55 ppm for residues in/on peanut hay, and 0.20 ppm for residues in/on
peanut oil.

Mustard greens:  A revised Section F should be submitted to reflect
HED-recommended tolerance level of 9.0 ppm.

Okra and eggplant:  The proposed tolerances for okra and eggplant should
be withdrawn.

cc: G. Kramer (RAB1), L. Austin (RAB1)

RDI: Branch (9/13/06); RAB1 Chemists (9/13/06)

G.F. Kramer:S10781:PY-S:(703)305-5079:7509P:RAB1

Diflubenzuron	Human-Health Risk Assessment		DP# 328204

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Diflubenzuron	Human-Health Risk Assessment		DP# 328204

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Diflubenzuron	Human-Health Risk Assessment		DP# 328204

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