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Thiamethoxam - Pesticide Petition Filing 6/02

ENVIRONMENTAL PROTECTION AGENCY
[OPP-2002-0115; FRL-7183-2]

Notice of Filing a Pesticide Petition to Establish a Tolerance
for a Certain Pesticide Chemical in or on Food

AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice.

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SUMMARY: This notice announces the initial filing of a pesticide
petition proposing the establishment of regulations for residues of a
certain pesticide chemical in or on various food commodities.

DATES: Comments, identified by docket control number OPP-2002-0115,
must be received on or before July 29, 2002.

ADDRESSES: Comments may be submitted by mail, electronically, or in
person. Please follow the detailed instructions for each method as
provided in Unit I.C. of the SUPPLEMENTARY INFORMATION. To ensure
proper receipt by EPA, it is imperative that you identify docket
control number OPP-2002-0115 in the subject line on the first page of
your response.

FOR FURTHER INFORMATION CONTACT: By mail: Dani Daniel, Registration
Support Branch, Registration Division (7505C), Office of Pesticide
Programs, Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460; telephone number: (703) 305-5409; e-mail address:
daniel.dani@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this Action Apply to Me?

     You may be affected by this action if you are an agricultural
producer, food manufacturer or pesticide manufacturer. Potentially
affected categories and entities may include, but are not limited to:

------------------------------------------------------------------------
                                                          Examples of
           Categories                 NAICS codes         potentially
                                                       affected entities
------------------------------------------------------------------------
Industry                          111                 Crop production
                                  112                 Animal production
                                  311                 Food manufacturing
                                  32532               Pesticide
                                                       manufacturing
------------------------------------------------------------------------

     This listing is not intended to be exhaustive, but rather provides
a guide for readers regarding entities likely to be affected by this
action. Other types of entities not listed in the table could also be
affected. The North American Industrial Classification System (NAICS)
codes have been provided to assist you and others in determining
whether or not this action might apply to certain entities. If you have
questions regarding the applicability of this action to a particular
entity, consult the person listed under FOR FURTHER INFORMATION
CONTACT.

B. How Can I Get Additional Information, Including Copies of this
Document and Other Related Documents?

    1. Electronically. You may obtain electronic copies of this
document, and certain other related documents that might be available
electronically, from the EPA Internet Home Page at http://www.epa.gov/.
To access this document, on the Home Page select "Laws and
Regulations," "Regulations and Proposed Rules," and then look up the
entry for this document under the "Federal Register--Environmental
Documents." You can also go directly to the Federal Register listings
at http://www.epa.gov/fedrgstr/. A frequently updated electronic
version of 40 CFR part 180 is available at
 http://www.access.gpo.gov/nara/cfr/cfrhtml_00/Title_40/40cfr180_00.html,
a beta site currently under development.
    2. In person. The Agency has established an official record for
this action under docket control number OPP-2002-0115. The official
record consists of the documents specifically referenced in this
action, any public comments received during an applicable comment
period, and other information related to this action, including any
information claimed as confidential business information (CBI). This
official record includes the documents that are physically located in
the docket, as well as the documents that are referenced in those
documents. The public version of the official record does not include
any information claimed as CBI. The public version of the official
record, which includes printed, paper versions of any electronic
comments submitted during an applicable comment period, is available
for inspection in the Public Information and Records Integrity Branch
(PIRIB), Rm. 119, Crystal Mall ι2, 1921 Jefferson Davis
Highway, Arlington, VA, from 8:30 a.m. to 4 p.m., Monday through
Friday, excluding legal holidays. The PIRIB telephone number is (703)
305-5805.

C. How and to Whom Do I Submit Comments?

     You may submit comments through the mail, in person, or
electronically. To ensure proper receipt by EPA, it is imperative that
you identify docket ID number OPP-2002-0115 in the subject line on the
first page of your response.
    1. By mail. Submit your comments to: Public Information and Records
Integrity Branch (PIRIB), Information Resources and Services Division
(7502C), Office of Pesticide Programs (OPP), Environmental Protection
Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
    2. In person or by courier. Deliver your comments to: Public
Information and Records Integrity Branch (PIRIB), Information Resources
and Services Division (7502C), Office of Pesticide Programs (OPP),
Environmental Protection Agency, Rm. 119, Crystal Mall ι2, 1921
Jefferson Davis Highway, Arlington, VA. The PIRIB is open from 8:30
a.m. to 4 p.m., Monday through Friday, excluding legal holidays. The
PIRIB telephone number is (703) 305-5805.
    3. Electronically. You may submit your comments electronically by
e-mail to: opp-docket@epa.gov, or you can submit a computer disk as
described above. Do not submit any information electronically that you
consider to be CBI. Avoid the use of special characters and any form of
encryption. Electronic submissions will be accepted in Wordperfect 6.1/
8.0 or ASCII file format. All comments in electronic form must be
identified by docket ID number OPP-2002-0115. Electronic comments may
also be filed online at many Federal Depository Libraries.

D. How Should I Handle CBI That I Want to Submit to the Agency?

     Do not submit any information electronically that you consider to
be CBI. You may claim information that you submit to EPA in response to
this document as CBI by marking any part or all of that information as
CBI. Information so marked will not be disclosed except in accordance
with procedures set forth in 40 CFR part 2. In addition to one complete
version of the comment that includes any information claimed as CBI, a
copy of the comment that does not contain the information claimed as
CBI must be submitted for inclusion in the public version of the
official record. Information not marked confidential will be included
in the public version of the official record without prior notice. If
you have any questions about CBI or the procedures for claiming CBI,
please consult the person identified under FOR FURTHER INFORMATION
CONTACT.

E. What Should I Consider as I Prepare My Comments for EPA?

     You may find the following suggestions helpful for preparing your
comments:
    1. Explain your views as clearly as possible.
    2. Describe any assumptions that you used.
    3. Provide copies of any technical information and/or data you used
that support your views.
    4. If you estimate potential burden or costs, explain how you
arrived at the estimate that you provide.
    5. Provide specific examples to illustrate your concerns.
    6. Make sure to submit your comments by the deadline in this
notice.
    7. To ensure proper receipt by EPA, be sure to identify the docket
ID number assigned to this action in the subject line on the first page
of your response. You may also provide the name, date, and Federal
Register citation.

II. What Action is the Agency Taking?

    EPA has received a pesticide petition as follows proposing the
establishment and/or amendment of regulations for residues of a certain
pesticide chemical in or on various food commodities under section 408
of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a.
EPA has determined that this petition contains data or information
regarding the elements set forth in section 408(d)(2); however, EPA has
not fully evaluated the sufficiency of the submitted data at this time
or whether the data support granting of the petition. Additional data
may be needed before EPA rules on the petition.

List of Subjects

    Environmental protection, Agricultural commodities, Feed additives,
Food additives, Pesticides and pests, Reporting and recordkeeping
requirements.

    Dated: June 17, 2002.
Debra Edwards,
Acting Director, Registration Division, Office of Pesticide Programs.

Summary of Petition

     The petitioner summary of the pesticide petition is printed below
as required by section 408(d)(3) of the FFDCA. The summary of the
petition was prepared by Sygenta Crop Protection Inc. and represents
the view of Sygenta. EPA is publishing the petition summary verbatim
without editing it in any way. The petition summary announces the
availability of a description of the analytical methods available to
EPA for the detection and measurement of the pesticide chemical
residues or an explanation of why no such method is needed.

PP 0F6142

     EPA has received a pesticide petition (0F6142) from Syngenta Crop
Protection Inc., P.O. Box 18300, Greensboro, NC 27419-8300 proposing,
pursuant to section 408(d) of the Federal Food, Drug, and Cosmetic Act
(FFDCA), 21 U.S.C. 346a(d), to amend 40 CFR part 180, by establishing a
tolerance for residues of thiamethoxam and its metabolite in or on the
raw agricultural commodity corn forage at 0.10 parts per million (ppm);
corn stover at 0.05 ppm; and popcorn, corn grain and sweet corn (kernal
and cob with husk removed) at 0.02 ppm. EPA has determined that the
petition contains data or information regarding the elements set forth
in section 408(d)(2) of the FFDCA; however, EPA has not fully evaluated
the sufficiency of the submitted data at this time or whether the data
support granting of the petition. Additional data may be needed before
EPA rules on the petition.

A. Residue Chemistry

    1. Plant metabolism. The primary metabolic pathways of thiamethoxam
in plants (corn, rice, pears, and cucumbers) were similar to those
described for animals, with certain extensions of the pathway in
plants. Parent compound and CGA-322704 were the major residues in all
crops. The metabolism of thiamethoxam in plants and animals is
understood for the purposes of the proposed tolerances. Parent
thiamethoxam and the metabolite, CGA-322704, are the residues of
concern for tolerance setting purposes.
    2. Analytical method. Syngenta Crop Protection Inc. has submitted
practical analytical methodology for detecting and measuring levels of
thiamethoxam in or on raw agricultural commodities. The method is based
on crop specific cleanup procedures and determination by liquid
chromatography with either ultraviolet (UV) or mass spectroscopy (MS)
detection. The limit of detection (LOD) for each analyte of this method
is 1.25 nanogram (ng) injected for samples analyzed by UV and 0.25 ng
injected for samples analyzed by MS, and the limit of quantitation
(LOQ) is 0.005 ppm for milk and juices and 0.01 ppm for all other
substrates.
    3. Magnitude of residues. A residue program was performed for
thiamethoxam used as a seed treatment for corn. Seed was treated at
label rates of 100 to 450 (maximum) grams of thiamethoxam per 100
kilograms of seed. A 3X exaggerated rate trial was also conducted to
determine the magnitude of the residue in processed field corn
commodities.
     Thirty-six field trials were conducted in 19 states representing
typical corn growing areas of the United States, including 21 field
corn, 12 sweet corn, and 3 popcorn field trials. There were no
detectable residues (<0.01 ppm) of either thiamethoxam or the major
metabolite in any grain, ear or field corn processed fraction. The
maximum residues in animal feed commodities were 0.09 ppm in forage and
0.03 ppm in stover (total thiamethoxam equivalents).

B. Toxicological Profile

    1. Acute toxicity. The acute oral LD50 for thiamethoxam
in the rat is 1,563 milligrams/kilogram body weight (mg/kg bwt). The
acute dermal LD50 of thiamethoxam is >2,000 mg/kg bwt.
Thiamethoxam is non-toxic at atmospheric concentrations of 3.72 mg/L.
Thiamethoxam is minimally irritating to the eye, non-irritating to skin
and is not a dermal sensitizer.
     In an acute neurotoxicity screening study in rats (OPPTS
870.6200), the no observed adverse effect level (NOAEL) was 100 mg/kg/
day with a NOAEL of 500 mg/kg/day based on drooped palpebral closure,
decrease in rectal temperature and locomotor activity and increase in
forelimb grip strength (males only). At higher dose levels, mortality,
abnormal body tone, ptosis, impaired respiration, tremors, longer
latency to first step in the open field, crouched over posture, gait
impairment, hypo-arousal, decreased number of rears, uncoordinated
landing during the righting reflex test, slight lacrimation (females
only) and higher mean average input stimulus value in the auditory
startle response test (males only).
    2. Genotoxicty. In gene mutation studies with S. typhimurium and E.
coli (OPPTS 870.5100 and 870.5265, there was no evidence of gene
mutation when tested up to 5,000 [mu]g/plate and there was no evidence
of cytotoxicity.
     In a gene mutation study with chinese hampster V79 cells at
hypoxanthine guanine phophoribosyl transferase (HGPRT) focus (OPPTS
870.5300), there was no evidence of of gene mutation when tested up to
the solubility limit.
     In a chinese hampster ovary (CHO) cell cytogenetics study (OPPTS
870.5375), there was no evidence of
chromosomal aberrations when tested up to cytotoxic or solubility limit
concentrations.
     An in vivo mouse bone marrow micronucleus study (OPPTS 870.5395)
was negative when tested up to levels of toxicity in whole animals;
however, no evidence of target cell cytotoxicity.
     An unscheduled DNA synthesis (UDS) assay (OPPTS 870.5550) was
negative when tested up to precipitating concentrations.
    3. Reproductive and developmental toxicity. A prenatal
developmental study in the rat (OPPTS 870.3700) resulted in maternal
and developmental NOAELs of 30 mg/kg/day and 200 mg/kg/day,
respectively. The maternal lowest observed adverse effect level (LOAEL)
is 200 mg/kg/day based on decreased body weight, body weight gain and
food consumption. The developmental LOAEL was 750 mg/kg/day based on
decreased fetal body weight and an increased incidence of skeletal
anomalies.
     A prenatal developmental study in the rabbit (OPPTS 870.3700)
resulted in maternal and developmental NOAELs of 50 mg/kg/day. The
maternal and developmental LOAEL is 150 mg/kg/day. The maternal LOAEL
is based on maternal deaths, hemorrhagic discharge, decreased body
weight and food intake during the dosing period. The developmental
LOAEL is based on decreased fetal body weights, increased incidence of
post-implantation loss and a slight increase in the incidence of a few
skeletal anomolies/variations.
     In a reproduction and fertility effects study in rats (OPPTS
870.3800) the parental/systemic NOAEL is 1.84 (males), 202.06 (females)
mg/kg/day; the reproductive NOAEL is 0.61 (males), 202.06 (females) mg/
kg/day; and the offspring NOAEL is 61.25 (males), 79.20 (females) mg/
kg/day. The parental/systemic LOAEL is 61.25 (males), not determined
(females) mg/kg/day based on increased incidence of hyaline change in
renal tubules in F0 and F1 males. The reproductive LOAEL is 1.84
(males), not determined (females) mg/kg/day based on increased
incidence and severity of tubular atrophy observed in testes of the F1
generation males. The offspring LOAEL is 158.32 (males), 202.06
(females) mg/kg/day based on reduced body weight gain during the
lactation period in all litters.
    4. Subchronic toxicity. A 90-day oral toxicity study in rats (OPPTS
870.3100) resulted in a NOAEL of 1.74 (males), 92.5 (females) mg/kg/
day. The LOAEL is 17.64 (male), 182.1 (female) mg/kg/day based on
increased incidence of hyaline change of renal tubules epithelium
(males), fatty change in adrenal-gland of females, liver changes in
females, all at the LOAEL. A 90-day oral toxicity study in mice (OPPTS
870.3100) resulted in an NOAEL of 1.41 (males), 19.2 (females) mg/kg/
day. The LOAEL was 14.3 (male) 231 (female) mg/kg/day based on
increased incidence of hepatocellular hypertrophy. At higher dose
levels: Decrease in body weight and body weight gain, necrosis of
individual hepatocytes, pigmentation of Kupffer cells, and lymphocytic
infiltration of the liver in both sexes; slight hematologic effects and
decreased absolute and relative kidney weights in males; and ovarian
atrophy, decreased ovary and spleen weights and increased liver weights
in females.
     In a 90-day oral toxicity study in dogs (OPPTS 870.3150), the
NOAEL is 8.23 (males), 9.27 (females) mg/kg/day. The LOAEL is 32.0
(male), 33.9 (female) mg/kg/day based on slightly prolonged prothrombin
times and decreased plasma albumin and A/G ration (both sexes);
decreased calcium levels and ovary weights and delayed maturation in
the ovaries (female); decreased cholesterol and phospholipid levels,
testis weights, spermatogenesis, and spermatic giant cells in testes
(male).
     In a 28-day dermal study in rats (OPPTS 870.3200), the NOAEL was
250 (male), 60 (female) mg/kg/day. The LOAEL was 1,000 (male), 250
(female) mg/kg/day based on increased plasma glucose, triglyceride
levels, and alkaline phosphatase activity and inflammatory cell
infiltration in the liver and necrosis if single hepatocytes in females
and hyaline change in renal tubules and a very slight reduction in body
weight in males. At higher dose levels in females, chronic tubular
lesions in the kidneys and inflammatory cell infiltration in the
adrenal cortex were observed.
     In a subchronic neurotoxicity screening study in rats (OPPTS
870.6200), the NOAEL was 95.4 (male), 216.4 (female) mg/kg/day, both at
highest dose tested. The LOAEL was not determined. No treatment related
observations at any dose level. LOAEL was not achieved. May not have
been tested at sufficiently high dose levels; however, a new study is
not required because the weight of the evidence from other toxicity
studies indicates no evidence of concern.
    5. Chronic toxicity. In a chronic toxicity study in dogs (OPPTS
870.4100), the NOAEL was 4.05 (male), 4.49 (female) mg/kg/day. The
LOAEL was 21.0 (male), 24.6 (female) mg/kg/day based on increase of
creatinine in both sexes, transient decrease in food consumption in
females, and occasional increase in urea levels, decrease in ALT, and
atrophy of seminiferous tubules in males.
     In a mouse carcinogenicity study (OPPTS 870.4200), the NOAEL was
2.63 (male), 3.68 (female) mg/kg/day. The LOAEL was 63.8 (male), 87.6
(female) mg/kg/day based on hepatocyte hypertrophy, single cell
necrosis, inflammatory cell infiltration, pigment deposition, foci of
cellular alteration, hyperplasia of kupffer cells and increased mitotic
activity, also an increase in the incidence of hepatocellular adenoma
(both sexes). At higher doses, there was an increase in the incidence
of hepatocelluar adenocarcinoma (both sexes) and the number of animals
with multiple tumors, evidence of carcinogenicity.
     In a combined chronic caricinogenicity study in rats (OPPTS
870.4300), the NOAEL was 21.0 (male), 50.3 (female) mg/kg/day. The
LOAEL was 63.0 (male), 255 (female) mg/kg/day based on increased
incidence of lymphocytic infiltration of the renal pelvis and chronic
nephropathy in males and decreased body weight gain, slight increase in
the severity of hemosiderosis of the spleen, foci of cellular
alteration in liver and chronic tubular lesions in kidney in females.
No evidence of carcinogenicity.
     In a hepatic cell proliferation study in mice, the NOAEL was 16
(male), 20 (female)mg/kg/day. The LOAEL was 72 (male), 87 (female) mg/
kg/day based on proliferative activity of hepatocytes. At higher dose
levels, increases in absolute and relative liver weights, speckled
liver, heptocellular glycogenesis/fatty change, heptocellular necrosis,
apoptosis and pigmentation were observed.
     In a 28-day feeding study to assess replicative DNA synthesis in
the male rat, the NOAEL was 711 mg/kg/day. The LOAEL was not
established. Immunohistochemical staining of liver sections from
control and high dose animals for proliferating cell nuclear antigen
gave no indication for a treatment related increase in the fraction of
DNA syntesizing hepatocytes in S-phase. CGA293343 did not stimulate
hepatocyte cell proliferation in male rats.
     In a special study to assess liver biochemistry in the mouse, the
NOAEL was 17 (male), 92 (female)mg/kg/day. The LOAEL was 74 (male), 92
(female) mg/kg/day based on marginal to slight increases in absolute
and relative liver weights, a slight increase in the microsomal protein
content of the livers, moderate increases in the cytochrome P450
content, slight to moderate increases in the activity of several
microsomal enzymes, slight to
moderate induction of cytosolic glutathionw S-transfersase activity.
Treatment did not affect peroxisomal fatty acid B-oxidation.
    6. Animal metabolism. The metabolism of thiamethoxam in rats and
livestock animals is adequately understood. The residues of concern
have been determined to be parent thiamethoxam and its metabolite (N-
(2-chloro-thiazol-5-ylmethyl)-N' methyl-N'-nitro-guanidine.
    7. Metabolite toxicology. For risk assessment purposes, residues of
the metabolite corrected for molecular weight are considered to be
toxicologically equivalent to parent thiamethoxam.

C. Aggregate Exposure

    1. Dietary exposure. Permanent tolerances have been established (40
CFR 180.565) for the combined residues of the insecticide thiamethoxam,
3-[(2-chloro-5-thiazolyl) methyl]
tetrahydro-5-methyl-N-nitro-4H-1,3,5-
oxadiazin-4-imine and its metabolite (N-(2-chloro-thiazol-5-ylmethyl)-
N'-methyl-N'-nitro-guanidine), in or on a variety of RACs at levels
ranging from 0.02 ppm to 1.5 ppm (including barley, canola, cotton,
sorghum, wheat, cucurbit vegetables, fruiting vegetables, pome fruits
and livestock commodities). Pending tolerances include coffee, grapes,
raisins, grape juice, pecans, peanut nutmeats, peanut hay, corn grain,
sweet corn (kernal with husk removed), pop corn, corn forage and
stover, head and stem brassica, leafy brassica greens and leafy
vegetables.
    i. Food--a. Acute risk. The acute dietary exposure evaluation (food
only) for thiamethoxam (CGA-293343) was based on a point residue
(highest average field trial residue value) DEEM acute analysis. This
assessment was based on a Monte Carlo analysis (1,000 iterations) and
utilized an acute endpoint of 100 mg/kg-bw/day (acute neurotoxicity
study). Residue values for thiamethoxam (CGA-293343) and its
corresponding acid metabolite (CGA-322704) were compiled using data
from field trial studies. For those field trial samples which had non-
detectable residues, a value of 1/89/21/13/23/85/83/8 the
statistically derived limit of detection
(1/89/21/13/23/85/83/8 sLOD) was used. Non-nursing infants (<1
year old) were the most sensitive subpopulation with a total exposure
of 0.42% of the acute reference dose (aRfD). The next most sensitive
subpopulation was all infants <1 year old) with an exposure of 0.37% of
the aRfD. Acute exposure for the U.S. population was 0.12% of the aRfD
at the 99.9th percentile of exposure. Therefore, it is
expected that the proposed tolerances for corn commodities will have
minimal impact on acute dietary risk and that the aggregate exposure
will not exceed 100% of the acute RfD.
    b. Chronic and lifetime risk. For the chronic and lifetime exposure
assessments, all of the DEEMTM inputs including residue and
percent of crop treated (%CT) for currently registered uses were from
EPA's August 28, 2000 dietary exposure assessment on thiamethoxam (DP
Barcode D268606, PC Code 060109). For these assessments, the 1996-1998
CSFII was used and %CT value for apples was 2%. All residue data were
from field trials where thiamethoxam was applied at the maximum
intended use rate and the samples were harvested at the minimum pre-
harvest interval (PHI) to obtain maximum expected residues. All values
from the EPA "baseline" assessment assumed one-half limit of
quantitation (1/89/21/13/23/85/83/8 LOQ) for all non-detects
in the field trial samples.
    c. Chronic risk. The chronic dietary exposure from food use
indicated that chronic dietary exposure from food utilizes 3.5% of the
chronic RfD for the U.S. population and 7.9% of the chronic RfD for
children 1-6 years old. Addition of corn field trial residues to the
assessment caused a negligible increase in chronic exposure (0.1% for
the U.S. population and 0.3% for children 1-6 years old). Therefore,
the proposed tolerances for corn commodities will have minimal impact
on chronic dietary risk and that the aggregate exposure will not exceed
100% of the chronic RfD.
    d. Lifetime risk. Results from the lifetime dietary exposure
analysis (food only) show that there are acceptable safety margins with
respect to chronic exposures incurred by the dietary consumption of
thiamethoxam-treated commodities, including corn. Lifetime exposures to
the U.S. population (48 states, all seasons) resulted in a value of
8.13 x 10-7 which represents 81.3% of the lifetime risk
limit of 1 x 10-6 This represents a slight increase (2.1%)
in the lifetime risk of 7.92 x 10-7 (79.2%) associated with
currently registered uses of thiamethoxam.
    ii. Drinking water. EPA used the Pesticide Root Zone/Exposure
Analysis Modeling System (PRZM/EXAMS) to estimate pesticide
concentrations in surface water and SCI-GROW, which predicts pesticide
concentrations in ground water. None of these models include
consideration of the impact processing (mixing, dilution, or treatment)
of raw water for distribution as drinking water would likely have on
the removal of pesticides from the source water. The primary use of
these models by the Agency at this stage is to provide a coarse screen
for sorting out pesticides for which it is highly unlikely that
drinking water concentrations would ever exceed human health levels of
concern. Based on the SCI-GROW and PRZM/EXAMS models, EPA calculated
that estimated environmental concentrations (EECs) of thiamethoxam at
the highest use rate of 0.125 pound active ingredient per acre (lb
a.i./acre) are 1.94 parts per billion (ppb) for acute and chronic
exposure to ground water and 8 ppb and 0.6 ppb for acute and chronic
exposure, respectively, to surface water. Based on both field and
laboratory data, Syngenta predicts that the potential exposure to
ground water is much lower than that predicted by the conservative SCI-
GROW model. EPA determined EECs are used for comparison to drinking
water levels of comparison (DWLOC).
    a. Acute risk. Acute drinking water levels of comparison were
calculated based on an acute populated adjusted dose (aPAD) of 0.1 mg/
kg/day. For the acute assessment, the non-nursing infants (<1 year old)
subpopulation generated the lowest acute DWLOC of approximately 996
ppb. EPA has determined that the surface water acute EEC is 8 ppb and
the ground water EEC is 1.94 ppb. Since the surface water value is
greater than the ground water value, the surface water value will be
used for comparison purposes and will protect for any concerns for
ground water concentrations. Since the acute DWLOC of 996 ppb is
considerably higher than the acute EEC of 8 ppb, EPA should not have a
concern for acute risk to either surface or ground water.
    b. Chronic risk. Chronic drinking water levels of comparison were
calculated based on a chronic populated adjusted dose (cPAD) of 0.0006
mg/kg/day. For the chronic assessment, the non-nursing infants
subpopulation generated the lowest chronic DWLOC of approximately 5.5
ppb. EPA has determined that the surface water chronic EEC is 0.6 ppb
and the ground water EEC is 1.94 ppb. Since the ground water value is
greater than the surface water value, the ground water value will be
used for comparison purposes and will protect for any concerns for
surface water concentrations. Since the chronic DWLOC of 5.5 ppb is
higher than the chronic EEC of 1.94 ppb, EPA should not have a concern
for chronic risk to either surface or ground water.
    c. Cancer risk. Based on currently registered uses for
thiamethoxam, EPA has determined a drinking water level of comparison
for cancer (cancer DWLOC) of 2.14 ppb based upon a 2% market share for
apples. Based on the addition of the proposed corn seed treatment use,
the cancer DWLOC would be 2.12 ppb, representing only a minimal change.
At the currently registered maximum use rate of 0.125 lb. a.i./acre per
growing season, EPA has used the SCI-GROW model to predict a ground
water EEC of 1.94 ppb; therefore, the cancer DWLOC (2.12 ppb) is not
exceeded. For the proposed corn seed treatment uses, the maximum use
rate on a per acre basis is 0.123 lb active ingredient. This maximum
rate (0.123 lb) would be applicable only to field corn and would
represent only 0.18% of all corn acres grown. Ninety-seven percent of
thiamethoxam treated corn (5.4% of all corn acres grown) will be
planted with a maximum rate on a per acre basis of 0.070 lbs a.i. per
acre. Using EPA determined input values, the SCI-GROW model predicts an
EEC of 1.90 ppb for the 0.123 lb rate and an EEC of 1.08 ppb for the
0.070 lb rate. Neither of these EECs (1.90 or 1.08 ppb) exceeds the
cancer DWLOC (2.12 ppb).
     The SCI-GROW model uses extremely conservative assumptions.
However, even when using the conservative SCI-GROW model, it can be
concluded that the proposed corn seed treatment use of thiamethoxam
presents a negligible risk concern for exposure through drinking water.
    2. Non-dietary exposure. Thiamethoxam is not currently registered
for use on any sites that would result in residential exposure.

D. Cumulative Effects

    The potential for cumulative effects of thiamethoxam and other
substances that have a common mechanism of toxicity has also been
considered. Thiamethoxam belongs to a new pesticide chemical class
known as the neonicotinoids. There is no reliable information to
indicate that toxic effects produced by thiamethoxam would be
cumulative with those of any other chemical including another
pesticide. Therefore, Syngenta believes it is appropriate to consider
only the potential risks of thiamethoxam in an aggregate risk
assessment.

E. Safety Determination

    1. U.S. population. Syngenta concludes, as described above, that
there is reasonable certainty that no harm to the U.S. population will
result from aggregate acute or chronic dietary exposure to thiamethoxam
residues including the proposed tolerances for corn commodities.
    2. Infants and children. Syngenta concludes, as described above,
that there is reasonable certainty that no harm to infants and children
will result from aggregate acute or chronic exposure to thiamethoxam
residues including the proposed tolerances for corn commodities.

F. International Tolerances

    There are no codex MRLs established for residues of thiamethoxam on
corn commodities.
[FR Doc. 02-16276 Filed 6-26-02; 8:45 am]