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       Post-Application Risks
       The Agency also assessed post-application risks to workers who may be exposed to
disulfoton when they enter previously treated fields, because their skin may contact treated
surfaces. Exposures are directly related to the kind of tasks performed. EPA estimates the
amount of pesticide exposure to post-application workers over tune based on various studies.
The Agency evaluates this information to determine the number of days following application
that must elapse before the pesticide residues dissipate to a level where worker MOEs equal or
exceed 100 while wearing baseline attire. Baseline attire is defined as long-sleeved shirt, long
pants, shoes and socks. Based on the results of the post-application worker assessment, the
Agency establishes restricted entry intervals (REIs) before workers may enter treated areas.  At
present, the Worker Protection Standard designates the disulfoton REI to be 48 hours, or 72   .
hours in regions where the annual rainfall is less than 25 inches.

       The Agency completed a post-application exposure assessment for disulfoton for the
following scenarios: irrigating, scouting, thinning, and weeding immature or low-foliage crops
(i.e., asparagus, barley, cotton, potatoes and wheat). The short-term dermal NOAEL of 0.5
mg/kg/day based on a 3-day dermal toxicity study in rats (Table 6) was used to assess potential
dermal exposure to workers re-entering treated fields.  The post-application assessment is also
based on 8 hours of worker daily exposure and the default transfer coefficients (Tcs) shown in
Table 11. Although three chemical-specific dislodgeable foliar residue (DFR) studies were
conducted for disulfoton, EPA has determined that none of these studies are sufficient for use in
the post-application assessment. Therefore, EPA roughly estimated the exposure and risk to
post-application workers and handlers using an assumption that 20% of the initial application
remained as a DFR immediately following application, and the residue degraded into nontoxic
by-products at a rate of 10% per day.

       For post-application risks to disulfoton, an MOE of 100 or greater is not of concern to the
Agency, and REIs for the assessed crops are determined when the MOE reaches 100.  Table 11
summarizes the occupational post-application risks following foliar applications of disulfoton.
In summary, for foliar applications of disulfoton, EPA has  a post-application risk concern for all
crops except cotton.

Table 11. Occupational Post-Application Risks from Foliar Applications of Disulfoton
Crop
Asparagus
Barley
Cotton (SLN)
Application
Rate (Ib ai/A)
1.0
1.0
0.2
Tasks of
Concern
Irrigating,
scouting,
thinning,
weeding
immature or
low foliage
plants
Timing of
Application
fem stage (3 per
year; 120 DTK)
after tillering
(30 DTK)
Before boll
opens (30 DTK)
Transfer
Coefficient
300
100
100
MOE
6.5
101
20
105
108
Days
After
Treatment
1
26
1
16
1
                                           38

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Crop
Potatoes (East
of Rockies)
Potatoes
(OR, ID, UT,
WA only)
Wheat
Wheat (SLN)
Application
Rate (Ib ai/A)
0.5
3.0
• 0.75
1.0
Tasks of
Concern

Timing of
Application
When pest
appears (3 per
season; 30 DTH)
As needed (1 per
season; 60 DTH)
Post-plant (after
tillering; 30
DTH)
Two per season
(30 DTH)
Transfer
Coefficient
300
300
100
100
MOE
14
107
2.4
51
100
29
102
20
105 ,
Days
After
Treatment
1
20
1
30
37
1
13
1
16
DTH - Days to harvest
                    e.     Incident Reports
       Human Incident Reports

       The Agency also reviews any incident data that may be available and applicable. There
have been a significant number of occupational poisoning incidents associated with disulfoton,
resulting in adverse health effects. Poison Control Center data from 1985 to 1992 indicate that
disulfoton ranked third highest among OPs for the percent of individuals hospitalized for
occupational poisoning, with 27 individuals hospitalized following exposure to disulfoton alone
and 28 individuals hospitalized following exposure to multiple chemicals, including disulfoton.
Data from the California Department of Pesticide Regulation show that disulfoton ranked 11th
highest in the number of worker poisonings, with 0.22 poisonings per 1000 pesticide
applications from 1982 to 1989.

       Pet Incident Reports

       Recent incidents of accidental pet poisonings (dogs) have been reported through the
National Pesticide Information Center, NPIC (formerly the National Pesticide
Telecommunication Network, NPTN).  These incidences have been associated with the 1 and 2%
granular products used by homeowners. According to the American Society for the Prevention
of Cruelty to Animals, disulfoton is the second most common pesticide associated with
veterinary poisonings.  Because of its high toxicity, only a small amount is required to poison a
cat, dog, or other domestic animal.
       B.
Environmental Risk Assessment
       A summary of the Agency's environmental risk assessment is presented below.  For
                                          39

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detailed discussions of all aspects of the environmental risk assessment, see the document,
Reregistration Eligibility Decision for Disulfoton, September 5, 2000 and its addendum March
25, 2002; and Endangered Species Addendum to EFED 's Disulfoton Science Chapter, January
24, 2002, which are available in the public docket and on the internet.

              1.     Environmental Fate and Transport

       In soil, disulfoton is not expected to undergo significant hydrolysis or volatilization.
Disulfoton parent photochemically degrades rapidly by sunlight on soil, and in water where light
can penetrate. Disulfoton is metabolized or oxidized in soil to the corresponding sulfoxide and
sulfone degradates, and the half-life of disulfoton parent in soil is less than 6 days. Field
dissipation studies confirm that disulfoton does not persist in the environment.  Disulfoton is not
considered mobile under convective-dispersive processes, but it has been detected in
groundwater monitoring conducted in highly vulnerable areas. The mobility of disulfoton,
which can be represented as a K^, ranged from 383 to 888 mL/g carbon with a mean Koc of 551.

       Disulfoton's major degradates, disulfoton sulfone and sulfoxide, are more persistent and
.mobile than the parent. Two aerobic soil metabolism studies showed an average half life of 166
days. In a field study, as much as 35% of the applied disulfoton remained in soil as disulfoton
sulfone after 367 days. Thus the sulfone and sulfoxide degradates appear to be much more
persistent than parent in soil.  The other degradates were either not identified or occurred at
much lower concentrations. The Agency is concerned that the sulfoxide and sulfone degradates
have a high potential to reach ground and surface water. In field testing, degradates were
detected at a depth of 18  inches, indicating potential mobility. The Agency has limited data
regarding the persistence of the degradates and lacks the absorption/desorption data necessary to
confirm the mobility of the degradates.  EPA does not have data on the aerobic or anaerobic
aquatic metabolism of disulfoton and its degradates, nor does it have data on the mobility and
leaching potential of the degradates.  Thus, these data are necessary to confirm the findings in
the disulfoton IRED.

              2.     Ecological Risk Assessment

       The Agency's ecological risk assessment compares toxicity endpoints from ecological
toxicity studies to estimated environmental concentrations (EECs) based on environmental fate
characteristics and pesticide use data. To evaluate the potential risk to nontarget organisms from
the use of disulfoton products, the Agency calculates a Risk Quotient (RQ), which is the ratio of
the EEC to the toxicity endpoint values, such as the median lethal dose (LD50) or the median
lethal concentration (LC50). These RQ values are then compared to the Agency's levels of
concern (LOCs), which indicates whether a chemical, when used as directed, has the potential to
cause undesirable effects on nontarget organisms.  In general, the higher the RQ the greater the
concern. When the RQ exceeds the LOG for a particular category, the Agency presumes a risk
of concern to that category. The LOCs and the corresponding risk presumptions are presented in
Table 12.
                                           40

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Table 12. LOCs and Associated Risk Presumptions
IF...
THEN the Agency presumes...
Mammals and Birds
The acute RQ > LOG of 0.5,
The acute RQ >LOC of 0.2,
The acute RQ > LOG of 0,1 ,
The chronic RQ > LOG of 1
Acute risk
Risk that may be mitigated through restricted use
Acute effects may occur in Endangered species
Chronic risk and
Chronic effects may occur in Endangered species
Fish and Aquatic Invertebrates
The acute RQ > LOG of 0.5
The acute RQ > LOG of 0. 1
The acute RQ >LOC of 0.05
The chronic'RQ > LOG of 1
Acute risk
Risk that may be mitigated through restricted use
Acute effects may occur in Endangered species
Chronic risk and
Chronic effects may occur in Endangered species
Plants
TheRQ>LOCofl .
Acute risk and endangered plants may be affected
                     a.     Ecological Hazard Profile

       The Agency has a robust toxicity database for disulfoton and the two primary degradates,
disulfoton sulfoxide and disulfoton sulfone. Data for birds showed disulfoton to be highly to
very highly toxic for acute oral gavage testing, and highly toxic for subacute dietary testing.
Additionally, the major degradates are moderately to highly toxic to avian species on a dietary
basis.  The effects in avian reproduction testing included decreased adult and hatchling body
weight. The results of small mammal acute oral studies indicated that disulfoton and the sulfone
degradate are very highly toxic. Rat reproductive toxicity studies demonstrated decreased litter
size, lowered pup survival, and decreased pup weight.  Acute contact studies on honey bees
showed disulfoton to be moderately toxic to honey bees, while disulfoton sulfone and sulfoxide
are very highly toxic.                          .

       The laboratory data for freshwater fish indicate that disulfoton is slightly to very highly
toxic in acute tests. The two major degradates,  disulfoton sulfone and sulfoxide are  slightly to
highly toxic to freshwater fish on an acute basis. In a fish early life stage test on fresh water fish,
disulfoton impacted the growth of fry. For freshwater invertebrates, the results indicate that
disulfoton and its degradates are very highly toxic in acute tests, and affects survival, growth,
and the number of young/adult in chronic tests.  Disulfoton is highly toxic to estuarine fish in
acute tests, and in chronic tests, disulfoton impacts the  reproduction, as well as larval growth and
survival.  In testing with estuarine/marine invertebrates, disulfoton is highly to very  highly toxic
in acute tests, and production and survival of young were adversely affected in chronic tests.
                                            41

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                     b.
Risk to Birds and Mammals
       EPA uses models to estimate exposure of animals to disulfoton. For terrestrial birds and
mammals, the Agency estimates peak and average concentrations of pesticide residues over time
on various wildlife food items. Acute risk to birds and mammals, including endangered species,
were predicted for both the granular and liquid formulations. The Agency estimated chronic risk
to birds and mammals from the liquid formulation only, because of the uncertainty in calculating
fate and exposure of the active ingredient as the granules dissipate.

       The Agency's assessment suggests the potential for the liquid formulation to cause acute
and chronic effects to birds and mammals  for uses other than soil injection and in-furrow
applications. An analysis of the use patterns other than soil injection and in-furrow application
indicate that the least risk is from the Texas 24(c) use on cotton and the greatest is from
chemigation to potatoes in the Pacific Northwest. Based on peak exposure estimates, the acute
RQs for birds range from 0.01 to 2.2 and for mammals from 0.05 to 360.  Chronic RQs are
calculated from both peak and average concentrations over time. Therefore, chronic RQs for
birds range from 0.02 (average for granivores) to 19 (peak for herbivores feeding on short grass).
However, the latter RQ declines to 3.4 when based on the average residue value for herbivores
feeding on short grass. Using the same scenarios, chronic RQs range from 0.9 (average for
granivores) to 900 (peak for herbivores feeding on short grass) with a decrease in the latter value
to 158 for average residues in short grass.  In summary, except for soil injection and in-furrow
applications, all use patterns are of concern to the Agency for acute and chronic effects to birds
and mammals, including endangered species.

       Birds and mammals may be exposed to granular pesticides by ingesting granules when
foraging for food or grit. They also may be further exposed by other routes, such as walking on
exposed granules or drinking water contaminated by granules. The Agency's assessment
suggests potential for the granular formulation to cause acute risk to birds from a single
application at or above the lowest application rate of 1.0 Ib ai/A, even when the material is
incorporated. The acute RQs for small birds range from 0.1 for the in-furrow, 1 Ib ai/A rate on
cotton to approximately 75,200 for 78 Ib ai/A, unincorporated spot treatment to Christmas trees.
For the same use patterns, small mammal acute RQs range from 0.3 to 257,300. However, at a
lower application rate of 4.5 Ib ai/A to Christmas trees, the highest avian and mammalian RQs
are reduced to 4,350 and 14,900, respectively. When the Christmas tree use is excluded, RQs for
birds range from 0.1 to 346, and RQs for mammals range from 0.3 to 1184. The highest ELQs are
associated with use of disulfoton on some  commercially grown ornamentals.

       The North Carolina Christmas Tree community has submitted numerous testimonials
emphasizing the ever increasing numbers and diversity of wildlife, including game animals, such
as turkey rearing young amidst the trees, song birds,  rodents, and foxes. Although this
information is intended to suggest there is  little or no negative population impact from disulfoton
use in combination with other pesticides or cultural practices as well, documented surveys or
research is needed for the Agency to corroborate these  conclusions.  Although it is not clear
whether there are population effects, the risk assessments suggests that there is acute risk to
                                          42

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nontarget birds and mammals exposed to disulfoton.

                    c.     Risk to Insects

       Disulfoton is moderately toxic to honey bees and its sulfoxide and sulfone degradates are
highly toxic to bees. A 24-hour residual study on the liquid formulation indicated no toxicity to
honey bees following exposure to alfalfa that had been treated 3 hours earlier at a rate of 1.0 Ib
ai/A.  However, there is some uncertainty as to the risk from higher application rates associated
with aerial and foliar applications, and from later exposure and longer time periods to the more
toxic degradates.

                    d.     Risk to Aquatic Animals

       To assess potential risk to aquatic animals, the Agency uses a computer model to
generate EECs of disulfoton in surface water.  Unlike the drinking water assessment described in
the human health risk assessment section  of this document, the ecological water resource
assessment does not include the index reservoir and percent crop area factor. .The index
reservoir and percent crop area factor represent a drinking water reservoir, not the variety of
aquatic habitats, such as ponds adjacent to treated fields, relevant to a risk assessment for aquatic
animals. Therefore, the EECs used to assess exposure to aquatic animals are not the same as the
DWEC values used to assess human dietary exposure from drinking water sources.

       Freshwater Fish

       The  acute risk level of concern (LOG) to freshwater fish is not exceeded for any use
patterns, with RQs ranging from O.01 to 0.21. When disulfoton is applied at rates greater than
or equal to 1.0 Ib ai/A; the LOG for restricted use is exceeded. Also, the endangered species
LOG is exceeded from either a single, unincorporated application at rates greater than or equal to
0.75 Ib ai/A or 2 or more unincorporated applications at 0.2 Ibs ai/A. The RQs for chronic risk
to freshwater fish are less than or equal to 0.8, and therefore do not exceed the acute LOG.
These RQs do not preclude possible fish kills from the use of disulfoton.  There are three
incident reports offish kills associated with disulfoton use. However, only one of the three
reported fish kills was attributed solely to disulfoton, whereas use of disulfoton and other
pesticides were associated with the other two reported fish kills.

       Freshwater Invertebrates

       The  freshwater invertebrate acute risk is of concern for some disulfoton uses with RQs
ranging from O.01 to 2.1.  Similarly, chronic risk is of concern for nearly all modeled sites and
application regimes with RQs ranging from <0.01 to 149. For both acute and chronic risks to
invertebrates, the highest RQ is based on multiple applications to barley and asparagus. Risks to
endangered species are of concern for all uses, except those where disulfoton  is applied by soil
injection.
                                            43

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       The North Carolina Christmas tree industry provided information that has contributed to
a refinement of the Agency's risk assessment for aquatic organisms from Christmas tree farming.
Specifically, this information indicate limited and localized potential exposure from use of the
granular formulation on Christmas trees, and that any estuarine exposure is precluded.
Moreover, because the primary aquatic sites adjacent to tree farms are streams and not ponds,
disulfoton residues in these streams will be lower and of shorter duration than those that would
have been predicted if standard models had been used. In addition, two rapid assessment macro
invertebrate surveys of streams in the Western region of North Carolina  indicate that when
conservation measures associated with Christmas tree farming are implemented, there may be
only slight, short-term impact to aquatic macro invertebrates from disulfoton use.

       Estuarine/Marine Fish

       The acute risk to estuarine and marine fish is low with RQs for all modeled crops are less
than 0.05. However, there is some uncertainty to these risk estimates due to the limitations of
the pond scenario to predict exposure to marine/estuarine organisms, and that the only species
tested (i.e., Sheepshead minnow) probably does not represent the true range of sensitivity of
marine or estuarine fish.

       Modeling and the results of the fish full life-cycle test indicate that only some of the uses
on barley and asparagus, if located adjacent to estuaries, may be of chronic risk concern with
RQs ranging from 2 to 3.  All other modeled uses had RQs less than or equal to 1 and are not of
concern. In addition to the previously stated uncertainties, other uncertainties concerning
chronic risk are the duration adult fish must be exposed to disulfoton for their reproductive
systems to be affected, and when in their reproductive cycle is the impact occurring. For
example, even if adults are affected after an exposure of only a week, disulfoton residues may
dissipate from an area within several days resulting in little or no chronic risk. Therefore, there
is some uncertainty in acute and chronic risk to estuarine and marine fish.

       Estuarine/Marine Invertebrates

       Similar to the risks to estuarine fish, the same uncertainties associated with exposure
apply to estuarine invertebrates. Most of the modeled scenarios do not exceed the acute or
restricted use criteria for marine and estuarine invertebrates. The RQs range from <0.01 to 0.55,
with the highest RQ reflecting multiple applications of the liquid formulation to barley and
asparagus.  Although nearly all uses result in endangered species risk concerns, currently there
are no marine or estuarine invertebrates listed as endangered. The modeled crop scenarios do
not show the potential for chronic risk to marine and estuarine invertebrates, except for some
uses on cotton, barley, and asparagus, which have RQs between  1.2 and  2.3.
                    e.
                           Risk to Plants
       EPA was unable to conduct a risk assessment for nontarget plants due to a lack of test
data. Nontarget plant testing was not required in the Registration Standard because disulfoton is
                                           44

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not a herbicide. However, because of phytotoxicity statements on the current Di-Syston SEC
label, the Agency is concerned about potential risk to nontarget plants. Given that disulfoton is
applied to growing crops, it is unlikely to result in significant nontarget risks to plants.
Confirmatory data are needed to determine the extent of any risk that may exist. To address this
concern, Tier I plant toxicity data are required (OPPTS Guidelines 850.4100 and 850.4150).

                     f.     Risks to  Endangered Species

       Disulfoton was included in the formal Section 7 consultation with the US Fish and
Wildlife Service (USFWS) under the Endangered Species Act for the  1983 cluster reviews for
corn, cotton, soybean and sorghum. The Biological Opinion, which is the formal USFWS
response, stated that these uses of disulfoton would jeopardize the continued existence of the
valley elderberry longhorn beetle, delta green ground beetle, and the Everglade snail kite.

       Disulfoton was also included in the reinitiated Biological Opinion of 1989 from the
USFWS. In this opinion, the Service found jeopardy to two amphibian species, fifteen species of
freshwater fish, and one bird species from the uses on crops and forests. Terrestrial insects were
not considered hi this opinion. Reasonable and Prudent Alternatives (RPAs) were given for each
jeopardized species. Reasonable and Prudent Measures (RPMs) were also given for 35 non-
jeopardized species to minimize incidental take of these species.  However, the consultations and
findings expressed in the two USFWS  Opinions are based on old  labels and application methods,
less refined risk assessment procedures, and an older approach to consultation, which is currently
being revised through interagency collaboration.

       EPA's current assessment of ecological risks uses both more refined methods to define
ecological risks of pesticides and new data, such as that for spray drift. Therefore, the RPAs and
RPMs in the Biological Opinion(s) may need to be reassessed and modified based on these new
approaches.

       The Agency is currently engaged in a Proactive Conservation Review with FWS and the
National Marine Fisheries Service under section 7(a)(l) of the Endangered Species Act. The
objective of this review is to clarify and develop consistent processes  for endangered species risk
assessments and consultations. Subsequent to the completion of this process, the Agency will
reassess the potential effects of disulfoton use to Federally listed threatened and endangered
species. At that time, the Agency will  also consider any regulatory changes recommended in the
IRED that are being implemented. Until; such time as this analysis is completed, the overall
environmental effects mitigation strategy articulated in this document will serve as interim
protection measures to reduce the likelihood that endangered and threatened species may be
exposed to disulfoton at levels of concern.

       Recently, the Agency completed a comprehensive preliminary assessment for potential
risk to endangered birds and mammals from disulfoton use.  Because risks to aquatic species
were addressed in the 1989 Biological  Opinion, they were not addressed in this assessment. To
conduct this assessment, the Agency used information from the Agency's OPP Endangered
                                           45

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r
                   Species database, which compares the USDA's Agriculture Census information on crop and
                   county overlap with USFWS information on the location of endangered species to the county
                   level. The results of this assessment are described in detail in the following documents:
                   Endangered Species Addendum to EFED's Disulfoton Science Chapter, dated January 24, 2002,
                   and Puerto Rican Plain Pigeon and Disulfoton, dated April 23, 2002. This document is
                   available in the public docket and on the internet. This comparison included the use sites and
                   regions identified below, because they comprise the majority of soil surface or foliar use of
                   disulfoton that could potentially affect endangered species that are exposed to such applications.
                   For purposes of endangered and threatened species evaluations, risks below EPA's  criteria of
                   concern are considered to be a "no effect." Therefore, a finding of "no concern for risk" is
                   equivalent to a "no effect" for the species.

                                 Asparagus— foliar application of liquid in CA and WA
                                 Barley - foliar application of liquid in CO, ID, MT and WA
                          •      Christmas trees — spot broadcast of granular in NC
                                 Coffee — spot broadcast of granular in Puerto Rico
                                 Cotton — m-furrow application of granular and liquid in LA, MO, OK, NC and
                                 SC
                          •      Potatoes — foliar application of liquid in ID and WA
                                 Wheat — foliar application of liquid in KY

                          The results of a screen of this information and other correspondence are as follows:

                   •      Puerto Rico has no endangered mammals; however, two endangered ground feeding
                          birds, the Yellow shouldered blackbird and Puerto Rican plain pigeon, could potentially
                          consume granules as grit. The Agency's screening level analysis indicated that the Puerto
                          Rican plain pigeon once lived in municipalities where coffee was grown. This is no
                          longer the case.  At present, neither of these avian species utilize coffee plantations for
                          habitat or occur near coffee plantations.  Therefore, there is no concern for risk for these
                          two species.

                   •      Concerning disulfoton use on barley, only the Mountain plover (a species that is not
                          currently listed as endangered, but is proposed to be listed) would be potentially at risk
                          from ingesting soil invertebrates in soil that has been sprayed directly or received wash
                          off from the foliage.  However, the residues would likely be lower on these soil
                          invertebrates than what would be required to cause an adverse effect in the Mountain
                          plover. Like other plovers, the Mountain plover prefers unvegetated, open areas;
                          therefore, if the barley is taller than 3 inches before it is sprayed, there is little likelihood
                          the bird would utilize the field.  Since disulfoton is. not used until later in the growing
                          season, after the plants are taller, it is exceedingly unlikely that Mountain plovers will be
                          utilizing  the treated fields. Therefore, there is no concern for risk to Mountain plovers.
                          There are 14 counties in Colorado and 17 counties in Montana where both barley is
                          grown and the bird may occur.
                                                               46

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There is no county overlap between asparagus grown in Washington and California, and
endangered species.

Carnivorous birds (i.e., owls and eagles) and mammals (i.e., Black-footed ferret, grizzly,
Gray wolf and Red wolf) are not at risk, based on secondary poisoning studies on
representatives from these two classes.  Therefore, there is no concern for risk to these
species.

Bats would not be  at risk as they would only be feeding on flying insects from dusk to
dawn.  Assuming spraying does not occur at those times, bats would not be at risk.  Also,
bats would not be exposed to granules.

Concerning Christmas trees grown in North Carolina, in addition to some of the
organisms stated above, there are several birds and mammals which, although they could
be in or around the vicinity of Christmas tree plantations, are not considered at risk
especially from granules. Specifically, because the Wood stork feeds on fish, and the
Piping plover resides on sand bars and feeds on aquatic invertebrates, there is no concern
for risk to these species.

Concerning Christmas trees grown in North Carolina, because disulfoton is systemic,
there is a slight potential for low, undetermined dietary exposure to the Northern flying
squirrel and the Red-cockaded woodpecker.  In addition to lichens and fungi, the squirrel
consumes insects,  buds, and seeds. However as the squirrel is a cavity nester, it prefers
deciduous trees to conifers in the same proximity. Its habitat is taller trees, because it has
adapted to gliding. The woodpecker requires old living pine trees (at least 60 years) in
which to make cavities, and they feed on insects found under the bark in conifers where
the trunk is larger  and more accessible than in Christmas trees. Therefore, disulfoton use
poses no concern for risk to these species.

Concerning use  sites other than Christmas trees and coffee, the following are forest
dwellers and/or are not associated with agricultural sites: Northern Idaho Ground
squirrel; Marbled murrelet (feeds on fish); Woodland caribou; Brown pelican (feeds on
fish); Red-cockaded woodpecker; Carolina northern flying squirrel; Treble's meadow
jumping mouse (resides in high elevation meadows); and Wood stork (feeds on fish).
Hence, disulfoton  use poses no concern for risk to these species.

Concerning the use sites other than Christmas trees and coffee, disulfoton poses no
concern for risk to the following species: the Whooping crane feeds on aquatic
invertebrates; the Black capped vireo resides in scrub areas and feeds  on flying insects;
and the Piping plover resides principally on sand bars and feeds on aquatic invertebrates.

              g.     Ecological Incident Reports

Several reports of wildlife poisonings are associated with disulfoton.  These poisoning
                                     47

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 incidents are summarized in Table 13.
 Table 13.  Chronological List of Ecological Incidents for Disulfoton
Date
6/12/95
6/14/94
1/24/94
6/18/93
6/22/91
4/26/91
Misuse?
unknown
unknown
unknown
No
unknown
unknown
Incident Description
Johnston County, NC: Fish kill occurred in commercial fish pond. Crop fields nearby
treated with pesticides. Water, soil and vegetation samples analyzed for a variety of
pesticides. Disulfoton, as well as several other pesticides, was found at 0.2-2.5 ppm in
vegetation samples. Possible certainty index for disulfoton. (Incident Report No.
1003826-002).
Arapahoe, CO: Fish kill following application of Di-Syston EC to wheat just before
heavy rain. Water samples contained disulfoton sulfoxide at 29.5-48.7 ppb and
disulfoton sulfone at 0.0199-0.214 ppb. (Incident Report No. 1001 167r001).
Puerto Rico: 6 grackles fell dead from a tree in a yard of private residence. Dead heron
and owl also found in vicinity. Use site and method not reported. Birds had depressed
acetyl cholinesterase. Analysis of GI contents of a grackles showed disulfoton at 2.37
ppm wet weight. Highly probable certainty index for disulfoton. (Incident Report No.
1003966-004).
Young County,TX: 1 8 Swainsons hawks dead, 1 severely disabled in a cotton field.
Cotton seed had been treated with disulfoton prior to planting, -10 days before the birds
were discovered. No additional applications of OP or carbamate pesticides made in
vicinity of field. Autopsies showed no trauma or disease. Lab analysis showed insect
material in GI tracts; this material contained disulfoton (~7 ppm); no other OP or
carbamate insecticides were present. Hawks fed on insects, which had been feeding on
the young cotton plants, which contained disulfoton residues. (L. Lybn, Div. of
Environmental Contaminants, U.S. Fish and Wildlife Service, Arlington, VA.)
Onslow County, NC: Fish kill in pond at private residence. Pond received runoff from
neighboring tobacco field; pondwater analysis showed disulfoton and several other
pesticides, including endosulfan. Disulfoton sulfoxide found in water at 0.32 ppb.
Endosulfan had highest concentration (1.2 (tg/L), and is toxic to fish, but disulfoton
cannot be ruled out as a possible cause of death. No tissue analysis. Possible certainty
index for disulfoton. (Incident Report No. B00002 1 6-025).
Sussex County, DE: 9 American robins dead following application of granular
disulfoton at tree nursery. Corn and soybeans also in vicinity. No laboratory analysis.
Probable certainty index for disulfoton. (Incident Report No. 1000 1 16-003).
       c.
Alternatives and Benefits
              1.
       Alternatives
       Only a limited number of alternative pesticides are available for controlling aphids on
agricultural crops. Some pesticides, such as lambda-cyhalothrin have some potential as a
disulfoton alternative; however, they also act on beneficial, predatory insects as well as targeted
insect pests, and can not be used in Integrated Pest Management (IPM) Programs.  Disulfoton
can be used in IPM programs because its systemic activity does not target beneficial insects. In
addition, lambda-cyhalothrin is a member of the chemical group synthetic pyrethroids, which are
prone to resistance problems. Imidacloprid is a potential alternative when used at-plant for
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short-lived crops, but this chemical loses its efficacy after 4-5 weeks. Also, imidacloprid is
currently more expensive than disulfoton.  Other alternatives are other OPs which are also under
review. Alternatives for crops representing primary uses are summarized in Table 14.

Table 14.  Registered Alternatives to Disulfoton for Agricultural Crops*
Crop/Target Pest
Asparagus/European Asparagus Aphid
Barley/Russian Wheat Aphid, other
aphids and thrips
Cotton/Thrips
Lima Beans/Thrips
Snap Beans/Potato Leafhopper, Thrips
Broccoli, Cabbage, Cauliflower &
Brussel Sprouts/Cabbage Aphid, other
aphids
Bell and Chili Peppers/Green Peach
Aphid, Symphylan
Lettuce/Lettuce Root Aphid
Potatoes/Green Peach Aphid, Potato
Aphid
Radish (grown for seed)/Cabbage Aphid,
Turnip Aphid
Wheat/Russian Wheat Aphid
Ornamentals, including shrubs, trees,
flowers, groundcover, and potted plants
(field or nursery stock)
Coffee Trees/Leafrniner
Christmas Trees (Firs)
Alternative Pesticide (Chemical Class)
Chlorpyrifos and dimethoate (OPs)
Imidacloprid (Chloronicotinyl), Lambda cyhalothrin (Synthetic
pyrethroid, Section 3 registration pending) • - •
Phorate, Aldicarb (OPs)
Acephate (OP)
Carbaryl (carbamate), acephate, methomyl, or dimethoate (OPs)
Chlorpyrifos, Dimethoate, Oxydemeton-methyl (OPs), Imidacloprid
(Chloronicotinyl)
Chlorpyrifos, Diazinon, Dimethoate, Malathion, Oxydemeton-
methyl (OPs), Imidacloprid (Chloronicotinyl), Pyrethroids
Imidacloprid (Chloronicotinyl)
Methamidophos, Dimethoate, Malathion (OPs), Pymetrozine
(Triazine), Imidacloprid, Thiomethoxam (Chloronicotinyls)
Pirimicarb (Carbamate), Chlorpyrifos (OP), Pymetrozine (Triazine)
Chlorpyrifos, Dimethoate, Malathion, Phorate (OPs), Endosulfan
(chlorinated hydrocarbon), Imidacloprid (Chloronicotinyl),
Lambda-cyhalothrin (Synthetic pyrethroid), Methomyl (carbamate),
Pyrethrins
Imidacloprid, Hexythiazox, Bifenazate, Abamectin, Acephate,
Chlorpyrifos (OP), Bifenthrin
Aldicarb, Azadirachtin (no residual activity)
Chlorpyrifos (OP)
* Not all alternatives are efficacious; see the following text for details.

              2.      Benefits

       The Agency has assessed the benefits of a number of registered uses of disulfoton,
including asparagus, barley and wheat, snap and lima beans, cabbage, cole crops, cotton, lettuce,
peanuts, peppers, potatoes, radish grown for seed, coffee, ornamentals, and Christmas trees.
Because occupation risks were low for disulfoton use on clover grown for seed, benefits
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information associated with this use was not collected. A summary of the Agency's benefits
findings is presented below; for more information, see the following documents: Asparagus
Benefits Assessment for Disulfoton, September 11, 2001; Benefits ofDisulfoton on Selected
Vegetable Crops and Cotton, September 27, 2001; Benefits Assessment for Disulfoton Use on
Potatoes and Radish Seed, September 28, 2001; Use ofDisulfoton on Bell and Pimento Peppers,
November 3, 2001; Cursory Assessment ofDisulfoton Use in Coffee in Puerto Rico, November
26, 2001; Response to Questions Concerning Disulfoton Posed by Special Review and
Reregistration Division [Regarding Ornamentals], December  17, 2001; and Cursory Analysis of
Disulfoton Use on Fraser Fir Christmas Trees in Western North Carolina, July 9, 2002. All of
these documents are available in the public docket and on the internet.

       Asparagus

       Liquid disulfoton is used on asparagus in Arizona, California, North Carolina, Oregon,
and Washington. These states have  Special Local Need (SLN) registrations under FIFRA
Section 24(c). Most disulfoton use on asparagus is in California and Washington; these two
states account for 96% of use on this crop. In Washington, 50% of the asparagus crop is treated
with disulfoton, and in California, 70% of the crop is treated. Growers in these states have a
critical need for Di-Syston 8E. The  target pest is the European asparagus aphid, which severely
damages  asparagus plants and weakens the crowns.  Asparagus is a high value perennial crop
grown for 10 years or more. The asparagus plants rely on energy produced by vegetative growth
and stored in the root crowns to produce the shoots that are harvested the following year.
Registered pesticide alternatives are chlorpyrifos and dimethoate, but secondary aphid flare ups
occur with chlorpyrifos, and both chlorpyrifos and dimethoate  have a short residual half-life.
Therefore, none of these alternatives is considered viable. Disulfoton is long lived and spares
beneficial insects, preventing secondary flare ups of insect pests.

       Disulfoton is applied once or twice a year during the fern stage (after harvest) at a rate of
2 Ib ai/A. At this point in the asparagus life cycle, there are no activities (other than pest control)
requiring the presence of workers in the fields. Vegetation is up to 5 feet high and wide at this
stage of the life cycle, so the rows are virtually impassible.  Growers have difficulty getting
application equipment into the fields and aerial application  is the most feasible method of
pesticide application at this stage. The liquid formulation is needed because of its translaminar
action; liquid is quickly taken up by foliage where it penetrates the outermost cell layers and
spreads out, providing aphid control. Even though the granular also has systemic action, it is not
taken up by asparagus roots quickly  enough to control aphids.  Therefore, the granular
formulation is not registered for use on asparagus.

       In Washington, 98% of disulfoton used on asparagus is applied aerially for the reason
stated above. In California, 65% of disulfoton is applied aerially. The remaining 35% of
disulfoton used on asparagus in California is applied by groundboom to the field edges to stave
off aphid infestation. Based on the 1977 Agriculture Census from the USD A National
Agricultural Statistics Service (NASS), the overall average  asparagus farm size in California is
219 acres. Also, for asparagus farms in Washington, no farm is greater than 300 acres, and the
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average asparagus farm size is 62 acres.  Other sources indicate that the maximum area that can
be aerially treated in a day is about 75-150 acres in Washington, and about 150-200 acres in
California.

       Barley and Wlieat

       Liquid disulfoton is applied by air for late-season control of aphids on barley and wheat
as the seed head nears maturity. Nationally, < 1% of crop is treated for both barley and wheat,
with most use on malting barley in the states of Idaho, Montana, Colorado, Wyoming, and
Washington. Disulfoton use on wheat is limited to a few states, where Kentucky is reported to
have the greatest use.  The potential alternative for aphid control on these crops is lambda
cyhalothrin (Warrior®), which is scheduled for a FIFRA Section 3 registration in 2002.
Warrior® is already available in some states as a FIFRA Section 18 registration. There are
concerns that, because Warrior® is a pyrethroid, aphids may develop resistence, and a secondary
control for resistance .management may be needed.

       Nearly 50% of all barley produced in the US is marketed as malting barley, which
receives a premium price over regular barley.  Disulfoton is used primarily on malting barley to
control aphids, especially the Russian wheat aphid, to ensure plumpness and fullness of the
barley grain. Aphid infestations in barley fields are localized and sporadic, and require
immediate control to prevent spreading. Aphid damage to malting barley can result in up to a
50% loss in crop revenue. Approximately 3% of all acres planted in barley experience aphid
infestation. In these cases, the liquid formulation of disulfoton is  generally applied aerially to
localized pockets of aphid infestation. Imidacloprid is registered for late-season control aphids
in malting barley, but does not appear to be as effective as disulfoton in controlling aphids by
foliar application. However, lambda cyhalothrin (Warrior®), which is  expected to be available
as a Section 3 registration within the next year, is considered to be the product of choice, because
it is recognized as a safer alternative to disulfoton, especially for aerial  application due to drift
concerns to nearby inhabited areas and adjacent fields. Disulfoton use  has been declining in
recent years due to the use of Warrior® as the primary tool for aphid control in the states where
it is currently used under FIFRA Section 18 registrations.

       Disulfoton is used on wheat to control the Barley Yellow Dwarf Virus, which is
transmitted by aphids. Ground applications of the liquid are used late-season. In Kentucky, the
state with the greatest use, most disulfoton is applied by custom applicators. Lambda
cyhalothrin is the main alternative for wheat, which may be more expensive than disulfoton.
Other registered alternatives include chlorpyrifos, malathion, methomyl, and pyrethrins.

       Beans, Lima and Snap

       Growers use both liquid and granular formulations of disulfoton for lima and snap beans.
Most use on lima beans-is in Georgia, with 20-30% of crop treated. Disulfoton is applied at-
plant to control thrips. Acephate is  currently the only viable alternative for lima beans, and
foliar application would be used to control thrips.
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       Use on snap beans is sporadic in states that produce snap beans and use is declining.
Disulfoton is applied at-plant to control potato leaf hopper, an intermittent pest that does not
require control every year.  Some processing companies will not purchase snap beans treated
with a systemic insecticide unless a pest problem requiring such treatment is substantiated by
extension agents. Alternatives to disulfoton on snap beans include acephate, carbaryl,
methomyl, or dimethoate.

       Cabbage

       Both the liquid and granular formulations are registered for use on cabbage for aphid
control. The liquid formulation is shank injected, and the granular formulation is applied as a
soil incorporated band or side-dressing. According to USDA NASS data for 2000, 3,400 Ib ai of
disulfoton was applied that year, with 3% of all cabbage grown nationally being treated with
disulfoton In California, from 1997 to 1999, an average of 3,117 Ibs ai of disulfoton was
applied to cabbage, primarily in Ventura County. The major advantage of disulfoton over
imidacloprid is its long residual activity, which protects cabbage plants for the entire season.

       Cole Crops  (Broccoli, Brussels Sprouts, Cauliflower)

       Both the liquid and  granular formulations of disulfoton are registered for use on cole
crops. The liquid formulation is used exclusively in California's Salinas Valley, whereas the
granular formulation is used nationally, wherever cole crops are grown.  Liquid disulfoton is
applied by shank injection,  and is used as a rescue remedy to control cabbage and green peach
aphids. Within the Salinas Valley, Monterey County appears to be where the predominant use of
the liquid formulation of disulfoton is used. Usage data from 1997 to 1999 for Monterey
County, California indicate that as much as 60%  of broccoli, 87% of Brussels sprouts, and 52%
of cauliflower that was grown was treated with disulfoton. Nationally, less than 3% of the crop
was  treated in 2000.

       Registered alternatives to disulfoton on cole crops include imidacloprid and the  OP
pesticides oxydemeton-methyl, dimethoate, and chlorpyrifos.  Currently, imidacloprid is applied
at-plant, but it does not control the cabbage aphid throughout the entire growing season due to its
limited period of residual effectiveness. Imidacloprid is not effective as a foliar application.
Chlorpyrifos is toxic to beneficial insects and also causes phytotdxicity at the high rates required
to control the cabbage aphid.

       Cotton

       Liquid disulfoton is used as a safener to protect cotton seedlings from the effects of the
herbicide clomazone (Command®), which is the  herbicide of choice to control velvet leaf,
primrose, morning glory, and wild poinsettia. The liquid formulation is preferred, because it
appears to be both a better safener and more effective than the granular formulation at protecting
the cotton seedlings against thrips. Alternatives include phorate and aldicarb.  However,
phorate, which is applied as a granular formulation, is not as efficacious against thrips.  Aldicarb
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is very effective against thrips, but does not act as a safener.

       Use of disulfoton in cotton has been declining and this decline has been attributed to the
introduction of genetically modified glyphosate tolerant (RoundUp-Ready®) cotton. However,
the percentage of acreage that can be planted with glyphosate tolerant cotton is limited.
Therefore, disulfoton is still important in areas that use clomazone for weed control.  Most use is
in Louisiana, Missouri, Mississippi, and Texas, with some use in Alabama, Arkansas, Georgia,
Florida, Tennessee, the Carolinas, and Virginia.

       Lettuce

       Only the liquid formulation of disulfoton is registered for use on lettuce.  Disulfoton is
applied preplanting or at planting by banding, sometimes in combination with fertilizer or
herbicide. Most iceberg lettuce (96%) and leaf lettuce (97%) grown in the United States is
produced in California and Arizona. California treated about 2-3% of the iceberg and 1% of the
leaf lettuce acreage with disulfoton hi 1999. USDA reported no use of disulfoton in Arizona for
the year 2000.                            ,

       Disulfoton use on lettuce in California is mostly limited to the Salinas Valley, which
includes Monterey County. Approximately 59% of the total amount of disulfoton that is used on
head lettuce is used in Monterey County, and 57% of the total amount of disulfoton that is used
on leaf lettuce is also used in Monterey  County.  Disulfoton is used in this area primarily  to
control the lettuce root aphid, which is harbored in Lombardy poplars, a popular ornamental,
when other methods fail.  California has been actively removing Lombardy poplar trees so that
the lettuce root aphid does not have an alternate host. If disulfoton is not used, the main
pesticide alternative is imidacloprid, which has short residual activity and therefore  does not
provide adequate control.

       Peanuts

       Only the granular formulation is registered on peanuts.  Thrips are the main target pest,
but disulfoton is also used for aphid control. In the year 2000,  disulfoton was used in Alabama,
Georgia, North Carolina, and Oklahoma. Disulfoton is applied in-furrow or as a soil
incorporated side-dressing to control thrips and aphids. Since the time the risk assessment was
prepared, Bayer, the technical registrant, had reduced the maximum application rate for the
Section 3 registration from 2 Ibs ai/A to 1 Ib ai/A.  Disulfoton is applied once a year at a rate of 1
Ib ai/A, except in North Carolina where an SLN registration permits two applications for  a
seasonal maximum of 2 Ibs ai/A.

       Peppers

       Disulfoton is used on chili, bell, and pimento peppers to control the green peach aphid
and the garden symphylan, a non-insect pest. Most disulfoton use on peppers is in California
and New Mexico.  Aphids, especially the green peach aphid, transmit mosaic viruses which kill
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pepper plants. The green peach aphid has developed insecticide resistance and is difficult to
manage. The green peach aphid prefers shade-grown plants, such as those in the Salinas Valley.

       Both liquid and granular formulations are registered for use on peppers.  The liquid
formulation is registered only in California as a Section 24(c) SLN registration.  The liquid is
shank injected when the plants are 4-5 weeks old and the aphids have exceeded the economic
threshold. There is a FIFRA Section 3 registration for the granular, which is used outside
California.

       Registered alternatives to disulfoton on peppers include irnidacloprid, chlorpyrifos,
diazinon, dimethoate, malathion, oxydemeton methyl, and pyrethrins.  Neither diazinon nor
malathion is effective against the green peach aphid. Dimethoate is an inexpensive, frequently
used alternative, but it is no longer effective for aphid control in some areas of California and
New Mexico. Chlorpyrifos harms beneficial insects and has been shown to cause phytotoxicity
at the rates necessary for  aphid control. Although oxydemeton methyl is registered, it is not
recommended for use on  cole crops. Use of irnidacloprid is increasing, but it does not provide
effective control in some parts of California.  Pyrethroids are not often used because they are not
compatible with integrated pest management (IPM) programs.

       Potatoes

       Both the liquid and granular formulations of disulfoton are registered for use on potatoes
to control aphids. Based on 1987-1998 usage data, an average of approximately 58,000 acres of
potatoes were treated annually, with an average of 4% of the nations potato acreage treated with
disulfoton. The liquid is  used mainly in the Pacific Northwest (PNW) (i.e., Oregon, Idaho,
Washington, and Utah), where it is predominantly applied either aerially or by chemigation
(sprinkler irrigation) as an alternative to methamidophos (Monitor®).  The liquid is used for late-
season aphids control in sensitive areas where growers cannot aerially apply Monitor®.  The
granular formulation appears to be used mostly outside the PNW, where it is applied to the soil
and incorporated.

       As mentioned above, the liquid formulation is applied in the PNW by overhead sprinkler
irrigation to control aphids.  According to the National Potato Council, growers apply disulfoton
by chemigation (sprinkler irrigation) when methamidophos (Monitor®), the product of choice,
cannot be aerially applied, due to weather conditions or lack of availability of aerial applicators,
or for potatoes that are grown next to sensitive areas, where aerial application is an issue.
However, the Agency believes that there are a number of other alternative products that are
available'to control aphids that can be chemigated, such as pymetrozine (Fulfill) and
thiamethoxam  (Actara), which seem promising, although growers are learning how to use these
new chemistries. Further, methamidophos is labeled for application by chemigation.
Imidacloprid can also be applied at-plant for control of early to mid season aphid and Colorado
potato beetle infestations.

       Although growers may view disulfoton as the only cost-effective, reliable, and consistent
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aphid material that can be chemigated, the Agency believes the available alternatives are
adequate to achieve effective aphid control. Both pymetrozine and thiomethoxam can be applied
by chemigation and are effective at late-season aphid control.  Further, pymetrozine is less
expensive than disulfoton. The average cost of post-emergence foliar treatment for potatoes is
about $16.00 per acre for disulfoton and $13.00 per acre for pymetrozine. No data were
available for thiomethoxam. Because these two chemicals are relatively new, they have yet to be
widely used or accepted by growers; however, efficacy field trials show promising results for
aphid control.

       In summary, the Agency does not believe that disulfoton is critical to potato growers,
because use of disulfoton on potatoes is declining and new, effective alternatives that can be
applied by chemigation, the application method that is most critical to growers in the PNW, are
now available.

       Radish Grown for Seed

       Both the  liquid and granular formulations are registered for use on radish grown for seed
in Washington only through a 24(c) SLN registration. As part of this registration, disulfoton use
is limited to the Columbia River Basin in Washington to control cabbage and turnip aphids,
which cause premature plant death and crop loss. Both formulations are applied to the soil and
are either shank injected or soil incorporated. In the year 2000, only about 635 acres total of this
crop was produced. Even though it is a minor crop, it is an economically important crop for
producers in the  Columbia River Basin.

       The only registered alternatives available to growers are pirimicarb, chlorpyrifos, and
pymetrozine. Pirimicarb is used solely to control late-season aphid infestations; chlorpyrifos
cannot be used during bloom when aphids can occur; and pymetrozine is more expensive than
disulfoton and does not provide good lower canopy control. Also, disulfoton is  also
advantageous because it allows predatory and parasitic insects to develop in the seed radish
fields.

       Coffee Trees

       Granular disulfoton is registered in Puerto Rico to control leafminers, which can cause
up to a 40% reduction in yield in the coffee crop, valued at approximately $30 million.  In the
year 2000, about 15% of acreage planted in coffee was treated with disulfoton. The current
application rate of 8.3 Ibs a.i./A is supported by efficacy data.  Government sponsored custom
applicators broadcast disulfoton by hand, with a bucket and spoon. Growers and agricultural
extension staff appear to be receptive to alternative application methods involving closed
systems.  At present, the only viable alternative is aldicarb. Azadirachtin, a registered
alternative, does  not have the residual activity needed to control leafminers.
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       Christinas Trees

       DIsulfoton is used on Christmas trees, on Fraser, Balsam, and other firs, in 16 states
including Oregon, Michigan, Washington, Ohio, and Wisconsin. The greatest use is in western
North Carolina, where 1,600 growers produced 34-million trees on 24,000 acres in 1996.  Two-
thirds of North Carolina Christmas tree farms are small, with 10 acres or less in production.

       Disulfoton is used to control balsam twig aphid and spruce spider mite, widespread and
perennial pests. Disulfoton is used in conjunction with chlorpyrifos and esfenvalerate.
Disulfoton is applied at bud break in early spring, followed by foliar applications of chlorpyrifos
and'esfenvalerate.  Disulfoton and esfenvalerate may be alternated if resistance management
becomes an issue.  Chlorpyrifos and esfenvalerate must be foliarly-applied by a commercial
applicator by mist blower or high-powered hose sprayer. Further, the chlorpyrifos foliar spray is
phytotoxic in some situations.  Foliar applications are problematic, because they are usually
uneven, which significantly affects efficacy. Esfenvalerate has the advantage of also controlling
balsam wooly adelgid to a limited extent, but the disadvantage of allowing spider mite
populations to increase.  Disulfoton control of both balsam twig aphid and spruce spider rnite is
systemic, conserving beneficial insect predators.

       Christmas trees are a perennial crop with a 6-10 year growth cycle. The target pests can
cause significant cosmetic damage in the last year or two before harvest, leading to a significant
decrease in crop value and/or crop loss.  Value was $78 million in 1996 and $122 million in
1999.  Fraser firs represented 27% of all US grown Christmas trees sold in 1999.  Impacts are
greatest near harvest when trees may be downgraded for cosmetic damage. Without disulfoton,
a significant amount of loss from downgrading and extra application costs would be sustained
over the region annually. Disulfoton is important in resistance management and conserving
beneficial insects.  Disulfoton is an important component of the Fraser fir integrated pest
management (IPM) program developed by the North Carolina Agricultural Extension Service
and North Carolina State University.  The Agency concludes that disulfoton use on Christmas
trees, especially Fraser firs  grown in the mountains of western North Carolina, is critical to
growers.

       Commercially Grown Ornamentals

       The granular formulation is registered for use on shrubs, trees, flowers, and ground
covers (field or nursery stock) to control a variety of pests, including aphids, thrips, lacebugs,
and mites. The current label rate is up to 7.5 grams per foot of shrub height or 2.5 oz per trunk
diameter of trees, which is extrapolated to 109 Ibs ai/A. The nursery industry claims to need a
ininimurn rate of 13 Ibs ai/A; however, EPA can not substantiate this rate for all uses. Available
data show use of ^6 Ibs ai/A in California and 13 Ibs ai/A on hollies and birches in New York,
with 2% of the production area treated. Disulfoton is applied by broadcast or soil injection.
According to preliminary data from a USD A NASS floriculture survey, very little disulfoton is
used on ornamentals. Of 4,000 operations surveyed, only 22 operations reported using
disulfoton. After extensive research and contacting all major stakeholders, including the
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American Nursery and Landscape Association, Rutgers's IR4, and state departments of
agriculture, EPA has found only small pockets of use. Further, many agricultural extension
agents who work with ornamentals do not recommend the use of disulfoton. Alternatives are
available, including imidacloprid, abamectin, aeephate, bifenthrin, and chlorpyrifos.  Therefore,
the Agency concludes that on a national basis, there is not a critical need for disulfoton use on
ornamentals grown for field or nursery stock.
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IV.    Interim Risk Management and Reregistration Decision

       A.     Determination of Interim Reregistration Eligibility

       Section 4(g)(2)(A) of FIFRA calls for the Agency to determine, after submissions of
relevant data concerning an active ingredient, whether products containing the active ingredient
are eligible for reregistration. The Agency has previously identified and required the submission
of the generic (i.e., an active ingredient specific) data required to support reregistration of
products containing disulfoton active ingredient.                                        '

       The Agency has completed its assessment of the occupational and ecological risks
associated with the use of pesticides containing the active ingredient disulfoton, as well as a
disulfoton-specific dietary risk assessment that has not considered the cumulative effects of OPs
as a class. Based on a review of these data and public comments on the Agency's assessments
for the active ingredient disulfoton, EPA has sufficient information on the human health and
ecological effects of disulfoton to make interim decisions  as part of the tolerance reassessment
process under FFDCA and reregistration under FIFRA, as amended by FQPA. The Agency has
determined that products containing disulfoton are eligible for reregistration provided that (i)
current data gaps and additional data needs are addressed; (ii) the risk mitigation measures
outlined in this document are adopted, and label amendments are made to reflect these measures,
including the phase out of disulfoton use on barley, wheat, potatoes, and ornamentals by June
2005; (iii) cumulative risks  considered for the OPs support a final reregistration eligibility
decision; and tolerances are issued (if appropriate) for commodities lacking tolerances as
identified in the tolerance summary.

       As part of the Agency's ongoing process to review and take the necessary risk reduction
measures as required by FQPA, on December 4, 2001, EPA released the preliminary cumulative
risk assessment for OP pesticides for public comment. That assessment is based on evaluation of
the potential exposure of 31 total OP pesticides from eating food, drinking water, and residential
sources.  The assessment also takes into account EPA's past regulatory actions on various
pesticides, such as eliminating uses. Continuing the effort to ensure transparency of decision
processes, EPA conducted a technical briefing and presented the assessment to the Scientific
Advisory Panel for peer review and comment.  The Agency intends to release a revised
cumulative risk assessment during the summer of 2002.

       Although the Agency has not yet considered its final cumulative risk assessment for the
OPs, the Agency is issuing this interim decision now in order to identify risk reduction measures
that are necessary to support continued use of disulfoton. Based on its current evaluation of
disulfoton alone, the Agency has determined that disulfoton products, unless labeled and used as
specified in this document, would present risks inconsistent with FIFRA.  Accordingly, should a
registrant fail to implement any of the risk mitigation measures identified hi this document, the
Agency may take regulatory action to address the risk concerns from use  of disulfoton.

       At the time that the cumulative assessment is considered, the Agency will address any
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outstanding risk concerns.  For disulfoton, if all changes outlined in this document are
incorporated into the labels, then all currently identified risks will be mitigated. But, because
this is an IRED, the Agency may take further actions, if warranted, to finalize the RED for
disulfoton after considering the cumulative risk of the OP class. Such an incremental approach
to the reregistration process is consistent with the Agency's goal of improving the transparency
of the reregistration and tolerance reassessment processes. By evaluating each OP pesticide in
turn and identifying appropriate risk reduction measures, the Agency is addressing the risks from
the OPs in as timely a manner as possible.

       Because the Agency has not yet considered the cumulative risks  for the OPs, this IRED
does not fully satisfy the reassessment requirement for existing disulfoton food residue
tolerances as called for by FQPA. When the Agency has considered cumulative risks, disulfoton
tolerances will be reassessed in that light. At that time, the Agency will reassess disulfoton
along with the other OP pesticides to complete the FQPA requirements and make a final
reregistration eligibility determination. By publishing this IRED and requesting mitigation
measures now for the individual chemical disulfoton, the Agency is not  deferring or postponing
FQPA requirements; rather, EPA is taking steps to assure that uses which exceed FIFRA's
unreasonable risk standard do not remain on the label indefinitely, pending completion of an
assessment required under the FQPA. This  decision does not preclude the Agency from making
further FIFRA or FQPA determinations and tolerance-related ralemakings that may be required
on this pesticide or any other in the future. If the Agency determines, before finalizing the RED,
that any of the determinations described in this IRED are no longer appropriate, the Agency will
pursue appropriate  action, including but not limited to, reconsideration of any portion of this
IRED.

       Label changes for disulfoton are described in Section V. Appendix B identifies the
generic data the Agency reviewed as part of its IRED of disulfoton, and lists the studies that the
Agency found acceptable.

       B.     Summary of Phase 5 Comments

       When making its IRED for disulfoton, the Agency took into account all comments
received during Phase 5 of the OP Public Participation Process.  Comments were received from
the technical registrant, Bayer Corporation; the American Landscape and Nursery Association;
the California Asparagus Commission; the American Bird Conservancy; North Carolina
Cooperative Extension Service; and from numerous individual North Carolina Christmas tree
growers. A brief summary of the comments is provided below. All of the submitted comments
in their entirety are available in the public docket, and the Agency's response to the comments is
also available in the docket and on the internet.,

       A number of Christmas tree growers in North Carolina provided comments relating to
their use practices, farm sizes, the number of acres they treat with disulfoton, the frequency of
their applications, the number of workers involved in disulfoton application activities, and the
length of time it takes to make the pesticide  applications.  The Agency has validated much of this
                                          59

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information and used it to revise the risk assessments for disulfoton.

       The North Carolina Cooperative Extension Service commented on both the worker and
ecological risks assessments for disulfoton and provided extensive information on disulfoton use,
cultural practices, and impacts of disulfoton on stream fauna. EPA has considered this
information in both the revised risk assessment and the regulatory decision for disulfoton.

       The American Nursery and Landscape Association commented on pest management
issues in the nursery industry.  Disulfoton allows nurserymen to use less pesticide overall
because disulfoton is compatible with Integrated Pest Management (IPM). The American
Nursery and Landscape Association urges EPA to allow time for  development of data to refine
the worker risk assessment. The California Asparagus Commission commented on the use of
disulfoton in asparagus and provided information about cultural practices. EPA has considered
information on integrated crop management, cultural practices, and feasibility of various
mitigation measures in its interim regulatory decision for disulfoton.

       The American Bird Conservancy recommended elimination of all aerial applications as
well as foliar sprays by ground equipment in wheat and sorghum. The American Bird
Conservancy also recommended use of a less friable non-clay based granular formulation.  EPA
has considered these suggestions in the risk mitigation strategy for disulfoton.

       Bayer Corporation, the technical registrant, provided comments that focused on further
refining assessed risks and potential risk mitigation measures for disulfoton. Bayer's efforts to
reduce risks include repackaging the liquid formulation into a closed mixing/loading system,
reformulating and repackaging the 1% granular home use product. EPA has considered all of
this new information in the revised risk assessment for disulfoton.

       C.    Regulatory Position

             1.     FQPA Assessment

                     a.     "Risk Cup" Determination

       As part of the FQPA tolerance reassessment process, EPA assessed the risks associated
with this OP. The assessment was for this individual OP, and does not attempt to fully reassess
these tolerances as required under FQPA.  FQPA requires the Agency to evaluate food
tolerances on the basis of cumulative risk from substances sharing a common mechanism of
toxicity, such as the toxicity expressed by the OPs through a common biochemical interaction
with the' cholinesterase enzyme. The Agency will evaluate the cumulative risk posed by the
entire class of OPs once the methodology is developed and the policy concerning cumulative
risks is resolved.

       EPA has determined that dietary risk from exposure to disulfoton is within its own. "risk
cup." In other words, if disulfoton did not share a common mechanism of toxicity with other
                                           60

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 chemicals, EPA would be able to conclude today that the tolerances for disulfoton meet the
 FQPA safety standards, provided the risk mitigation measures outlined in this document are
 adopted and additional data needs are addressed. In reaching this determination EPA has
 considered the available information on the special sensitivity of infants and children, as well as
 the chronic and acute food exposure.  An aggregate assessment was conducted for exposures
 through food, residential uses, and drinking water.  Based on the results of this aggregate
 assessment, the Agency has determined that the human health risks from these combined
 exposures are considered to be within acceptable levels.  While the screening-level modeling
 estimates indicate that disulfoton may in fact fill its aggregate risk cup, the Agency has
 determined that actual drinking water exposures are likely lower than predicted by the model,
 and has made an interim determination that disulfoton does "fit" within the dietary risk cup.
 However, EPA will seek additional data to help refine and confirm this assessment.  Except for
 those tolerances that are to be lowered or revoked, the current disulfoton  tolerances will remain
 in effect and unchanged until a full reassessment of the cumulative risk from all OP pesticides is
 considered later this year.

                     b.     Tolerance Summary

       Tolerances for residues of disulfoton in/on plant commodities [40 CFR §180.183] are
 presently expressed in terms of the combined residues of disulfoton and its cholinesterase-
 inhibiting metabolites, calculated as demeton. The tolerance expression for disulfoton should be
 modified to include the combined residues of parent, the sulfoxide and sulfone degradates, and
 the oxygen analogues of the sulfoxide and sulfone degradates. Specifically, tolerances should be
 modified to include the combined residues of O,O-diethyl S-[2-(ethylthio)-ethyl]phosphoro-
 dithioate; O,O-diethyl S-[2-(ethylthio)-ethyl]phosphorothioate; O,O-diethyl S-[2-(ethylsulfmyl)-
 ethyl] phosphorodithioate; O,Q-diethyl S-[2-(ethylsulfinyl)-ethyl]phosphorothioate; O,O-diethyl
 S-[2-(ethylsulfonyl)-ethyl]phosphorodithioate; and O,O-diethyl S-[2-(ethylsulfonyl)-
 ethyl]phosphorothioate. The Agency is changing the tolerance expression to include all
 degradates of toxicological concern.

       The Agency will commence proceedings to  revoke and modify the existing tolerances,
 and correct commodity definitions. The establishment of a new tolerance or raising tolerances
 will be deferred, pending consideration of cumulative risk for the OPs.  "Reassessed" does not
 imply that all of the tolerances have been reassessed as required by FQPA, since these tolerances
 may only be reassessed once the cumulative risk assessment of all OP pesticides is considered,
 as required by the statute.  Rather, this IRED provides reassessed tolerances for disulfoton in/on
 various commodities,  supported by all of the submitted residue data, only for the single OP
 chemical disulfoton. EPA will finalize these tolerances after considering the cumulative risks for
 all OP pesticides.

       The Agency's tolerance summary is provided in Table 15.  This table lists several
tolerances associated with uses that are no longer registered, as announced in several FIFRA
6(f)(l) Notices of Receipt of Requests from the registrant for cancellation and/or use deletion,
which EPA approved. Therefore, the associated tolerances should be revoked.  This table also
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lists uses that are to be phased out and the associated tolerances that are to be revoked after 2004.
Last, this table lists livestock tolerances that must be established following consideration of the
cumulative assessment for all OPs.  Livestock feeding studies for disulfoton indicate that
residues transfer from feed to meat and milk; therefore, tolerances should be established for
livestock commodities, pending consideration of the cumulative assessment for all OPs.
Table 15. Tolerance Summary for Disulfoton _ _
Commodity

Barley, grain
Barley, straw
Beans, dry
Beans, lima
Beans, snap
Beans, vines
Beets, sugar, roots
Beets, sugar, tops
Broccoli
Brussels sprouts
Cabbage
Cattle, meat
Cattle, meat
byproducts
Cattle, fat
Cauliflower
Coffee beans
Current
Tolerance (ppm)
Reassessed1
Tolerance (ppm)
Comment/
[Correct Commodity Definition]
Tolerances Listed Under 40 CFR §180.183(a)(l)
Raw Agricultural Commodities
0.75
5.0
0.75
0.75
0.75
5.0
0.5 '
2.0
0.75
0.75
0.75
-
—
-
0.75
0.3
0.20
5.0
Revoke
0.75
0.75
Revoke
Revoke
Revoke
0.75.
0.75
0.75
0.05
0.05
0.05
0.75
0.2
Available data for wheat support lowering
barley tolerance. Wheat data may be
translated to barley. EPA expects to revoke
tolerance after the use is phased out;
however, tolerance should be lowered in the
interim.
EPA expects to revoke after the use is
phased out.
Use on dry beans deleted; therefore,
tolerance should be revoked.
[Bean, succulent]
[Cowpea, forage]
Use on cowpeas was deleted; therefore,
tolerance should be revoked.
No registered uses on sugar beets; therefore,
associated tolerances should be revoked.



Tolerance should be proposed based on
LOQ, pending outcome of OP cumulaitive
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.

[Coffee, bean, green] Available data support
lowering the tolerance.
                                             62

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Commodity
Com, field, fodder
Corn, field, forage
Com, grain
Corn, pop
Corn, pop, fodder
Corn, pop, forage
Com, sweet, fodder
Corn, sweet, forage
Corn, sweet, grain
(K+CWHR2)
Cottonseed
Goats, meat
Goats, meat
byproducts
Goats, fat
Hog, fat
Hog, meat
Hog, meat
byproducts
Hog, fat
Hops
Horse, meat'
Horse, meat
byproducts
Current
Tolerance (ppm)
5.0
5.0
0.3
0.3
5.0
5.0
5.0
5.0
0.3
0.75
~
- -
,
~
--'
-
-
0.5
.--
- -
Reassessed1
Tolerance (ppm)
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
0.75
0.05
0.05
0.05
0.05
0.05
0.05
0.05
Revoke
0.05
0.05
Comment/
[Correct Commodity Definition]
Use on com deleted; therefore associated
tolerances should be revoked.


[Cotton, undelinted seed]
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
No registered uses on hops; therefore
tolerance should be revoked.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
63

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Commodity
Horse, fat
Lettuce
Milk
Oats, fodder, green
Oats, grain
Oats, straw
Peanuts
Peas
Peas, vines
Pecans
Peppers
Pineapples
Potatoes
Rice
Rice, straw
Sheep, meat
Sheep, meat
byproducts
Current
Tolerance (ppm)
-
0.75
.--
5.0
0.75
5.0
0.75
0.75
5.0
0.75
0.1
0.75
0.75
0.75
5.0
-
-
Reassessed1
Tolerance (ppm)
0.05
0.75 head
TBD leaf3
0.01
Revoke
Revoke
Revoke
0.10
Revoke
Revoke
Revoke
0.10
Revoke.
0.50
Revoke
Revoke
0.05
0.05
Comment/
[Correct Commodity Definition]
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
[Lettuce, head]
[Lettuce, leaf] Tolerance to be raised for
leaf lettuce, pending completion of
additional field trial data and the outcome of
the OP cumulative assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Use on oats deleted; therefore, associated
tolerances should be revoked.
Available data for peanuts support lowering
tolerance.
[Peanut]
Use on peas deleted; therefore, associated
tolerances should be revoked.
Use on pecans deleted; therefore, associated
tolerances should be revoked.
[Pepper, bell]
[Pepper, nonbell]
No registered uses on pineapple; therefore,
tolerance should be revoked.
[Potato] Available data for potatoes support
lowering tolerance. EPA expects to revoke
tolerance after the use is phased out;
however, tolerance should be lowered in the
interim.
No registered uses on rice; therefore,
tolerance was revoked.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
64

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Commodity
Sheep, fat
Sorghum, fodder
Sorghum, forage
Sorghum, grain
Soybeans
Soybeans, forage
Soybeans, hay
Spinach
Sugarcane
Tomatoes
Wheat, fodder,
green
Wheat, grain
Wheat, straw
Current
Tolerance (ppm)
-
5.0
5.0
0.75
0.1
0.25
0.25
0.75
0.3
0.75
5.0
0.3
5.0
Reassessed1
Tolerance (ppm)
0.05
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
Revoke
5.0
0.2
5.0
Comment/
[Correct Commodity Definition]
Tolerance should be proposed based on
LOQ, pending outcome of OP cumulative
assessment.
Use on sorghum deleted; therefore,
associated tolerances should be revoked.

Use on soybeans deleted; therefore,
associated tolerances should be revoked.

No registered use on spinach; therefore,
tolerance should be revoked.
No registered use on sugarcane; therefore,
.tolerance should be revoked.
Use on tomatoes deleted; therefore,
tolerance should be revoked.
[Wheat, forage] EPA expects to revoke
tolerance after the use is phased out.
Available data support lowering tolerance.
EPA expects to revoke tolerance after the
use is phased out; however, tolerance should
be lowered in the interim.
EPA expects to revoke tolerance after the
use is phased out.
Tolerances Listed Under 40 CFR §180.183(a)(2)
Livestock Feed Items
Sugar beet pulp
Pineapple bran
Aspirated grain
factions
Cotton, gin
>yproducts
5
5
'
.
Revoke
Revoke
0.3
TBD4
No registered use on sugar beets; therefore,
tolerance should be revoked.
No registered use on pineapple; therefore,
tolerance should be revoked.
Based on wheat tolerance and concentration
factor from processing study. EPA expects
to establish a temporary tolerance, which
will be revoked following the phase out of
the use on wheat and barley, pending the
outcome of the OP cumulative assessment.
Animal feed item; tolerance to be
determined pending completion of field trial
study and outcome of OP cumulative
assessment.
Tolerances Listed Under 40 CFR § 1 80. 1 83(c)
Regional Registrations
65

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Commodity
Asparagus
Current
Tolerance (ppm)
0.10
Reassessed1
Tolerance (ppm)
0.10
Comment/
[Correct Commodity Definition]

1  "Reassessed" does not imply that the tolerances have been reassessed as required by FQPA; tolerances may only
be reassessed once the cumulative risk assessment of all OP pesticides is considered.
2  K+ CWHR, kernel plus cob with husks removed.
3 TBD, to be determined pending completion of outstanding field trial data (OPPTS GDLN 860.1500) and pending
the outcome of the cumulative assessment. Available data support a separate, higher tolerance for leaf lettuce.
4  TBD, to be determined. Field trial data (OPPTS GDLN 860.1500) are now required for cotton gin byproducts.

       Raw Agricultural Commodities, 40 CFR § 180.183(a)(l)

       The following tolerances should be revoked because there is no longer a registered use on
these commodities:
       Sugar Beets, all tolerances
       Hops
       Spinach
Pineapples, all tolerances
Rice, all tolerances
Sugarcane
       The following tolerances should be revoked because the technical registrant has
requested, and EPA has approved, voluntary cancellation of disulfoton use on these
commodities:
       Beans, dry
       Beans, vines
       Corn, all tolerances
       Oats, all tolerances
       Peas, all tolerances
Pecans
Sorghum, all tolerances
Soybeans, all tolerances
Tomatoes
       The following tolerances will be lowered based on available residue data:
       Barley, grain
       Coffee beans
       Peanuts
Potatoes
Wheat, grain
       In addition, the Agency expects to propose revocation of tolerances on barley, potatoes,
 and wheat because these uses are being phased out.  The revocation will allow sufficient time for
 legally treated commodities to clear the channels of trade.

       Livestock Feed Items, 40 CFR §180.183 (a) (2)

       A tolerance must be established for residues of aspirated grain fractions.  The
 concentration factors for wheat aspirated grain fractions was 1.35x. The reassessed tolerance for
 wheat grain is 0.2 ppm.  Multiplying concentration factors by the reassessed tolerances gives 0.3
 ppm for aspirated grain fractions of wheat.
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       As explained in the Agency's definition of livestock feed commodities (OPPTS
 Guideline 860.1000, Table 1), tolerances are required for cotton gin byproducts. The appropriate
 tolerance levels for these commodities will be determined when adequate field trial data (OPPTS
 GDLN 860.1500) have been submitted and evaluated.

       A tolerance of 0.05 ppm, the level of quantification, would address potential residues on
 meat, fat, and meat byproducts of cattle, hogs, horses, sheep, and goats. A tolerance of 0.01
 ppm, the level of quantification, should be established for milk.

       Residue Analytical Methods

       Adequate methods are available for data collection and tolerance enforcement for plant
 and livestock commodities. The Pesticide Analytical Manual (PAM) Vol. II lists the
 enforcement methods for demeton, paper chromatography and colorimetric methods, as Method
 I. A gas chromatography (GC) method (Method II) with potassium chloride thermionic
 detection is listed for the determination of disulfoton, its oxygen analogue, and their sulfoxides
 and sulfones in/on  plant commodities.  The GC enforcement Method in PAM calculates residues
 in terms of disulfoton, whereas the tolerance expression states that residues are calculated as
 demeton. The majority of data used for tolerance reassessment were collected using the
 enforcement GC method (or modification thereof). Therefore, the tolerance expression will be
 revised to state that residues are to be calculated as disulfoton.  This revision will also make the
 tolerance expression compatible with the Codex expression.

       Multiresidue methods are also available for disulfoton. PAM Volume I, Appendix I
 indicates that disulfoton, its sulfoxide and sulfone, demeton-S (disulfoton oxygen analogue), and
 its sulfoxide and sulfone are completely recovered (>80%) using Multiresidue Method Section
 302. Disulfoton is partially recovered (50-74%) and metabolites disulfoton sulfone and
 demeton-S are not recovered using Multiresidue Method §303.  Disulfoton is not recovered
 using §304.

                    c.     Endocrine Disrupter Effects

       EPA is required under the FFDCA, as amended by FQPA, to develop a screening
 program to determine whether certain substances (including all pesticide active and other
 ingredients)  "may have  an effect in humans that is similar to an effect produced by a naturally
 occurring estrogen, or other such endocrine effects as the Administrator may designate."
 Following the recommendations of its Endocrine Disrupter Screening and Testing Advisory
 Committee (EDSTAC), EPA determined that there were scientific bases for including, as part of
 the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone
 system. EPA also adopted EDSTAC's recommendation that the Program include evaluations of
potential  effects in wildlife.  For pesticide chemicals, EPA will use FIFPxA and, to the extent that
 effects in wildlife may help determine whether a substance may have an effect in humans,
FFDCA authority to require the wildlife evaluations. As the science develops and resources
allow, screening of additional hormone systems may be added to the Endocrine Disruptor
                                           67

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Screening Program (EDSP).

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

       D.     Regulatory Rationale

       EPA has determined that label amendments are necessary in order for disulfoton products
to be eligible for reregistration.  Provided the following risk mitigation measures are
incorporated in their entirety into labels for disulfoton-containing products, the Agency finds that
certain currently registered uses of disulfoton are eligible for reregistration, pending
consideration of cumulative risks of OP pesticides.  The regulatory rationale for each of the
mitigation measures is discussed below.  Where labeling revisions are warranted, specific
language is set forth in the summary table of Section V.

              1.     Human Health Risk Mitigation

                     a.     Dietary Mitigation

       Dietary risk from food sources alone are not of concern. Screening level modeling
estimates indicate that aggregate disulfoton exposure from food and drinking water may fill the
risk cup; however, the Agency has determined that drinking water exposures are likely lower
than predicted. Therefore, the Agency has made an interim determination that no additional
mitigation are necessary at this time.  EPA will require additional data to refine the drinking
water modeling values an'd confirm this interim conclusion.

       Acute (Food)

       The acute dietary (food) risk estimate is less than 100% of the aPAD for the general  ;
population and all  population subgroups. Children (1-6 years), the most highly exposed
population group, are exposed to disulfoton at a level of 9.6% of the aPAD (0.0025 mg/kg/day)
at the 99.9th exposure percentile. The acute dietary  (food) risk estimate is not of concern;
therefore, no additional mitigation measures are necessary to reduce these risks.

       Chronic (Food)

       The chronic dietary (food) risk estimate is less than 100% of the cPAD for the general
population and all  population subgroups. Children  (1-6 years), the most highly exposed
population group, are exposed to disulfoton at a level of 3.5% of the cPAD (0.00013 mg/kg/day).
The chronic dietary (food) risk estimate  is not of concern; therefore, no additional mitigation
measures are necessary to reduce these risks.                                            ••
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       Drinking Water - Surface

       Surface water drinking water estimated concentrations (DWECs) were derived from the
 Tier IIPRZM-EXAMS model with the Standard Index Reservoir and percent crop area (PCA),
 which is a screening-level model designed to provide high-end estimates of potential pesticide
 exposure. Model predictions provide a screen to eliminate those chemicals that are not likely to
 cause concerns in drinking water. Exceedances in drinking water risk assessments using the
 screening model estimates do not necessarily mean a risk of concern actually exists, but may
 indicate the need for better data (e.g., monitoring studies specific to use patterns and drinking
 water sources) on which to confirm decisions.

       Based on model predictions of currently registered uses, the DWECs for disulfoton
 (parent only) in surface water range from 2.8 to 15.5 ppb for acute exposure, and from 0.2 to 1.6
 ppb for chronic exposure.  The DWECs for total disulfoton (parent + degradates) range from 8.0
 ppb to 39.0 ppb for acute exposure, and from 2.0 to 16.7 ppb for chronic exposure and are
 summarized in Table 5.

       As part of the Agency's measures to mitigate occupational risks associated with the use
 of disulfoton (discussed later in this section), certain use sites are to be phased out or
 discontinued.  Among the uses to be discontinued are barley, potatoes, and wheat.  However,
 disulfoton use on these crops and cotton were selected to assess overall drinking water exposures
 from surface water sources.  Excluding the crop scenarios  for barley, potatoes, and wheat would
 result in cotton use as being the only remaining drinking water crop scenario from which to
 assess drinking water risks. However, disulfoton is used on many other crops, such as
 asparagus, beans, broccoli, brussels sprouts, cabbage, cauliflower, chilli peppers, lentils, lettuce,
 peanuts, and peas.  T;hese use sites were not specifically modeled, because the  barley, cotton,
 potatoes, and wheat crop scenarios were selected to be representative of all sites vulnerable to
 runoff. Thus, to represent the use of disulfoton on all the use sites subject to reregistration, it is
 appropriate to use the DWEC model estimates from the original barley, cotton, potatoes, and
 wheat crops scenarios to assess drinking water risks from surface water sources.

       For disulfoton, the fate of the parent compound and its degradates once in surface water
 and sediments, and the likely concentrations therein, cannot be modeled with a high degree of
 certainty, since aerobic and anaerobic aquatic degradation  data are not available. Because there
 are no studies for individual degradates, a 259 day half-life was used for a model input, which is
 the upper 90% confidence bound on the mean of total residue half-lives in aerobic soil
 metabolism studies. The assessment.could be refined if studies for the individual degradates
 were conducted and model inputs could be derived from these studies. In addition, the aerobic
 soil metabolism half-life is used to estimate the aerobic aquatic half-life when aerobic aquatic
 data are not available, and has also contributed to the uncertainty of the  water assessment.

       In addition, the water model scenarios on disulfoton use on barley and potatoes, which
result in the highest DWECs, include the default PCA value of 87%. This factor translates to
 87% of the modeled drainage basin is planted with crops which are treated with disulfoton. This
                                           69

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default value may be an overestimate, since some of the disulfoton use areas are highly mixed
agricultural regions where other crops that are not treated with disulfoton are also grown or areas
where no crops are grown and disulfoton is not applied.

       Because modeling without complete fate data was employed to develop DWEC values to
assess drinking water risks for disulfoton, the Agency has some level of uncertainty of whether
actual concentrations of disulfoton in surface water sources of drinking water would be as high
as the model predictions. Therefore, to confirm these estimates, aerobic and anaerobic aquatic
metabolism, and mobility, leaching, absorption and desorption studies (OPPTS Guidelines
835.4300, 835.4400, and 835.1240) on both the parent and degradates are required.

       For many chemicals where there are uncertainties in the modeling estimates, the Agency
also relies on actual  monitoring data to confirm these estimates. Thus, for disulfoton, the
Agency is also requiring confirmatory surface water monitoring data to evaluate actual acute and
chronic concentrations of disulfoton in the drinking water sources. This monitoring data is to be
generated from a multi-year sampling program involving community water systems from surface
water sources in multiple locations in different regions of the country to represent different use
sites, crops,  soil types, and rainfall regimes.  Water samples are to be analyzed to determine the
concentrations of parent disulfoton and each of the  environmental degradates of toxicological
concern. Also, prior to initiating this sampling program, the registrant is required to submit a
study protocol to the Agency to ensure that the sampling locations and procedures are adequate
to address the drinking water risk concerns.

       Drinking Water - Ground

       The DWEC to assess drinking water risks from disulfoton concentrations in ground water
sources is 1.2 ppb. A Tier I screening-level model  (SCI-GROW)  was employed to estimate the
maximum ground water concentrations from the application of a pesticide to crops. The model
is based on the fate properties of the pesticide and the annual application rate. For disulfoton,
fate data were not available for the degradates of concern; thus, estimates of fate properties were
factored into the model estimates, which comprise a significant contribution to the predicted total
concentration of disulfoton. Furthermore, the model assumes the  pesticide is applied at its
maximum rate in areas where the ground water is particularly vulnerable to contamination. In
most cases, a considerable portion of any use area will have ground water that is less vulnerable
to the contamination than the use areas used to derive the model estimates. As such, the DWECs
from this model should be considered a high-end to bounding estimate that is generally more
appropriate for acute rather than chronic exposure.

       In addition, the available monitoring data do not indicate that there is a concern of
disulfoton concentrations in drinking water from ground water sources.  For these reasons, the
Agency believes that actual concentrations of disulfoton in ground water sources of drinking
water are not of risk concern, and that no further mitigation nor monitoring is necessary.
                                           70

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                     b.     Homeowner Risk Mitigation

       Handler Risk

       Disulfoton is currently registered for residential use on small flower gardens, ornamental
 flowers and shrubs, including rose bushes and small trees, and outdoor potted plants. Most
 application methods for residential uses are not of risk concern to the Agency with MOEs > 100;
 however, some uses result in MOEs < 100 and are of risk concern. As indicated in Table 8,
 MOEs for residential uses of disulfoton range from 1.1 to 1900.  Residential risks are not of risk
 concern fMOEs > 100) for the following use scenarios and application rates:

 •      Loading/applying graniilars using a push-type spreader:
       -use on flower gardens at an application rate of 0.3 Ib ai/1000 ft2
       -use on ornamental shrubs and small trees at an application rate of 0.01 Ib ai/4 ft shrub
       -use on rose bushes at an application rate of 0.00126 Ib ai/bush
                                                            ^
       Loading/applying granulars using a spoon, measuring scoop, shaker can or by hand:
       -use on potted plants at an application rate of 0.00034 Ib ai/6 inch pot
       -use on rose bushes at an application rate of 0.00126 Ib ai/bush

 •      Loading/applying granulars using a measuring cup/lid:
       -use on flowerbeds at an application rate of 0.21 Ib ai/1000 ft2
       -use on shrubs at an application rate of 0.01  Ib ai/4 ft shrub
       -use on rose bushes at an application rate of 0.0013 Ib ai/bush

 Residential risks are of risk concern CMOEs < 100) for the following use scenarios and
 application rates:

 •      Loading/applying granulars using a belly grinder:
       -use on flower gardens at an application rate of 0.3 Ib ai/1000 ft2

       Loading/applying granulars using a spoon, measuring scoop, shaker can or by hand:
       -use on flower gardens at an application rate of 0.3 Ib ai/1000 ft2
       -use on ornamental shrubs and small trees at an application rate of 0.01 Ib ai/4 ft shrub

The following measures are necessary to mitigate residential risks that are of concern:

•      Prohibit application of disulfoton with a belly grinder.

       Prohibit application to flower gardens and ornamental shrubs with a spoon, measuring
       scoop, shaker can,  or by hand, unless the  packaging and method of application of the
     ,  end-use product conforms with the performance of a measuring cup/lid packaging
       currently manufactured for the Bayer Advanced Garden 2-in-l Systemic Rose and
       Flower Care® Disulfoton 1% granular product.
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       If the end-use registrant elects to change container packaging to conform with the subject
       Bayer product, the new packaging must be child resistant with a self-contained
       measuring device, which serves as the container lid and clearly measures the quantity to
       be applied. Although the Bayer Advanced Garden 2-in-l Systemic Rose and Flower
       Care® Disulfoton 1% granular product is the only such packaging of this type currently
       available at the time of this IRED, other similar packaging which meets or exceeds the
       safety specifications given above may also be used.               ;

•      Limit the maximum label rates for disulfoton to 0.3 Ib ai/1000 ft2 for use on flowerbeds;
       0.01 Ib ai/4 ft bush for use on shrubs; and 0.0013 Ib ai/bush for use on rose bushes.
       Although the residential risk assessment for hand application with a self-contained
       measuring cup/lid was based on a rate of 0.21 Ib ai/1000 ft2 on flowerbeds (Table 8), the
       MOEs calculated for the rate of 0.3 Ib ai/1000 ft2 for use on flowerbeds would also be
       greater than 100 and not of risk concern. To be consistent with the maximum application
       rate to flowerbeds with a push type spreader, EPA is allowing the higher maximum
    .   application rate 0.3 Ib ai/1000 ft2 for use on flowerbeds for disulfoton packaged for hand
       application with a self-contained measuring cup/lid.

       As previously stated, all disulfoton products intended for hand application must be
       packaged with a self-contained measuring cup/lid that clearly measures the appropriate
       amount to be applied.  These packaging must also meet EPA criteria for child-resistant
       packaging.

       Disulfoton products intended for application with a push-type spreader must limit the
       maximum application rates to 0.3 Ib ai/1000 ft2 for use on flowerbeds; 0.01  Ib ai/4 ft bush
       for use on shrubs; and 0.0013 Ib ai/bush for use on rose bushes, as specified above. Also,
       these products must be labeled "Do not apply by hand." and "Not for commercial use."

•      All homeowner products must be soil incorporated or watered in.

       Delete the following uses from all product labels to comply with the technical label: all
       indoor uses, use in greenhouses, and use on home vegetable gardens, including use on
       spinach and tomatoes.

       Only homeowner products containing 2% active ingredient or less  are eligible  for
reregistration. (All products containing >2% active ingredient are classified as restricted use,
based on the acute oral and dermal toxicity of disulfoton).

       Residential risk from use of fertilizer spikes impregnated with disulfoton can not be
determined at this time, because the Agency has no exposure monitoring data for this use
scenario. Similarly, EPA can not determine the reregistration eligibility for this use without
exposure monitoring data (i.e, OPPTS Guidelines 875.1100, 875.1600, and 875.1700). La some
cases, the Agency would require these data as a condition of continued registration. However,
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 on March 28, 2002, the end-use registrant requested voluntary cancellation of all product
 registrations for fertilizer spikes impregnated with disulfoton (EPA Reg Nos 46260-2,46260-12,
 46260-35, and 46260-36); therefore, the Agency does not intend to include these data
 requirements in the DCI. Consistent with the existing stocks provision of this IRED, the end-use
 registrant will be allowed 26 months from the date of issuance of this document to distribute and
 sell products and 50 months for persons other than the registrant to distribute or sell products

       Post-Application Risk

       As mentioned previously in this document, the upper-bound .residential post-application
 assessment of incidental soil ingestion (oral exposure) to toddlers results in MOEs > 100, which
 are not of risk concern to the Agency.  Therefore, the Agency does not have a concern for post-
 application risk to toddlers from any activities, and no additional mitigation is necessary.

                     c.      Aggregate Risk Mitigation

       The Agency's aggregate risk assessment for disulfoton is based on exposure estimates for
 food and residential uses, and uses, a screening-level assessment of modeled estimates for
 drinking water contamination. Dietary (food) risk estimates are based on a refined assessment
 that incorporates percent crop treated data, monitoring data, and processing data.

       Acute Exposure

       The acute aggregate risk assessment for disulfoton combines exposure from food and
 drinking water sources only. Acute dietary (food) risk estimates are below 100% of the aPAD
 for the US population and all population subgroups.  Children 1-6 years old is the most highly
 exposed population subgroup and result in an acute drinking water level of comparison
 (DWLOC) of 23 ppb. Based on screening-level model predictions of the remaining supported
 uses, the acute (peak) drinking water estimated concentration (DWECs) in surface water is 15.5
 ppb for parent disulfoton and 39.0 ppb for total disulfoton (parent + degradates). The DWEC of
 parent disulfoton is less than the DWLOC and not of concern; however, the DWEC of total
 disulfoton (parent + degradates) is greater than the DWLOC and is of potential risk concern to
 the Agency as modeled. Also, the screening-level model predictions of acute DWECs in ground
water is 1.2 ppb for total disulfoton, which is less  than the DWLOC and not of risk concern to
the Agency.

       As stated previously, exceedances of the DWLOC by screening-level model estimates do
not necessarily indicate a risk of concern, but generally indicate the need for better data, due to
the uncertainties and limitations of the model predictions. The Agency believes that actual acute
concentration of disulfoton in surface water is likely less than the DWLOC and is not of concern.
To demonstrate this, confirmatory surface water monitoring data is to be generated to address
this risk concern.     .
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       Chronic Exposure

       The chronic aggregate risk assessment for disulfoton combines exposure from food and
drinking water sources only.  Chronic dietary (food) risk estimates are well below 100% of the
cPAD for the US population and all population subgroups. Children 1-6 years old is the most
highly exposed population subgroup with a chronic DWLOC of 1.3 ppb. Based on screening-
level model predictions of the remaining supported uses, the average (chronic) DWECs in
surface water is 1.6 ppb for parent disulfoton and 16.7 ppb for total disulfoton (parent +
degradates). The DWEC of parent disulfoton is of the same magnitude as the chronic DWLOC
and is not of concern. Although the DWEC for total disulfoton is greater than the DWLOC for
children 1-6 and is of potential risk concern, the uncertainties and limitations of the model
predictions lessen this concern. The Agency also believes that actual chronic concentrations of
disulfoton in surface water are less than the DWLOC and are not of concern. To demonstrate
this, confirmatory laboratory fate and surface water monitoring data are to be generated to
address the risk concern.

       The screening-level model predicts a chronic DWECs in ground water of 1.2 ppb, a value
lower than the corresponding DWLOCs.  Therefore, the Agency believes that concentrations of
disulfoton in ground water sources of drinking water are not of risk concern, and that no further
mitigation or monitoring is necessary.

       Short-Term Exposure

       The short-term aggregate risk assessment for disulfoton combines exposure from food
uses, residential uses, and drinking water sources. Residential use is assessed for dermal
exposure to adult handlers and oral exposure to children through incidental soil ingestion.  .
Inhalation exposure is not part of the short-term aggregate assessment as data indicate negligible
exposure. Short-term DWLOC estimates are calculated for disulfoton based on chronic dietary
(food) exposure and dermal exposure values from residential exposure scenarios that have MOEs
> 100. Residential exposure  scenarios with MOEs < 100 were  not included in the short-term
aggregate assessment (see Table 8).

       The short-term DWLOC is 14 ppb for children 1-6 years old, the most highly exposed
population.  As indicated above, the average (chronic) DWECs in surface water is 1.6 ppb for
parent disulfoton and 16.7 ppb for total disulfoton (parent + degradates).  The DWEC of parent
disulfoton is less than the short-term DWLOC and not of concern. Although the DWEC for total
disulfoton is slightly greater than the DWLOC, th Agency believes this exceedance does not
necessarily indicate a risk of concern due to the uncertainties associated with model estimates.
Confirmatory laboratory fate and surface water monitoring data are to be generated to address
the potential risk concern.

                    d.     Occupational Risk Mitigation

       As described in PR Notice 2000-9, Worker Risk Mitigation for OP Pesticides, it is the
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 Agency's policy to mitigate occupational risks to the greatest extent necessary and feasible with
 personal protective equipment and engineering controls. In managing risk, EPA considers a
 wide range of factors are considered in making risk management decisions for worker risks. EPA
 must take into account the economic, societal, and environmental costs and benefits of the
 pesticide's use. In addition to the calculated MOEs, incident data, the nature and severity of
 adverse effects, uncertainties in the risk assessment, availability and relative risk of alternatives,
 importance of the chemical in integrated pest management (IPM) programs, and other similar
 factors.

       Worker Handler Risks

       As summarized in Table 10, occupational risks are of concern (i.e., MOEs < 100) for all
 scenarios, even when maximum PPE (i.e, double layer clothing, gloves, and a respirator) are
 utilized.  These handler risks are also of concern for many scenarios with engineering controls,
 even at a level that provides protection from inhalation exposure (closed mixing/loading,
 enclosed cabs with ah- filtration). Engineering controls with inhalation protection are considered
 to be the maximum feasible mitigation.  For workers wearing the maximum PPE described
 above, MOEs range from 1.5 (barley) to 61 for mixer/loaders and from <1 (ornamentals grown
 for field or nursery stock) to 69 for applicators. For workers using the engineering controls
 described above, MOEs range from 3.1 to 800 for mixer/loaders and from 1.8 to 160 for
 applicators.  To remain eligible for reregistration, the following mitigation measures must be
 implemented for all occupational handler scenarios.

 •      Closed mixing/loading systems for all liquid formulations (see below);

       Closed transfer/loading systems for all granular formulations by June 2004;

       Enclosed cabs plus a dust-mist respirator for all ground equipment applicators (i.e.,
       groundboom and tractor drawn spreader). The respirator requirement may be relaxed
       when using engineering controls that provide equivalent inhalation protection (such as air
       filtration), under the provisions of the Worker Protection Standard (WPS).

•      Enclosed cockpits for aerial applicators;

       Mechanical flaggers for aerial application; or the use of global positioning system (GPS)
       equipment that negates the need for flaggers;,

•      When engineering controls are not feasible for applicators, handlers must wear maximum
       PPE (i.e., double layer clothing, chemical-resistant gloves and footwear, and a dust-mist
       respirator); and                                                                  ,

       Application by open, handheld equipment, including belly grinders and bucket and spoon
       will be prohibited after June 2004. Where this is currently the application method of
       choice, growers will be allowed until June 2004 to transition to another method.
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       The closed mixing/loading system used for liquid disulfoton should contain a dry
disconnect or dry coupler that allows no more than 2 mL drippage, such as the Secure-Link G®
or other comparable system.  Closed mixing/loading systems for all liquid formulations of
disulfoton end-use products are currently in use and should be fully implemented by December
31,2002.
                                                                           V
       Post-Application Risk

       Post-application (re-entry) risks are of concern for workers performing tasks in areas that
have received foliar applications of disulfoton.  In lieu of satisfactory dislodgeable foliar residue
(DFR) data, the Agency relied on assumptions for its re-entry assessment. Restricted-entry
intervals (REIs) for these types of applications of disulfoton are stipulated in the crop specific
regulatory rationale section below. The Agency acknowledges thatjidditional DFR data (OPPTS
Guideline 875.2100) could refine the post-application risk assessment and likely reduce the REI
for certain crops. If the registrant wishes to generate such data to refine this assessment, the
study needs to include residue data on both the parent and degradates.

       For soil directed applications of the liquid and granular formulations, most of which are
either in-furrow, shank injected, or other types of soil incorporation, the Worker Protection
Standard designates the REI to be 48 hours, or 72 hours in regions where the annual rainfall is
less than 25 inches. In addition, based on the use of the chemical and the timing of applications
to these crops, the Agency does not expect significant  soil contact from typical worker re-entry
activities. Therefore, the Agency has no risk concerns for the post-application exposures to
agricultural workers for these types of disulfoton applications, and no risk mitigation measures
beyond the 48 or 72 hour REI are necessary for applications made to the soil.

       Uncertainty in and Refinements to the  Occupational Risk Assessment

       There is some uncertainty associated with the toxicity of disulfoton. Numerous animal
studies in several species show cholinesterase inhibition. The NOAEL used to assess  short-term
dermal exposure to workers is 0.5 mg/kg/day from a special 3-day dermal toxicity study in rats
conducted on the 1% granular product.  The LOAEL from this study is 1 mg/kg/day based on
plasma and brain cholinesterase inhibition. The Agency believes that the NOAEL from this
study is sufficient to assess dermal exposure of 1 to 7 days,  which would cover most agricultural
workers.  However, the Agency is concerned that commercial handlers could be exposed for up
to 14 days.  To fully characterize the hazard associated with exposure ranging from 14 to 30
days, the Agency is requiring a confirmatory 21-day dermal study in the rat, the most  sensitive
species. In the interim, the Agency will base the short-term dermal risk assessment for
commercial applicators on the 3-day dermal study. The Agency acknowledges that the
occupational risk assessment based on the 3-day dermal toxicity study may underestimate risk to
some commercial applicators.

       There is also some uncertainty in the Agency's assessment of exposure to agricultural
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 workers. EPA used exposure monitoring data from PHED, which either lacks or contains
 limited exposure monitoring data for some application methods, including shank injection, in-
 furrow, and with a motorcycle mounted with a granular spreader. In these specific examples, the
 closest available exposure monitoring data scenario from PHED was used to assess potential
 exposure.  The Agency made the following extrapolations based on PHED data:

 •     Data for mixers/loaders and applicators using a groundboom to apply liquid formulations
       were used to estimate exposure from at-plant, in-furrow application of liquid products.

 •     Data for loaders and applicators using a tractor drawn spreader to apply granular
       formulations were used to estimate  exposure from in-furrow, at-plant application and
       exposure from broadcast of granulars using a motorcycle.

       The Agency believes that in-furrow or  shank injecting methods of applications result in
 less exposure to applicators than does the tractor drawn spreader or groundboom methods, from
 which the estimated risks were derived. Although the Agency does not have data at this time to
 corroborate this understanding, it is reasonable to expect the risk associated with applying
 disulfoton with soil incorporated methods are lower than currently estimated. Because of the
 uncertainties associated with the use of these surrogate scenarios, the Agency is requiring
 confirmatory exposure monitoring data (passive dosimetry) to better characterize exposure and
 risk for these scenarios. However, because of the uncertainties associated with the dermal
 endpoint, the registrant has the option to generate, and the Agency will accept biomonitoring
 data in lieu of the passive dosimetry to characterize exposure to applicators.

       Last, the Agency typically uses default assumptions with regard to acreage treated per
 day for field crops depending upon the application method. However, crop-specific information
 shows that many minor crops grown in the Salinas Valley of California are planted in blocks,
 and that in many cases the actual acreage treated per day is lower than the Agency default
 assumptions. Because California's Department of Pesticide Regulation has stringent pesticide
 use reporting requirements, EPA verified acreage treated with disulfoton in that state, and
 concluded that for some crops that are grown in California, the actual acreage treated per day is
 lower than the assumptions used by the Agency to assess worker risks. Information on the
 acreage treated for specific crops grown in California, and its impact on corresponding worker
 MOEs are summarized with crop-specific mitigation in Section IV.D.3, Crop Specific Mitigation
 of this document.

             2.     Environmental Risk Mitigation

       The Agency's ecological risk assessment for both the liquid and granular formulations
shows RQ values which exceed the various  levels of concern (LOCs) for acute risks to terrestrial
birds and mammals and freshwater and estuarine invertebrates and chronic risks to birds and
mammals, freshwater invertebrates, as well  as marine and estuarine fish and invertebrates.  The
Agency also has risk concerns to endangered species, and potential concern to nontarget plants.
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      Birds and Mammals

      The Agency has some acute risk concerns for birds and mammals potentially exposed to
the liquid formulation. Acute RQs for birds range from 0.01 to 2.2, with the highest RQ
associated with use on potatoes.  EPA also has a risk concern for endangered avian species.
Acute RQs for mammals range from <0.1 to 360, again with the highest RQ associated with
potatoes. Note also that there is some uncertainty in the mammalian risk estimates,  because they
are based on rat toxicity studies, which were not designed to assess risk to wild mammals. In
lieu of wild mammal acute toxicity data, EPA extrapolated an LC50 value based on an LD50 from
an acute oral rat study to calculate acute RQs for mammals, which may account for  the
comparatively high RQs for mammals. In addition, EPA has some chronic risk concerns for
birds and mammals potentially exposed to the liquid formulation.  Chronic risk estimates for the
liquid formulation range from 0.02 to 3.4 for birds and from 0.9 to 158 for mammals.  The
highest RQ is for use on potatoes in the Pacific Northwest.  The Agency's phase out of
disulfoton use on potatoes will address the highest avian and mammalian acute and  chronic risks.

       The Agency also has acute risk concerns for the granular formulation, with potential risk
concerns at the lowest application rate of 1 Ib ai/A.  Acute avian RQs range from 0.1 to 75,200
and mammalian RQs range from 0.3  to 257,300. The highest RQs for both birds.and mammals
are associated with the Christmas tree use at the current Section 3 registration label  rate of 78 Ib
ai/A. To mitigate this risk, the maximum application rate for disulfoton on Christmas trees is to
be reduced to 4.5 Ibs ai/A, the use is to be limited to fir species only, and disulfoton must be
either soil incorporated, watered in, or applied to areas with permanent groundcover. At the
lower application rate of 4.5 Ibs ai/A for Christmas trees, peak RQs are significantly reduced to
4,350 for birds and 14,900 for mammals. Although the residual risks for the Christmas tree use
are still high, Christmas tree growers hi the region have submitted numerous testimonials
emphasizing the ever increasing numbers and diversity of wildlife, including game  animals.
Although it is not clear whether there are population effects, the risk assessments suggests that
there is acute risk to nontarget birds and mammals exposed to disulfoton. Excluding Christmas
tree  use, RQs for birds range from 0.1 to 346, and RQs for mammals range from 0.3 to 1184,
with the highest RQs associated with use of disulfoton by nurseries on ornamental flowers.

       Because of the toxicity of disulfoton, to help protect terrestrial birds and mammals, it is
very important to minimize their potential exposure to disulfoton products that have been
applied.  Many of the mitigation measures previously described in this document to mitigate
occupational and other risks of concern will also serve to minimize risk to birds and mammals,
such as deleting certain uses (i.e., potatoes, barley, wheat, ornamentals), injecting or
incorporating the chemical into the soil during application,  reducing maximum application rates,
and  limiting the number of applications on asparagus, coffee, peanuts (North Carolina only), and
potatoes.

       Aquatic Organisms

       Acute risks are of concern for some aquatic organisms. Acute RQs range from <0.01 to
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 0.33 for freshwater fish, and from <0.01 to 0.02 for estuarine fish, and are not of concern.
 However, acute RQs  range from O.01 to 2.1 for freshwater invertebrates, and from <0.01 to
 0.55 for estuarine invertebrates. Some of the acute values for invertebrates are of concern.

        Chronic risks are of concern for freshwater invertebrates, but not for freshwater fish. The
 Agency has a greater chronic risk concern for freshwater invertebrates than for estuarine
 invertebrates. Chronic RQs range from <0.01 to 149 for freshwater invertebrates, and from
 <0.01 to 2.3 for estuarine invertebrates.  For freshwater fish, chronic RQs range from <0.01 to
 0.8, and for estuarine fish, chronic RQs range from <0.01 to 3.0.

        The highest RQs of concern to fish and invertebrates are associated with multiple aerial
 applications to potatoes, barley, and asparagus. The phase out of disulfoton use on potatoes and
 barley will mitigate some of these risks, and the RQs associated with use on asparagus may be
 an overestimate.  Disulfoton use on asparagus is predominately in Washington and California,
 where there is little to no rainfall during the application period to cause runoff and potentially
 exposure aquatic  organisms.

        Many of the measures previously described in this document to mitigate occupational and
 terrestrial risks will also serve to mitigate, aquatic risks of concern. For instance, deleting certain
 uses, injecting or incorporating the chemical into the soil, reducing maximum application rates,
 and limiting the number of applications will reduce potential runoff of disulfoton to nearby water
 bodies.  To further.mitigate aquatic risks, a 25 foot vegetative buffer between treated fields and
 all permanent water bodies will be necessary.

       Plants

       Because test data was not available to conduct a risk assessment for nontarget plants, and
 because of a phytotoxicity statement on the labels, the Agency has a potential phytotoxicity risk
 concern. Given that disulfoton is applied to growing crops it is unlikely to result in significant
 nontarget risks to plants. Confirmatory data are needed to determine the extent of any risk that
 may exist.  Therefore, Tier I test data for terrestrial plants (OPPTS 850.4100 and 850.4150) are
 required.

      Insects

      The results of an acute contact study show that disulfoton is moderately toxic to bees and
 disulfoton sulfone and sulfoxide are very highly toxic to bees on an acute contact basis.  A
toxicity  study of residue of the liquid EC (Di-Syston 8) on honey bees showed that disulfoton
residues on foliage are not toxic to bees.  The Agency believe that a precautionary label
statement will be sufficient to  address risk concerns.  Specific label language is given in Table
 16 of this document.
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       Endangered Species

       As mentioned in Section III.B.3 of this document, the Agency included disulfoton in two
formal consultations with the USFWS on endangered species. These consultations occurred in
1983 and 1989. As a result of these consultations, the USFWS issued jeopardy opinions
identifying several endangered species, as well as reasonable and prudent alternatives and
measures to address the risk concern. These opinions are reflected in the EPA's endangered
species protection program county level interim bulletins. The disulfoton registration and use
patterns have changed significantly since 1989, and many uses have been deleted, maximum
application rates have been lowered, and the number of applications have been reduced.
Therefore, the Agency conducted an additional endangered species assessment on the remaining
registered disulfoton uses that would result in potential exposure to endangered species. From
these remaining uses, potential impacts were identified for.two bird species: the Puerto Rico
Plain Pigeon and the Mountain Plover. The Agency does not believe that any measures are
necessary to protect the Mountain Plover at this time.  The Plover is found in western states
where barley is grown, and this bird feeds on barley when the barley is young and less than three
inches tall. Because disulfoton is used on barley late in the season, when the crop is quite tall,
the Mountain Plover is not expected to be impacted by disulfoton use. Further, the use of
disulfoton on barley is being phased out by June 2005. The Agency does not believe that any
measures are necessary to protect the Puerto Rico plain pigeon. Potential exposure of this
species was an issue associated with the use of disulfoton on coffee. However, technical
assistance from the Puerto Rico office of the Fish and Wildlife Service revealed that this species
does not utilize or otherwise occur in areas of Puerto Rico where coffee is produced.  Therefore,
because there will be no effect on this species, no mitigation measures are necessary.

              3.      Crop-Specific Decisions

       The technical registrant, Bayer Corporation, has made a number of voluntary changes to
their FIFRA Section 3 disulfoton labels to address risk concerns. These voluntary label changes
include reducing maximum application rates or number of applications for some crops  and
deleting numerous uses. However, these voluntary measures were  not sufficient to fully address
the Agency's risk concerns. Therefore, EPA has identified additional measures necessary to
mitigate risks on a crop-by-crop basis, after considering all potential risk mitigation options, the
availability of alternatives and their effectiveness, and the benefits  associated with each use (see
Section HI.C, Alternatives and Benefits). These measures included additional reductions in the
rate and frequency of applications, where these are feasible.  In the process ?of developing crop-
specific mitigation measures, EPA considered current agricultural practices and the actual use of
disulfoton in the field.  In some cases, the current agricultural practices are protective of human
health and the environment given the benefits of continued use. In such instances, pesticide
product labels must be modified to reflect the current practice.  In developing mitigation, EPA
also considered personal protective equipment and engineering controls for workers and
precautionary labeling.

       As previously mentioned in the section describing measures necessary to mitigate worker
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 risks, growers will need to utilize engineering controls, which include the use of enclosed cabs.
 Growers with enclosed cabs that do not provide inhalation protection will also need to wear a
 dust-mist respirator; however, growers who have enclosed cabs with air filtration will not need
 any further inhalation protection.  The Agency recognizes that there may be some growers of
 minor crops who may not own the necessary equipment and therefore may be economically
 impacted by adopting engineering controls. However, EPA believes that custom applicators who
 have equipment with the necessary engineering controls are available to growers who may not
 have the necessary equipment themselves.

        Risk estimates are provided in the following section for both groundboom and tractor
 drawn spreader applicators that are in an enclosed cab and wearing a dust-mist respirator.
 Typical disulfoton labels specify maximum PPE (i.e., double layer clothing, and with or without
 a respirator).  For groundboom applicators of the liquid formulation with maximum PPE and
 without a respirator, the corresponding MOEs increase by a factor of 3x for an applicator in an-
 enclosed cab and wearing a dust-mist respirator (80% protection factor); and for groundboom
 applicators with maximum PPE and with a respirator, the MOEs increase by a factor of 1.9x.
 Similarly, for tractor drawn spreader applicators of the granular formulation with maximum PPE
 and without a respirator, the corresponding MOEs increase by a factor of 3.6x for an applicator
 in an enclosed cab and wearing a dust-mist respirator; and for tractor drawn spreader applicators
 with maximum PPE and with a respirator, the MOEs increase by a factor of 1.4x. The tabulated
 MOEs for applicator scenarios utilizing an enclosed cab with a dust-mist respirator are not
 included in Table 10 of this document, but the basis of these calculations are available in Revised
 Occupational Exposure Assessment for the Reregistration Eligibility Decision Document for
 Disulfoton, June 15, 2001, which can be found on the internet or the public docket.

       Despite all of the mitigation measures previously described in this document, residual
 worker risks are still of concern for some crops and application methods. The Agency's decision
 considered the risks and benefits of continued disulfoton use as well as the availability of
 effective alternatives. EPA's risk-benefit findings, residual risks, and crop-specific decisions are
 summarized below.

       Asparagus

       The liquid formulation only is registered for use on asparagus through FIFRA Section
 24(c) Special Local Need (SLN) registrations in Arizona, California, North Carolina, Oregon,
 and Washington.  The granular formulation is not registered on asparagus. Most disulfoton use
 on asparagus is in California and Washington, which account for 96% of its use on this crop. In
 Washington, 50% of the asparagus crop is treated with disulfoton, and in California, 70% of the
 crop is treated. The liquid product is  mostly aerially applied, but is sometimes applied by
 groundboom to the field edges to control the target pest, the European asparagus aphid. The
 current labels allow for up to three applications of disulfoton.  The available alternatives to
disulfoton are chlorpyrifos and dimethoate, but are not sufficiently efficacious in controlling the
European asparagus aphid; therefore,  the Agency believes that the critical need for the use of this
chemical outweigh the risks.
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       Based on information from the USDA National Agricultural Statistics Service (NASS),
the overall average asparagus farm size in California is 219 acres. Also, for asparagus farms in
Washington, no farm is greater than 300 acres, and the average asparagus farm size is 62 acres.
Other sources indicate that the maximum area that can be aerially treated in a day is about 75-
150 acres in Washington, and about 150-200 acres in California. This information indicates an
approximate 2 to 4-fold reduction in the default 350 acres treated per day used to assess
occupational risks associated with aerial applications.

       Applications of liquid disulfoton to asparagus are for foliar treatment; therefore, the REI
for workers  to re-enter treated fields is 26 days.  However, because disulfoton is applied to
asparagus post-harvest, during the fern stage when growers do not need to re-enter treated fields,
this long REI is not expected to pose an undue hardship to growers. Also, the WPS allows REI
exemptions  to cover certain critical activities.
Scenario
Aerial
Groundboom
Worker MOE with Engineering Controls
Mixer/Loader
22
46
Applicator
34
(66)
REI
26 days •
The aerial scenario is based on 175 acres treated/day

       Asparagus Decision. Use of the liquid formulation only is eligible for reregistration,
and only in states where disulfoton is registered as a 24(c) SLN for asparagus.  The maximum
number of allowable applications for asparagus must be reduced from three times per year to two
times per year to help mitigate ecological risks.  Also, the REI is to be extended to 26 days.

       Barley and Wtieat

       Both liquid and granular formulations are registered for use on barley and wheat, but
late-season aerial application of the liquid appears to be the predominant use. Use of disulfoton
on these crops has been declining in recent years with <1% of either crop being treated
nationally. Disulfoton is used to control late-season infestations of Russian wheat aphid in
malting barley, which is used in beer production. Approximately 3% of all acres planted in
barley experience localized pockets of aphid infestation. The limited acreage of malting barley
crops that are affected by aphid damage are sometimes downgraded to lower value feed barley,
depending upon the plumpness of the kernel.

       The main alternative available to malting barley growers is lambda cyhalothrin
(Warrior®), which is currently only available as a FIFRA Section 18 registration in certain
states. Imidacloprid is also available to barley growers.  Barley growers have been increasingly
using lambda cyhalothrin to control aphids, which is contributing to the decline in disulfoton use.
Although lambda cyhalothrin is more expensive'than disulfoton, the cost differential does not
appear to be a disincentive for growers, because it is clearly the preferred choice for treating
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malting barley and is considered a safer alternative to disulfoton.  However, growers have
expressed some concern about the potential of aphids to develop resistance to the synthetic
pyrethroid, lambda cyhalothrin.  The Agency recognizes that resistence has been a problem with
certain synthetic pyrethroids, but is unable to use this information to predict likely grower
experience with lambda cyhalothrin in future years.  A FIFRA Section 3 registration for lambda
cyhalothrin on wheat, barley, and other cereal grains is pending and is expected to be granted in
2002.

       As with its use on barley, only a small percentage of wheat fields are treated with
disulfoton. When disulfoton is used on wheat, it is to control the Barley Yellow Dwarf Virus,
which is transmitted by aphids.  The highest reported use of disulfoton on wheat is in Kentucky,
where a late-season application of the liquid is made by custom applicators. In addition to the
pesticides that are available to barley growers, some of the key alternatives available to wheat
growers are chlorpyrifos, malathion, methomyl and pyrethrins.  The Agency considers the
benefits associated with the use of disulfoton on barley, including the availability and
effectiveness of alternatives, including lambda cyhalothrin, to be similar to its use on wheat.

       Foliar applications of liquid disulfoton resulted in post-application risk concerns for up to
16 days after application to barley, and  13 days after application to wheat.  Therefore, the REI
for workers to re-enter treated fields is 16 days for barley and 13 days for wheat for this type of
application. Because barley and wheat  are mechanically harvested, this longer REI is not
expected to pose an undue hardship to growers.  Also, the WPS allows REI exemptions to cover
critical activities,  such as irrigation, agricultural emergencies, or short-term activities.  MOEs
and REIs are summarized.below for barley and wheat use.
Scenario
Worker MOEs with Engineering Controls
Mixer/Loader
Applicator
REI
BARLEY
Aerial (liquid)
Aerial (granular)
Groundboom
Granular Tractor-Drawn Spreader
3.1
53
18
320
5.1
1.8
(27)
(37)
16 days for foliar
applications with
liquid formulation
48/72 hours for
granular
formulation
WHEAT
Aerial (liquid)
Aerial (granular)
Groundboom
Granular Tractor-Drawn Spreader
4.1
53
18
320
6.8
1.8
(27)
(37)
13 days for foliar
applications with
liquid formulation
48/72 hours for
granular
formulation
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( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Barley and Wheat Decision: Use of both the liquid and granular formulation on barley
and wheat are to be phased out by June 2005 to allow time for growers to transition to
alternatives, including lambda cyhalothrin. In the interim, the REI for foliar application is to be
extended to 16 days for barley and 13 days for wheat. For disulfoton applications that are soil
directed, the REI remains at 48/72 hours. Also, the technical registrant had requested the liquid
(Di-Syston SEC) label for use on wheat be changed to reduce the number of foliar applications
from two to one, for a seasonal maximum rate of 0.75 Ib ai/A.

       Snap and Lima Beans

       Both the liquid and granular formulations are registered for use on beans, and growers
use both formulations.  Based on data from 1987 to 1998, approximately 12% of planted beans
are treated with disulfoton. Disulfoton is applied at-plant and soil incorporated (i.e., in-farrow
and injected as a side-dressing) to control thrips.  Most of disulfoton use on lima beans is in
Georgia, where 20-30% of the crop is treated. At present, foliar application of acephate is the
only alternative pesticide to control thrips on lima beans. Disulfoton use on snap beans to
control the potato leaf hopper is sporadic and appears to be declining. The target pest occurs
intermittently and does not require control every year.  Registered alternatives to disulfoton on
snap beans include other organophosphates (acephate and dimethoate) or carbamates (carbaryl
and methomyl).

       The occupational risk estimates for this use are summarized below.  As stated earlier, the
Agency has some uncertainty regarding risk  estimates for crops where disulfoton is either shank
injected or applied in-furrow, such as beans. The Agency believes that these soil incorporated
methods of application result in less exposure to the applicator than does the groundboom or
tractor spreader methods, from which the estimated risks are derived.
Scenario
Groundboom
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Mixer/Loader
23
800
Applicator
(33)
(91)
REI
48/72 hours
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Bean Decision: Use of both the liquid and granular formulation on snap and lima, beans
are eligible for reregistration. The technical registrant has reduced the maximum rate for the
granular formulation from 2 Ibs ai/A to 1 Ib ai/A (which is reflected in the above table). Because
disulfoton applications are soil directed, the REI remains at 48/72 hours.

       Cabbage

       Both the liquid and granular formulations are registered for use on cabbage, and are used

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mostly as a rescue remedy for cabbage aphid and green peach aphid infestations. The liquid
formulation is shank injected and the granular formulation is applied as a soil incorporated band
or side-dressing.  Chemigation is an application method no longer being practiced by growers.
According to USDAISTASS data for the year 2000, approximately 3,400 Ib ai of disulfoton was
applied, with 3% of all cabbage grown nationally being treated with disulfoton. Most .disulfoton
use on cabbage is in California, where from 1997 to 1999, an average of 3100 Ibs ai of disulfoton
was applied to cabbage, primarily in Ventura County.  Both the liquid and granular formulations
of disulfoton are used in California. Imidacloprid is the main alternative, but it does not provide
the same long residual control as disulfoton.  Disulfoton provides the advantage of protecting
cabbage plants from aphid infestation for the entire season, and if it were not available, may
necessitate multiple applications imidacloprid.

       The occupational risk estimates for this use are summarized below.  As stated earlier, the
Agency has some uncertainty regarding risk estimates for crops where disulfoton is either shank
injected or applied in-furrow, such as cabbage. The Agency believes that these soil incorporated
methods of application result in less exposure to the applicator than does the groundboom or
tractor spreader methods, from which the estimated risks are derived.
Scenario
Groundboom
Tractor-Drawn Spreader
Chemigation
Worker MOEs with Engineering Controls
Mixer/Loader
23
530
Applicator
(33)
(62)
5.3
REI
48/72 hours
( ,) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Cabbage Decision: Use of both the liquid and granular formulation on cabbage are
eligible for reregistration, provided the Chemigation application methods is deleted from labels.
Because disulfoton applications are soil directed, the REI remains at 48/72 hours.

       Cole Crops (Broccoli, Brussels Sprouts, Cauliflower)

        Both the liquid and granular formulations are registered for use on broccoli, Brussels
sprouts, and cauliflower.  The liquid is used exclusively in California's Salinas Valley, where it
is applied by shank injection once per season as a rescue remedy to control cabbage and green
peach aphids.  Within the Salinas Valley, Monterey County appears to be where the liquid
formulation is used predominantly. The importance of disulfoton use on cole crops in California
is demonstrated by the usage data from 1997 to 1999 for Monterey County, California which
indicate that as much as 60% of broccoli, 87% of Brussels sprouts, and 52% of cauliflower that
was grown was treated with disulfoton.  The granular formulation is mainly used on cole crops
grown outside  California.

       Registered alternatives to disulfoton on cole crops include imidacloprid and the OP
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pesticides oxydemeton-methyl, dimethoate, and chlorpyrifos.  Currently, imidacloprid is applied
at-plant, but it does not control the cabbage aphid throughout the entire growing season, due to
its limited period of residual effectiveness.  Also, imidacloprid is not effective as a foliar
application. Chlorpyrifos is toxic to beneficial insects and also causes phytotoxicity at the high
rates required to control the cabbage aphid.

       Commercial applicators in California, who treat many farms and therefore receive the
most exposure, generally treat no more than 40 acres per day. Private growers treat even less
acreage. While commercial applicators may treat more than one farm during severe aphid
outbreaks, they typically apply disulfoton no more than two or three times in one week.  To
assess risk based on typical current practices in California, the Agency adjusted worker MOEs in
the table below to reflect the assumption that no more than 40 acres are treated per day for cole
crops. Also, the Agency has some uncertainty regarding risk estimates for crops where
disulfoton is either shank injected or applied in-furrow, such as cole crops. The Agency believes
that these soil incorporated methods of application result in less exposure to the applicator than
does the groundboom or tractor spreader methods, from which the estimated risks are derived.
Scenario
Groundboom
Tractor-Drawn Spreader
Chemigation
Worker MOEs with Engineering Controls
Mixer/Loader
92
800
Applicator _
(132)
(91)
96
REI
48/72 hours
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator
MOEs for both groundboom and chemigation use are adjusted to reflect 40 acres treated/day

       Cole Crop Decision: Based on the reduced acreage treated assumption for the
groundboom and chemigation scenarios, the corresponding MOEs for mixers/loaders and
applicators are near or above the target MOE of 100, and are therefore not of concern to the
Agency. Hence, use of both the liquid and granular formulation'on cole crops are eligible for
reregistration. However, because the liquid formulation is used exclusively in California, the
Section 3 label is to be modified to limit use to California only, which reflects current
agricultural practice.  Because disulfoton applications are soil directed, the REI remains at 48/72
hours. Also, to mitigate ecological risk, the technical registrant has reduced the number of soil
applications for broccoli and cauliflower from two to one, for a seasonal total of 1 Ib ai/A.  •

       Lettuce

       Only the liquid formulation of disulfoton is registered for use on lettuce. Disulfoton is
applied pre-plant or at-plant by banding. Nearly all (>95%) iceberg lettuce and leaf lettuce
grown in the United States is produced in California and Arizona. Based  on 1987 to 1998 usage
information, a weighted average of approximately 13,000 Ibs ai of disulfoton was applied to
lettuce nationally. However, most of disulfoton use on lettuce is in California, where frorja 1997
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 to 1999 an average of approximately 11,000 Ibs ai of disulfoton was applied to lettuce.  No use
 of disulfoton has been reported in other major lettuce producing states, including Florida and
 Arizona.

       Disulfoton use on lettuce in California is mostly limited to the Salinas Valley, which
 includes Monterey County. Approximately 59% of the total amount of disulfoton that is used on
 head lettuce is used in Monterey County, and 57% of the total amount of disulfoton that is used
 on leaf lettuce is also used in Monterey County. The surrounding counties that encompass
 Salinas Valley consume much of the remaining amount of disulfoton used on lettuce. Disulfoton
 is used in this area primarily to control the lettuce root aphid, which is harbored in Lombardy
 poplars, a popular ornamental.  Growers have indicated that root aphid infestation could result is
 as much as 20-30% of individual field loss. The main  pesticide alternative available is
 imidacloprid,  which has a short residual activity and therefore does not provide adequate control.
 As such, disulfoton is used as a rescue remedy, when other methods of pest control fail.

       As mentioned previously, private growers and commercial applicators in the Salinas
 Valley generally treat fewer acres per day than was assumed in the occupational risk assessment.
 To assess risk based on typical current practices in California, the Agency adjusted worker
 MOEs in the table below to reflect the assumption that no more than 40 acres are treated per day
 for lettuce.
Scenario
Groundboom
Chemigation
Worker MOEs with Engineering Controls
Mixer/Loader ,
46
Applicator
(66)
46
REI
48/72 hours
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator
MOEs for both groundboom and chemigation use are adjusted to reflect 40 acres treated/day

       Lettuce Decision; Use of the liquid formulation on lettuce is eligible for reregistration.
However, because the liquid formulation is used exclusively in California, the Section 3 label is
to be modified to limit use to California only, which reflects current agricultural practice.
Because disulfoton applications are soil directed, the REI remains at 48/72 hours.

       Cotton

       Both the liquid and granular formulations are registered for use on cotton.
Approximately half of all disulfoton annually produced is used on cotton (420,000 Ibs ai), with
5-8% of the crop being treated.  Most use is in Louisiana, Missouri, Mississippi, and Texas, with
some use in Alabama, Arkansas, Georgia, Florida, Tennessee, the Carolinas, and Virginia.
Disulfoton is predominately used as a safener to protect cotton seedlings from the effects of the
herbicide clomazone (Command®), which is the herbicide of choice to control velvet leaf,
primrose, morning glory, and wild ppinsettia. Disulfoton is applied in-furrow with the seed,
while clomazone is applied as a band on top.  Roughly equal amounts of both the liquid and
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granular formulation are used by cotton growers, which is largely determined by the type of
equipment available to the grower. If either formulation were no longer available, growers
would incur substantial costs to convert their equipment to the other formulation. Also, because
aerial applications are not being made by growers, this method of application is not being
supported for reregistration and is being voluntarily cancelled.

       Alternatives to disulfoton use on cotton include phorate and aldicarb.  However, phorate,
which is applied as a granular formulation, is not as efficacious against thrips; and aldicarb,
which is very effective against thrips, does not act as a safener. Although use of disulfoton on
cotton has been declining, due to the introduction of genetically modified glyphosate tolerant
(RoundUp-Ready®) cotton, the percentage of acreage that can be planted with glyphosate
tolerant cotton is limited. Therefore, disulfoton is still important in areas that use clomazone for
weed control.

       The occupational risk estimates for this use are summarized below. As stated earlier, the
Agency has some uncertainty regarding risk estimates for crops where disulfoton is either shank
injected or applied in-farrow, such as cotton.  The Agency believes that these soil incorporated
methods of application result in less exposure to the applicator than does the groundboom or
tractor spreader methods, from which the estimated risks are derived.
Scenario
Aerial (SLN)
(Voluntary Cancellation)
Groundboom
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Mixer/Loader
15
18
320
Applicator
25
(27)
(37)
REI
48/72 hours
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Cotton Decision:  Use of both the liquid and granular formulation on cotton are eligible
for reregistration. Also, labeling shall specify at-plant and in-furrow applications only, and for
use as safener, which reflects current agricultural practice.  Because disulfoton applications are
to be limited to at-plant and in-furrow as a safener, the current REI of 48/72 hours is still
protective and shall remain. Also, because aerial application to cotton is no longer being made
by growers, it is not being supported for reregistration.  Therefore, labels for disulfoton use on
cotton use will need to be amended to prohibit aerial application, including the 24(c) SLN
registration for aerial use in Texas. Moreover, to help mitigate ecological risk concerns, the
technical registrant removed foliar application from the Section 3 disulfoton labels, and reduced
the number of soil applications from three to one per year at a rate of 1 Ib ai/A.

       Peanuts

       Only the granular formulation of disulfoton is registered for use on peanuts. Based on
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 1987 to 1998 usage data, a weighted average of 47,000 Ib ai of disulfoton was applied annually
 to peanuts, which accounts for approximately 3% of the crop being treated. In the year 2000,
 disulfoton use on peanuts was reported in Alabama, Georgia, North Carolina, and Oklahoma.
 Disulfoton is applied in-furrow or as a soil incorporated side-dressing to control thrips and
 aphids.  Since the time the occupational risk assessment was prepared, Bayer, the technical
 registrant, had reduced the maximum application rate for the Section 3 registration from 2 Ibs
 ai/A to 1 Ib ai/A. Moreover, North Carolina has also voluntarily agreed to reduce the maximum
 application rate to 1 Ib ai/A for their 24(c) SLN registration. The occupational risk estimates
 based on the 1 Ib ai/A rate are summarized below. Also, the Agency has some uncertainty
 regarding risk estimates for crops where disulfoton is either shank injected or applied in-furrow,
 such as peanuts.  The Agency believes that these soil incorporated methods of application result
 in less exposure to the applicator than does the groundboom or tractor spreader methods, from
 which the estimated risks are derived.
Scenario
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Loader
800
Applicator
(91)
REI
48/72 hours
 ( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Peanuts Decision;  With the reduction of the maximum application rate for disulfoton
 use on peanuts, the corresponding MOEs for loaders and applicators are near or above the target
 MOE of 100, and are therefore not of concern to the Agency. Hence, use of the granular
 formulation on peanuts is eligible for reregistration. Because disulfoton applications are soil
 directed, the REI remains at 48/72 hours. The technical registrant has reduced the maximum
 application rate on Section 3 labels from 2 Ib ai/A to 1 Ib ai/A. Similarly, North Carolina has
 also voluntarily agreed to reduce the maximum application rate to 1 Ib ai/A for their 24(c) SLN
 registration; however, in accordance with the current 24(c) registration, two applications of
 disulfoton on peanuts is still permitted.

       Peppers

       Both the liquid and granular formulations are registered for use on a variety of peppers.
 The liquid registration is limited to a 24(c) SLN registration in California, where it is applied to
 the soil by shank injection.  This is the.application method of choice in California, because
 growers are not equipped to apply the granular formulation.  Based on 1987 to 1998 usage data,
 a weighted average of 4,000 Ib ai of disulfoton was applied annually to chili peppers, which
 accounts for approximately 25% of the crop being treated. Although a significant percentage of
peppers grown in the US are harvested in New Mexico and California, peppers are also grown in
other regions of the country. For instance,  USD A NASS data for the year 2000 indicate that
New Mexico harvested 57% of the chili peppers produced in the US, and California harvested
41% of the bell peppers produced in the US.  These figures indicate that a considerable amount
of peppers are grown outside these states as well. Most of the use of the liquid formulation is in
the Salinas Valley of California where disulfoton is used as a rescue remedy to control the green
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peach and cabbage aphid and the garden symphylan, a non insect pest.  The green peach aphid
vectors for several mosaic viruses lethal to pepper plants. The granular formulation, which is
used outside California, is applied in a soil incorporated band.

       Registered alternatives to disulfoton on peppers include imidacloprid, diazinon,
dimethoate, malathion, chlorpyrifos, oxydemeton-methyl, and pyrethrins.  Neither diazinon nor
malathion is effective against the green peach aphid.  Dimethoate is an inexpensive, frequently
used alternative, but it is no longer effective for aphid control in some areas of California and
New Mexico. Use of imidacloprid is increasing, but it does not provide effective control in some
parts of California. Chlorpyrifos is toxic to beneficial insects and also causes phytotoxicity at
the high rates required to control the cabbage aphid. Pyrethroids are not often used, because they
are not compatible with integrated pest management (IPM) programs. Therefore, the Agency
believes that there is a critical need for disulfoton use on peppers.

       As mentioned previously, private growers and commercial applicators hi the Salinas
Valley generally treat fewer acres per day than was assumed in the occupational risk assessment.
To assess risk based on typical current practices hi California, the Agency adjusted worker
MOEs in  the table below for the groundboom scenario to reflect the assumption that no more
than 40 acres are treated per day for peppers. MOEs for the granular tractor drawn spreader
scenario were not adjusted because it is primarily used outside California. Also, the Agency has
some uncertainty regarding risk estimates for crops where  disulfoton is either shank injected or
applied in-furrow, such as peppers. The Agency believes that these soil incorporated methods of
application result in less exposure to the applicator than does the groundboom or tractor spreader
methods,  from which the estimated risks are derived.
Scenario
Groundboom
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Mixer/Loader
46
400
Applicator
(66)
(45)
REI
48/72 hours •
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator
MOEs for the groundboom scenario are adjusted to reflect 40 acres treated/day

       Pepper Decision; Use of both the liquid and granular formulations on peppers are
eligible for reregistration. Because the liquid formulation is used exclusively in California, its
use is limited to an existing FIFRA 24(c) SLN registration in California, which reflects current
agricultural practice.  Also, because disulfoton applications are soil directed, the REI remains at
48/72 hours.

       Potatoes

       Both the liquid and granular formulations of disulfoton are registered for use on potatoes
to control aphids.  The liquid is mainly used hi the Pacific Northwest (PNW) (i.e.," Oregon,
Idaho, Washington, and Utah), where it is predominantly applied either aerially or by
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 chernigation (sprinkler irrigation) as an alternative to methamidophos (Monitor®), the pesticide
 of choice.  The liquid formulation is generally applied as a foliar application for late-season
 aphid control in sensitive areas where growers cannot aerially apply methamidophos. The
 granular formulation appears to be used mostly outside the PNW, where it is applied to the soil
 and incorporated. Based on 1987-1998 usage data, an average of 4% of the nations potato
 acreage were treated with disulfoton. However, use of disulfoton on potatoes in recent years
 appears to be declining with only about 1% of the crop treated nationally in 1999.  In Idaho,
 however, disulfoton use is slightly higher than the national average where 4% of the total potato
 acres grown were treated.

       There are a number of alternative pesticides that are available that can be applied by
 chemigation to control aphids, which include pymetrozine, thiomethoxam (late-season),
 imidacloprid (early-season), and methamidophos.  Methamidophos (Monitor®), the pesticide of
 choice for aerial applications is  available to control aphids via chemigation. Imidacloprid can be
 applied at planting for control of early to mid-season aphid and Colorado potato beetle
 infestations. Both pymetrozine  and thiomethoxam can be applied by chemigation, and are
 effective at late-season aphid control. Further, pymetrozine is less expensive than disulfoton;
 however, no cost data were available for thiomethoxam.  Because pymetrozine  and
 thiomethoxam are relatively new, they have yet to be widely used; however, efficacy field trials
 show promising results for aphid control.  Moreover, the Agency believes that the economic loss
 resulting from substituting disulfoton with either methamidophos or the other alternatives
 mentioned  would cause negligible economic impact to the overall potato industry. Because of
 the availability of these alternatives, which may be contributing to the decline in disulfoton use,
 and the negligible economic impact to the industry, the Agency believes that potato growers no
 longer have a critical need for disulfoton.
Scenario
Aerial (liquid)
(East of the Rockies)
Groundboom
Chemigation
Aerial (granular)
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Mixer/Loader
21
15
Applicator
35
(22)
3.5
61
270
2.1
(31)
REI
20 days
(Foliar Application)
37 days
(Foliar Application)
48/72 hours
(Soil Directed
Application)
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Potato Decision:  Use of both the liquid and granular formulations are to be phased out
by June 2005 to allow growers time to transition to the newer and safer alternatives. In the
interim, the REI for foliar application to potatoes is to be extended to 37 days for overhead
sprinkler irrigation and groundboom applications, and 20 days for aerial applications East of the
Rockies. For disulfoton applications that are soil directed, the REI remains at 48/72 hours.
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       Also, to help further mitigate occupational and ecological risks, the technical registrant
has reduced the total number of soil applications from two to one per year; has discontinued all
foliar application West of the Rockies, except overhead sprinkler irrigation (chemigation); and
reduced the maximum application rate from 3 to 0.5 Ib ai/A for foliar applications East of the
Rockies.

       Radish Grown for Seed

       Both the liquid and granular formulations are registered for use on radish grown for seed
in Washington only through a 24(c) SLN registration.  As part of this registration, disulfoton use
is limited to the Columbia River Basin in Washington to control cabbage and turnip aphids,
which are a pest not seen in other areas that can cause premature plant death and crop loss. Both
formulations are applied to the soil and are either shank injected or soil incorporated.  In the year
2000, only about 635 acres total of this crop was produced. Even though it is a minor crop, it is
an economically important crop for growers in the Columbia River Basin, and disulfoton
provides a niche use to this industry.

       The only registered alternatives available to growers are pirimicarb, chlorpyrifos, and
pymetrozine. Pirimicarb is used solely to control late-season aphid infestations; chlorpyrifos
cannot be used during bloom when aphids can occur; and pymetrozine is more expensive than
disulfoton and does not provide good lower canopy control. Another advantage of disulfoton is
that it allows predatory  and parasitic insects to develop in the seed radish fields.

       The occupational risk estimates for this use are summarized below. As stated earlier, the
Agency has some uncertainty regarding risk estimates for crops where disulfoton is either shank
injected or applied in-furrow, such as radish. The Agency believes that these soil incorporated
methods of application result in less exposure to the applicator than does the groundboom or
tractor spreader methods, from which the estimated risks are derived.
Scenario
Groundboom
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Mixer/Loader
23
400
Applicator
(33)
(45)
REI
48/72 hours
 ( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

        Radish Grown for Seed Decision: Use of both the liquid and granular formulations on
 radish grown for seed are eligible for reregistration, through the existing FIFRA 24(c) SLN
 registration in Washington only. Because disulfoton applications are soil directed, the REI
 remains at 48/72 hours.

        Clover Grown for Seed

        Only the granular formulation is registered for use on clover grown for seed in

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Washington only through a 24(c) SLN registration. One soil directed application of disulfoton is
made per crop season with a tractor drawn spreader to control aphids and mites. The
occupational risk estimates for this use are summarized below.  Because the occupational risks
are low, information on the benefits associated with this use was not collected.
Scenario
Tractor-Drawn Spreader
Worker MOEs with Engineering Controls
Loader
800
Applicator
(91)
REI
48/72 hours
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Clover Grown for Seed Decision: The MOEs for loaders and applicators are near or
above the target MOE of 100, and are therefore not of concern to the Agency. Hence, use of the
granular formulation on clover grown for seed is eligible for reregistration, through the existing
FIFRA 24(c) SLN registration in Washington only. Because disulfoton applications are soil
directed, the REI remains at 48/72 hours.

       Coffee Trees

       The  granular formulation is registered for use in Puerto Rico only on coffee trees.
Disulfoton is applied to the soil by custom applicators only using a bucket and spoon at a rate of
8.3 Ibs ai/A. This rate is much a higher rate than that used for most other crops, but is validated
by efficacy data. The benefits associated with the use of disulfoton on coffee trees in Puerto
Rico are high, largely because of the need to control leafrniners, which can cause up to a 40%
reduction in yield. The only alternatives available to growers are aldicarb and azadirachtin;
however, azadirachtin does not have the residual activity needed to control leafrniners.

       The  occupational risk estimates for handling and applying disulfoton to coffee trees are
summarized below. The Agency assessed risks using two application methods: hand application
with a bucket and spoon with PPE, which is currently used by custom applicators in Puerto Rico;
and a tractor drawn spreader with engineering controls, which serves as a surrogate for other
potential application methods.  The Agency believes that risks can be reduced by use of a closed
loading/transfer system, with performance specifications similar to the device currently under
development by Tuthill Sotera in cooperation with the North Carolina Cooperative Extension
Service for use on Christmas trees. For comparison purposes, assuming this closed
loading/transfer device being developed will provide at least the  same level of protection as a
closed system currently available for tractor drawn spreaders, the MOE for an individual loading
the granulars with a closed transfer handheld device could be as high as 1500, based on the
individual applying up to 5 acres in a day. The Agency acknowledges that this estimate does not
include the exposure the same individual would received from also applying the chemical with
this device, because data to complete  this  analysis is not yet available. However, the Agency
expects that the protection provided by this type of device will be significantly better than the
current bucket and spoon application practice.
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Scenario
Bucket & Spoon
Tractor-Drawn Spreader
Worker MOEs
Loader
Applicator
0.2 - 0.4 [Minimum PPE]
96 [Eng. Controls]
(11)
REI
48/72 hours
( ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Coffee Tree Decision; Use of the granular formulation on coffee trees in Puerto Rico  .
only is eligible for reregistration provided that a closed transfer system is implemented by June
2004 and the REI remains at 48/72 hours.

       Christmas Trees (Fraserfirs)

       Only the granular is registered for use on conifers raised for the Christmas tree market.
There is also a 24(c) SLN registration in North Carolina for use of disulfoton at a rate of 4.5 Ibs
ai/A to control balsam wooly algedid and spruce spider mite on Fraser firs. The Section 3
registration is for a rate of 3.75 to 7.5 grams per foot of tree height or 2.5 oz/inch of tree
diameter at 4 feet above ground (diameter chest height), which extrapolates to 78 Ib ai/A.
According to the National Christmas tree association, disulfoton is used on firs grown for
Christmas trees in 16 states. North Carolina represents the greatest use, with 60,000 Ibs ai
applied annually and 65% of the crop being treated. The target pests named above cause
significant crop  damage, resulting in downgrading of trees and reduced sale value. In cases of
severe pest damage,  trees must be held over for an additional year, at a cost to the grower, or
infested trees must be destroyed.

       Disulfoton is applied at bud break in early spring, followed by foliar applications of
chlorpyrifos and esfenvalerate. Chlorpyrifos  and esfenvalerate must be foliarly-applied by a
commercial applicator by mist blower or high-powered hose sprayer. Foliar applications are
problematic because they  are usually uneven, which significantly affects efficacy.  Further, the
chlorpyrifos foliar spray is phytotoxic in some situations, and although esfenvalerate controls the
balsam wooly adelgid to a limited extent, it allows the spider mite populations to increase.  In
comparison, disulfoton controls both the balsam twig aphid and spruce spider mite, while
conserving beneficial insect predators. This information indicates that the need for disulfoton is
critical, especially for use on Fraser firs in North Carolina, because firs are a  high value
perennial crop.

       The occupational risk estimates for the predominant application methods used in North
Carolina are summarized below, and represent the worse case for use on firs. The Agency
believes that risks can be reduced by use of a closed loading/transfer  system currently under
development by Tuthill Sotera in cooperation with the North Carolina Cooperative Extension
Service for use on Christmas trees.
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Scenario
Bucket & Spoon
Tractor-Drawn Spreader
(Motorbike)
Worker MOEs
Loader
Applicator
0.4 - 0.7 [Minimum PPE]
280 [Eng. Controls]
23 [Maximum PPE]
REI
48/72 hours
       Christmas Tree Decision;  Use of the granular formulation on Christmas trees is eligible
for reregistration, provided the Section 3 label maximum application rate is reduced to 4.5 Ib
ai/A, and use is limited to firs, and a closed transfer system is implemented by June 2002, and
confirmatory exposure data for loader/applicators demonstrate that exposure and risk are
comparable to other high benefit scenarios. Also, disulfoton must be soil incorporated, watered
in, or applied to areas with permanent groundcover. Because disulfoton applications are soil
directed, the REI remains at 48/72 hours.

       Commercially Grown Ornamentals

       Only the granular formulation is registered for use on numerous species of ornamental
plants, including shrubs, trees, flowers and groundcover, and potted ornamental plants (field or
nursery stock). The current label specifies application rates of 3.75 to 7.5 grams  per foot of
height for a tree or shrub; 2.5 oz per inch of trunk diameter measured 4 feet from the ground for
trees; or 5 Ib product (0.75 Ib a.i.) per 1000 linear feet of row. For purposes of risk assessment,
the Agency has converted these rates to 37 Ib ai/A for trees, 109 Ib ai/A for shrubs, and 29 Ib
ai/A for field grown ornamental flowers and groundcover.  The Agency also assessed risks based
on 13 Ib ai/A, the lowest rate that the American Nursery & Landscape Association stated was
necessary to ensure efficacy.

       There is very little documented use of disulfoton on ornamentals and many alternative
pesticides are available. Based on preliminary results of recent USDA NASS data for pesticide
use in the  nursery and floriculture industry, only 22 of 4,000 operations reported  use of
disulfoton. The California use reporting database also shows little use of the chemical for
ornamental plants. Moreover, after conducting exhaustive outreach to major states which
produce ornamentals, very little use was disclosed and many agricultural extension agents who
work with ornamental plants do not recommend use of disulfoton. Also, there are significant
uncertainties associated with potential post-application exposure from routine activities,  such as
transplanting.  To adequately assess risks for these type of activities, post-application exposure
monitoring, which include soil residue dissipation (OPPTS 875.2200) and dermal exposure
(OPPTS 875.2400) data, would need to be provided to the Agency. These data might indicate
the need for further REI restrictions.

       Given the limited use and availability of cost-effective efficacious alternatives, the
benefits of continued use are low, particularly when compared to the worker MOEs and
uncertainty associated with post-application activities and risks. Worker risk estimates for the
predominant use of disulfoton on field grown ornamental shrubs, trees, flowers, and groundcover
                                           95

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at an application rate of 13 Ib ai/A are summarized below.
Scenario
Loading/Applying with
Scoop & Bucket
Loading/Applying with
Belly Grinder
Tractor-Drawn Spreader
Worker MOEs
Loader
Applicator
0.1 - 0.3 [Minimum PPE]
0.1 [Maximum PPE]
120 [Eng. Controls]
(14)
REI
48/72 hours
 [ ) Indicates risk estimate for an applicator in an enclosed cab with a dust/mist respirator

       Ornamentals Decision: Use of the granular formulation is to be phase out by June
 2005, because of the limited existing need and use of the chemical, and the absence of
 information on the benefits of its continued use. For disulfoton applications that are soil
 directed, the REI remains at 48/72 hours.

       E.     Labeling

       In order to remain eligible for reregistration, other use and safety information needs to be
 placed on the labeling of all end-use products containing disulfoton.  For the specific labeling
 statements, refer to Table 16 in Section V of this document.

              1.     Endangered Species Statement

       The Agency has developed the Endangered Species Protection Program to identify
 pesticides whose use may cause adverse impacts on endangered and threatened species, arid to
 implement mitigation measures that address these impacts. Disulfoton has potential to result in
 effects to several aquatic species, in the absence of additional safeguards.  EPA has adopted
 Reasonable and Prudent Measures (RPMs) provided by the U.S. Fish and Wildlife Service
 Biological Opinions and has or will implement these measures, as appropriate, through
 Endangered Species Interim Bulletins.

       The Endangered Species Protection Program as described in a Federal Register notice (54
 FR 27984-28008, July 3, 1989) is currently being implemented on an interim basis.  As part of
 the interim program, the Agency has developed County Specific Pamphlets that articulate many
 of the specific measures outlined in the Biological Opinions issued to date. The Pamphlets are
 available for voluntary use by pesticide applicators on EPA's website at www.epa.gov/esp.p,

              2.      Spray Drift Management

        The Agency has been working with the Spray Drift Task Force, EPA Regional Offices,
 State Lead Agencies for pesticide regulation, and other parties to develop improved spray drift
 management practices. The Agency has completed its evaluation of the new database submitted

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by the Spray Drift Task Force and is developing policy on how to appropriately apply the data
and the AgDRIFT computer model to its risk assessments for pesticides applied by air, orchard
airblast, or ground hydraulic spray. After the policy is in place, the Agency may impose further
refinements in spray drift management practices to reduce off-target drift and risks associated
with aerial application or other application methods associated with drift, where appropriate.

       Based on these analyses, the Agency is in the process of developing more appropriate
label statements for spray, and dust drift control to ensure that public health, and the
environment are protected from unreasonable adverse effects. In August 2001, EPA published
draft guidance for label statements in a pesticide registration (PR) notice ("Draft PR Notice
2001 -X" http://wwwiepa.gov/ PR_Notices/#2001). A Federal Register notice was published on
August 22,2001 (http://www.epa.gov/fedrgstr) announcing the availability of this draft guidance
for a 90-day public comment period. After review of the comments, the Agency will publish
final guidance in a PR notice for registrants to use when labeling their products.

       In the interim, registrants may choose to use the proposed statements. Registrants should
read and refer to the draft PR notice to obtain a full understanding of the proposed guidance and
its intended applicability, exemptions for certain products, and the Agency's willingness to
consider other versions of the statements.

       Registrants may elect to adopt the appropriate sections of the proposed language below,
or a version that is equally protective, for their end-use product labeling for the purpose of
complying with the deadlines for label submission outlined in this document. The proposed
label language is as follows:

       For products applied outdoors as liquids:

       "Do not allow spray to drift from the application site and contact people, structures
       people occupy at any time  and the associated property, parks and recreation areas,
       nontarget crops, aquatic and wetland areas, woodlands, pastures, rangelands, or animals."

       "For ground boom applications, apply with nozzle height no more than 4 feet above the
       ground or crop canopy, and when wind speed is 10 mph or less at the application site as
       measured by an anemometer.  Use	(registrant to fill in blank with spray quality,
       e.g. fine or medium) or coarser spray according to ASAE 572 definition for standard
       nozzles or VlylD for spinning atomizer nozzles."

       "For aerial applications, the boom width must not exceed 75% of the wingspan or 90% of
       the rotary blade.  Use upwind swath displacement, and apply only when wind speed is  3 -
       10 mph as measured by an anemometer. Use	(registrant to fill in blank with spray
       quality, e.g. fine or medium)  or coarser spray according to ASAE 572 definition for
       standard nozzles or VMD for spinning atomizer nozzles. If application includes a no-
       spray zone, do not release spray at a height greater than 10 feet above the ground or the
       crop canopy."
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      For overhead chemigation:

      "Apply only when wind speed is 10 mph or less."

      On all product labels:

      "The applicator also must use all other measures necessary to control drift."
      "For ground rig applications, apply product no more than 4 feet above the ground
      or the crop canopy, and only when wind speed is 10 mph or less at the application
      site as 'measured by an anemometer."

      "For aerial applications, use upwind swath displacement, and apply only when wind
      speed is 3 - 10 mph as measured by an anemometer.  If application includes a no-spray
      zone, do not release dust at a height greater than 10 feet above the ground or the crop
      canopy."

      "The applicator also must use all other measures necessary to control drift."

      For hand-applied products, including home and garden products, to he applied as sprays
      or dusts:

      "Do not allow spray or dust to drift from the application site, and contact people,
      structures people occupy at any time, and the associated property, parks and recreation
      areas, nontarget crops, aquatic and wetland areas, woodlands, pastures, rangelands, or
      animals. Apply only when wind speed is not more than 10 mph. For sprays, apply
      largest size droplets possible."

      Alternatively, registrants may elect to use the following language, which is the current
Agency policy on drift labeling:

      For products that are applied outdoors in liquid sprays (except mosquito adulticides").
      regardless of application method, the following must be added to the labels:

      "Do not allow this product to drift."

      The Agency recognizes that the above option does not address other application types.
Registrants may therefore wish to adapt some variation of the old, and proposed new language
for their particular products,  depending on their application methods.

       F.     Disulfoton Risk Mitigation Summary

       Based on the rationale for the interim decisions associated with the use of disulfoton, the
following risk mitigation measures are also necessary  to be incorporated in their entirety into
labels for disulfoton-containing products in order for disulfoton to be eligible for reregistration.
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Specific language of these revisions is set forth in the summary tables ,of Section V of this
document.  Likewise, the data required to be provided to the Agency to confirm these regulatory
decisions are also listed in Section V.

       Dietary Risk

•      No label changes are necessary, however certain confirmatory data listed in Section V is
       required.

       Residential Risk

       Only end-use products containing 2% active ingredient or less are eligible for
reregistration. The following measures are necessary to mitigate residential risk:

•      Limit maximum label rates for disulfoton packaged for hand application with a self
       .contained measuring cup/lid to 0.3 Ib ai/1000 ft2 for use on flowerbeds; 0.01 Ib ai/4 ft
       bush for use on shrubs; and 0.0013 Ib ai/bush for use on rose bushes.

•      Limit the maximum label rate for disulfoton packaged for application with a push type
       spreader to 0.3 Ib ai/1000 ft2.  Products to be applied by this method do not need to be in
       child resistant packaging, and commercial use of this product is prohibited.

•      Prohibit application of disulfoton with a belly grinder.

•      Prohibit application to flower gardens and ornamental shrubs with a spoon, measuring
       scoop, shaker can, or by hand, unless the packaging and method of application of the
       end-use product conforms with the performance of a measuring cup  and lid packaging
       currently manufactured for the Bayer Advanced Garden 2-in-l  Systemic Rose and
       Flower Care® Disulfoton 1% granular product.

•      Package all products marketed and labeled for hand application in child resistant
       packaging with a self-contained measuring device, which serves as the container lid and
       clearly measures the quantity to be applied. Products marketed and labeled for
       application with a push type spreader do not need to be in child resistant packaging, but
       must be labeled "not for application by hand." Commercial use of the homeowner
       product is prohibited.

•      Delete the following uses from all product labels:  all indoor uses, use in greenhouses,
       and use on home vegetable gardens, including use on spinach and tomatoes.

       Occupational Risk

       The following measures are necessary to mitigate  handler risk:
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       Closed mixing/loading systems for liquid formulations by December 31, 2002;

•      Closed loading systems for granular formulations by June 2004;

       Enclosed cabs plus a dust-mist respirator for all ground equipment applicators;

•      Enclosed cockpits for all aerial applicators;

       Mechanical flaggers for aerial application; or the use of global positioning system (GPS)
       equipment that negates the need for flaggers;

       When engineering controls are not feasible, handlers must wear maximum PPE (i.e.,
       double layer clothing, chemical-resistant gloves and footwear, and a dust-mist respirator);

•      Use on cotton is limited to at plant, in furrow, and use as a herbicide safener only;

•      Reduction of maximum application rate from 2 Ib ai/A to 1 Ib ai/A for beans and
       peanuts;

       For coffee and Christmas trees, application by open, handheld equipment, including belly
       grinders and bucket and spoon will be prohibited after June 2004. Where this is currently
       the application method of choice, growers will be allowed until June 2004 to transition to
       another method; and

       Use on barley, wheat, potatoes, and commercially grown ornamentals (field or nursery
       stock)  is phased out by June 2005.

       The following measures are necessary to mitigate risk to post-application workers:
       i                                                 •-                           	
       For soil directed application of the liquid formulation and for all granular formulations,
       the Worker Protection Standard designates the REI to be 48 hours, or 72 hours in regions
       where  the annual rainfall is less than 25 inches. These are the current REIs on disulfoton
       product labels.

       For foliar application of the liquid formulation, a 26 day REI is necessary for asparagus.
       Longer REIs are also necessary for foliar application to barley (16 days), wheat (13
       days),  and potatoes (20 or 37 days depending upon method of application). As
       mentioned above, the uses on barley, wheat, potatoes, and ornamentals are to be phased
       out by June 2005.

       Ecological Risks

       The following measures are necessary to mitigate ecological risks.  Disulfoton is eligible
 for reregistration provided that:
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•      A precautionary bee statement is added to all product labels for liquid formulations of
       disulfoton

•      Use is prohibited within a level, well maintained 25 foot vegetative buffer between
       treated fields and all permanent water bodies. (Refer to the March 2000 USDA Natural
       Resources Conservation Service  document: Conservation Buffers to Reduce Pesticide
       Losses for guidance.)

       No more than one application of disulfoton per calendar year for all crops, except for
       asparagus, barley, coffee, peanuts (North Carlina only), and potatoes (foliar application
       West of the Rockies only), for which no more than two applications of disulfoton per
       calendar year are permitted.

       Aerial application to cotton is prohibited;

       The maximum application rate for Christmas trees is reduced from 78 to 4.5 Ibs ai/A
       nationally, the use is limited to fir species only, and disulfoton is soil incorporated,
       watered in, or applied to areas with vegetative groundcover.

•      Uses on barley, wheat, potatoes,  and ornamental plants, including trees, shrubs, and
       groundcovers (field or nursery stock), are phased out by June 2005.  The phase out of
       these uses addresses ecological, as well as worker and  drinking water risks1 of concern.

       Eligible Uses

       The following uses are eligible for reregistration, pending consideration of the
cumulative assessment for the OPs:

•      Asparagus: Liquid formulation only

•      Beans, lima and snap: Both the liquid and granular formulations

*      Cabbage:  Both the liquid and granular formulations

       Cole Crops (broccoli, Brussels  sprouts, cauliflower): Both liquid (California only) and
       granular formulations

•      Lettuce: Liquid formulation only; California only

       Peppers:  Both the liquid and granular formulations

•      Peanuts: Granular formulation only

       Cotton:  Both the liquid and granular formulations
                                           101

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Radish Grown for Seed:  Both the liquid and granular formulations

Clover Grown for Seed:  Granular formulation only

Coffee Trees:  Granular formulation only

Christmas Trees:  Granular formulation only

Uses to be Phased Out

Barley and Wheat: Both the liquid and granular formulations

Ornamentals: Granular formulation only for field grown trees, shrubs, flowers and
groundcover, and potted ornamentals (field or nursery stock)

Potatoes: Both the liquid and granular formulations
                                   102

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V.     What Registrants Need to Do

       In order to be eligible for reregistration, registrants need to implement the risk mitigation
measures outlined in Section IV and submit the following:

       A.    Data Call-in Responses

       For disulfoton technical grade active ingredient products, registrants need to submit the
following items.

       Within 90 days from receipt of the generic data call-in (DCI):  (1) completed
response forms to the generic DCI (i.e., DCI response form and requirements status and
registrant's response form); and (2) any time extension and/or waiver requests with a full written
justification.

       Within the  time limit specified in the generic DCI: (1) cite any existing generic data
which address data requirements or submit new generic data responding to the DCI.

       Please contact Christina Scheltema at (703) 308-2201 with questions regarding generic
reregistration and/or the DCI. All materials submitted in response to the generic DCI should be
addressed as follows:
Bv US mail:
Document Processing Desk .(DCI/SRRD)
Christina Scheltema
US EPA (7508C)
1200 Pennsylvania Ave., NW
Washington, DC 20460
By express or courier service:
Document Processing Desk (DCI/SRRD)
Christina Scheltema
Office of Pesticide Programs (7508C)
Room 266A, Crystal Mall 2
1921 Jefferson Davis Highway
Arlington, VA 22202
       For products containing the active ingredient disulfoton, registrants need to submit the
following items for each product.

       Within 90 days from the receipt of the product-specific data call-in (PDCI): (1)
completed response forms to the PDCI (i.e., PDCI response form and requirements status and
registrant's response form); and (2) any time extension or waiver requests with a full written
justification.

       Within eight months from the receipt of the PDCI:  (1) two copies of the confidential
statement of formula (EPA Form 8570-4); (2) a completed original application for reregistration
(EPA Form 8570-1) (Indicate on the form that it is an "application for reregistration");
(3) five copies of the draft label incorporating all label amendments outlined in Table 16 of this
document; (4) a completed form certifying compliance with data compensation
requirements (EPA Form 8570-34); (5) if applicable, a completed form certifying compliance
                                          103

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with cost share offer requirements (EPA Form 8570-32); and (6) the product-specific data
responding to the PDCI.

       Please contact Jane Mitchell at (703) 308-8061 with questions regarding product
reregistration and/or the PDCI. All materials submitted in response to the PDCI should be
addressed:
Bv US mail:
Document Processing Desk (PDCI/PRB)
Jane Mitchell
US EPA (7508C)
1200 Pennsylvania Ave., NW
Washington, DC 20460
Bv express or courier service only:
Document Processing Desk (PDCI/PRB)
Jane Mitchell
Office of Pesticide Programs (7508C)
Room 266A, Crystal Mall 2
1921 Jefferson Davis Highway
Arlington, VA 22202
       B.    Manufacturing-Use Products

       Generic Data Requirements for Disulfoton

       The generic database supporting the reregistration of disulfoton for the above eligible
uses has been reviewed and determined to be substantially complete, except for the following
additional required confirmatory data:

1. Anaerobic Aquatic Metabolism (OPPTS 835.4400) (for parent, disulfoton sulfone, and
disulfoton sulfoxide)

2. Aerobic Aquatic Metabolism (OPPTS 835.4300) (for parent, disulfoton sulfone, and
disulfoton sulfoxide)

3. Mobility/Leaching and Absorption/Desorption (OPPTS 835.1240) (for parent, disulfoton
sulfone, and disulfoton sulfoxide)

4. Terrestrial Plant Toxicity, Tier 1, Seedling Emergence (OPPTS 850.4100) and Vegetative
Vigor (OPPTS 850.4150) for a typical liquid product, such as Di-Syston 8EC.

5. Certified Limits (OPPTS  830.1750)

6. UV/Visible Absorption of the PAI (OPPTS 830.7050)

7. Applicator Exposure Monitoring - Dermal Exposure, Outdoor (OPPTS 875.1100) and
Applicator Exposure Monitoring, Inhalation Exposure, Outdoor (OPPTS 875.1300)
for the following scenarios:
       - Liquid formulation, groundboom, enclosed cab + respirator
       - Granular formulation, tractor drawn spreader, enclosed cab + respirator
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8.  Mixer/Loader/Applicator Exposure Monitoring, Dermal and Inhalation Exposure, Outdoor
(OPPTS 875.1100 and 1300) for the following scenarios:
       - Handheld closed loading, transfer, delivery system (NC Applicator)
       - Motorcycle mounted granular spreader with closed loading

9.  Mixer/Loader Exposure Monitoring - Dermal Exposure, Outdoor (OPPTS 875.1100) and
Mixer/Loader Exposure Monitoring - Inhalation Exposure, Outdoor (OPPTS 875.1300)
for the following scenarios:
       - Liquid closed loading system, e.g.,, SecureLink
       - Granular, closed loading system, e.g., Smartbox, Lock 'N Load

10. 21-Day Dermal Toxicology in Rats (OPPTS 870.3200)

11. Crop Field Trials for Cotton Gin Byproducts (OPPTS 860.1500)

12. Crop Field Trials for Lettuce (OPPTS 860.1500)

13. Storage Stability for all Livestock Commodities (OPPTS 860.1380)

14. Drinking Water Monitoring for Surface Water Sources (OPPTS 835.7200)

       Also, a Data Call-In Notice (DCI) was sent to registrants of OP pesticides currently
registered under FIFRA (August 6, 1999 64FR42945-42947, August 18 64FR44922-44923).
DCI requirements included acute, subchronic, and developmental neurotoxicity studies. The
developmental neurotoxicity study is scheduled to be submitted in November 2004, and the
registrant has satisfied the guideline requirements for the acute and subchronic neurotoxicity
studies in rats.

       Labeling for Manufacturing Use Products

       To remain in compliance with FIFRA, manufacturing-use product (MUP) labeling should
be revised to comply with all current EPA regulations, and address PR Notices and applicable
policies, as appropriate. The MUP labeling should bear the labeling contained in Table 16 at the
end of this section.

       C.    End-Use Products

       Additional Product-Specific Data Requirements

       Section 4(g)(2)(B) of FIFRA calls for the Agency to obtain any needed product-specific
data regarding the pesticide after a determination of eligibility has been made.  Registrants must
review previous data submissions to ensure that they meet current EPA acceptance criteria and if
not, commit to conduct new studies. If a registrant believes that previously submitted data meet
current testing standards, then the study MRID numbers should be cited according to the
                                          105

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instructions in the Requirement Status and Registrants Response Form provided for each
product.  A product-specific data call-in, outlining specific data requirements, accompanies this
IRED.                                                                        .     <

       Labeling for End- Use Products

       Labeling changes are necessary to implement the mitigation measures outlined in Section
IV above. Specific language to incorporate these changes is specified in Table 16 at the end of
this section.

       D.    Existing Stocks

       Registrants may generally distribute and sell products bearing old labels/labeling for 26
months from the date of the issuance of this IRED document.  Persons other than the registrant
may generally distribute or sell such products for 50 months from the date of the issuance of this
IRED document. However, existing stocks time frames will be established case-by-case,
depending on the number of products involved, the number of label changes, and other factors.
Refer to "Existing Stocks of Pesticide Products; Statement of Policy," Federal Register, Volume
56, No. 123, June 26, 1991.

       The Agency has determined that registrant may distribute and sell disulfoton products
bearing old labels/labeling for 26 months from the date of issuance of this IRED document.
Persons other than the registrant may distribute or sell such products for 50 months from the date
of the issuance of this IRED document. Registrants and persons other than the registrant remain
obligated to meet pre-existing label requirements and existing stocks requirements applicable to
products  they sell or distribute.

       E.    Labeling Changes Summary Table

       In order to be eligible for reregistration, all product labels are to be amended to
incorporate the risk mitigation measures outlined in Section IV. The following table describes
how language on the labels should be amended.
                                          106

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