Diflubenzuron
Decision Document
        Richard Troast,  Project Manager
        Joanne Sanders,  Project Manager
        Special Pesticide Review Division
        Environmental Protection Agency
        March 26, 1979

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                                                            27498
               ACKNOWLEDGEMENTS

EPA Technical Support Team

Frederick Betz, Biologist, EEB, HED
George Beusch, Chemist, RGB, HED
Salvatore Biscardi, Toxicologist,  TB,  HED
Richard Bozof, Attorney, OGC
Carroll Collier, Chemist, EFB, HED
James Horst, Economist, EAB, TSD
Cara Jablon, Attorney, OGC
Kevin Keaney, Senior Regulatory Policy Analyst,  SPED
George Ludvik, Entomologist, ASB,  TSD
Joanne Sanders, Project Manager, SPRD
Richard Troast, Project Manager, SPRD
Richard Tucker, Biologist, EEB, HED

U.S. Department of Agriculture and State Land  Grant Universities

Helene Cecil, USDA, SEA/FR
Homer Fairchild, USDA, APHIS
G. W. Ivie, USDA, SEA/FR  '
Richard Ridgway, USDA, SEA/FR
Charles H. Schaefer, University of California
John. R. Schaub, USDA, ESCS
Patrick J. Shea, USDA, FS
Merle Shepherd, Clemson University
C. Dayton Steelman, Louisiana State University

EPA Environmental Research Laboratory, Athens, Georgia

James W. Falco, Research Chemical  Engineer
Lee A. Mulkey, Chemical Engineer
Kenneth F. Hedden, Sanitary Engineer

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                    Table of Contents

I.  Background	1

    A.  Chemical and Physical Characteristics	1

    B.  Registered Uses, Production, and Tolerances	1
        1.  Registered Uses	 ..1
        2.  Production	2
        3.  Tolerances	2

    C.  Fate in the Physical Environment	3
        1.  Soil	3
        2.  Water	5
        3.  Photochemistry	6

    D.  Fate in the Biological Environment....	6
        1.  Plants	6
        2.  Animals	8
            a.  Mammals	9
            b.  Poultry	11
            c.  Fish	14

    E.  Residues	16

    F.  Regulatory History	22
        1.  Experimental Use Permits	22
        2.  Registration and Tolerances	24
            a.  Cotton	24
            b.  Soybeans	24
            c.  Mosquito Control	...25
            d.  Gypsy Moth	26
            e.  Douglas Fir Tussock Moth	27
        3.  Referral for Rebuttable Presumption
              Against Registration	27

II.  Risk Analysis	28

     A.  Chronic Effects	26
         1.  Oncogenicity	28
             a.  Mouse Study - Oral (Thompson-Hayward)	29
                 (i) Results	30
                 (ii) Quality of the Study	36
                 (iii) Conclusions on the Mouse Study	39
             b.  Rat Study - Oral (Thompson-Hayward)	40
                 (i) Results	41
                 (ii) Quality of the Study	42
                 (iii) Conclusions on the Rat Study	44

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             c.  4-Chloroaniline-Oral Study in
                 Rats and Mice (NCI)	44
             d.  Overall Conclusions on the Carcinogenic
                 Risk of Diflubenzuron	46
         2.  Methemoglobinemia and Sulfhemoglobinemia	47
         3-  Mutagenicity	'.	50
             a.  Ames Test	50
             b.  Other Studies	51
         4.  Hormonal Effects	52

     B.  Nontarget Effects	= 53
         1.  Aquatic Invertebrates	53
         2.  Avian Reproductive Effects	57

     C.  Exposure	58
         1.  Dietary Exposure	56
         2.  Mixer-Loader, Applicator and Bystander
             Exposure	61

     D.  Risk Calculations	63
         1.  Oncogenicity	63
             a.  Dietary	63
             b.  Applicators and Bystanders	65
         2.  Methemoglobinemia and Sulfhemoglobinemia	67
         3.  Hormonal Effects	67
         4.  Nontarget Effects	68

III.  Benefits	•	69

      A.  Biological Assessment	69

      B.  Economic Assessment	72
          1.  Boll Weevil Control	72
          2.  Boll Weevil Eradication (APHIS)	77

IV.  Risk/Benefit Analysis of Alternative Courses of
     Action	79

     A.  Introduction	 .79

     B.  Basis for the Development of Regulatory Options...79

     C.  Alternative Pesticides	82

     D.  Regulatory Options Selected	85

     E.  Impact of Regulatory Options	87
         1.  Option 1.  Conditionally Register Diflu-
             benzuron for Use on Cotton until January 1,
             1984, under the Condition that Required
             Studies Are Submitted	87

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         2.   Option 2.  Conditionally Register Diflu-
             benzuron until'January 1, 1984, with the
             Same Data Requirements Set Forth in Option 1
             and Restrictions on Use 	90
             a.  Classify Diflubenzuron as a Restricted
                 Use Pesticide Requiring Certified
                 Applicators	91
             b.  Require the Use of Protective Clothing
                 during the Mixing, Loading, and
                 Application of Diflubenzuron.  Require
                 Respirators during Mixing, Loading,
                 and Ground Application of Diflubenzuron...92
             c.  Prohibit Application of Diflubenzuron
                 within the Coastal Zone of the Gulf
                 States	93
             d.  Prohibit Application of Diflubenzuron
                 Near Persons and Dwellings.  Prohibit
                 the Use of Flagmen in the Field	93
             e.  Prohibit Workers from Entering Treated
                 Fields until the Day after Application
                 and the Spray Deposit Has Dried	94
             f.  Limit Use of Diflubenzuron to Six 1-
                 Oz.-AI/Acre Applications per Season
                 with 5- -to 7-Day Intervals between
                 Applications	94
          3.  Option 3-  Deny the Application for the
              Registration of Diflubenzuron for Use
              on Cotton	95

V.  Recommended Decision	96

Appendices	99

     II-l	;	99

     II-2	100

Bibliography	101

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I.  Background

    A.  Chemical and Physical Characteristics

        Diflubenzuron (N^-[ [(4-chlorophenyl)amirio]carbonyl]-2
                                                   T)
6-difluorobenzamide) is the common name for Dimilin ,
           V
PH-6040R, and TH-60MOR.  It belongs to a new class of
                    i
chemicals known as  insect growth regulators.  Diflubenzuron

prevents insect growth by inhibiting the deposition of a

chitin exoskeleton  in insect larvae.

        Some of diflubenzuron's physical characteristics are:
                                        /
        Melting point              210-230°C

        Molecular Weight           210.7

        Appearance     "            White crystals

        Solubility                 0.2 mg/liter in water

        Partition Coefficient      > 50 (dichloromethane/H20)

        The structure of diflubenzuron is:
    B.  Registered Uses, Production, and Tolerances

        1.  Registered Uses

            The only registration for diflubenzuron in the

United States is to control gypsy moths in hardwood forests.
                                             /
EPA issued this registration in  1976.

                            -1-

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        2-  Production
            Diflubenzuron is manufactured by Phillips-Duphar,
B. V., in the Netherlands.  It is imported into the United
States and formulated as a 25% wettable powder by Thompson-
Hayward Chemical Company.  The amount of diflubenzuron produced
and imported is a trade secret protected by Section 10 of the
Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as
amended.
        3.  Tolerances
            The Agency has received three applications for
the registration of diflubenzuron.  The proposed uses are
for controlling boll weevils on cotton; green cloverworms,
velvetbean caterpillars, and Mexican bean beetles on soybeans;
and mosquito larvae in temporary flood waters.  Under the
Federal Food, Drug, and Cosmetic Act (FFDCA), the Agency
grants tolerances for the amount of the pesticide that may
persist as residues on raw agricultural commodities, feed,
and food.  Accordingly, Thompson-Hayward has requested
tolerances for two of the three registrations for which they
have applied:
        0.2 ppm in/on cottonseed
        0.05 ppm in/on soybeans
        0.05 ppm in/on meat, milk, eggs, and meat
                 byproducts of cattle, goats, hogs, sheep,
                 and fowl.
                             -2-

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        c'  Fate in the Physical Environment
            1.  Soil
                Diflubenzuron degrades in soil with a
half-life in the range of 0.5 to 1 week for technical material
pulverized to 2 micron (u) particles and applied at 1 ppm
(Nimmo and de Wilde, 1975).  Particle size and formulation
appear to be critical factors in the rate of degradation in
soil.  The work of Nimmo and de Wilde (1973, 1974, 1975)
indicates a ten-fold difference in degradation rates and
persistence in the particle size, which ranges from 2 to
10 u, with the larger particles degrading at a slower rate.
The initial products of soil degradation are 2,6-difluroben-
zoic acid and 4-chlorophenyl urea, which degrade respectively
to 2,6-diflurobenzamide and 4-chloroaniline.
                Binding of diflubenzuron degradation products
to soil increases with time.  The half-life for the conversion
of 4-chlorophenyl urea and 2,6-diflurobenzoic acid to the
respective chloroaniline and benzamide was 2 to 3 weeks and
4 weeks, respectively (Nimmo and de Wilde, 1973, 1974,
1975).  Information on the degradation rate of 4-chloroan-
iline in soil is not available, but it is presumed to
degrade slowly.
                           -3-

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                Soil temperature affects the breakdown
of diflubenzuron.  In a report*by Bull and Ivie  (1978) there
was a more -rapid breakdown of diflubenzuron in the summer
than in the cooler spring and fall.  Winter residues of
diflubenzuron were the most persistent. The data presented
by Bull and Ivie indicate that approximately 16% of the
previous year's diflubenzuron application would  remain in
the soil as carryover for the next growing season, presup-
posing the normal agricultural practice of plowing under
crop stubble.
                Diflubenzuron is a nonionic pe'sticide with
low water  solubility.  It shows little mobility  in organic
soils  (Carringer et al., 1975) and consequently  has little
potential  to leach from the soils. Very little leaching of
diflubenzuron can be expected to occur under normal field
conditions.  Helling (1975) observed that downward movement
decreased  as soil organic matter increased. Rieck (undated)
found  that the soil metabolite 4-chlorophenyl urea leached
more rapidly than the parent compound.
                Booth (undated) reported in Pesticide
Petition 7F1898 that field application of diflubenzuron in a
variety of aquatic environments resulted in residues in
sediment ranging from less than 50 to 200 ppb.   Single and
multiple applications were made to both fresh and salt water
ecosystems.  About two-thirds of sediment samples showed no
detectable residues « 0.05 ppm).
                             -4-

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               Runoff of diflubenzuron and its metabolites
                              »
is in part dependent on the organic matter content of the
soil since diflubenzuron will bind into organic soil
matter. Suspended sediment containing diflubenzuron and
4-chloroaniline could be expected to be found in the runoff.
Carringer et al. (1975) reported a partition coefficient
of 4000 between organic matter and water.  Thus, for a
soil containing 1% organic matter the overall coefficient
will be 4000/100 or 40:1.  This suggests that in typical
river water where the suspended sediment represents only a
small percentage of the total mass, the preponderance of
the diflubenzuron will be in the water phase.
        2.  Water
            Hydrolysis of diflubenzuron yields 4-chlorophenyl
urea and 2,6-diflurobenzoic acid.  Diflubenzuron is stable
at neutral or mildly acidic pH levels with half-lives
expected to exceed 2 weeks (Nimmo and DeWilde, 1975).  Under
alkaline conditions, tested up to pH 12, the half-life is
reported as being under 2 weeks (Phillips-Duphar, December
8, 1975).  Under field conditions diflubenzuron exhibited a
half-life of 1 day in alkaline pastures whereas in neutral
lake water (pH 7) the half-life was 10 to 15 days (Nimmo and
deWilde, 1975).
                             -5-

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1978). Residues were analyzed in rotational crops grown in
                              »

soils receiving multiple applications of diflubenzuron.


However, only very low levels (< 0.01 ppm wet weight) were


found in various rotational crops following six to ten


applications of diflubenzuron to cotton at a rate of 1


oz. per acre (Bull and Ivie, 1978).


        Cottonseed was analyzed in two different studies


after the plants had been sprayed with diflubenzuron.  In a


greenhouse  study, leaves of cotton plants were sprayed three


times with  labeled diflubenzuron. After 45 days, radioactivity


equal to 53 to 94 ppb diflubenzuron was found in the cotton-


seed. The authors, Mansager and Still (unpublished), attempted


to extract  and identify the radioactivity but were unsuccessful.


However, they concluded that, since no extractable residue


was released, the radioactivity was not due to diflubenzuron


but to a contaminant (USDA/State, 1978).  This,study was not


repeated.


        A field study by Bull and Ivie (1978) also demonstrated


low radioactive residues « 0.01 ppm) in cottonseed. This


study employed six to ten applications of labeled diflubenzuron.


The authors made no attempt to identify the radioactive


materials (USDA/State, 1978).
                           -7-

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        3.  Photochemistry
            Diflubenzuron was photochemically stable on leaf
surfaces under natural sunlight (Bull and Ivie, 197&).  In
studies with soil and water mixtures, negligible degradation
was measured under natural light (Phillips-Duphar, December
19, 1973; October 7, 1974).
    D.  Fate in the Biological Environment
        1.  Plants
        Diflubenzuron applied to various types of plant
leaves was neither absorbed into the plant nor degraded on
the leaf surface (USDA/State, 1978).  However, it appeared
that diflubenzuron adsorbed, onto the plant leaf surface
within the initial 24 to 48 hours after application.
Once the material was adhered to the leaf surface, only
wind-abrasion, rain-washing, or the fall of senescent leaves
moved the material into the soil.  Only negligible amounts
of diflubenzuron were measured, as total radioactivity, in
leaves, stems, bolls, and other fruiting structures of the
plant (USDA/State, 1978).
        Uptake of diflubenzuron from soils has been measured
in several plant species.  Most of the material found,
measured by total radioactivity, was in the aerial portions
of the growing plants.  Lesser amounts of diflubenzuron or
its metabolites were found in the root structures (USDA/State,
                               -6-

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        EPA scientists have analyzed the residue data


presented by Thompson-Hayward (Pesticide Petition 7F1898)


and concluded that the use of diflubenzuron at 1 oz. per


acre before cotton bolls open may lead to occasional trace


residues of diflubenzuron on the undelinted cottonseed.


However, the possible contaminative residues in delinted


cottonseed and processed commodities derived from cottonseed


would be below detectable levels of 0.05 ppm.  They anticipated


no detectable residues of diflubenzuron metabolites in


either cottonseed or processed commodities from cottonseed


(Hummel, 1976a).


        2.  Animals


            This section is based on a review of the literature


submitted by a USDA/State team in the report "Effects of
                      •D
Diflubenzuron (Dimilin ) on Non-Target Avian and Aquatic


Organisms and Its Fate in the Environment" (USDA/EPA/State,


1978), the USDA/EPA/State Assessment Team report "Potential


Exposure of Diflubenzuron to Birds, Non-Target Aquatic


Organisms and Humans" (USDA/EPA/State, 1978), and reports


compiled by the Residue Chemistry Branch of the Office of


Pesticide Programs on the data submitted by Thompson-Hayward


(Pesticide Petition 7F1898).
                               -8-

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            a.  Mammals
                Metabolism studies with diflubenzuron have
been perfo'rmed in rats, cows, and sheep.  Rats administered
14
  C-labeled diflubenzuron excreted 70 to 95% of the
dose in the urine and feces within 6 days of administration.
Radioactivity remaining in the carcasses was quantified as
5% of the dose.  No unmetabolized diflubenzuron was found in
the urine.  Metabolites identified were 2,6-diflurobenzoic
acid and 4-chlorophenyl urea.  Other compounds were present
but were not characterized (USDA/State, 1978).
                Diflubenzuron was metabolized and almost
totally excreted by cows and sheep. About 0.2% of the dose
fed to cows was found in their milk. Metabolites excreted by
both species include 4-chlorophenyl urea; 2,6-difluorobenzamide;
and 2,6-difluro-3-hydroxyl-diflubenzuron; 2,6-diflurobenzoic
acid; and the glycerine conjugate of 2,6-difluorobenzoic
acid (USDA/State, 1978).
                Further studies on the metabolism of diflu-
benzuron indicated that microsomal activity may be responsible
for the metabolism of the molecule.  Labeled diflubenzuron
                        -9-

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was metabolized by sheep livetr microsomes into 2,6-difluro-
benzoic acid, 2,6-diflurobenzamide, 4-chlorophenyl urea,
4-chloroacetanilide, 4-chloroaniline and the N,N-dimethyl
derivative of 4-chloroaniline (USDA/State, 1978).
                The Agency reviewed a 28-day feeding study
in which 250, 5, 0.5 and 0.05 ppm diflubenzuron was fed to
lactating dairy cattle. This study indicated that milk did
not contain  detectable residues of diflubenzuron except at
the two highest feeding levels of 5 and 250 ppm.  Difluben-
zuron residues were measured as 0.013 and 0.22 ppm, respec-
tively.  At  the lower feeding levels, 0.05 and 0.5 ppm, any
diflubenzuron residues were below 0.3 and 1.4 ppb, respectively.
In the only  segment of the study designed to show decline
levels, the  5 ppm dose, a withdrawal period of 4 days
reduced any  diflubenzuron levels below the detection
limit, 1.6 ppb (Hummel, 1977b). Chromatographic analyses of
the detectable residues in milk indicated that the residues
found were not diflubenzuron.  However, there was no indication
of what metabolites were present (USDA/State, 1978).
                Analyses of tissue extracts indicated that
in the liver, the metabolite 2,6-diflurobenzoic acid was
predominantly found, but diflubenzuron, 4-chlorophenyl urea,
and 4-chloroaniline were also found.  Residue levels,
                          -10-

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expressed as the parent compound diflubenzuron, were measured
at all feeding levels (Table 1-1).  A 7-day withdrawal
period did not reduce the residues (Hummel, 1977b)~.
            b.  Poultry
                White Leghorn and Plymouth Rock-Rhode
Island Red Cross hens excreted 80-90/& of the diflubenzuron
administered to them within 3 days (Opdycke et al., 1976).
From 0.3 to 0.8? of the dose was found in the eggs 12 days
after treatment.  Most of the labeled compound in these eggs
was unmetabolized diflubenzuron.  Tables 1-2 and 1-3 list
the residues found in the hens and their eggs.  Major
diflubenzuron metabolites -were 2,6-diflurobenzoic acid,
4-chlorophenyl urea, and 4-chloroaniline.
                Additional studies cited in the USDA/EPA
State report (USDA/EPA/State, 1978) also indicated that, in
poultry, labeled diflubenzuron was secreted into the eggs
and retained in muscle, liver, fat, and kidney tissue.
In addition, the metabolite 4-chlorophenyl urea was identified
in the eggs and kidney.  Additional work with unlabeled
diflubenzuron gave essentially similar findings and provided
an indication that different strains of chickens differed
somewhat in their ability to accumulate residues of difluben-
zuron.  Leghorn chickens accumulated diflubenzuron residues in
eggs at twice the levels found in New Hampshire strain
chickens.
                            -11-

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Table 1-1. Liver Residues of Diflubenzuron
Feeding Level (ppm)

     0.05
     0.5
     5.0
   250.0
            Residues Found (ppm)

                   0.01
                   0.08
                   0.54
                   6.00
Table 1-2.
Total Activity Expressed as Diflubenzuron
  Found in Chickens.
Commodity
                       Feeding Level, ppm
         0.05
 0.5
Fat
Kidney
Liver
Breast Muscle
Leg Muscle
Whole Egg
         0.0175
         0.0026
         0.0026
         0.0017
         0.0016
         0.0029
 0.033
 0.013
 0.044
<0.005
<0.005
 0.100
1.160
0.338
0.453
0.054
0.099
0.833
                         -12-

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Table 1.3.  Components of Diflubenzuron Expressed as  1% of
              Total Activity Ethyl Acetate Extractable
             Difluben-
Commodity      zuron
           4-CPU    2,6-DFBA
                  Nori-Extrable
                  Extractable
                  (Not identified)
Fat
Leg Muscle
Liver
Kidney
Egg
100
 66.3
Breast Muscle   63.4
 18.6
 23.8
 68.8
 0


13


22.1


49.8


40.0


11.2
0


6-8


9.2


7.4


0


3.7
 1.

_o	
 5.3

19.0
 5.2

36.2
 0

16.3
 0
                           -13-

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            c.  Fish
                Booth et al. (1976) studied the accumulation
and fate of' diflubenzuron in rainbow trout and bluegill
sunfish in water treated with 1.0 ppm   C-labeled material.
After 20 days, about 60$ of the total radioactive residues
in fish meat was 4-chloroaniline, 12 to 15% was difluobenzoic
acid, and 1 to 5% was 4-chlorophenyl urea.  Intact diflubenzuron
comprised 1 to 2% of total meat residues.  A rapid depletion
of these residues was reported. Apperson et al. (1978) also
reported accumulations of diflubenzuron with maximum residues
of 355 ppb in white crappie from a lake treated with 5 ppb
diflubenzuron.
                The analysis of the residues found in the
Booth study is reported in Table 1-4.  The data shows that
fish (trout and bluegill) metabolize diflubenzuron to
4-chloroaniline.  The unidentified component was material
which did not migrate in the chromatography and was not
further characterized (Hummel, 1976).
                          -14-

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TABLE  1-4.  Residues of Diflubenzuron and Metabolites in Rainbow Trout and
             Bluegill Sunfish
                                        Percent of Extractable Residue
                                  - Rainbow Trout	Bluegill Sunfish
  Component                         Water      Fish         Water        Fish


                              Day 9   Day 20   Day 20   Day 9   Day 20   Day 20


Diflubenzuron                   83      74        19       41      19       14
2,6-Difluorobenzoic acid         1       3        19       20      37       30
4-Chlorophenyl urea              1       4        16       10      23        7
4-Chloroaniline                 15      17        29       29      16       21
Unidentified                     0       2	17	0	5	28
                                   -15-

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            Table 1-5 shows £he general metabolic pathway
for diflubenzuron in soil, water, plants, and animals.  The
pathway is common for the production of 4-chloroaniline
and 2,6-diflurobenzoic acid in all situations (Opdyck et al.,
1976; Philips-Duphar, December 1, 1975, and December 22,
1975; Booth et al.,  1976; Bull and Ivie, 1978; and Nimmo and
de Wilde, 1975).  The metabolism beyond 4-chloroaniline was
reported by Metcalf  et al. (1975) in a model ecosystem, to
include 4-chloroacetanilide and the 4-chloro-N,N-dimethyl-
aniline.  The production of 4-chlorophenyl hydroxylamine and
4-chloronitrobenzene in animals was theorized by O.K. Offringa
of Phillips-Duphar in a statement filed by Thompson-Hayward
Chemical Company  (1977).
        E.  Residues
            In order to estimate the potential levels of di-
flubenzuron which may be found in local rivers in treated
areas, EPA researchers constructed a computer-simulated model
of cotton and soybean fields to estimate the agricultural
runoff from four applications of 4 or 3 or 2 or 1.5 oz.
diflubenzuron/acre on cotton (Falco et al., 1979).  Key
assumptions in the simulation included:  1) all diflubenzuron
was applied to cotton in late June and early July, and was
degraded by October, 2) cotton grown in irrigated areas was
not considered, even though the affected acreage is extensive,
                               -16-

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Table 1-5.  Metabolic Pathway of Diflubenzuron
                 Diflubenzuron
      [
4-chlorphenyl urea
C                 ]
          I
                     0.1
4-chloroaniline
 4-chloroacetanilide
        2,6-diflurobenzoic acid
          ^                ]
        2,6-diflurobenzamide
4-chloro-NN-dimethylaniline
                                                C»
                                            I
                             4-chlorophenyl hydroxylamine (proposed)
                                          I
                             4-chloronitroso benzene (proposed)
                                  C    /=\     3
                           ON  *•
                                 -17-

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because the possibility of runoff from these areas is low,
3) rainfall was based on data for Beeville, Texas,  4)
rainfall in Beeville, Texas, was representative of rainfall
occurring throughout the cotton areas analyzed, 5) difluben-
zuron is sprayed throughout a river basin on a simultaneous
and uniform treatment schedule.
        As a result of the assumptions used to make the
model, it is likely that the predicted concentrations of
diflubenzuron are too high and that the duration of the
predicted concentrations is too short.  However, the
researchers estimated that the error would not exceed one
order of magnitude.
        Table 1-6 shows the maximum diflubenzuron and
4-ehloroaniline levels predicted at the mouths of the
modeled rivers.  Table 1-7 shows the predicted average
concentrations of diflubenzuron and 4-chloroaniline at the
mouths of the modeled rivers during the summer months.
Table 1-8 shows the average summer concentration of
diflubenzuron in sediment at the mouth of the modeled
rivers.
        EPA chemists reviewed the model and pointed out that
the 4-chloroaniline levels predicted by the model probably
were much less than actual levels to be expected because the
model did not account for 4-chloroaniline formation in soil
                             -18-

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TABLE I-b.  Maximum Daily Diflubenzuron and 4-Chloroaniline
            Concentrations at the Mouth of Each River from
            Use on Cotton

                       Diflubenzuron4-Chloroaniline
                       Concentration     Concentration
                       from Cotton       from Cotton
                       Application       Application
Basin        Year          ug/1             ug/1
Mississippi
Atchafalaya
Tombigbee
Brazos
Colorado
Nueces
Rio Grande
1971
1971
1972
1974
1971
1975
1971
1.9
2.2
0.22
3.7
13. B
25.0
109.3
7.8
IB. 5
O.B5
11.9
22.0
3.3*
bb.b
Note:These are the projected residues from four
1.5-oz. applications.

•Occurred in 1973-
                          -19-

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Table I-?.
Average Summer Concentrations of Difluben-
zuron and 4-Chloroaniline at the Mouth of
Each River from Use on Cotton
                         Diflubenzuron  4-Chloroaniline
                         Concentration  Concentration
Basin        Year            ug/1           ug/1
Mississippi




Atchafalaya


Tombigbee




Brazos


Colorado




Nueces


Rio Grande




1971
1972
1973
1974
1975
1971
1972
1973
1971
1972
1973
1974
1975
1973
1974
1975
1971
1972
1973
1974
1975
1973
1974
1975
1971
1972
1973
1974
1975
0.20
0.09
0.11
0.06
0.05
0.2B
0.13
0.11
0.03
0.05
0.05
0.01
0.01
0.49
0.71
0.29
1.5
1.3
0.41
0.20
O.Ob
1.3
0.08
1.2
b.4
0.49
0.23
0.41
0.01
0.94
0.41
0.49
0.26
0.20
1.7
0.75
0.52
0.06
0.07
0.07
0.02
0.02
0.90
1.3
0.45
1.3
1.2
0.35
O.lb
0.07
O.OB
0.05
O.OB
1.5
0.12
0.05
0.10
0.004
NOTE:
1.5-oz. applications,
                           -20-

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Table 1-8.   Average Summer Concentrations of
             Diflubenzuron in Sediment at the
             Mouth of Each River from Use on Cotton.

                               Diflubenzuron
                               Concentrations
Basin
Mississippi




Atchafalaya


Tombigbee




Brazos


Colorado




Nueces


Rio Grande




Year
1971
1972
1973
1974
1975
1971
1972
1973
1971
1972
1973
1974 -
1975
1973
1974
1975
1971
1972
1973
1974
1975
1973
1974
1975
1971
1972
1973
1974
1975
ug/gm
0.39
0,17
0.21
0.12
0.09
0.56
0.26
0.22
0.07
0.09
0.09
0.03
0.03
0.96
1.40
0.56
2.88
2.59
0.81
0.39
0.16
2.51
1.63
2.37
12.6
0.96
0.46
0.81
0.03
NOTE:  These are  the  projected residues  from
four 1.5-oz. applications
                          -21-

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before runoff (Collier and Severn, 1978).  This 4-chloroaniline
formed in the soil would be additive to the 4-chloroaniline
formed in the water.  The 4-chloroaniline values calculated
are reported in Table 1-9.
     F.  Regulatory History
         1.  Experimental Use Permits
             The Agency issued an Experimental Use Per-
mit (EUP) in 1976 to allow for efficacy testing of diflu-
benzuron on large plots of cotton.  A temporary tolerance
of 0.2 ppm on cottonseed was issued in conjunction with
the EUP to permit the sale of the seed.
             After the 1976 season was completed, the
EUP lapsed and Thompson-Hayward requested an extension for
the 1977 season. The Agency approved Thompson-Hayward1s
application for the 1977 season but stipulated that the seed
could not be used for food because of adverse toxicological
findings.  In 1978, Thompson-Hayward once again applied for
an extension of the EUP with a temporary tolerance.  The
Agency granted both the EUP and the tolerance after it
performed a risk estimate which indicated that the use for
which the permit was requested would not have a significant
adverse effect on human health.
                              -22-

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Table 1-9.   Predicted Levels of 4-Chloroaniline in Five Representative Rivers
Diflubenzuron*
River Cone, ug/1
Mississippi
Atchafalaya
Tombigbee
Brazos
Colorado
0.55
0.80
0.2b
0.95
3.2
4-Chloroan-
iline Cone.
ug/1 (calc)
0.25
0.40
0.14
0.48
1.6
4-Chloroan-
iline Potential Ingestion **
Range ug/1 exposure ug/yr
0.1-1
0.2-2
0.05-0.5
0.2-2
0.5-5
18-180
36-360
9-90
36-36
90-900
•Highest average summer concentration of diflubenzuron predicted from four appli-
cations at 2 oz/acre for cotton and four applications at 1 oz/acre for soybeans.

"The potential ingestion exposure may then be calculated as follows Cassuming that
water treatment works have no effect on the 4-chloroaniline concentration):

0.1-1.0 ug/1 4-Chloroaniline x 21/day x 90 days per season = 18-180 ug/yr
ingestion of 4-Chloroaniline.  These data are included in the table.
                                -23-

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             c.  Mosquito Control
                             »
                 The original registration  filed by Thompson-
Hayward indicated the possible accumulation of residues in
fish and potable water  (Pesticide Petitions 6H5130, 6F17731).
Therefore, a tolerance  was necessary  for potable water and
fish to allow residues  in these  items.  EPA scientists
concluded that the data did not  provide a basis for the
establishment of permanent tolerances for these major
reasons: the tolerance  must be addressed in terms of
diflubenzuron and its metabolites for fish  and potable
water, the analytical methodology for enforcement of the
tolerance is inadequate, further characterization of
residues may be needed  once levels  of residue in fish meal
are established, studies reflecting residues of diflubenzuron
in additional fish and  shellfish are  needed, and data from
processed food products derived  from  fish are needed
(Hummel, 1976).
                 Thompson-Hayward subsequently submitted a
version of the proposed revised  label for diflubenzuron
that eliminated the need for tolerances.  The proposed label
limits application to temporary  rain  pools; drainage ditches
and lagoons from dairy, poultry, and  swine-holding areas;
overflow; and intermittently flooded  sites  associated with
urban and residential areas.  Aerial  application of diflubenzuron
                           -25-

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         2.  Registration and Tolerances
             a.  Cotton
                 Use of diflubenzuron on cotton requires a
tolerance for residues on cotton seed.  EPA scientists,
in reviewing the data presented by Thompson-Hayward in
Pesticide Petition 7F1898, concluded that diflubenzuron
residues would not exceed the requested tolerance provided
appropriate rotational crop restrictions and restrictions on
grazing and feeding of treated foliage were placed on the
product label.  However, unresolved toxicological issues
precluded granting the requested tolerance at the time of
EPA's review of Thorapson-Hayward's petition.
             b.  Soybeans
                 Diflubenzuron use on soybeans requires a
tolerance for diflubenzuron residues in soybeans.  The
data submitted to EPA does not yet provide a basis for
establishment of a tolerance because the issue of whether
the diflubenzuron residues concentrate in soybean hulls and
soapstock is unresolved.  EPA has determined that the
concentration of diflubenzuron in the hulls and soapstock
requires a Feed Additive Tolerance.  The registrant is
questioning this conclusion.  Consequently, until this issue
is resolved, no further review will be conducted on this
application.
                                -24-

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is proposed.  The EPA has notified Thompson-Hayward that
                            »
deficiencies exist in the application which preclude issuance
of a registration for this use  (Gee, 1979).  Data requirements
include environmental fate of the diflubenzuron in water and
sediment and efficacy data for  the granular formulation.
Labeling changes required by the Registration Division
include removal of aerial application instructions.
Consequently, as with soybeans, this use will not receive
further review at this time.
             d.  Gypsy Moth
                 Diflubenzuron  was registered to control
gypsy moths in forests in 1976.  This use is limited to
application by State and Federal personnel.  Currently,
there are two separate programs designed to control the
spread of the gypsy moth:  an eradication program and a USDA
control program.  The Animal Plant Health Inspection Service
(APHIS) uses diflubenzuron in an eradication program to
control outbreaks of gypsy moth in geographical locales
distinct from the original infestation.  The Forest Service
of USDA and state governments use diflubenzuron to control
active infestations within the  area of the original outbreak.
This use, registered for forests only, will not be dealt
with further until a Generic Standard is proposed for this
chemical.
                           -26-

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             e.  Douglas Fir Tussock Moth
                 The Forest Service of USDA had an experimental
use permit (EUP) for diflubenzuron to control the Douglas
Fir Tussock Moth, a pest of the Pacific Northwest forests.
At present no application is on file with the Agency for
this proposed use.  Consequently, although diflubenzuron has
a potential use  for control of the Douglas Fir Tussock Moth,
no decisions with respect to the  registration of the compound
for this use can be made in this  document.

         3.  Referral  for Rebuttable Presumption Against
             Registration
             Diflubenzuron was referred to the Special
Pesticide Review Divison for rebuttable presumption against
registration review in October 1977 because the^compound was
suspected to cause tumors and chronic blood effects in
humans  (methemoglobinemia and sulfhemoglobinemia), testosterone
depression in domestic animals, reproductive effects in
birds  (diminished egg  production  and reduced hatching), and
effects to nontarget organisms (acute toxicity to crustaceans
from direct application to water, and acute and chronic
toxicity to crustaceans from runoff from treated fields
(Campt, 1977)).
                            -27-

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•II.  Risk Analysis
     A.  Chronic Effects
         1.  Oncogenicity
             Thompson-Hayward  Chemical  Company  presented
two chronic feeding  studies  conducted  by  Huntingdon Laboratory
in support of  its application  for the  registration of difluben-
zuron:  "Effects of  DU  11230?  in  Dietary  Administration to
Rats for 10M Weeks"  (Huntingdon,  1976)  and  "Tumorigenicity
of DU  112307 to Mice"  (Huntingdon,  1977).   These  studies were
reviewed by EPA's Carcinogen Assessment Group  (CAG).
CAG also considered  in  its  cancer assessment a  National
Cancer Institute  (NCI)  chronic feeding  study in which
4-chloroaniline, a metabolite  of  diflubenzuron  found in
mammalian systems, was  administered to  rats and mice.
             CAG  concluded  that the Thompson-Hayward studies
suffered from  several  severe deficiencies in design which
greatly reduced their  sensitivity with  respect  to the
detection of a carcinogenic  response.   These deficiencies
preclude any interpretation  of the results  of  these studies
as evidence of a  negative  response.  In addition, CAG
concluded, based  on  the diagnoses of several pathologists,
that the Thompson-Hayward  mouse study  provides  suggestive
evidence of a  carcinogenic  response in  lymphoreticular
tissues.
                          -28-

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             Additional evidence  that  diflubenzuron may pose
a carcinogenic risk to humans  is  provided  by  the NCI study
on 4-chloroaniline in which  an increase  in mesenychymal
tumors in the spleen of male rats and  hemangiomatous tumors
in mice appeared to be associated with the administration
of the test compound.  A more  detailed discussion of these
studies, their results, and  their deficiencies is provided
below.  The source of this discussion  is the  CAG report on
diflubenzuron (hereafter "CAG  Report") (Albert, 1979).
             a.  Mouse Study - Oral  (Thompson-Hayward)
                 Mice (CFLP) of known  litter  origin were
randomly distributed according to body weight in five test
groups of 52 males and 52  females in each  group.  Four mice
were housed in each cage.  The diet  was  powdered laboratory
food mixed with  the required amounts of  diflubenzuron (DU
112307 batch P 7227).  Dietary levels  of 0, H, 8, 16, and 50
ppm diflubenzuron were fed for 80 weeks  to groups 1-5,
respectively.  All animals were examined daily for signs of
ill health, toxicity, and  behavioral changes.  Food and
water consumption were recorded.   On completion of the
treatment period, all the  surviving  mice were killed with
C02.  Gross pathology was  done on all  animals.  All
abnormalties were recorded including appearance and size.
Microscopic examination was  routinely  performed on lymph
                           -29-

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nodes (cervical and mesenteric),  liver,  spleen, ovaries,
thyroid, adrenals, pituitary  glands,  and all macroscopically
observed lesions suggestive of  neoplasia.  Blood and bone
marrow smears were made.
                 (i) Results
                 A significant  increase  in lymphoreticular
tumors  (lymphosarcoma,  reticulum  cell sarcoma, myeloid leu-
kemia) according to Fisher's  exact  test  (p=0.0l4) was diag-
nosed originally by Huntingdon  Laboratory in the group of
female mice  treated with  16 ppm diflubenzuron compared to
controls.  No significant increase  of lymphoreticular tumors
was found in any other  treatment  group of female mice or in
any treatment group of  male mice.
                 In addition, according  to the Huntingdon
Laboratory's original diagnosis,  lymphosarcomas in female mice
were found as early as  14 weeks in  the 16 ppm treatment group,
6 and 37 weeks  in the 50  ppm  treatment groups, and 44 weeks in
the control  group.  This  suggests a carcinogenic response with
a decrease in latency period  as doses increase.
                 Huntingdon Laboratory reassessed the
histopathology  results  for lymphoreticular tumors (Huntingdon,
1975) and presented results slightly  different from those in
its original submission.   A comparison of the original
diagnosis with  the reassessment is  summarized in Table II-1.
                          -30-

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                 Dr. D. Goodman  of  Clement Associates
performed an histopathologie  evaluation  of all slides from
all female mice. Her conclusion  was that diflubenzuron was
noncarcinogenic in this study.   However,  according to her
diagnoses, there was a significant  increase  of lymphoreticular
tissues tumors in the 16  ppm  group  of  female mice as compared
to controls by Fisher's exact test  (p=0.035).
                 Thompson-Hayward Chemical Company requested
Clement Associates to convene an independent panel of patholo-
gists to review the diagnosis of lymphoreticular tumors in the
female mice from the Huntingdon  study.   The  panel consisted of
Drs. D. Goodman, R. Squire, S. Vesselinovitch, and A. Rogers.
                 The panel  reviewed animal tissue from all
female mice in all dose groups previously diagnosed by
Huntingdon Laboratory as  having  hematopoietic tumors, plus
all additional female mice  from  the 0,  16, and 50 ppm dose
groups that were found to have hematopoietic tumors by
either Dr. Goodman or Dr. Vesselinovitch.  This panel
concluded that there was  no evidence of  a carcinogenic
effect in the lymphoreticular tissues  from female mice in
this study.  However, according  to  their diagnoses, there
was a significant increase  of lymphoreticular tissue tumors
in female mice dosed at the 16 ppm  level as  compared to
controls by Fisher's exact  test  (p=0.035).
                          -32-

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  The first report  indicated that the tissue in some  cases  had
  autolyzed and that  a histopathological evaluation was  not
  performed..  Inexplicably,  the second report included the
  histopathology  for  these tissues.

                       Table  II-l
        Total Number of Lymphoreticular Tissue Tumors in
         Male and  Female Mice (Huntingdon Laboratory)
Groups	0 ppm    4 ppm    8 ppm     16 ppm
Original Diagnosis
Males
Females
Revised Diagnosis
Males
Females

8
7

9
9

3
11

5
10

6
10

7
12

9
15 (peO.019)

9
15 (p=0.0577)

5
13

6
13
                    As can be seen, Huntingdon, in its reevalua-
  tion, changed its original finding of a significant increase
  by Fisher's  exact test of lymphoreticular tumors in the  16
  ppm treatment group, into an insignificant increase.
  Because  of this revision, further review of microscopic
  slides from  the study was done by several pathologists at
  the request  of either the registrant or EPA.
                                  -31-

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                  Dr.  N. Dubin, consultant to CAG, reviewed all
available  tissues from female mice in the 0, 16, and 50 ppm dose
•groups.  He stated that there was no evidence for the carcin-
ogenicity  of diflubenzuron.  However, according to his diag-
noses  there was a borderline response at 16 ppm (Fisher's exact
test P=0.059).
                  A panel consisting of Drs. Werner Kirsten,
James  Varinman, and Diana Variakojis of the Department of
Pathology  at the University of Chicgo Medical School reviewed
31  related cases (approximately 300 slides) from the study.
These  cases were selected for either background baseline
lesions (which had uniform positive or negative findings)  or
for confirmation of the presence (or absence) of lymphore-
ticular tumors where pathologists had not previously
been able  to completely agree.  The diagnoses of Dr. Kirsten's
panel, when combined with the unanimous findings of the other
pathologists, demonstrated a significant response by Fisher's
exact  test in both the 16 and 50 ppm treatment groups.
 (P=0.0050  and P=0.04, respectively).
                  The data from all the pathological diagnoses
other  than those of the Kirsten panel are summarized in Table
II-2.   The Data from the Kirsten panel are summarized in Table
II-3.
                             -33-

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Table II-2.  This  table shows the incidence of lymphoreticular tumors  in female
mice and the statistical significance values by Fisher's exact test  between
control and respective  treatment groups.
Diflu-
benzuron
Dosage     Dr.  I.N.
Group	Dubin
  Clement
Associates
(Dr. Squire
 & Panel
Huntingdon
Laboratory
(original)
Huntingdon
Laboratory
(revised)
                                                                Dr. D. Goodman
 0 ppm

Ib ppm


50 ppm
  12/49

  IB/43
p=0.05Bb

  17/49
p=0.1751
                            B/49

                           15/43
                          p=0.0345

                           10/49
                          p=0.3645'
                7/49

               15/143
              p=0.0190

               13/50
              p=0.1117
              9/49

             15/43
            p=0.057«

             13/50
            p=0.2352
                   B/49

                  15/43
                 p=0.0345

                  10/49
                 p=0.3b45
                                   -34-

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                                    Table II-3
              Dr. Kirsten's
Diflubenzuron Group Positive
Dosage        for Lymphoreti-
Group         cular Tumors  (a)
                    Previous
                    Pathologists
                    Unanimous  for
                    Lymphoreticular
                    Tumors  (b)
                        Total Positive
                        Diagnoses Attributed
                        Dr. Kirsten's  Panel (c)
0 ppm
Ib ppm
3/12
2/7
3/27
14/35
b/49
lb/43 H
50 ppm
(Dr. Kirsten
only reviewed
positive cases)
4/9
10/40 (Clement Assoc.
Drs. Squire, Goodman,
etc.) or

10/41 (Dr. Dubin &
      Huntingdon)
  14/49,
p=0.035  or
                                                                     14/50
                                                                   p=0.0430
a/ Slides were selected  for review on the basis of conflicting diagnoses.
b/ Slide to which all pathologists agreed on positive diagnosis.
c/ Assuming that the Kirsten's panel would have agreed to the unanimous diagnosis
   of positive findings  by pathologists listed in Table II-2.
£/ Statistically significant values were calculated according to Fisher's  exact  test.
                                        -35-

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                  (ii)  Quality  of  the  Study
                  The mouse  study suffered  from several
severe deficiencies which greatly  reduced  its sensitivity
for detecting a carcinogenic  response.   These deficiencies
are discussed in  detail  in  the  CAG Report.  Briefly summarized,
these deficiencies are as follows:
                  1.  There  is no indication that the maximum
tolerated dose (MTD) was used in this  experiment.  According
to the National Cancer Institute Guidelines for Carcinogenic
Bioassay in Small Rodents (Sontag  et al.,  1976), the MTD is
defined as "the highest  dose  of the test agent given during
the chronic study that can  be predicted  not to alter the
animal's normal longevity from  effects other than carcino-
genicity."  It is important that the MTD be used to maximize
the ability to detect a  carcinogenic response.
                  Several steps  need to be  taken in determining
the MTD.  One important  step  is to conduct a subchronic test
on both sexes of  the test animal to be used in the chronic
study.  The highest dose of the test agent to be used in the
subchronic study  should  be  the  maximum dose which has not
been demonstrated to cause  toxic effects in properly con-
ducted acute studies.  According to these  procedures Hun-
tingdon Laboratory should have  used doses  possibly as high
as 50,000 ppm in  the diet on  both  sexes  of mice in its
                            -36-

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subchronic study.  Instead,^it  used  only male mice in the
subchronic study and used a highest  dose of only 50 ppm in
the test.  On this basis, it  chose 50  ppm as the MTD to be
used in the chronic study.  If  the subchronic study had been
properly conducted, the MTD might have been demonstrated to
be several orders of magnitude  higher.
                 It appears that the Huntingdon Laboratory
selected 50 ppm as the MTD for  the chronic test because it
observed foci of liver cell necrosis in three of eight male
mice that received 50 ppm diflubenzuron for 6 weeks in the
subchronic study.  However, the fact that no liver necrosis
was found in the mice administered 50  ppm over 80 weeks in
the chronic study suggests that the  liver lesions found in
the subchronic study were not caused by the diflubenzuron,
but rather had some other etiology.  In addition, if several
doses higher than 50 ppm had  been administered in the
subchronic study, an absence  of liver  necrosis at the
higher dose levels would have demonstrated that the liver
necrosis found at the 50 ppm  level was not caused by the
test agent.
                 It should be noted  that two Thompson-Hayward
consultants, Dr. Robert A. Squire and  Dr. Jack L. Radomski,
have questioned (Appendices II-1 and II-2) whether the MTD
was used in this study.  In fact, Dr.  Radomski was of the
                             -37-

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opinion that the highest  doge  used  in  the  chronic study was
substantially lower than  the MTD.
                 2.   Another deficiency  of the mouse study
is that only seven tissues  (lymph nodes, spleen, liver,
thyroid, ovaries, adrenal gland, and pituitary gland) were
routinely examined microscopically.  The NCI guidelines
specify over 30 tissues and organs  that  should be routinely
examined microscopically.  Many  of  the organs not examined
microsopically were examined macroscopically.  However, this
procedure alone is inadequate  since many small tumors could
have been missed.  It should be  noted  that the lungs were
excluded from routine microscopic examination even though
this is frequently found  to be a target  tissue.
                 3.   There  is  no indication in the report
of the chronic mouse  study  that  the doses  of diflubenzuron
administered to the mice  were  verified by  chemical analysis
of the diet of the treated  mice  during the course of the
experiment.  Thus, there  is some question  as to whether the
mice were in fact administered the  doses indicated in the
report.
                 4.   The  experiment was  of suboptimal
length (80 weeks).  The mice should have been administered
diflubenzuron at least 104  weeks before  sacrifice.   If the
study had been conducted  longer, a  greater number of tumors
may have been observed.
                             -38-

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             b-  Rat Study - Oral  (Thompson-Hayward)
                 Sprague-Dawley rats of  the CD strain
(five groups) each composed of 45  female and 45 male rats
constituted the main group for the  carcinogenic study.  The
15 male and 15 female rats which constituted the satellite
group to the toxicity study were randomly distributed
according to body weight  into five  test  groups.  Rats were
housed five to a cage. Animal room  temperature and humidity
were controlled at 21° +  2°C and 50% +_  .0%, respectively.
Lighting was controlled to give 12  hours light and 12 hours
dark per 24 hours.  The diet was powdered laboratory food
mixed with the designated amount of diflubenzuron (DU
112307).  Dietary levels  of 0, 10,  20,  40, and 160 ppm
diflubenzuron were fed for 104 weeks.   All rats were examined
daily for signs of ill health, toxicity, and behavioral
changes.  Food and water  consumption were recorded including
utilization of the food.
                 All rats were examined  macroscopically to
determine the cause of death.  Urine and blood were examined
frequently.  At termination, all surviving rats were killed by
COp asphyxiation.  The microscopic  examination was routinely
performed on seven tissues (adrenals, thyroid, ovaries, liver,
spleen, lymph' nodes, and  pituitary  gland) and all macroscopically
observed lesions suggestive of neoplasia.  Blood smears were

                            -40-

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                        Conclusions  on  the Mouse Study
                 Because the 'mouse study suffers from several
severe deficiencies which make  it insensitive for purposes of
detecting an oncogenic response, it  cannot, according to any
interpretation of its results be considered valid evidence
of a negative oncogenic response.
                 The study did  provide  suggestive evidence
of a carcinogenic response. Most of  the pathologists who
reviewed the lymphoreticular slides  from the female mice
found a statistically significant increase in lymphoreticular
tumors in the 16 ppm treatment  group compared to controls by
Fisher's exact test.  If CAG had used the practice now
common at NCI in multiple-dose  experiments, of using the
Bonferroni upper bound as a significant level for a single
dose comparison, only the Kirsten panel diagnoses would have
provided statistically significant results.  The Bonferroni
upper bound is the normal significance  level divided by the
number of dosage levels.  However, CAG  has not followed the
approach of using the Bonferroni procedure with Fisher's
exact test since this procedure tends to mask weak carcinogenic
responses. Furthermore, the Agency concludes that the more
conservative approach of not using the  Bonferroni correction
in evaluating an insensitive and poorly conducted study such
as this one is especially justified.
                            -39-

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also routinely made.   Abnormalities detected  on  the  blood  smear
were confirmed by  examination of bone marrow  sections.
                  (i)   Results
                  No  significant difference  was found in  the
control versus experimental  groups for any  type  of tumor.
                  (ii)   Quality of the Study
                  As  was the  case with the mouse  study, the
rat study suffered from several severe deficiencies  which
made it incapable  of detecting a carcinogenic response.  The
discussion  of these  deficiencies,  from the  CAG Report, is
summarized  as follows:
                  1.   There is no indication that the maximum
tolerated dose  (MTD)  was used in this study.  The definition
of the MTD,  the  importance of using the MTD to maximize  the
ability to  detect  a  carcinogenic response,  and the appropriate
method of determinining the  MTD have already  been discussed.
In the subchronic  study to determine the MTD, the highest
dose of diflubenzuron in the diet was only  200 ppm.
Based on the results of preliminary acute toxicity studies,
doses possibly as  high as 50,000 ppm diflubenzuron in the
diet should have been used.   If much higher doses had been
used in the subchronic study, it is possible  that the MTD
would have  been  determined to be much higher  than 160 ppm,
the highest dose used in the chronic study.
                           -41--

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                 It appears that Huntingdon Laboratory
selected 160 ppm as the MTD for the  chronic test because it
observed "piecemeal" necrosis  of the hepatocytes in rats of
both sexes administered 50 and 200 ppm  diflubenzurbn in
the subchronic study (Phillips-Duphar,  B.V.,  1973b). However,
independent evaluations of liver slides from  this study by
Drs. A.J. Newman and C.A. van  der Heyden (Phillips-Duphar)
did not confirm these  findings.  Moreover, no liver necrosis
was reported among any of the  experimental groups in the 104-
week chronic study.
                 The registrant has  suggested that the
presence of methemoglobinemia  in rats treated with 160 ppm
diflubenzuron in the chronic study is evidence that the MTD
was used in that study.  However, the level of methemoglo-
binemia found in the 160 ppm group was  not significantly
different from the level found in the controls.  Furthermore,
even if it had been significantly different,  this fact could
not have been used as  a basis  for determining the MTD since
a life-shortening toxic effect must  be  found  in  the subchronic
study.  The methemoglobinemia  was found only  in  the chronic
study and was not established  to shorter life.
                 Two Thompson-Hayward consultants, Robert A.
Squire and Jack I. Radomski, have questioned  whether the
MTD was used in this study  (Appendices  II-l and  II-2).
                             -42-

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                        Conclusions on the Rat Study

                 This study is'not valid in view of the

defects discussed above.  Thus, the Agency is precluded from

using the results of this study as evidence of the ojncogenic

potential of diflubenzuron.

             c.  4-Chloroaniline  - (Oral study in rats and
                 mice)  (NCll	

                 A bioassay testing for the possible carcino-

genicity of 4-chloroaniline was conducted by the NCI bioassay

program using Fischer 3^ rats and B6C3F1 mice.  The NCI

camera-ready report of  this bioassay was reviewed by CAG

and the summary of the  report was accepted by CAG as an

accurate interpretation of the results (NCI, unpublished).

The NCI summary is presented in its entirety below:

          P-Chloroaniline was administered in the
     feed, at either of two concentrations, to groups
     of 50 male and 50  female animals of each species.
     Twenty animals of  each sex and species were
     placed on test as  controls.  The high and low
     dietary concentrations of p-chloroaniline were,
     respectively, 500  and 250 ppm for rats and 5000
     and 2500 ppm for mice.  The  compound was
     administered in the diet for 78 weeks, followed
     by an observation  period of  24 weeks for rats
     and 13 weeks for mice.

          There were no significant positive associa-
     tions between the  dietary concentrations of
     p-chloroaniline administered and mortality in
     female rats or in  mice of either sex; however,
     there was a significant positive association
     between concentration and mortality in male
     rats.  Adequate numbers of animals in all groups
     survived sufficiently long to be at risk from
                             -44-

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                  2.   Another severe deficiency in this  study
is that only  seven  tissues wer'e routinely examined microsco-
.pically in-spite  of the fact that the NCI guidelines  specify
over 30 tissues and organs which should be so examined.
As a consequence, many small tumors could have been missed
in the other  tissues and organs, which were examined  only
macroscopically.
                  3.  The strain of rats used was not  suitable
for this  experiment for two reasons.  First, the female
control rats  had  an unusually high incidence of tumors
(91-98J).   Second,  the survival rate for all groups of  rats,
including the controls, was very low.  Terminal percent
survival  (e.g.  percentage of animals living through the  term
of the experiment)  for male and female rats ranged from  only
1%% to 36% and  was  only 21% and 36$ in male and female
controls,  respectively.
                  Both of these factors (high spontaneous tumor
rate and  lower terminal survival) make it very difficult to
detect an oncogenic response.
                  4.  The report of the results of the chronic
rat studies did not indicate that the doses of diflubenzuron
were verified by  chemical analysis of the diet of the treated
rats during the course of the experiment.
                            -43-

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late-developing tumors^  Mean  body weight
depression, in relation  to  controls, was observed
in high dose female rats and dosed mice of both
sexes, indicating that the  concentrations of
p-chloroaniline administered to these animals
may have approximated  the maximum tolerated '
concentrations.  Although splenic lesions were
observed in male rats, no mean body weight"
depression relative to controls was associated
with administration of p-chloroaniline to
the animals.  Therefore, it is possible that
these animals may have been able to tolerate a
higher dietary concentration of the compound.

     The only neoplastic lesions found that
might be related to administration of the
compound were mesenchymal tumors in the spleens
of male rats and hemangiomatous tumors in mice.
In male rats, there was  significant positive
association between compound administration and
the incidences of fibroma or fibrosarcoma of the
spleen. The incidences of these tumors were
not significantly elevated  when compared to
those in control rats, but  the rarity of these
tumors in male Fischer 344  rats (0/360 in
historical male control  rats in this laboratory)
strongly suggests a chemically related effect.
In adddition, three sarcomas of other types were
found in high dose male  rats.  In mice of both
sexes, hemangiomas and hemangiosarcomas were
found at elevated incidences,  when compared to
control mice, in the spleen, liver, kidney, and
multiple body sites.   The increased incidences
in dosed mice were statiscally related to dose
but were not statistically  significant when
compared directly to matched control animals.
In comparison to historical control data, the
incidences of hemangiomatous tumors in the dosed
mice were elevated, but  not greatly.  The
evidence was considered  insufficient to conclu-
sively relate the hemangiomatous tumors in mice
to compound administration.  Nonneoplastic
proliferative and chronic inflammatory lesions
were also found in the spleens of dosed rats and
mice.
                        -45-

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     and  sarcomas in the spleens of male rats was
     considered strongly suggestive of carcinogenicity
     because of the rarity of these tumors in the
     spleens of control rats. Hemangiomatous tumors
     in dosed mice may also have been associated with
     administration of p-chloroaniline.  However, it
     is concluded that, under the conditions of this
     bioassay, sufficient evidence was not found to
     establish the carcinogenicity of p-chloroaniline
     for Fischer 3^4 rats or B6C3F1 mice.
                 d.  Overall Conclusion on the Carcinogenic
                     Risk of Diflubenzuron

                     The rat study suffered such severe

deficiencies that the data cannot be used to determine

whether or not diflubenzuron is an oncogen. Because of the

invalidity of this study and the deficiencies of the mouse

study, the Agency is not able  to fully assess the oncogenic

potential of diflubenzuron". However, the Agency has

determined that the increase of lymphoreticular tumors in

female mice in the 16 ppm dosage group was suggestive of a

positive effect.  These  results were used to estimate the

risk resulting from diflubenzuron use on cotton that is

developed in the following section.


                     In  addition, the NCI study provides

strongly suggestive evidence of the  oncogenicity of 4-

chloroaniline, a metabolite of diflubenzuron, that has been

identified in mammalian  systems,  plants, soil, and water.
                            -46-

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         2-  Methemoglobinemia and Sulfhemoglobinemia
                             »

             Methemoglobinemia and Sulfhemoglobinemia


are impairments of the oxygen transport  capability of


the blood. The formation  of methemoglobin is reversible


in adults, but is not known to be reversible in children.


The formation of sulfhemoglobin  is not known to be


reversible in either adults or children.  Therefore,


methemoglobinemia in children and Sulfhemoglobinemia


will persist until the affected  red  blood cells are


replaced by red blood cells subsequently manufactured


by the body.


             Methemoglobinemia has been  demonstrated


after inhalation, oral, and dermal exposure to difluben-


zuron in rats, mice, rabbits, and sheep.  Sulfhemoglo-


binemia was demonstrated  only after  oral exposure of


diflubenzuron to rabbits  and rats.   A study using


beagle dogs was negative  for both methemoglobinemia and


Sulfhemoglobinemia.


             Table II-4 summarizes the results of these


studies.   Methemoglobinemia and  Sulfhemoglobinemia were


detected in rabbits orally administratered 19.2 mg/kg


diflubenzuron.  A no-observed-effect level (NOEL) was not


demonstrated in the rabbit.  In  rats, methemoglo-


binemia was detected at a dietary dosage level of 40
                         -47-

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Table II-4.   Methemoglobinemia Formation
Test Aminal
Sex Report No.
Dosage
Result
Oral Exposure
Mice
Rabbit
Rabbit
Sheep
Rats
Rats
Beagle Dog

Rat

Rabbit
Rabbit
M 5bb45
M 56645/2/77
M 56645/13/77
M/F 229/77226
M 56645/15/77
M/F 243/77208
M/F 169/74157

M/F 197/741013

M/F 200/74b5
M/F 146/73845
10,000 mg/kg
(Gastric Intubation)
19.2 mg/kg
(Dietary;
4640 mg/kg
(Gastric)
20 mg/kg
100 mg/kg
400 mg/kg
(Dietary)
5000 mg/kg
(Gastric Intubation)
40 mg/kg
200 mg/kg
1000 mg/kg
" 5000 mg/kg
(Dietary)
0.41 mg/kg
0.84 mg/kg
1.64 mg/kg
6.24 mg/kg
(Dietary)
Inhalation Exposure
0.1 mg/L
0.8 mg/L
I.b5 mg/L
Dermal Exposure
69 mg/Kg
150 mg/kg
320 mg/kg
170 mg/kg
425 mg/kg
Me Hb detected
Su Hb detected
Me Hb
Me Hb detected
Me Hb detected
100 mg/kg
Me Hb and
Su Hb
Me Hb detected
in Male all
levels Me Hb
detected in
female at 200 mg/kg
level or higher
No Me Hb
detected

Me Hb all
levels

Me Hb detected
all levels
both sexes
Me Hb detected
all levels both
                                                           sexes
                                      -48-

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mg/kg, the lowest level  tested.   A  response was not
demonstrated at dietary  dose  levels from 0.41 to 6.24
mg/kg in the beagle  dog.   Thus,  an  NOEL was not shown in
either the dermal or inhalation  tests  in rats and rabbits.
As a matter of policy, the Agency bases its risk assessments
on the most sensitive species tested,  which in this case
appears to be the rabbit.
             The causative agent for methemoglobinemia
and sulfhemoglobinemia is  believed  to  be 4-chlorophenyl-
hydroxylamine, a metabolite of diflubenzuron.  Identifi-
cation of 4-chlorophenylhydroxylamine  was made in Phillips-
Duphar study 56654/8/77  (Phillips-Duphur BV,  1977).
In this study rats  developed  methemoglobinemia after dietary
exposure to diflubenzuron.  Analysis of the urine revealed
4-chloroaniline and  its  N-oxidation product 4-chlorophenyl-
hydroxylamine.  N-Hydroxylamines are known to be potent
agents for induction of  methemoglobinemia.
             A similar mechanism is believed  to
be responsible for  the induction of sulfhemoglobinemia.
The major difference between methemoglobinemia and
sulfhemoglobinemia  is that in sulfhemoglobinemia a
permanent change in the  chemical structure results.
             In summary, while studies are available to
demonstrate that diflubenzuron induces methemoglobinemia
                           -49-

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and sulfhemoglobinemia  in  test  animals,  the  studies did
not demonstrate NOEL's.  The  A'gency must have studies
conducted in the most sensitive species  and  with a
demonstrated NOEL  in order to fully evaluate the effect
of methemoglobinemia and sulfhemoglobinemia.
         3.  Mutagenicity
             a.  Ames Test
                 This test is the best validated test
for the correlation between mutagenicity and carcinoge-
nicity.  Diflubenzuron  and its  metabolites have been
tested in a  full or partial Ames battery of  Salmonella
typhimurium  strains by  a number of different laboratories
with varying protocols  and-results.   Seuferer (December
1977 thesis) reported 2,6-diflurobenzoic acid as a base-pair
and frame-shift mutagen in all  strains.  This is in conflict
with the results of Litton and  Borough (1977). Several other
diflubenzuron  metabolites  including 4-ehloroaniline were
considered slightly mutagenic.
                 Litton Bionetics [proprietary data, Thompson
HaywardJ performed an Ames test with  negative results on
diflubenzuron.  However, 4-chloroaniline was found to
be mutagenic.
                 Dorough (1977) [proprietary data, Thompson-
Hayward], used the TA-1537 and  TA-98  strains of bacteria.
                           -50-

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He did not find activity with  diflubenzuron but did obtain
positive dose-response  results for  4-chloroaniline in Strain
TA-98 with metabolic  activation.  Subsequently, he tested
diflubenzuron more  extensively in the  entire Ames tester set
using the spot test.  It also  included a Salmonella
typhimurium bacteria  repair  test with  strain TA-1978.  These
were also negative. Other metabolites  tested were negative
(MacGregor et al.,  1979).
             b.   Other  Studies
                  Negative  results in  mutagenicity studies
on diflubenzuron  were obtained in the  following: yeast
(Saccharomyces),  a  mouse micronucleous test, unscheduled
DNA synthesis in  mammalian cells, and  the  dominant-lethal
test  [proprietary data, Thompson-Hayward].
                  In summary, diflubenzuron is  not mutagenic
in the Ames test.  This result was  confirmed in a number of
laboratories.  Other  mutagenicity  tests performed do not
meet  the multi-test criteria.  Diflubenzuron is a halogenated
compound.  This  class of  compound  correlates poorly in terms
of mutagenicity/carcinogenicity test  results.  A metabolite,
4-chloroaniline,  is mutagenic  in  the  Ames  test.  However,
this  one positive finding  is not  sufficient to declare that
the metabolite poses  a  mutagenic  potential.
                            -51-

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         4.  Hormonal Effects
                           t>
             The Agency has reviewed several papers and
summary"reports dealing with the  effect of diflubenzuron
on testosterone levels in  avians  and animals.  Most of this
work (two reported studies) was done at the USDA's Veterinary
and Toxicological Entomology Research Laboratory in College
Station, Texas.  One additional study was conducted by
the USDA at the Poultry Research  Laboratory, Beltsville,
Maryland.
             The Texas studies were judged invalid by
the USDA investigator for  technical reasons.  An EPA team
of scientists  reviewing these studies agreed with the
assessment of  the USDA investigator  (Chitlik and Biscardi,
1979).  The Beltsville study shows a trend of decreasing
testosterone levels with diflubenzuron  treatment. This
result was not statistically significant.
             EPA has recently completed a study to determine
the effect of  diflubenzuron  on  testosterone  levels in the
rat.  Preliminary results  have  been  received, but until a
validation of  the entire  study  can  be  completed, no con-
clusions can be made.
                           -52-

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     B.  Nontarget Effects

         .1.  Aquatic Invertebrates
                                                 X
             Effects to  nontarget organisms constitute a

major concern of the Agency.   The projected use  patterns and

registered use patterns  of  diflubenzuron  could impact

significantly on the life-cycles of nontarget organisms

which come in contact  with  diflubenzuron  through the use of

habitats common  to areas of diflubenzuron use or difluben-

zuron  runoff. The  Agency reviewed  the area of potential

significant  adverse effects for nontarget exposure  to

aquatic  invertebrates  including estuarine crustaceans.

              Data  available to EPA indicated  that difluben-

zuron  has  acute  and chronic effects on several  aquatic

invertebrates.   The effects on specific organisms are listed

in  Table II-5.   These data clearly indicate that difluben-

zuron, in laboratory situations, is toxic at extremely  low

levels to aquatic invertebrates.  The aquatic species at

risk are located primarily in estuaries and other areas in

the coastal zone.

              Tables II-6 and  II-7  compare the levels of

diflubenzuron exposure  resulting in  toxic effects in various

aquatic species with  the levels of diflubenzuron predicted

 by the Athens Environmental Research  Laboratory model to

 occur at the mouths of  certain  rivers.   These tables
                             -53-

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                        Table  II-5
   Effects of Diflubenzuron Upon Aquatic Invertebrates

                     Acute Effects
Organism                                   Effect Level
Daphnia (water flea)                        1.5 ppb LCc0
Gammarus (sand flea)                       30-45 ppb LCc0
Eulimnadia (clam  shrimp)                    0.15 ppb LC50
Triops (tadpole shrimp)                    >0.75 ppb LC5Q
Mysidopsis (mysid shrimp)                   2.0 ppb LCc0
Artemia (brine shrimp)   -                   10 ppb LC^Q
         SubAcute or Chronic  Reproductive  Effects
                        Test  Duration         Effect Level
Mysid shrimp                27  days            0.2 - 0.6 ppb
Grass shrimp                35  days            0.45 ppb
Blue Crab                   6-18  days         0,50 ppb
Daphnia                     42  days            0.61 ppb
March Crab                  20-30  days         1.0 ppb
Brine Shrimp                BO  days            2.0 ppb
                           -54-

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Table II-6.  Mean Summer Concentrations of Diflubenzuron at the Mouth of Selected Rivers From Applications
To Cotton* And the Nontarget Aquatic Invertebrates Likely to Be Exposed
Basin
Mississippi
.



Ataohafalaya


Tomblgbee


i

Brazos


Colorado




Nueces


Year
1971
1972
1973
1974
1975
1971
1972
1973
1971
1972
1973
1974
1975
1973
1974
1975
1971
1972
1973
1974
1975
1973
1974
1975
Mean Diflu-
benzuron Cone.
For Cotton
Application (ppb)
0.40
0.17
0.22
0.12
0.09
0.57
0.26
0.23
0.07
0.09
0.09
0.03
0.02
0.98
1.43
0.57
2.93
2.63
0.83
0.40
0.17
2.55
1.65
2.40
Nontarget Aauatice Effects (Lowest Effect Level)
Mysid
Shrimp
>0.2 ppb
X

X


X
X
X





X
X
X
X
X
X
X

X
X
X
Grass
Shrimp
>0.45 ppb





X



i



X
X
X
X
X
X


X
X
X
Blue Marsh Brine
Crab Crab Shrimp
>0.5 ppb >1.0 ppb >2.0 ppb

f



X





V

X
X X
X
XXX
XXX
X


X X ' X
X X
XXX
   Total amount applied to cotton is 12 oz.  AI/A/season(Note that operational use would call for 6 applications
   at 2 oz./application but the EPA model  used 4 applications at 3 oz./application for predicting concentrations
   in water).
                                                      -55-

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Table II?-7. Mean Summer Concentrations of Diflubenzuron at the Mouth of Selected Rivers From Applications
To Cotton* And the Nontarget Aquatic Invertebrates  Likely to Be Exposed
Basin
Mississippi
•



Atachafalaya


Torabigbee




Brazos


Colorado




Nueces


Year
1971
1972
1973
1974
1975
1971
1972
1973
1971
1972
1973
1974
1975
1973
1974
1975
1971
1972
1973
1974
1975
1973
1974
1975
Mean
Diflubenzuron Cone.
For Cotton 4 Soybean
Application (ppb)
0.20
0.09
0.11
0.06
0.045
0.28
0.13
0.11
0.035
0.045
0.045
0.015
0.01
0.49
0.71
0.29
1.46
1.31
0.41
0.20
0.08
1.28
0.82
1.20
Nontarget
Mysid
Shrimp
>0.2 ppb
X




X







X
X
X
X
X
X
X

X
X
X
Aquatice Effects (Lowest Effect Level)
Grass Blue Marsh Brine
Shrimp Crab Crab Shrimp
>0.45 ppb >0.5 ppb >1.0 ppb >2.0 ppb









•



X
X X

XXX
XXX



X X X '
X X
XXX
 •Total amount applied to cotton is 6 oz.  ai/A/season   (Note that the operational use of Dimilin would call for
  6 applications at 1 oz. ai/A but the EPA model used  4 applications at 1.5 oz./application for predicting
  concentrations in water).
                                                   -56-

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indicate that diflubenzuron  runoff may affect several
important species at  the maximum  use  rates  on the proposed
label for cotton (e.g., a maximum of  12  oz. per season for
cotton).
             At a lower use  rate  of 6 oz. per season for
cotton, the potential for reproductive and  acute effects is
reduced. The data indicate that the effluent in the south-
eastern rivers has  a  lower hazard potential to aquatic
invertebrates than  the effluent in  the southwestern rivers.
The data also indicate that  among the threatened species are
economically important crustaceans  and aquatic invertebrates
which are environmentally important as indicator organisms.
However, there is little-field data available to confirm
or deny the results predicted in  the  model.
         2.  Avian  Reproductive Effects
             A study  performed on bobwhite  quail by Cannon
Laboratories was submitted by Thompson-Hayward.  An initial
review by the Agency  indicated that at dietary levels of 10
ppm and 40 ppm lowered fertility  and  decreased egg production
and hatchability resulted.
             This study was  again reviewed  by the Agency
after referral to SPRD.   The Agency scientists who conducted
this review concluded that the adverse effects observed
were artifacts of the improper methodology  of the study.
                           -57-

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Flaws included improper male:female  ratios  and  lighting
which invalidated the  data  generated.   The  registrant has
subsequently submitted other  studies on bobwhite quail which
did not demonstrate  adverse reproductive effects at feeding
levels up to 250 ppm.  They also  submitted  reports of field
studies of diflubenzuron  treatments  which did not show any
adverse effects on wild avians  (Tucker  and  Rabert, 1978).
     C.  Exposure
         1.  Dietary Exposure
             In developing  the  exposure profiles, a "worst
case" situation was  assumed in  which residues on cottonseed,
meat, milk, poultry, and  eggs were projected to approach
levels as high as  the  minimum sensitivity of the analytical
enforcement method  (0.05  ppm),  or the tolerance level. It
was also assumed that  all cottonseed products were derived
from diflubenzuron-treated  crops. The typical human diet
contains about 0.15% cottonseed products according to the
Lehman food factor  (Table II-8).  On the basis of these
assumptions, it was  estimated that the  direct consumption of
cottonseed products  will  result in a worst  case dietary
intake of diflubenzuron  of  0.00000186 mg/kg/day.
             Under worst  case exposure  of cattle to cotton-
seed from treated  crops,  the  levels of  diflubenzuron  expected
in milk and edible  tissues  are  predicted to be  in the
                            -58-

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Table II-B.  Human Dietary Intake of Diflubenzuron  Residues9-
Human Food Source
Cottonseed
Meats, red -'
Milk and dairy
products
Poultry
Eggs
Proposed
Tolerance %
(ppm)
0.2
0.05
0.05
0.05
0.05
Percentage
of a
Diet
0.15
10.81
2B.62
2.91
2.77
Projected maximum
residue present (tug/kg)
0.05
0.00001
O.OOOOOB
0.001
0.001
Specific commodity
Intake (kg food/
160 kg person^-
0.00225
0.16215
0.1293
0.0111
t
0.01155
Total
Maximum difl.
Intake (mg dlf/
60 kg person/day
0.00011250
0.00000162
0.000003«0
0.00001110
0.00001155
0.00020317
Maximum difl
intake (mg/dif/kg
body weight/day)
0. 00000 1BO
0.00000003
0.00000006
0.00000071
0.00000069
0.00000310
aEstimates from Lehman, (1962).
 Average "residue for edible tissues of red meat producing animals
°Based  on 1.5 kg food intake/day/bo kg person.
                                                           -59-

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subparts per billion  range.   Data  generated in studies
performed by Smith and  Merricks  using  radio-labeled diflu-
benzuron projected that residues of  diflubenzuron and its
metabolites were  in the 8  x  10"7 ppm range for milk and
        —4
8.6 x 10~  ppm range  for liver.  A  study by Miller using
unlabeled diflubenzuron gave values  of 2  x 10~7 ppm for
milk and 7.5 x  10~7  ppm for the  liver.
              The maximum calculated  residue  in the eggs and
edible tissue  of poultry fed  cottonseed  from treated crops
falls within  the M.5  x 10"^ ppm range  for  eggs and 3 x
10   to 6  x 10"  ppm  range for the edible  tissues.
              The likelihood of fish  accumulating significant
residues of diflubenzuron is  thought to  be quite low.
It is possible that,  through  runoff, drift,  or a combination
thereof, water concentrations of diflubenzuron as high as
0.001 ppm  might, on occasion, be sustained over a period of
at least a few days.  If such  were the case,  residues in fish
meat might reach levels approaching  0.05 ppm, assuming
a biomagnification of 50 times (Aperson  et al., 1978; Booth
et al., 1976;  Schaefer et al., 1978).  Although fish are
capable of limited biomagnification of diflubenzuron from
water, appreciable water contamination from  the cotton use
should be  infrequent, since diflubenzuron is not highly
persistent in water (Schaefer and Dupras,  1976).  Fish are
                         -60-

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also capable of rapidly  depleting  residues  of  diflubenzuron
from the body once  exposure^ to the compound is terminated
(Booth et al., 1976;  Schaefer et al.,  1978). Thus,  the
potential for significant  human dietary exposure  to
diflubenzuron via  residues in fish would appear to  be
slight.
             Using  the proposed tolerance values  for cotton,
the "worst  case"  of the total dietary  exposure to difluben-
zuron is estimated  to be 3.^0 x 10  mg/kg  body weight for
a 60-kg person.   The contributions of  the individual food
items are listed  in Table  II-8.
             These  dietary exposure levels  reflect  the
normal human adult  average daily diet.
         2.  Mixer-Loader, Applicator, and  Bystander Exposure
             The  exposure  levels projected  for mixer-loaders
for ground  spray  applications, mixer-loaders for  aerial
applications,  pilots, boom-spray drivers and bystanders
are reported in  Table II-9 for the cotton use. The  key
assumptions utilized in calculating exposure are  listed
below.
              1)   Mixer-loaders will receive their primary
                  exposure by contact with dust.
              2)   No flagman will be utilized in the spray
                  operations.
                          -61-

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Table II-9. Lifetime Exposure and Cancer Risk to Various Groups Exposed to Dirtubenzuron from Use on Cotton
Worker Group Number
Exposed
1) Mixer Loader 110
(Aerial)
Dermal
Inhalation
Total
2) Mixer Loader 1510
(Tractor Boom Spray)
Dermal
Inhalation
Total
3) Pilots 110
Dermal

Inhalation
*
Total
1) Tractor Drawn 1510
Boom Applicators

Dermal
Inhalation
Total
5) Area Residents
(Distance from Sprayed Area)
0-25 meters . 6875

26-M5 meters 6875

16-96 meters 6875
Levels
Total Risk from Application
Aerial Applicators


Total Risk including
Days/year Dose
Exposed mg/day
12

26.5
.31
26.81
10

26.5
•31
26.81
12
.08

.005

.085
10


5.6
.03
5.63


9 .61

9 .33

9 .15
2.01 x 10"2
6.35 x 10-5
2.01 x 10"5
Ground
5.82 x 10"3
2,6 x 10-6
Dose
mg/kg/year


18.55
.217
18.77


1.12
5.17 x 10~2
1.17

.056

.001

.060



.933
.005
.938


.096

.050

.023
Lifetime Avg. Lifetime Probability of
Dose (ppm) Tumors Due to
in Diet Diflubenzuron


1.16
1.1 x
1.17


.277
3.21 x
.280

3.5 x

2.5 x

3.75 x



.058
.0003
.0583


1.05 x

5.18 x

2.52 x


1.99 x 10~2
-2 -1
10 2.11 x 10
2.01 x 10~2


1.76 x 10~3
10~3 5.57 xlO ~5
1.82 x 10

10~3 6.01 x 10~5
-1 -6
10 3.11 x 10
-3 -5
1- J 6.35 x 10


-1
9.96 x 10
5.15 x 10"b
1.00 x 10~3


10~2 1.80 x 10"M
-3 -5
10 9.11 x 10
-3 -5
10 1.33 x 10

Expected Timor
per Year Due to •
Diflubenzuron


.125
.002
.127


.105
1.23 x 10~3
106

3.8 x 10 ~"
-5
2. 16 x 10 '
-1
1.02 x 10



.022
1.13 x 10""
2.21 x 10~2


1.77 x 10~2
-3
9.21 x 10
_3
1.26 x 10
' Levels -
Total Risk from Application M.B2 x 10~3
Ground Applicators 1.00 x 10-3

Aerial
2.01 x 10"2
2.6 x 10-6



5.b2 x 10~3
By-standers
1.80 x lO"*1
2.6 x 10-6



5.82 x 10
        ~3
                      2.01 x 10
                              "2
                                                1.82
                  -62-

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             3)  All spray areas will be posted to
                 minimize exposure  to bystanders.
             4)  Exposure via  ground application will
                 be similar  to that described by Wolfe
                 (1961)  for  dinoseb.
     D.  Risk Calculations
         1.  Qnoogenioity
             The Interim Cancer Guidelines state that when a
chemical is judged to  be a potential human carcinogen, the
Agency will estimate its possible impact on public
health at anticipated  levels of exposure. These guidelines
also recognize  that the  available techniques for assessing
the magnitude of cancer  risk to human populations based on
animal data are at best  very crude. This is due, among other
causes, to uncertainties in  the extrapolation of dose-response
data to very low dose  levels and  to differences in levels of
susceptibility  of animals and  humans.   Accordingly, the risk
estimates are neither  scientific  certainties nor absolute
upper limits, but are  used by  the Agency only as rough
approximations  of potential  health  risks.
             a. Dietary
                 The risk levels  were predicted from  the
one-hit model using the  proportion  of tumors in the controls
                            -63-

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and that in the 16 ppm  dose group.   This  equation is

expressed below.

                  B  =   logn [(1-PX)  -  (i-po)]!)!7.

                  B  =   logn [(1-15M3)/(1-7M9)]/16

                     = 1.718 x  10"2

             The  slope  of  the  one-hit  model,  (B, or 1.718 x
  _2
10  ), is used to calculate lifetime probability (P) of a

tumor caused by diflubenzuron.   This is shown below:

                      P =  Bx

                  (1.718 x 10"2)x

where x is the average  equivalent exposure  of difluben-
                  2 /
zuron in the diet.—
1/     B = slope
    logn = natural  logaritham
      Po = mice with  tumors  in  the  control group
      Px = mice with  tumors  in  the  treated group
       D = dose

2/  Another method  of conducting  a  conservative extrapolation
is to follow the approach  suggested by  Ian Nesbit in the
Clement Associates  submission.  He  fitted a linear model to
all the data points and  obtained  a  slope of .11 with an
estimated 99$ confidence bound  on the slope equal to .6.
However, it appears that a numerical error was made in the
estimation of the confidence limit.  The correct estimate
for the confidence  interval  of  the  slope would be .85.
Using this value, the risk would  be about one-half that found
by the CAG for all  exposure  situations.
                         -64-

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             The dietary  risks  were  determined  from the
dietary exposure after  adjusting  mg/kg  to  ppm in the
diet.  The calculated values  are  shown  in  Table 11-10.
Lifetime dietary exposure was assumed in making these
calculations. The  risk  resulting  from consumption of diflu-
benzuron-treated cottonseed,  meat, milk, poultry, and eggs
exceeds 2.6 x 10"  .  This represents roughly 2.6 tumors
per million people exposed to diflubenzuron for a lifetime.
             b.  Applicators  and  Bystanders
                 The oncogenic  risk  for these groups was
calculated from the exposure  levels  projected in Table II-9.
The risk estimates are  also provided in Table II-9.  Conversion
from mg/kg/year to equivalent ppm in the diet is expressed
in the equation below:
             x r (60 kg)        u3/     (40 years)
                 (365 days) (70 years)(1.5 kg)
               = 6.26 x 10"6  u
               =     per  lifetime diflubenzuron
                    mg  kg food  eaten per lifetime
where x is the ppm in the diet  and u is the mg/kg/year.
The 40 years refers to  work history  and 70 years is the
lifespan.  This equation  assumes  a 40-year exposure for
workers.  For bystanders,  a 70-year  exposure is assumed.
3/  U = mg/kg/year
                          -65-

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             The  oncogenic  risk  to applicators  from  the
mixing and loading  of  diflubenzuron and  the  oncogenic  risk
to bystanders  for cotton programs are shown  in  Table II-9.
For the use  on cotton  the oncogenic risk to  the mixer-loader
in aerial applications and  ground applications  is 2.01 x
10"2 and H.82  x 10~3,  respectively.  This means that,
assuming a MO-year  occupational  exposure, the number of
tumors produced from exposure to diflubenzuron  in the
respective groups is two per 100 for aerial  application
personnel and  five  per 1,000 for ground  application  personnel,
The pilots and tractor drivers would have risk  levels  of
6.35 x 10    and 9«96 x 10~   or roughly six tumors per
100,000 pilots and  one per  1,000 tractor drivers for a
40-year exposure.  If any of these personnel perform both
functions  (e.g.,  mixing-loading and applying the pesticide),
the risks produced  from each increment would be additive. In
all cases the  applicator risk is additive to the dietary
risk.
              The highest projected risk is to mixer-loaders,
with the majority of the risk coming from dermal exposure.
The risk from  inhalation is approximately one or two orders
of magnitude below  the risk from dermal exposure.
              Bystanders in the cotton areas are assumed
to include workers  in other fields as well as people living
                           -66-

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nearby. It was assumed  that  they  would  not  be  protected in
any special manner  other titan by  wearing  standard  clothing
common to field workers and  farm  families.   It was also
assumed that they would be exposed for  a  lifetime  of 70
years.
         2.  Methemoglobinemia and Sulfhemoglobinemia
             No-observed-effect levels  (NOEL's)  for methemo-
globenemia and Sulfhemoglobinemia have  not  been  established
for certain species of  animals including  the rabbit. However,
the lowest daily doses  causing observed effects  in all of
these  species were  considerably greater than the anticipated
exposure to humans  from the  diet  or pesticide  application.
In studies on other animals, such as beagle dogs,  where
NOEL's were demonstrated, these levels  were also greater
than  the theoretical exposure to humans.
             The Agency has concluded that  these studies
do not raise significant concern about  the  potential for
adverse effects  on  humans exposed to diflubenzuron. However,
further study of the relationship between diflubenzuron
exposure and methemoglobinemia and Sulfhemoglobinemia  is
necessary before the risk to humans can be  fully evaluated.
         3.   Hormonal  Effect
             The studies performed with avians at  VTERL
were  not valid.  The Beltsville study data  showed  a trend  of
                             -67-

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decreased testosterone levels,  but  this trend was not
                           »
statistically significant. The  study  in rats done by EPA
cannot be used as a measure  of  effects until the entire
report is reviewed and validated.   Thus, the data on
hormonal effects which have  been  reviewed  do not raise
significant concerns  about  the  potential for adverse effects
on humans exposed to  diflubenzuron.
         4.  Non-Target  Effects
             The risks to nontarget organisms posed through
use of diflubenzuron  on  cotton  are  qualitatively addressed
in Tables II-6 and II-7.  These risks impact several species
of aquatic invertebrates.   However, since  the exposure
levels used in determining  risks  are  based on a model which
has not been validated by field studies, there is no certainty
as to the actual levels  of  diflubenzuron to which nontarget
organisms may be exposed.   In the model, there was a signi-
ficant trend towards  reduction  of hazard with reduction of
diflubenzuron usage.  The data  indicate that the use
of 12 oz. of diflubenzuron  (A.I.) per season per acre
results in a linear  increase over the use  of 6 oz. in the
number of species subjected  to  hazardous levels of the
compound and in the  frequency of  adverse effects occurring
over a 5-year span.   The use of diflubenzuron, if limited to
6 oz. per acre per season,  may  well represent a tolerable
                             -68-

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risk.  A small number  of  aquatic  species may be significantly
affected even at this  application rate.  However, the Agency
does not have sufficient  data  on  the  extent to which
diflubenzuron runoff into bodies  of water  occurs to make any
definite risk assessments.

III.  Benefits
      This section  discusses  the  benefits  of the proposed
use of diflubenzuron to  control  bollweevils on cotton.
This analysis is based on the  "Preliminary Biological and
Economic Assessment of Diflubenzuron" which was prepared by
an Assessment Team  composed of scientists  and economists
from EPA, the U.S.  Department  of  Agriculture, and cooperating
State agencies and  land-grant  universities.  In order to
assess the benefits of the proposed use  of diflubenzuron on
cotton, the  Assessment Team had  to estimate the range of
diflubenzuron use,  the frequencies and rates of application,
the restrictions that  might be placed on its use, and the
cost.  Most  assumptions  are based on  expert opinion and
reflect the  best information available.
          A.  Biological Assessment
              The  boll weevil  (Anthonomus  grandis) infests
two-thirds of the  cotton belt, i.e.,  the eastern two-thirds
of the Southwest region,  the Delta region, and the Southeast
                               -69-

-------
region.  The Southwest  region  includes Texas and Oklahoma;
the Delta region consists  of Missouri, Arkansas, Tennessee,
Mississippi, Louisiana, and Kentucky; and  the Southeast
region is comprised  of  Virginia,  North Carolina, South
Carolina, Georgia, Florida, and  Alabama.
              The  boll  weevil  is an  insect causing extensive
damage to cotton in  the areas  listed above.  A total of 7.3
million acres of cotton are infested with  boll weevils.  These
insects lay their  eggs  in  cotton squares,  which become food
sources for the immature weevil.   Under  favorable weather
conditions, weevil populations can increase 2.5 times a week.
Dry weather may drastically reduce this  rate of increase.
              The  bollworm-budworm complex (Heliothis zea
and E. virescens)  also  causes  very extensive damage to cotton
in the area defined.  Other pests include  thrips, aphids, cut-
worms, plant bugs, fleahoppers,  and  spider mites.
              Cotton is currently treated  at frequent
intervals from early spring to late  summer to  control both
boll weevils and the bollworm-budworm complex.  The insecti-
cides  used for control  are predominantly organophosphorous
compounds.
               Diflubenzuron  does not kill adult  boll
weevils but inhibits egg  hatching and interferes  with the
growth of the weevil larvae  by inhibiting  enzymes  necessary
                           -70-

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for the synthesis of chitin.   Unlike  currently used insecti-
cides, diflubenzuron controls  boll  weevils  without signifi-
cantly reducing the populations  of  most  of  the natural
                                               v
parasites and predators  of cotton pests.  The boll weevil
appears early in the season at the  pinhead-square stage of
development of the  cotton.  Therefore, in order to control
the boll weevil, pesticide application must begin early in
the season.  On the other hand,  use of pesticides to control
the bollworm-budworm complex does not begin until mid-season,
when  these pests first  become  a problem.  Diflubenzuron
which does not kill the  bollworm-budworm complex, assists in
its control because it  does not kill  its natural predators
and parasites.  In  contrast,  the organophosphate pesticide
regime currently used  for cotton insect  control destroys the
predators and parasites  which  attack  the bollworm-budworm
complex.  Therefore, greater quantities  of  pesticides are
required to control the  bollworm-budworm complex when
alternative pesticides  are used to  control  the boll weevil
than  when diflubenzuron  is used.
              Predators  and parasites of cotton pests
include big-eyed bugs  (Geocoris spp.),  lady beetles
(Hippodamia spp.),  damsel bugs (Nubis spp.), and green
lacewings  (Chrysopa spp.). Under natural conditions,  these
insects frequently  hold  bollworm-budworm populations  below
                             -71-

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economic loss thresholds  early  in  the  season.   Thus, if
populations of these  beneficial species  can  be  preserved,
initial treatments  of conventional insecticides for control
of the bollworm-budworm  complex can be delayed. However, the
data available from field trials with  diflubenzuron do not
conclusively show that predators and parasites  will keep
bollworm-budworm populations  below economic  thresholds.
          B.  Economic Assessment
              This  economic analysis compares two  insecticide
regimes: that which is currently used, and a combination of
diflubenzuron and currently-used insecticides.   This analysis
is separated into a discussion  of  the  benefits  of  the use of
diflubenzuron by individual farmers in boll  weevil control,
and the impact of its use in  the APHIS program  to  eradicate
boll weevils.  The  savings in control  costs  realized when
diflubenzuron is used represents the measure of the benefit
of the compound.
               1.  Boll Weevil Control
                  Because diflubenzuron is not  currently
registered  for use  on cotton, several  assumptions  had  to be
made to perform this  analysis.   These  assumptions  follow:
                  - Six  1-oz. applications of  diflubenzuron
                    would be  applied at 5- to  7-day intervals
                    beginnning  when pinhead  squares appear
                              -72-

-------
                     on  the  plant  and terminating  no  later than
                     when  the. bolls  opened.
                  -  Diflubenzuron will cost  $3.00 per ounce.
                  -  The Farm Enterprise Data Systems (FEDS)-X
                     budgets represent the cost  of controlling
                     all cotton pests with currently-used insec-
                     ticides.
                  Because alternative pesticides  are
less expensive  and approximately  as efficacious as diflu-
benzuron, economists estimated that diflubenzuron could
probably be used  only where fields  are infested by both boll
weevils and the bollworm-budworm  complex and where current
control costs are high, i.e., $M5 or more per acre according
to the FEDS data.  The  extent of  the acreage where these
conditions exist  is  given in Table  III-1, Column  3-  The
average cost for  control  of all insects is listed in Column
4 by FEDS area.   These  figures were obtained by increasing
the 1975 costs, the  most  recent available,  by a composite
inflation factor  derived  from fourteen leading  economic
indicators.  This average cost includes the  price of control-
ling spider mites, thrips,  leafhoppers, and  other cotton
pests, as well  as boll  weevils and  the bollworm-budworm
complex.
17FEDS is a  system  of budgets and cost-estimating  procedures
operated by the  Economic Research Service of USDA  in coopera-
tion with Oklahoma  State University.  It provides  production
cost estimates and  projections.
                            -73-

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   Table III-1.   Representative Boll Weevil and Heliothls Control Costs for the Currently-Used Insecticide Regime and the Dlflubenzuron Regime
Acreage
Region and State FEDS Area in Area
(1,000)
Acres)
(1) (2) (3)
Control Costs With
Currently Used Insecticides
All . , Boll Weevils^
Insects^' Weevil
and
: Heliothiac/
(1) (5) (6)
Value of
Heliothis^ Natural f/
Preda torsi
(7) (B)
Cost of
Hellothis
Control in
the Diflih
benzuron™
Regime
(9)
Cost of
Weevil and Savings from Use of
Heliothis Diflubenzuron Regjune'
Control in Per,
Difluben- acre—
zuron
Regirae
uo; (it)
Feasible Aggregate
Acreage ($1,000)
(1,000
acres)
(12) (13)

 ;  Southeast
•:    Alabama

     Georgia

     North Carolina
 ;    South Carolina
 1

        Total
100-200
  500
  MOO
  500
  All
  100
  200
 50.81
 18.21
 92.2M
 80.89
 85.71
 51.73
101.97
11.91
39.80
90.12
79.03
61.71
19.80
92.79
18
18
30
30
21
18
21
23-91
21.80
60.12
19.03
10.00
28.80
71.79.
 7.66
 6.98
18.01
11.71
 8.00
 1.15
 2.87
16.28
11.82
12.08
31.32
32.00
27.65
68.92
12.68
11.22
71.18
63-72
61.10
51.65
95.95
    0
    0
18.61
15.31
 0.32
    0
    0
75.7
57.3
56.0
  0
  0
1,111.0
  877.3
   17.9
  0
  0
2,306.2
Delta
Lousiana
Mississippi
Total
Southwest
Texas

Total
TOTAL

100
100


600
600



289.0
712.5
1,001.5

55.5
55.9
111.1
1,513.1

65.00
68.29


16.62
53.16



58.18
62.11


11.96
53-16



15
15


21
21



13.18
17.11


17.96
29.16



16.11
22.16


10.78
17.68



26.77
21.98


7.18
11.78



51.67
51.38


38.08
38.78



3.51
7.76


3-88
11.68



289.0
712.5
1,001.5

55.5
55.9
111.
1,301.9

1,011.1
5.529.0
6,513-1

215.3
820.6

9,885.5
       a/_ USDA,  ERS, Firm Enterprise Data System, prepared in cooperation with Oklahoma State  University, Stillwater, Oklahoma, 1975.  All costs have  been
          inflated to 1977 price levels,
       b/ Includes spidermites, thrips, leaf hoppers, etc. in addition to boll weevils and  the bollwonn-budworm complex.
       c7 Cost of currently used insecticides regime.  Calculated by subtracting control costs for all  Insects except boll weevils and  the bollworm-budworm
          complex from Column 1.  The cost of controlling the other insects was obtained from  the Assessment Team survey.
       d/ Costs of insecticide, oil carrier, and application.
       e/ Column 5 minus boll weevil control costs.
       £/ Data from the Assessment Team Survey.
       g/ Column 7 minus Column 8
       h/ Column 9 plus the cost of diflubenzuron to control boll weevils.
       I/ Column 5 minus Column 10.
       Source:  USDA/EPA/State Assessment Report

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                   The  occurcence  of insects  other  than
the boll weevil and  the  bollworm-budworm  complex would make
the use of diflubenzuron impractical since organophosphates
would be needed to control  these  insects.
                   The  Assessment  Team conducted a  survey
to determine the  number  of  acres  in which the  simultaneous
infestation of boll  weevils and insects other  than the
bollworm-budworm  complex would occur.  Column  5 shows the
current cost of controlling cotton pests  when  these acres
are eliminated from  consideration.
                   Applying  organophosphates  to control
the boll weevil costs  $3.00 per treatment.   This cost was
multiplied by the number of applications  the survey showed
was needed in each region to generate the cost of  controlling
boll weevils  (Column 6).  This figure was subtracted from
the cost of controlling  boll weevils and  the bollworm-budworm
complex (Column 5) to  give  the cost of controlling the
bollworm-budworm  complex with the current insecticide regime
(Column 7).
                   The  Assessment Team used  this  survey  to
estimate where natural predators surviving  diflubenzuron
treatments would  be  able to control bollworm-budworm popula-
tions. The "Value of Natural Predators" (Column  8) shows the
savings in the cost  of organophosphate insecticides used to
                              -75-

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control the bollworm-budworm  complex  that  would  accrue when
diflubenzuron is used  for  boll  weevil control. Values in
                            t
Column 8 were subtracted from the  cost of  bollworm-budworm
complex control using  conventional insecticides  (Column 7)
to give the cost of  bollworm-budworm  complex  control in the
diflubenzuron regime (Column  9).
                   The  cost of six  diflubenzuron  applications
was added to the cost  of controlling  the  bollworm-budworm
complex, found  in  Column 9,  to  give the total cost  of treating
cotton with insecticides when diflubenzuron  is used (Column
10).  When the  diflubenzuron  regime was more  expensive than
currently used  insecticides,  a  zero was entered  in  the
column.
                   "Feasible Acreage"  (Column  12) represents
those areas where  diflubenzuron is less expensive than its
alternatives.   The feasible acreage was multiplied  by
the savings per acre to give the aggregate savings  (Column 13).
Analysts identified  1.3 million acres where  the  diflubenzuron
regime for suppression of  boll  weevil populations and
control  of the  bollworm-budworm complex would be used
because  it is more cost-efficient than the current insecticide
regime (Column  12).   These 1.3  million acres are approximately
18? of the cotton  fields that are infested with  boll weevils,
or 18% of the Southeast,  27% of the Delta, and 2% of the
Southwest.
                               -76-

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                  The total decrease in insect control costs
for all regions is roughly estimated at $9.9 million.  Most
of this savings ($6.5 milion) would go to growers in the
Delta, with smaller portions realized by growers in
the Southeast ($2.3 million) and in the Southwest ($1.0
million). The weighted average of the savings per acre was
$7.80.  In areas where diflubenzuron is likely to be used,
the average savings per acre ranged from $0.32 in North
Carolina to $18.64 in Georgia.
                  The Assessment Team did not associate use
of diflubenzuron with changes in crop yield. A number of
entomologists from cooperating State agencies and land
grant universities, however, believe that cotton yields
would increase because a  reduction in the amount of organo-
phosphate insecticide used would allow the crop to mature
earlier, and beneficial insects would provide greater
control of the resistant  strain of tobacco budworm.
              2.  Boll Weevil Eradication (APHIS)
                  USDA's  Animal and Plant Health Inspection
Service (APHIS) is investigating the technical and economic
feasibility of instituting a national boll weevil eradication
program (USDA/EPA/State,  1978).  They are now conducting
a trial eradication program in North Carolina.  If a complete
beltwide eradication program is initiated, it will begin  in
                             -77-

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this eastern area and gradually extend to contiguous affected
areas.
                  The currently proposed eradication tech-
nology integrates chemical, biological, and agricultural
control measures.  Specifically,  it  contains the following
elements: destruction of the  source  of food supply for
boll weevils by defoliation and stalk destruction, use of
pheromone traps, release of sterile  boll weevils, and use
of determinant strains of cotton.
              USDA has proposed the  use of diflubenzuron
to augment the present eradication strategy.  Diflubenzuron,
through its specific mode of  action, augments the effects
from the release of sterile insects  in the eradication
program; that is, it does not kill mature adults, but
rather, inhibits the synthesis of chitin, which disrupts
body wall formation and causes larval death.  At the same
time, it helps minimize flair-up  in  the bollworm-budworm
problem because the natural enemies  of the bollworm-budworm
complex are not eliminated as they are with the use of
conventional insecticides.  It is predicted that there could
be substantial cost savings in the eradication program if
diflubenzuron is utilized as  the  primary element of control.

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IV*  Risk/Benefit Analysis of Alternative Courses of Action
     A.  Introduction
         The foregoing review analyzes and summarizes infor-
mation on the risks and benefits of the use of diflubenzuron
on cotton.  This section presents  the basis for the Agency's
development of regulatory options, identifies the options
selected for consideration, and discusses the risks and
benefits of each of these options.
     B.  Basis for the Development of Regulatory Options
         The Administrator may register a pesticide only if
he has first determined that its use will not pose an unrea-
sonable risk to man or the environment.  This determination
must be made for each proposed use of a pesticide and must
take into account the risks and benefits associated with each
use.  Even if the Administrator determines that a pesticide
will pose an unreasonable risk if  used as proposed, before
denying registration he must consider whether prescribing
any restrictions on the pesticide's use will sufficiently
reduce the risks to warrant registration.
         It is therefore apparent  that the Administrator
must consider a spectrum of regulatory options for each use
of a pesticide.  Approval of registration with no added
restriction and denial of registration are the regulatory
options at opposite ends of this spectrum.  Between these
end points are options the Administrator may consider which
                              -79-

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approve registration but with prescribed  restrictions and
                            *
conditions designed to reduce risks.   For example, the
Administrator may specify the permissible sites for use, the
directions for use, the labeling  language, and may require
that the pesticide be used  by certified applicators only.
         Under special circumstances,  the Administrator
may conditionally register  a pesticide when the full comple-
ment of data required for full  registration under Section
3(c)(5) has not been submitted.   The conditional registration
provision of FIFRA which is applicable to diflubenzuron is
Section 3(c)(7)(B) of FIFRA as  amended in 1978.  Diflubenzuron
falls within the purview of Section 3(c)(7)(B) because it is
currently registered for use as a pesticide to control gypsy
moths.  This Section provides that the Administrator may
conditionally register additional uses of a currently
registered pesticide if he  determines:  first, that the
applicant has submitted satisfactory data pertaining to the
proposed additional use, and second, that the conditional
registration of the additional  use will not significantly
increase the risk of any unreasonable  adverse effect on the
environment.  The conditional registration of the new use is
not permitted if the Administrator has issued a notice
stating that the pesticide  or any of its  ingredients meets
or exceeds the risk criteria enumerated in MO CFR 162.11 for
human dietary exposure or if the  additional use of the
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pesticide involves a major  food  or  feed  crop  or  a minor food
or feed crop where an effective  alternative pesticide which
does not meet or exceed the  risk criteria  is  available.
         If the Administrator makes  these  determinations and
grants conditional registration,  the registrant  is required
to generate and submit data  required for full registration
within the time required  by  Section  3(c)(7)(B),  or if such
time requirements are inapplicable,  in the time  specified by
the Administrator.  Furthermore,  the Administrator may
impose other terms and conditions that he  deems  appropriate.
For example, the Administrator may  provide for the automatic
termination of the conditional registration after passage of
a specific interval of time  or if data generated after
conditional registration  has been granted  indicate that the
risks caused by the registration are significantly greater
than initially anticipated.  In  addition,  restrictions on
the use and method of application of the pesticide may be
imposed.
         If the Administrator determines that the registrant
has failed to take appropriate steps toward fulfilling any
condition imposed, or that  a condition has not been met
within the period prescribed for satisfying such a condition,
the Administrator shall issue a  notice of  intent to cancel
the conditional registration.
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     C.  Alternative Pesticides
         The weighing of regulatory  options includes
a consideration of the risks and  benefits  of  the alternative
pesticides that are available  for use.  Alternative pesticides
currently used on cotton are,  in  descending order of predomi-
nance of use, methyl parathion, a combination of toxaphene
and methyl parathion, azinphosmethyl  (Guthiori), monocrotophos
(Azodrin), and EPN.  Table  IV-1 summarizes the toxicological
hazards and the ^environmental  effects of these compounds.
Methyl parathion and the combination  of toxaphene and methyl
parathion, the most prevalently used  pesticides for the
control of cotton pests, have  a very  high acute toxicity for
humans and are very toxic to fish, birds, and bees.  The
other pesticides currently  in  use also have a high acute
toxicity for humans and also pose extremely high hazards to
various nontarget species.
         Toxaphene is currently under RPAR review for
oncogenicity.  The administration of  toxaphene to two mouse
strains resulted in a statistically  significant increase in
the incidence of hepatocarcinomas in  both male and female
animals.  A study with rats provided  suggestive evidence for
the increased incidence of  thyroid tumors  with toxaphene
treatment.  In addition, toxaphene has been shown to be far
more toxic to aquatic species  than diflubenzuron and is
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Table IV-1.  Alternate Chemicals for Cotton
RPAR ADI
Pesticide Candidate mg/kg/day
Methyl Parathion No 0.001
Toxaphene Yes 0.001
(with Methyl
Parathion)
Azinphosmethyl No 0.0025
Monocrotophos No 0.0003
EPN Yes None
Malathion No 0.02
Diflubenzuron Yes None
Acute
Toxicity
Category
Highly
Toxic
Highly
Toxic
Highly
Toxic
Highly
Toxic
Highly
Toxic
Moderately
Toxic
Slightly
Toxic
Environmental
Effects
Very Toxic to
Fish, Birds, and
Bees
Very Toxic to
Fish, Birds, and
Aquatic Inverte-
brates
Very Toxic to
Fish and Aquatic
Invertebrates
Very Toxic to
Birds, Aquatic
Invertebrates,
and Bees
Very Toxic to
Fish and Aquatic
Invertebrates
Very Toxic to
Fish, Aquatic
Invertebrates,
and Bees
Very Toxic to
Aquatic Inver-
Chetnical
Class
Organo-
phosphate
Organo-
chlorine
Organc-
phosphate
Organo-
phosphate
Organo-
phosphate
Organo-
phosphate
Organo-
chlorine
Use
Rate
Frequency
1-2 Ibs. AI/A
4-5 days
3 Ibs. AI/A
Weekly
intervals
0.25 lb. AI/A
as needed
0.75 lb, ,AI/A
as needed
1 lb. AI/A
5 days
1 lb. AI/A
as needed
O.Ob lb. AI/A
5-7 days
                                                                 tebrates
                                                      -83-

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apparently far more persistent  than  diflubenzuron.  The only
other alternative chemical  currently under  review in the
RPAR process is EPN, which  has  been  shown to  cause delayed
neurotoxic effects.
         As shown in Table  IV-1,  the application rates for
the most predominantly  used chemicals,  i.e.,  methyl parathion
and the combination of  toxaphene  and methyl parathion, are
much higher than those  for  diflubenzuron.   The remaining
alternative chemicals have  application  rates  ranging from
1/4 pound/acre for azinphosmethyl to 1  pound/acre for EPN.
There is no restriction on  the  number of applications per
season for these six alternatives; a minimum  of six applications
per season is generally required  to  obtain  control.
         The proposed application rate  for  diflubenzuron is
1 oz./aere with a maximum of six  applications per season to
control boll weevils on cotton.   Thus,  the  use of difluben-
zuron to replace methyl parathion, the  combination of methyl
parathion and toxaphene, and the  other  alternatives which
have higher application rates,  will  achieve a signifi-
cant reduction in the total poundage of pesticides used in
cotton pest control.  Most  significantly, the use of difluben-
zuron to replace toxaphene  will substantially diminish the
oncogenic hazard attributed to  toxaphene for  the human
population at risk.
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     D.  Regulatory  Options  Selected
         From the  range  of possible conditions of registra-
tion, the Agency has formulated three regulatory options  for
consideration in making  the  decision regarding registration.
In order of increasing restrictiveness,  the  options  selected
are:
         1)  Conditionally register diflubenzuron  until
January 1, 1984, under the condition that  required studies
are submitted by January 1,  1983.
         2)  Conditionally register diflubenzuron until
January 1, 1984, with the data  requirements  set  forth in
Option 1 and restrictions on use.
         3)  Deny  the application  for the  registration of
diflubenzuron on cotton.
          Granting full  ("unconditional")  registration of
diflubenzuron on cotton  was  not  selected as  an option
because some of the  data supporting  the petition for registration
are not sufficient to meet the  Agency's requirements for
full registration  under  Section  3(c)(5) and  therefore do not
warrant a balancing  of the risks and  benefits  resulting from
long-term use.  Specifically, the  chronic  feeding studies
submitted by the registrant  suffer  from severe deficiencies
in design which preclude  a long-term  risk  assessment.  The
Agency has also concluded that  insufficient  data exist for
                            -85-

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determining the long-term  hazard  to humans from methemoglobinemia
and sulfhemoglobinemia  and ,the  long-term hazard to  aquatic
species that might  result  from  runoff of diflubenzuron  into
streams, rivers, estuaries,  and other water bodies.   Finally,
the Agency has determined  that  field studies substantiating
the efficacy and benefits  of diflubenzuron are  necessary
before a long-term  risk/benefit analysis can be performed.
         Under both options of  conditional registration,
the Agency would require that more  studies be submitted
by January 1, 1983.   These include  additional chronic
feeding studies in  rats and mice, studies  establishing
NOEL's for methemoglobinemia and  sulfhemoglobinemia in an
appropriate species,  monitoring data on  the runoff  of
diflubenzuron and its breakdown products,  and field studies
on the benefits of  diflubenzuron.    Such field  studies should
confirm the measurable  benefit  of diflubenzuron from an
increase in crop yield  or  a decrease in  the costs of
controlling Heliothis spp.  In  addition,  the registrant
would be required to  develop a  method for  formulating the
pesticide that would  reduce exposure to  applicators.
Finally, the Agency may require the generation  and  submission
of any other data it  determines are necessary to meet the
requirements for full registration.
         Under Option 2 the following restrictions  would
be imposed.
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          1)  Diflubenzuron Vould be classified for restricted
 use by certified applicators only.
          2)  Applicators would be required to wear protective
 clothing and respirators while mixing, loading, and applying
 diflubenzuron.
          3)  Application of diflubenzuron would be prohibited
 in the coastal zone of the Gulf States.
          4)  Application of diflubenzuron near any person  or
 dwelling would be prohibited.  Use of flagmen in  the  field
 would be prohibited.
          5)  Workers would be prohibited  from entering
 treated fields until the-day following application and  the
 spray deposit has dried.
          6)  Use of diflubenzuron  would be  limited to six
 1-oz.  applications/acre per season.
          Under Option 2,  the Agency  could impose any other
 restrictions  on use which it determines are necessary to
 prevent  a significant increase  in  the  risk  of any  unreasonable
 adverse  effects during the period  of conditional registration.
      E*   Impact of  Regulatory Options
      1.   Option 1.   Conditionally  register  diflubenzuron for
          use  on cotton until January 1, 1964,  under the
          condition  that required studies  are  submitted.
          Choosing Option  1  would indicate that the Agency
had reached the  following  conclusions:  first,  the data
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pertaining to the use  of  diflubenzuron  on  cotton  is  satis-
factory for purposes of assessing  the risks  and benefits
resulting from this use over  a  period of four  growing
seasons; second, conditional  registration  for  this period
would not significantly increase the risk  of unreasonable
adverse effects on humans or  the environment;  and third,
granting conditional registration  of diflubenzuron would be
in the public interest.
         There is considerable  uncertainty as  to whether
diflubenzuron is an oncogen.  Section II of  this document
contains a "worst case" risk  assessment of the oncogenicity
of diflubenzuron that  is  based  on  the available data.  This
assessment shows that  the risks to the  general population
from a lifetime exposure  (70  years) to  the compound would be
slight.  The risk from using  diflubenzuron for four growing
seasons would be decreased proportionately.
         There is also uncertainty concerning  the risks of
methemoglobinemia and  sulfhemoglobinemia.  Although an NOEL
for this effect has not been  established for some of the
species of laboratory  animals tested, the  NOEL's  available
and the lowest daily doses causing observed  effects  in all
species studied were considerably  greater  than the anticipated
exposure to humans.  Thus, the  Agency has  concluded  that the
available studies on methemoglobinemia  and sulfhemoglobinemia
do not raise significant  concern about  the potential for
                              -88-

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adverse effects to humans  exposed  to diflubenzuron.   However,
further study of  these  effects  is  necessary  before  the  risks
to humans can be  fully  evaluated.
                                                V
         Conditionally  registering diflubenzuron "for  use
on cotton will result in some hazard to  certain aquatic
invertebrates from diflubenzuron  runoff.   Monitoring  studies
on the runoff of  diflubenzuron  and its metabolites, particularly
in areas of high  usage  and the  Gulf States,  are necessary
before the Agency can complete  its assessment  of risk.
         Although use of diflubenzuron on  cotton would
pose some risks,  conditionally  registering it  would reduce
the overall risks posed by pesticides used on  cotton.
Specifically, diflubenzuron would  replace  other pesticides
used to control boll weevils such  as the organophosphates
and toxaphene, which appear to  pose substantially greater
risks to man and  the environment.  Organophosphates are much
more acutely toxic to man  and substantially  more toxic to
aquatic species than diflubenzuron.  NCI and CAG have
determined that toxpahene  is a  carcinogen.  It is much
more toxic to aquatic species and  more persistent in  the
environment. Furthermore,  the risks, as  stated above, are
compounded by the fact  that the application  rates of  the
alternates are much higher than the diflubenzuron application
                                 i
rate.  It is anticipated that the  overall  risks would be
reduced by the fact that diflubenzuron's use for boll
                            -89-

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weevil control will  leave  the  populations  of  the  beneficial
                           »
insects intact, thereby  reducing  the  amount of  organophosphate
pesticides required  to control the  bollworm-budworm complex.
         Choosing Option 1 may also result in substantial
economic benefits.   As noted previously, diflubenzuron does
not kill the natural predators of the bollworm-budworm
complex.  Therefore,  use of diflubenzuron  for boll weevil
control instead of other pesticides that do kill  natural
predators would reduce the amount of  pesticides used to
control the bollworm-budworm complex.  This reduction in pesticide
use could result in  an overall saving  of up to $10 million a
year for cotton growers.
         Additional  significant economic benefits may be
realized if diflubenzuron  is used in  the boll weevil era-
dication program.
     2.  Option 2.   Conditionally register diflubenzuron
         until January 1,  198M, with  the same data requirements
         set forth in Option 1 and  restrictions on use.
         Choosing this option  would indicate  that the
Agency had reached the conclusions  described  under Option 1
regarding the adequacy of  the  data, the level of  risk, and
the serving of the public  interest, providing that the
specified restrictions were imposed.
                              -90-

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         The risks and benefits  of  this  option are the same as
                           »
those for Option 1 except  as modified  by restrictions.  These
restrictions and their impacts are  described  below.

         a)  Classify diflubenzuron as a restricted use
             pesticide requiring certified  applicators.
             Under FIFRA,  hazardous pesticides may be
classified  for  restricted  use  and may  be limited  to use only
by or under the direct supervision  of  certified applicators.
Certification programs are administered  primarily by the
States.  These  programs  use  various methods to certify
applicators, after  a determination  that  these applicators
are  competent to use restricted  .pesticides.
             The Agency  believes that  the classification of
diflubenzuron  for restricted use would ensure that  the
material would  be available  only to competent persons.
Preventing untrained persons from using the pesticide would
significantly  reduce the risk of human exposure  due to
misuse  or  carelessness.  Any marginal costs that  might  result
 from restriction to certified applicators would  be  minimal
 since programs to certify applicators are  operational
 in all  States,  there are many certified applicators,
 and cotton pesticides are usually  applied  by certified
 applicators.
                             -91-

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         b)  Require the use of protective clothing during
             the mixing, loading, and application of diflu-
             benzuron. Require respirators during mixing,
             loading, and ground application of diflubenzuron.
             Dermal exposure to diflubenzuron is of considerable
concern to the Agency.   This exposure may arise from mixing and
loading, spills, maintenance of application equipment, ground spray
application, and aerial  spray application (including wind drift).
             The estimates  of dermal and inhalation exposure
to mixers, loaders, and  applicators  set  forth in Section II
were made  with  the  assumption that  85*  of the body would be
clothed and  that respirators would  not  be worn.  Accordingly,
it was  assumed  that the  hands,  forearms, neck,  face, upper
chest,  and hair would be exposed.   Requiring  protective
finely-woven overgarments,  gloves,  and  a hat  would  leave
only  3.5%  of the body exposed.   Thus,  these protective
measures  would reduce the risk from dermal  exposure by more
than  15%.   Requiring a respirator designed  to filter dust
particles and spray mists would reduce inhalation exposure
 to  very low levels.  The Agency estimates that the economic
 impact of these protective measures would be very small,
 especially in light of  the fact that certified applicators
 ordinarily have protective clothing and respirators available.
                               -92-

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         c)  Prohibit application of diflubenzuron within
             the coastal zone of the Gulf States.
                           k
             The estuaries and waters of the Gulf Coast
contain-most of the aquatic species to which diflubenzuron
is very acutely toxic, including those aquatic species that
are most economically important.  Therefore, the Agency
considers the risk to aquatic species from use of difluben-
zuron greatest in these waters.  This zone includes:  1)
the area between the coastline and a parallel 3-mile line
from the coastline including any bays or estuaries that are
contiguous to the sea and 2) the area with 3 miles of
tidally-influenced waters including coastal salt marshes and
rivers.  Prohibition of the application of diflubenzuron in
these areas is anticipated to reduce the amount of runoff
into waterways where aquatic species would be most at
risk.
         d)  Prohibit application of diflubenzuron near
             persons and dwellings.  Prohibit the use of
             flagmen in the field.
             Bystanders in the vicinity of the cotton fields
at the time of diflubenzuron application may be exposed to
levels of the chemical that could present a hazard to these
individuals.  This option would require that the label
instructions state that the application of diflubenzuron
                            -93-

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near any person or dwellng is prohibited.  The instructions
would also recommend that the product be applied at least
300 feet from dwellings when they are downwind.  The use of
flagmen to mark the spray swath  or pattern would be prohibited.
         e)  Prohibit workers from entering treated fields
             until the day following application and the
             spray deposit has dried.
             Fieldworkers entering fields after application
may be dermally exposed to residues of  diflubenzuron on the
surface of cotton leaves.  Therefore, this option would
require that workers be prohibited from entering the fields
until the day following application and the spray deposit
has dried.
         f)  Limit use of diflubenzuron to six 1-oz. Al/acre
             applications per season with 5-  to 7-day intervals
             between applications.
             This option would require  that the label
limit the use of diflubenzuron to a maximum of six 1-oz.
Al/acre applications per season  with 5- to 7-day intervals
between applications.  The label would  also specify that
diflubenzuron may not be applied after  the bolls have
opened.
             Data available  to the Agency indicate that
this regime will adequately  control boll weevils.  Diflu-
                           -94-

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benzuron applied to open bolls could contaminate the fiber,
seed, oil, and meal, rendering the crop unfit for use.
                                                x ^
     3.  Option 3.  Deny the application for the regis-
         tration of diflubenzuron for use on cotton.
             Choosing this option would mean that the Agency
has reached one or more of the following conclusions:  1)
data satisfactory for making a short-term risk/benefit
assessment have not been submitted, 2) conditional registration
of diflubenzuron on cotton for four growing seasons would
significantly increase the risk of unreasonable adverse
effects on humans or the environment even if the restrictions
in Option 2 were adopted, or 3) conditional registration is
not in the public interest.
         Adopting this option would maintain the status
quo regarding pesticide use on this crop.  Therefore the
option would eliminate the possibility of reducing the
overall risk from pesticide use on cotton.  In addition,
this option would eliminate a potential benefit of $10
million per year for cotton growers and other possible
economic benefits resulting from the use of diflubenzuron in
a government-sponsored boll weevil eradication program.
                             -95-

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V.  Recommended Option
    The Agency has determined that Option 2 is the most
desirable course of action.  It would allow conditional
registration of diflubenzuron's use on cotton for four
growing seasons. Diflubenzurbn would be classified for
restricted use and would be applied only by certified
applicators.  These applicators would be required to wear
protective clothing and respirators.  Reentry intervals and
protective measures for bystanders would be established.  A
new method for formulating the pesticide, which would reduce
exposure to humans, would be required.  The rate of applica-
tion would be limited to six l-oz./acre applications per
season.  Application would be prohibited in the coastal zone
of the Gulf States.
    This option also requires more studies including addi-
tional chronic feeding studies in rats and mice, monitoring
studies of diflubenzuron runoff, studies establishing the
NOEL's for methemoglobinemia and sulfhemoglobinemia in an
appropriate species, and field studies demonstrating the
benefits of diflubenzuron's use on cotton.  The registrant
would also be required to develop a method for formulating
the pesticide that would reduce exposure to applicators.
These studies must be submitted by January 1, 1983, with
annual reports of progress.  Additional restrictions and
                             -96-

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studies may be required before or during the period of
conditional registration if the Agency determines that they
are necessary.
    Option 2 has been selected for several reasons. The data
submitted by the registrant are satisfactory for balancing
the risks and benefits resulting from the use of diflubenzuron
for four growing seasons.  Although the chronic feeding
studies on mice and rats submitted by the registrant
suffer from severe deficiencies, the Agency believes that
they are sufficient for concluding that the use of difluben-
zuron for the term of the conditional registration will
pose very small risks to humans, particularly when the
specified restrictions on use are considered.
    The Agency has determined that the conditional regis-
tration of diflubenzuron on cotton would not significantly
increase the risk of unreasonable adverse effects on man or
the environment.  Diflubenzuron would replace pesticides
currently used for boll weevil control that appear to be
more toxic to humans and more harmful to the environment.
In addition, it would reduce the amount of pesticides
required to control both boll weevils and the bollworm-
budworm complex.  As a consequence, conditional registration
of diflubenzuron for use on cotton would result in a reduction
of the overall risks posed by pesticides used on cotton.
                           -97-

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Moreover, use of diflubenzuron may result in economic
                           »
benefits to growers and potentially significant, although
unquantifiable, benefits in the proposed USDA eradication
program.
    Finally, conditional registration of diflubenzuron
for four growing seasons is in the public interest because
its use is anticipated to result in an overall reduction in
the risks to humans and the environment from pesticide use
on cotton.
    Option 1 was not chosen because the Agency anticipates
that the restrictions on use delineated in Option 2 will
significantly reduce the risks to humans and the environment
with only a minimal impact on the economic benefits.  These
precautions are particularly appropriate in light of the
weaknesses of the  risk data.
                            -  -98-

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                       APPENDIX-II-1
Thompson-Hayward's Consultant  (Submission October 19, 1977)
Robert A. Squire, D.V.M., Statements

     "Although the proportions of diflubenzuron absorbed
apparently do not increase proportionally with dosage,
greater amounts are nonetheless absorbed as dosage increases.

     The case may be made that bioavailability and potential
toxicity will not increase proportionally with dose, and
since the compound is relatively non-toxic at all levels
tested, one may conclude that  little toxicity could be
predicted at higher doses.  However, it must be recognized
that the only way to confirm this assumption is to actually
test the compound at a maximum tolerated dose (MTD)."

     Dr. Squire therefore, by  this  statement establishes
that the experiment was not done at the MTD.
                               -99-

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                      APPENDIX-II-2

              STATEMENT OF Jack L. Radomski
             (Thompson-Hayward1s Consultant)
             (Submission of October  19,  197?)

          Review of Chronic Toxicity Studies of
       DU112307 (Diflubenzuron) and p-chloroniline


     "I have the following comments in response to the
questions (1-7) asked:

     1)  It seems to me that both the rat and mouse study
were carried out at a dose well below the MTD.  This
probably happened because of the erroneous judgement that
200 ppm had a toxic effect in the sub-acute feeding study.

     2)  I see no evidence that there was any significant
increase in tumor incidence due to the feeding of DU112307
to rats at dietary concentrations up to  160 ppm for 104
weeks.

     3)  Perhaps the focal liver necrosis observed was
fortuitous, since it did not show up in  the chronic
experiment.

     4)  I see no evidences of a dose-dependent response or
an increased tumor incidence due to the  feeding of DU112307
to mice in concentrations up to 50 ppm in the diet for 80
weeks.  Statistical analyses were not performed.

     5)  In my opinion the absorption studies carried out
with DU112307 do not support the notion  that there would be
no point to testing this substance at concentrations higher
than 50 to 200 ppm in the diet for the following reasons:

          1)  The studies were carried out in aqueous
          suspension in gum tragacanth.  I have been unable
          to find out what the solubilities of this compound
          are in organic solvents, but my experience has been
          that gum tragacanth will tend  to retard absorption
          (being un-absorbed itself) particularly at the
          larger doses.  If the material is soluble in corn
          oil, studies in corn oil solution may have given
          quite different results.  In addition, these aqueous
          solutions are not analagous to the way the material
          is fed in a diet.  Usually the oil present in an
          experimental diet tends to promote absorption of
          oil soluble compounds.
                              -100-

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                   BIBLIOGRAPHY

Albert, Roy E.  1979.  The'Carcinogen Assessment Group's
risk assessment on diflubenzuron  (Dimilin).  March 20
1979.
                                               v
Apperson, C.S., C.H. Schaefer, and A.E. Colwell.. 1978.
Effects of diflubenzuron on Chaborus astictopus and
nontarget organisms and persistence of diflubenzuron
in lentic habitats.  Jour, of Econ. Entomol. In press.

Booth G.  (undated).  An evaluation of Dimilin and diflu-
benzuron toxicity to the aquatic  environment.  (Appendix c)
Relative risks of Dimilin  and alternative pesticides.
Clements Associates, Inc., Washington, D.C.

Booth G., J. Reed, R. Mortensen and C. Monson.  1976.  A
bioaccumulation study of Dimilin  W-25 in rainbow trout
(Salmo gardneri) and bluegill sunfish (Lapomis machrochirus).
A final report submitted to:  Thompson-Hayward Chemical
Company, Kansas City, Kansas.

Bull, D.L. and G.W. Ivie.  1978.  Fate of diflubenzuron
in cotton, soil, and rotational crops.  Agr. Food Chetn.
26:515-520.

Campt., D.D.  1977.  Letter of November H, 1977, to Dr. C.
Duane Ferrell.  Thompson-hayward  Chemical Company, concerning
RPAR criteria  that Dimilin may meet or exceed.

Carringer, R.D., J.B. Weber, and  T.J. Monaco.  1975.
Adsorption-desorption of selected pesticides by organic
matter and montmorrillimite. J. Agric. Food Chem. 24:568-572.

Chitlik, L., and S. Biscardi. 1979.  Memo of data validation.

Collier, L. and D.J. Severn, 1978.  Memo of January 22, 1978,
to R. Troast,  SPRD, concerning use of Athens ARM Dimilin
runoff model.

Dorough, H.W., October 7,  1977.   Screening of selected
Thompson-Hayward chemicals for activity in the Ames
Salmonella mutagenicity test.  [Proprietary]

Dorough, H.W., December 9, 1977.  Test of selected
Thompson-Hayward chemicals in the Ames S. typhimurium
mutagenic acid with (t) and without (-) the 5-9  rat liver
enzymes.  [Proprietary]
                              -101-

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Dubin, I.N.  (Medical College of Pennsylvania and Hospital).
1978.  Letter of November 13, 1978 to Adrienne J. Zahner
(CAG).  Final report on the pathologic effects of administering
Dimilin to female CFLP mice for 80 weeks.

Falco, J.W., L.A. Molkey, K.F. Hedden, C.N. Smith, T.O.
Barnwell, V.D. Dean, R.E. Lipcsei, and M. Smith." 1978.
Fate of Dimilin in selected waters of the southern United
States, EPA, ERL, Athens, Georgia.  [Proprietary]

Gee, F.D.R., 1979.  Letter of January 31, 1979, to Dr. C.
Duane Ferrell, Thompson-Hayward Chemical Co., concerning
environmental chemistry and safety reviews of Dimilin.

Goodman, D.G. (Sellers, Conner, and Cuneo).  1978.  Letter
of November 17, 1978 to Richard Troast (EPA) concerning
Dimilin W-25 for cotton, Dimilin W-25 for soybeans, and
Dimilin W-25 for control of mosquito larvae.

Helling, S.  1975.  Soil mobility of three Thompson-Hayward
pesticides.  Unpublished interim report  to USDA/ARS.
[Proprietary]

Hensley, W.H. et al.  1978.  Monitoring  runoff water  for
Dimilin residues.  North Carolina Dept.  of Agriculture,
Raleigh, NC.  unpublished.


Hummel, R.J., 1977(a).  Memo of June 8,  1977, to  M.H. Rogoff,
RD,  concerning Dimilin on cotton.

Hummel, R.J., 1977(b).  Memo of August 12, 1977,  to C.  Mitchell,
RD,  and Toxicology Branch, RD, concerning Dimilin on  cottonseed:
evaluation of analytical methods and residue data.

Hummel, R.J. 1977(c).  Memo of December  17,  1976,  to  C.  Mitchell,
RD,  and Toxicology Branch, RD, concerning Dimilin in  fish  and
water:  evaluation of analytical methods and residue  data.

Huntingdon Research Center.  June 15, 1972.  Acute inhalation
toxicity to the rat of DU112307 insecticide  powder.   Report
#4920/72/355.

Huntingdon Research Center.  December 14, 1973.   Acute
inhalation toxicity to the rat of DU112307 technical  grade
powder.  Report #PDR 174/73849.
                            -102-

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Huntingdon Research Center.  April 24, 1974.  DU112307 -
Preliminary assessment of the toxicity to male mice in
dietary administration for>six weeks.  Report #PDR 174/74199.

Huntingdon Research Center.  November 11, 1974.  DU112307
toxicity in repeated dietary administration to beagle dogs.
Report * PDR 169/74157.

Huntingdon Research Center.  December 17, 1974.  Acute
percutaneous toxicity to rabbits of DU112307 (technical).
Report #2171/D175/73.

Huntingdon Research Center.  June 17, 1975.  Acute inhalation
toxicity to the rabbit of DU112307 tehnical grade powder.
Report * PDR 198/74988.

Huntingdon Research Center.  December 23, 1975.  Tumorigenicity
of DU112307 to mice.  Dietary administration for 80 weeks.
Report #PDR 170/75685.  (Plus addendum dated April 5, 1977).

Huntingdon Research Center.  January, 1976.  Effect of
DU112307 in dietary administration to rats  for 104 weeks.
Report #PDR 171/75945.  (Plus addendum of April 5, 1977).

Huntingdon Research Center.  June 10, 1977.  Preliminary
assessment of the effect of DU112307  on  the rat.  Report
#243/77208.

Huntingdon Research Center.  August 17,  1977.  Tumorigenicity
of DU112307 to mice.  Dietary administration for 80 weeks.
Addendum:  Histological examination of additional tissues
(addendum to PDR/170/75685).  Report  #PDR/250.

Interagency Liaison Group  (IRLG) on Risk Assessment.
1979. Scientific bases for  identifying potential carcinogens
and estimating their risks.  Report dated February 6,
1979.

Kirsten, W.H. (University  of Chicago).   Letter of January
11, 1979 to Dr. E. Anderson (EPA) about  examination concerning
tissues brought to Drs. D.  Variakojis, J. Vardiman, and  W.
Kirsten by Dr. Haberman.

Litton Bionetics, Inc. May  17, 1977.  Mutagenicity evaluation
of diflubenzuron technical  batch FL 44/605201 - final report.
LBI Projecct 2683.   [Proprietary]
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Litton Bionetics, Inc.  August 2, 1977a.  Evaluation of
diflubenzuron in vitro malignant transformation in BALB/3T3
cells - final report LBI project 2688.

Litton Bionetics, Inc.  August 2, 1977b.  Evaluation of
diflubenzuron unscheduled DNA synthesis is WI-36 cells -
final report.  LBI Project 2688.

Litton Bionetics, Inc.  October 1977a.  Mutagenicity
evaluation of 2,6-difluorobenzoic acid.  LBI Project 20838.

Litton Bionetics, Inc.  October 1977b.  Mutagenicity evalua-
tion of 4-chlorophenylurea.  LBI Project 20838.

Litton Bionetics, Inc.  October 1977c.  Mutagenicity
evaluation of 4-chloroaniline.  LBI Project 20838.

MacGregor, et al. (1979).  Muta. Res. 66:45-63.

National Cancer Institute (NCI).  Bioassay of p-chloroaniline
for possible carcinogenicity.  Unpublished report of U.S.
Dept. of HEW, Public Health Service, National Institute of
Health, Bethesda, Maryland.  DHEW Publication #(NIH)79-1745.

Nimmo, W.B. and P.C. deWilde.  1973.  The fate of ph 60-40
in the environment.  Part One:  Natural water and soil/water
systems.  Interim report [Proprietary].

Nimmo, W.B. and P.C. deWilde.  1974a.   The fate of  pH  60-40
in the environment.  Part Two:  Hydrosoils and agricultural
soils.  Interim report [proprietary].

Nimmo, W.B. and P.C. deWilde.  1974b.   The fate of  pH  60-40
applied on the leaves of corn, soybean, cabbage, and apples
[Proprietary].

Nimmo, W.B. and P.C. deWilde.  1975a.   Degradation  of
diflubenzuron in soil and natural water [Proprietary].

Nimmo, W.B. and P.C. deWilde.  1975b.   Degradation  of
diflubenzuron in sterile water.  Phillips-Duphar report.

Opdycke, J.C.  1976.  Metabolism and fate of diflubenzuron
in chickens and swine.  Master's Thesis submitted to
University of Maryland.

Patel, Y.M. (EPA, Las Vegas).  1978.  Letter of August 29,
1978 to Salvatore F. Biscardi concerning protocol for  selected
toxicological studies of Dimilin in weanling male rats.
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Philips-Duphar, B.V.  March 1973.  Acute toxicity studies
with DU112307:  1)  Acute oral LD,-n - mice and rats; 2)
Acute dermal LD,-n - rabbits.; 3)  Toxicity to rabbit
eye.           y

Philips-Duphar, B.V.  November 1973a.  Acute toxicity
studies with DU112307 in mice and rats.  Report #56645/14/73.

Philips-Duphar, B.V.  November 1973b.  Dietary administration
of DU112307 to male and female rats for three months.  Report
#56645/13A/73.

Philips-Duphar, B.V.  December 1973a.  Acute toxicity
studies with DU112307 (25% W.P.) in mice and rats.  Report
#56645/15/73.

Philips-Duphar, B.V.  December 1973b.  Acute dermal toxicity
in rabbits with DU112307 W.P. 25?.  Report #56645/17/73.

Philips-Duphar, B.V.  December 19, 1973.  Preliminary
photodegradation study of pH 60-40 in water;  Report #56630VI/
97/73.

Philips-Duphar, B.V.  October 7, 1974.  Orientation on
photolytical deformation of pH 60-40 on their films of soil
and silica gel.  Report #56630/80/74.

Philips-Duphar, B.V.  December 8, 1975.  Degradation of
diflubenzuron  in soil and natural water.  Report  #56635/32/
1975.

Philips-Duphar, B.V.  December 22, 1975.  Degradation of
diflubenzuron  in soil and natural water.  Report  #56635/37/
1975.

Philips-Duphar, B.V.  April 1977,  Diflubenzuron:  Analysis
of metabolites connected with methaemoglobinemia.  Report
#56654/8/77.

Rieck, C.  (undated).  Soil leaching study.  Report to
Thompson-Hayward Chemical Co.  Submitted in Pesticide
Petition 7F1838 [Proprietary].

Seuferer,  S.L., Jr., 1977.  Metabolism of Dimilin micro-
organisms.  MS Thesis, Louisana  State University.  December
1977.
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Sontag, J.M., N.P. Page and U. Saffiotti.  1976.  Guidleines
for carcinogen bioassay in small rodents.  National Cancer
Institute, Bethesda, Maryland.

Tucker, R.K. and W.S. Rabert, 1978.  EPA memo of.June 2,  1976,
to Richard Troast. Review of selected fish and wildlife
literature on diflubenzuron.

Tucker, R.K. and R. Stevens, 1978.  Risk analysis of Dimilin
and alternatives for aquatic and terrestrial wildlife -
cotton, or soybeans, hardwood forests, and mosquito control.
EPA report dated August 21, 1978.

USDA.  1978.  Preliminary biological and economic assessment of
diflubenzuron.

USDA-State.  June  8, 1977.  Biological effects  of Dimilin on
vertebrates  and other selected organisms.

USDA/EPA/State.  1978.  Potential  exposure of diflubenzuron to
birds, non-target  aquatic organisms, and humans.

USDA/State.  1978.  Effects of diflubenzuron (Dimilin) on
non-target avian and aquatic organisms and its  fate on the
environment.
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