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triphenyltin hydroxide (TPTH) Proposed Determination To Terminate Special Review 9/00


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[Federal Register: October 20, 2000 (Volume 65, Number 204)]
[Notices]
[Page 63173-63190]
>From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr20oc00-131]

[[Page 63173]]

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Part IV

Environmental Protection Agency

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Triphenyltin Hydroxide; Proposed Determination To Terminate Special
Review; Notice

[[Page 63174]]

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ENVIRONMENTAL PROTECTION AGENCY

[OPP-30000/42A; FRL-6496-3]


Triphenyltin Hydroxide; Proposed Determination To Terminate
Special Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed Determination to Terminate Special Review.

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SUMMARY: This Notice sets forth EPA's preliminary determination
regarding the continued registration of pesticide products containing
triphenyltin hydroxide (TPTH) and sets forth the Agency's assessment of
the risks and benefits associated with pesticidal uses of TPTH. On
January 9, 1985, the Agency issued a Notice of Special Review of
pesticide products containing triphenyltin hydroxide based on
developmental toxicity (teratogenicity) concerns (50 FR 1107). Although
not a subject of the Special Review, the Agency also cited concerns for
reproductive toxicity, carcinogenicity, immunotoxicity, inhalation
toxicity and adverse effects to non-target organisms in the Position
Document 1. Due to voluntary actions by the registrants that have
reduced worker exposure to TPTH, as well as additional data that refine
the risk assessment, EPA has determined that the risks of using TPTH
are substantially lower than when the Special Review was initiated in
1985. This Notice proposes to terminate the triphenyltin hydroxide
Special Review based on the Agency's determination that the benefits of
TPTH use outweigh the risks.

DATES: Comments, data and information relevant to the Agency's proposed
decision, identified by the docket control number [OPP-30000/42A], must
be received on or before November 20, 2000.

ADDRESSES: Comments may be submitted by mail, electronically, or in
person. Please follow the detailed instructions for each method as
provided in Unit I. of the SUPPLEMENTARY INFORMATION. To ensure proper
receipt by EPA, it is imperative that you identify docket control
number OPP-30000/42A in the subject line on the first page of your
response.

FOR FURTHER INFORMATION CONTACT: Phil Budig, Special Review and
Reregistration Division (7508C), Office of Pesticide Programs,
Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460. Telephone (703) 308-8029; e-mail address:
budig.phil@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does This Action Apply to Me?

    You may be affected by this action if you are a pesticide
registrant with registered products which contain triphenyltin
hydroxide as an active ingredient, or if you are an agricultural
producer or a mixer, loader or applicator using products containing
triphenyltin hydroxide as an active ingredient. Since other entities
may also be interested, the Agency has not attempted to describe all
the specific entities that may be affected by this action. If you have
any 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 Support
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/.
    2. In person. The Agency has established an official record for
this action under docket control number OPP-30000/42A. 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 #2, 1921 Jefferson Davis Hwy.,
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.
    3. By mail. You may request copies of this document and supporting
documents by writing to: Public Information and Records Integrity
Branch, Information Resources and Services Division (7502C), Office of
Pesticide Programs, Environmental Protection Agency, 1200 Pennsylvania
Ave., NW., Washington, DC 20460. Be sure to include docket control
number [OPP-30000/42A] in your request.

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 control number OPP-30000/42A in the subject line on
the first page of your response.
    1. By mail. Submit your comments in triplicate 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 #2, 1921
Jefferson Davis Hwy., 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 control number OPP-30000/42A. 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 in response to this
document as confidential by marking any part or all of that information
as CBI. Information so marked will not be disclosed except in
accordance with procedures set forth in 40 CFR part 2.

[[Page 63175]]

A copy of the comment that does not contain 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.

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

    You may find the following suggestions helpful for preparing your
comments:
     Explain your views as clearly as possible.
     Describe any assumptions you used.
     Provide copies of technical information or data that
support your views.
     If you estimate potential burden or costs, explain how you
arrived at the estimate you provide.
     Provide specific examples to illustrate your concerns.
     Offer alternative ways to improve the Agency's proposed
action.
     Make sure to submit your comments by the deadline in this
notice.
     To ensure proper receipt by EPA, be sure to identify the
docket control 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. Introduction

    Triphenyltin hydroxide is most commonly sold under the trade names
Super Tin, Pro-Tex, Photon, and Brestan
H. TPTH is formulated both as a wettable powder in a water-
soluble pack and as a flowable concentrate requiring a mechanical
transfer (ground equipment applications) or closed system (aerial and
chemigation applications) for mixing and loading.
    Triphenyltin hydroxide was first registered as a fungicide under
the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) in 1971
and is a non-systemic protectant foliar fungicide currently registered
for use on pecans, potatoes and sugarbeets. The fungicide was formerly
registered for use on carrots, peanuts and tobacco. These uses were
subsequently canceled and the appropriate tolerances were revoked. In
addition to fungus control, TPTH is also registered as a suppressant of
Colorado potato beetle populations on potatoes.
    Triphenyltin hydroxide is classified by EPA as a Restricted Use
pesticide [Ref. 1] due to acute and developmental toxicity concerns.
Under section 3(d) of FIFRA this means, among other things, that only
certified applicators trained for and familiar with pesticide use, or
persons under their direct supervision, can use products containing
TPTH.
    A Special Review was initiated in 1985 to address the use of
triphenyltin hydroxide and examine the developmental toxicity risk to
mixers, loaders and applicators. Since the time the Special Review was
initiated, the Agency has identified carcinogenicity as an endpoint of
concern and the registrant has voluntarily taken actions that have
reduced worker exposure to TPTH. These actions include deletion of
certain uses, closed mixing/loading systems for aerial applications,
addition of protective clothing requirements to labels, adoption of
mechanical transfer systems for all liquid formulations, packaging of
the wettable powder formulation in water soluble packets, and reduced
maximum seasonal application rates. In addition, the registrant
submitted additional data, including a dermal developmental toxicity
study and an occupational exposure monitoring study for pecan mixer/
loaders and pecan harvesters, to refine the exposure estimates for this
site.
    EPA has refined its risk assessments for both developmental and
cancer concerns, and completed its risk/benefit analysis of TPTH.
Taking into account all of the worker mitigation measures that have
been adopted since the initiation of the special review, the Agency has
determined that the risks of using TPTH are no longer unreasonable.
Consistent with this finding, the Agency published its Reregistration
Eligibility Decision (RED) for TPTH in the Federal Register of December
1, 1999 (64 FR 67265) (FRL-6395-3) [Ref. 2], finding all uses of
registered products eligible for reregistration. As the benefits from
continued use of TPTH outweigh the risks, the Agency is proposing to
terminate the Special Review.

A. Legal Background

    In order to obtain a registration for a pesticide under FIFRA, an
applicant must demonstrate that the pesticide satisfies the statutory
standard for registration. The standard requires, among other things,
that the pesticide will not cause ``unreasonable adverse effects on the
environment'' [FIFRA section 3(c)(5)]. The term ``unreasonable adverse
effects on the environment'' means ``any unreasonable risk to man or
the environment, taking into account the economic, social, and
environmental costs and benefits of the use of any pesticide'' [FIFRA
section 2(bb)]. This standard requires a finding that the benefits of
each use of the pesticide outweigh the risks of such use, when the
pesticide is used in compliance with the terms and conditions of
registration and in accordance with commonly recognized practices.
    The burden of proving that a pesticide satisfies the statutory
standard is on the proponents of registration and continues as long as
the registration remains in effect. Under FIFRA section 6, the
Administrator may cancel the registration of a pesticide or require
modification of the terms and conditions of a registration if (s)he
determines that the pesticide product causes unreasonable adverse
effects to man or the environment. EPA created the Special Review
process to facilitate the identification of pesticide uses that may not
satisfy the statutory standard for registration and to provide a public
procedure to gather and evaluate information about the risks and
benefits of these uses.
    A Special Review may be initiated if a pesticide meets or exceeds
the risk criteria set out in the regulations at 40 CFR part 154. EPA
announces that a Special Review is initiated by publishing a notice,
Position Document 1 (PD 1), in the Federal Register. After a PD 1 is
issued, registrants and other interested persons are invited to review
the data upon which the review is based and to submit data and
information to rebut EPA's conclusions by showing that EPA's initial
determination was in error, or by showing that use of the pesticide is
not likely to result in unreasonable adverse effects on human health or
the environment. In addition to submitting rebuttal evidence, those
interested may submit relevant information to aid in the determination
of whether the economic, social and environmental benefits of the use
of the pesticide outweigh the risks. After reviewing the comments
received and other relevant materials obtained during the Special
Review process, EPA makes a decision on the future status of
registrations of the pesticide.
    The Special Review process may be concluded in various ways
depending upon the outcome of EPA's risk/benefit assessment. If EPA
concludes that all of its risk concerns have been adequately rebutted,
the pesticide registration will be maintained unchanged. If, however,
all risk concerns are not rebutted, EPA will proceed to a full risk/
benefit assessment for non-dietary risks. In determining whether the
use of a pesticide poses risks that are greater than the benefits, EPA
considers possible changes to the terms and conditions of registration
that can reduce risks to the level where the benefits outweigh the
risks, and it may require that such changes be made in

[[Page 63176]]

the terms and conditions of the registration. Alternatively, EPA may
determine that no changes in the terms and conditions of a registration
will adequately assure that use of the pesticide will not cause any
unreasonable adverse effects. If EPA makes such a determination, it may
seek cancellation, suspension, or change in classification of the
pesticide's registration. This determination would be set forth in a
Notice of Final Determination issued in accordance with 40 CFR 154.33.
    Issuance of this Notice means that the Agency has assessed the
potential adverse effects associated with the uses of triphenyltin
hydroxide and has preliminarily determined that the benefits override
the risks.

B. Regulatory Background

    The Registration Standard for TPTH was published in September 1984
[Ref. 1]. The Standard established the restricted use classification
based on concerns of acute and developmental toxicity; announced EPA's
intent to initiate a Special Review based on developmental toxicity
risks to workers; imposed label warnings regarding developmental
toxicity and potential adverse ecological effects; established a 24-
hour reentry period; and required submission of product chemistry,
toxicology, residue chemistry, environmental fate, and ecological
effects data.
    On October 23, 1984, EPA issued a letter notifying the TPTH
registrants that the Agency was concerned about developmental effects
from TPTH and was considering placing the fungicide into Special
Review. On January 9, 1985, the EPA issued a notice to initiate a
Special Review based on potential developmental toxicity risks to
mixers, loaders and applicators for registrations of products
containing TPTH (50 FR 1107). This document, also referred to as
Position Document 1 or PD 1, detailed the basis for the Agency's
decision to initiate a Special Review. The Agency determined that all
uses would be the subject of the Special Review for TPTH. The Agency
had reviewed data concerning the potential adverse effects associated
with uses of TPTH that indicated that TPTH produces developmental
toxicity effects in laboratory animals and had determined that
pesticide products containing TPTH met or exceeded the risk criterion
that, under regulations then in effect, would require EPA to initiate a
Special Review (40 CFR 162.11(a)(3)(ii)(B) (1975)). Current regulations
in 40 CFR 154.7(a)(2) (1985), set forth a similar criterion for
initiation of a Special Review by EPA. The PD 1 also noted EPA concerns
for reproductive toxicity, carcinogenicity, immunotoxicity, inhalation
toxicity and adverse effects to non-target organisms, however, these
were not cited as grounds for initiating Special Review.
    Since initiating the TPTH Special Review the Agency completed the
TPTH Reregistration Eligibility Decision (RED) in November 1999.
Although not triggers for Special Review, the TPTH RED assessed dietary
and ecological risk, along with occupational risk. The Agency did not
identify any dietary risks of concern at the time of the PD 1. However,
the TPTH RED assessed dietary risks on the basis of more recent data
under the Food Quality Protection Act of 1996. While the Agency found
that dietary risks from food consumption were acceptable, it could not
rule out the potential for dietary risk through drinking water
exposures from surface water sources. This potential risk was addressed
through buffer zones from water bodies to prevent TPTH run-off into
surface water. With these mitigation measures in place, the Agency has
determined that there is a reasonable certainty of no harm from TPTH
use on sugarbeets, potatoes, and pecans [Ref. 2]. The Agency also noted
in the PD 1 that TPTH is highly toxic to aquatic invertebrates,
warmwater fish and estuarine/marine organisms, and moderately to highly
toxic to avian species. While insufficient data on these effects were
available to trigger a special review, the Registration Standard
required additional studies to clarify the environmental fate and
potential ecological effects of TPTH. These studies were reviewed as
part of the RED. As a result of this review, the registrants amended
their labels to mitigate risks to non-target organisms through
reductions in the maximum seasonal use of TPTH on pecans, sugarbeets,
and potatoes, as well as through a 100 foot buffer from water bodies
for ground applications of TPTH, and a 300-foot buffer from water
bodies for aerial applications of TPTH [Ref. 2]. This document focuses
on reproductive and cancer risk to workers, as occupational risks
triggered the initiation of the TPTH Special Review in 1985.

C. Summary of EPA's Proposed Action

    EPA has determined that the benefits associated with the continued
use of TPTH under the current terms of TPTH's registration outweigh the
risks. Thus, EPA is proposing to terminate the Special Review of TPTH.

III. Summary of Toxicological Concerns

    The Special Review of TPTH was initiated in 1985 because of data
indicating that TPTH produces developmental toxicity effects in
laboratory animals and concerns about the adequacy of the
carcinogenicity assessment. The Agency's Registration Standard required
additional testing to verify the potential for TPTH to induce
developmental and carcinogenic effects [Ref. 1]. This section
summarizes the Agency's current assessment of developmental and
carcinogenic issues. [For a fuller treatment of the toxicity endpoints
see Refs. 2 and 3].

A. Developmental Effects

    Studies submitted in response to the Registration Standard,
including studies in rabbits [Ref. 4], rats [Refs. 5, 6, 7, 8, and 9]
and hamsters [Ref. 10], were reviewed and determined to be acceptable
for evaluating the potential for assessing maternal and developmental
effects in these three species [Ref. 3]. In a document dated January 9,
1991, the Peer Review Committee for Reproductive and Developmental
Toxicity concluded that these studies establish no-observed-adverse-
effect level (NOAEL) and lowest-observed-adverse-effect levels (LOAELs)
for maternal and developmental effects in all three species, with the
rabbit being the most sensitive [Ref. 11].
    The lowest NOAEL for developmental toxicity in rabbits was
established at 0.3 mg/kg/day based on decreased pup weight and the
presence of unossified hyoid in the rabbit fetuses at the LOAEL of 0.9
mg/kg/day [Ref. 7]. The lowest maternal toxicity NOAEL was 0.1 mg/kg/
day based on decreased maternal body weight gain in rabbits at the
LOAEL of 0.3 mg/kg/day. It was noted that 2 mg/kg/day could not be
tolerated in the rabbit since there were compound related resorptions
to preclude fetal examinations.
    Several rat studies were performed and reviewed, and some of these
included postnatal development phases. The rat was less sensitive than
the rabbit with a NOAEL of 1 mg/kg/day for maternal toxicity (decreased
body weight gain) occurring at 2.8 mg/kg/day. The developmental NOAEL
in rats was inconsistent among the several studies being either 1.0 or
2.8 mg/kg/day with a LOAEL of either 2.8 or 8 mg/kg/day since not all
of the same effects in the developing fetuses were seen in each study.
At higher doses there was deceased fetal weight and increased
resorptions and fewer pups. The new rat developmental toxicity studies
did not

[[Page 63177]]

show consistency in induction of hydrocephaly and hydroureter or
skeletal effects. Hamsters were still less sensitive than the rabbit
and rat with a NOAEL of 5.08 and 12 mg/kg/day for both maternal and
developmental toxicity, with maternal body weight being affected at the
LOAEL. Decreased fetal weight and viable fetuses and an increase in
minor skeletal effects were noted in offspring.
    Subsequent to the 1991 peer review meeting, the Agency requested a
developmental toxicity study by the dermal route in rabbits since
extrapolation of the rabbit oral toxicity study resulted in
unacceptable margins of exposure. The dermal developmental toxicity
study [Ref. 12] established a NOAEL of 3.0 mg/kg/day for both maternal
and developmental toxicity since there were no effects at this level,
which was the highest dose level tested.

B. Carcinogenicity

    In the PD 1, the Agency indicated some concern about the
carcinogenic effects of TPTH and did not consider the existing data
base adequate for carcinogenicity assessment. The registrant
subsequently submitted replacement rat [Ref. 13] and mouse [Ref. 14]
studies.
    1. Classification of carcinogenic potential. The Carcinogenicity
Peer Review Committee (CPRC) met on November 29, 1989, to conduct a
weight-of-the-evidence review of the data, including the replacement
rat and mouse carcinogenicity studies and mutagenicity data. The CPRC
concluded that TPTH was a B2 carcinogen with a Q1* of 2.8
(mg/kg/day)-1 [Ref. 15]. These conclusions were based on the
following: the significant increase in fatal pituitary gland adenomas
in female rats and Leydig cell tumors in male rats; and, the
significantly increased incidence of hepatocellular adenomas and
combined adenomas and/or carcinomas in male and female mice, a
significantly increasing dose-related trend for the incidence of
hepatocellular carcinomas in female mice. Other factors considered by
the Peer Review Committee included: the uncommon spontaneous occurrence
of hepatocellular carcinomas in female mice; an increase in tumor
incidences at relatively low dose levels of TPTH; and evidence for
immunotoxicity of the chemical [Ref. 15].
    2. Potency factor (Q1*). The CPRC revisited TPTH on
March 18, 1992, to reconsider the basis for quantification of the
cancer unit risk values of TPTH [Ref. 16]. This latter CPRC meeting was
conducted to address the conclusion of the September 18, 1991, FIFRA
Science Advisory Panel (SAP) meeting that the pituitary tumor data were
equivocal, due to the high spontaneous incidence of these tumors in the
female rat. The SAP also commented that the cancer dose-response
quantification for pituitary tumors should consider differences in
mortality.
    On March 18, 1992, CPRC members agreed to support their previous
conclusion that TPTH should be classified as a B2 carcinogen with the
Q1* based on fatal pituitary gland adenomas [Ref. 16]. The
Committee's decision was supported by the conclusion that the pituitary
gland tumors had an early onset and were fatal. Thus a Q1*
of 2.8 (mg/kg/day)-1 was determined using the multistage
Weibull (time to tumor) model because this model is considered the most
appropriate when there is a significant differential in mortality. In
the original Q1*, a 2/3 scaling factor was used to
extrapolate from animals to humans. The unit risk value was
subsequently revised to a Q1* of 1.83 (mg/kg/
day)-1 to reflect current Agency policy of a 3/4
interspecies scaling factor.
    3. Mutagenicity. TPTH is not considered to have a mutagenicity/
genetic toxicity concern. Most studies are negative for mutagenic/
genetic toxicity effects. Although there were some apparent positive
responses, other tests, particularly in vivo, conducted to verify the
significance of the apparent studies in vitro were negative [Refs. 2
and 17].

C. Immunotoxicity

    TPTH belongs to a class of chemicals (organotins) known to be
immunotoxic. The primary treatment related effects via oral exposures
are immunotoxicity as indicated by decreases in lymphocytes and
immunoglobulins in rats and mice, following both sub-chronic and
chronic exposures. To better characterize potential immunotoxic
effects, the Agency has called in a special developmental
immunotoxicity study as part of its reregistration eligibility
decision.

D. Summary of Endpoints

    The endpoints used in assessing the occupational risks for TPTH are
presented in Table 1 [Ref. 18].

                                             Table 1.-- Endpoints for Assessing Occupational Risks for TPTH
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                       Uncertainty
         Exposure Routes            Exposure Duration     Dose (mg/kg/day)          Effect               Study            Factor           Comment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dermal...........................  Short-term (1-7      NOAEL 3.0            No effect observed   Dermal                       100  Route-specific
                                    days)                                     at the highest       developmental                     study; MOE based on
                                                                              dose tested          toxicity (rabbit)                 UF for inter-
                                                                                                                                     species (10x)
                                                                                                                                     extrapolation and
                                                                                                                                     intra-species
                                                                                                                                     variability (10x)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dermal...........................  Intermediate-term    NOAEL 3.0            No effect observed   Dermal                       100  Route-specific
                                    (1 week to several                        at the highest       developmental                     study; MOE based on
                                    mos)                                      dose tested          toxicity (rabbit)                 UF for inter-
                                                                                                                                     species (10x)
                                                                                                                                     extrapolation and
                                                                                                                                     intra-species
                                                                                                                                     variability (10x)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inhalation.......................  Any time period      NOAEL 0.092a         Death following      Subchronic                   100  Route-specific
                                                                              lung lesions         inhalation study                  study; MOE based on
                                                                                                   (rat)                             UF for inter-
                                                                                                                                     species (10x)
                                                                                                                                     extrapolation,
                                                                                                                                     intra-species
                                                                                                                                     variability (10x)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dermal & Inhalation..............  Cancer Risk          Oral Q1* 1.83 mg/kg/ Probable human       Oral cancer rat and           NA   A dermal absorption
                                                         day-1                carcinogen           mouse studies                     of 10% should be
                                                                                                   showing pituitary,                used. Based on
                                                                                                   testicular, and                   comparison between
                                                                                                   liver tumors.                     rabbit oral and
                                                                                                                                     dermal studies.
                                                                                                                                     Inhalation
                                                                                                                                     absorption assumed
                                                                                                                                     to be 100%.
--------------------------------------------------------------------------------------------------------------------------------------------------------
a Inhalation dose in mg/L was converted to mg/kg/day using the following equation: Dose (mg/kg/day) = (NOAEL (0.00034 mg/L)* Respiration rate of a young
  adult Wistar rat (8.46 L/hr) * Study daily exposure duration (6 hr/day)) / Body weight of a young adult Wistar rat (0.187 kg)

[[Page 63178]]

IV. Occupational Exposure and Risk

A. Position Document 1

    In the January 1985 Notice of Special Review (PD 1), the Agency
concluded that potential developmental toxicity risks to mixers,
loaders and applicators for registrations of products containing
triphenyltin hydroxide may result in unreasonable adverse effects. The
Agency's risk analysis was limited to dermal exposure to TPTH resulting
from air blast application to pecan trees, as this was the use pattern
expected to generate the most exposure to workers. This analysis was
based on exposure estimates derived from Agency data and assumed dermal
absorption would be 100%.
    When conducting the 1985 risk assessment, the Agency assumed that
all workers were unprotected, wore cotton work clothes, short-sleeved
shirts, long pants and no hat, gloves or respirator. Three-thousand
square centimeters of the body surface was assumed to be uncovered.
Applicator exposure was calculated from a linear regression correlation
derived from Agency data for the air blast application to orchards. The
Agency's assumptions were conservative and may have overestimated
actual exposure.
    The Agency estimated a typical exposure value for a mixer/loader/
applicator of 0.74 mg/kg/day, based on ranges of 0.68 to 0.88 mg/kg/
day, due to variations in application rates.
    At the time of the PD 1, an available study on rats showed apparent
hydrocephalus and hydronephrosis at all dose levels. There were,
however, no data available to estimate the dermal penetration of TPTH.
Since dermal exposure was the greatest single source of exposure to
workers, this was an important parameter in the resulting risk. Due to
the lack of dermal absorption data, the Agency calculated the risk to
workers from TPTH by assuming that 100 percent of TPTH would be
absorbed. Potential exposure of pesticide applicators to TPTH occurred
at a level that was known to produce developmental effects in
laboratory animals, thereby resulting in a highly significant
developmental risk for pregnant women.

B. Label, Packaging, and Use Changes

    The TPTH Task Force has voluntarily implemented measures that have
reduced worker exposure to TPTH. These actions include deleting certain
crops, such as carrots and peanuts [Ref. 19], requiring the use of
closed cab tractors for TPTH applications and additional protective
clothing. The Task Force also adopted water soluble packaging to reduce
worker exposure to their wettable powder formulation, and added
protective clothing requirements to product labels. The flowable
concentrate formulation must be used with a mechanical transfer or
closed loading system, with workers required to wear a coverall over
long sleeve shirt and long pants, chemical-resistant gloves, chemical-
resistant apron (when mixing, loading or cleaning), and a respirator.
For workers using the wettable powder in water soluble packaging;
coveralls, long-sleeve shirt, long pants, chemical-resistant gloves and
a dust/mist respirator are required. To apply TPTH by airblast,
applicators must wear long-sleeve shirts, long pants, shoes and socks
(no gloves are required, since enclosed cabs are necessary to apply
TPTH). Flaggers must also be in enclosed cabs. The current risk
assessment for TPTH incorporates data submitted since the initiation of
the special review as well as the risk mitigation measures put into
place since 1985.

C. Refined Data

    EPA required that the registrants conduct a rabbit developmental
toxicity study to allow a direct determination of maternal and
developmental toxicity via the dermal route. This technique provides a
direct, more accurate estimate of dermal toxicity than extrapolating
from the rabbit oral study to dermal exposure. In addition, the TPTH
Task Force generated exposure data for pecan harvesters as no such data
were available for this unusual exposure scenario (pecan harvesting
involves shaking trees, sweeping pecans into rows under the trees
(windrowing), and collecting pecans). The current assessment also
reflects the revised Q1* for cancer risk assessment, updated
TPTH dermal absorption/penetration factor, a revised TPTH flowable
concentrate exposure assessment, and monitoring data for workers
mixing/loading the TPTH wettable powder in a water soluble pack
formulation and harvesters re-entering pecan groves after TPTH
treatment.

D. Occupational Handler Exposure Estimates

    Exposures to workers mixing, loading and applying TPTH were
assessed as part of the RED. Risks to flaggers were also assessed.
Assessments incorporating current label conditions were conducted for
both liquid and wettable powder formulations, as well as for the
different application methods (ground, aerial, and chemigation) for
each of the three use sites [Refs. 2 and 20].
    Dermal exposure is the most significant route of exposure for TPTH.
However, the Agency also assessed the potential for inhalation exposure
because although inhalation is a very minor route of exposure for
workers applying TPTH, subchronic inhalation studies have resulted in
lung injury and death to test animals at extremely low doses. The
current exposure assessment is based on data from the Pesticide
Handlers Exposure Database (PHED) Version 1.1 as well as chemical-
specific data from monitoring studies for mixing/loading TPTH wettable
powder in a water soluble pack formulation for application to pecan
groves and applying TPTH to pecans using an enclosed-cab airblast
sprayer [Ref. 21]. Assumptions for the exposure assessment included:
     An average body weight of 70 kg for an adult handler was
used in the inhalation and cancer assessments. A body weight of 60 kg
was used in the short- and intermediate-term dermal assessments (the
typical weight for a woman since the NOAEL is based on a developmental
study with developmental toxicity an endpoint of concern).
     The average workday interval is 8 hours per day (e.g., the
acres treated or volume of spray solution prepared in a typical day).
     The Agency assumed typical acres treated per workday as
follows: 40 acres for airblast application to pecan orchards, 150 acres
for groundboom application to potatoes and sugar beets, 1,000 acres for
aerial application to potatoes and sugar beets, and 400 acres for
aerial application to pecan orchards (this is rarely done). Since
specific data were not available for private growers using chemigation
for potatoes, or for flaggers during aerial application, a default
estimate of 350 acres representing the Exposure Science Advisory
Counsel estimate for aerial and chemigation applications in
agricultural settings was used. Although a typical aerial application
of TPTH involves treatment of 1,000 acres, the Agency assumed that an
automated means of flagging, rather than human flaggers would be
employed for applications to greater than 350 acres.
     For the non-cancer assessment, the Agency used the maximum
application rates for each crop.
     For the cancer assessment, the Agency used typical
application rates, typical number of acres treated per day, typical
number of applications per year, and assumed a worker life span of 70
years with a TPTH exposure period of over 35 years, and that workers
were exposed for 8 hours per day for the

[[Page 63179]]

typical number of days applied per year (this varied from 1-96 days
depending on type of equipment used and whether applicators were
private or commercial applicators).
     The following generic protection factors (PF) were used to
represent various risk mitigation measures on the labels: 50 percent PF
for body exposure with a double layer of clothing, 90 percent PF for
hand exposure for use of chemical resistance gloves, and 80 percent PF
for use of dust/mist mask for respiratory protection.
     A dermal absorption factor of 10% was used for the cancer
assessment based on the comparison of the LOAELs of the oral and dermal
developmental toxicity studies in rabbits [Refs. 3 and 22].

E. Occupational Handler Risk Characterization

    Because different toxic effects were selected for the assessment of
non-cancer dermal and inhalation risks, separate risk assessments were
conducted for dermal and inhalation exposures. Both short- and
intermediate-term Margins of Exposure (MOEs) for occupational handlers
were derived based upon comparison of dermal exposure estimates against
a NOAEL of 3 mg/kg/day from a dermal developmental study in the rabbit.
Inhalation MOEs were derived based upon comparison of inhalation
exposure estimates against a NOAEL of 0.00034 mg/L or 0.092 mg/kg/day.
The cancer assessment used the oral Q1* of 1.83 (mg/kg/
day)-1 based on fatal pituitary gland adenoma tumors in
female rats. To calculate exposure for the cancer assessment, a 10
percent dermal absorption (based on comparison between rabbit oral and
dermal studies) was used, while inhalation absorption was assumed to be
100 percent. The dermal and inhalation exposures were summed to
calculate a total exposure, which was combined with the Q1*
to estimate cancer risk [Ref. 17].
    1. Non-cancer risk assessment. The non-cancer occupational risk
estimates are summarized in the following Table 2. Since the
uncertainty factors and target MOEs for occupational workers are 100
for short- and intermediate-term dermal and inhalation risk, MOEs over
100 represent acceptable occupational risks to workers, whereas MOEs
below 100 would represent a risk concern for the Agency. Non-cancer
inhalation risks were acceptable across all use scenarios. Dermal non-
cancer risks were also acceptable across all use scenarios, when
mitigation measures were considered, with the exception of mixing and
loading liquids for aerial application to sugar beets at maximum
application rates (MOE of 84) and mixing and loading wettable powder in
water-soluble bags for aerial and chemigation application for all three
use sites (MOEs of 33 to 82).

                                                   Table 2.-- Summary of Occupational Handler Dermal and Inhalation Non-Cancer Risk Estimates
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                 Dermal Short- and Intermediate-Term (MOE = 100)                         Inhalation (MOE = 100)
                                                              Application  ---------------------------------------------------------------------------------------------------------------------
         Exposure Scenario                    Crop          Rate (lb ai/A)                                                Engineering                                                Engineering
                                                                                   Baseline                 PPE             Controls          Baseline                 PPE             Controls
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mixer/Loader Risk..................
  Mixing/Loading Liquids for Aerial/ Pecans                          0.375  See Eng.               See Eng.                     140    See Eng.               See Eng.                     520
   Chemigation Application.                                                 Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Potatoes                       0.1875  See Eng.               See Eng.                     110    See Eng.               See Eng.                     410
                                                                            Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  See Eng.               See Eng.                      84    See Eng.               See Eng..............        310
                                                                            Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets               0.125 (Typ)  See Eng.               See Eng.                     170    See Eng.               See Eng.                    N/A2
                                                                            Control..............  Control..............               Control..............  Control..............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Liquids for         Potatoes                       0.1875  See Eng.               See Eng.                     740    See Eng.               See Eng.                   2,800
   Groundboom Application.                                                  Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  See Eng.               See Eng.                     560    See Eng.               See Eng.                   2,100
                                                                            Control..............  Control..............               Control..............  Control..............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Liquid for Orchard  Pecans                          0.375  See Eng.               See Eng.                    1400    See Eng.               See Eng.                   5,200
   Airblast Sprayer Application.                                            Control..............  Control..............               Control..............  Control..............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Wettable Powder     Pecans                          0.375  See Eng.               See Eng.                      55    See Eng.               See Eng.                     600
   (WSB) for Aerial/Chemigation                                             Control..............  Control..............               Control..............  Control..............
   Application.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Pecans                     0.25 (Typ)  See Eng.               See Eng.                      82    See Eng.               See Eng.                    N/A2
                                                                            Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Potatoes                       0.1875  See Eng.               See Eng.                      44    See Eng. Control       See Eng.                     480
                                                                            Control..............  Control..............                                      Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 63180]]

                                     Potatoes                  0.125 (Typ)  See Eng.               See Eng.                      65    See Eng.               See Eng.                    N/A2
                                                                            Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  See Eng.               See Eng.                      33    See Eng.               See Eng.                     360
                                                                            Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets               0.125 (Typ)  See Eng.               See Eng.                      65    See Eng.               See Eng.                    N/A2
                                                                            Control..............  Control..............               Control..............  Control..............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Wettable Powder     Potatoes                       0.1875  See Eng.               See Eng.                     290    See Eng.               See Eng.                   3,200
   (WSB) for Groundboom Application.                                        Control..............  Control..............               Control..............  Control..............
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  See Eng.               See Eng.                     220    See Eng.               See Eng.                   2,400
                                                                            Control..............  Control..............               Control..............  Control..............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Wettable Powder     Pecans                          0.375  See Eng.               See Eng.                     550    See Eng.               See Eng.                   6,000
   for Orchard Airblast Sprayer                                             Control..............  Control..............               Control..............  Control..............
   Application.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Applicator Risk....................
  Applying Sprays with a Fixed-Wing  Pecans                          0.375  No Data, See Eng.      No Data, See Eng.            240    No Data, See Eng.      No Data, See Eng.            630
   Aircraft.                                                                 Cont.                  Cont.                               Cont.                  Cont.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Potatoes                       0.1875  No Data, See Eng.      No Data, See Eng.            190    No Data, See Eng.      No Data, See Eng.            510
                                                                             Cont.                  Cont.                               Cont.                  Cont.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  No Data, See Eng.      No Data, See Eng.            140    No Data, See Eng.      No Data, See Eng.            380
                                                                             Cont.                  Cont.                               Cont.                  Cont.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Applying Sprays with a Groundboom  Potatoes                       0.1875  460                    580                        1,300    310                    1,500                      5,300
   Sprayer.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  340                    440                          960    230                    1,100                      4,000
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Applying Sprays to Orchards with   Pecans                          0.375  33                     55                           630    95                     480                          950
   an Airblast Sprayer.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Pecans                     0.25 (Typ)  50                     82                           950    140                    720                        1,400
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mixer/Loader/Applicator Risk.......
  Mixing/Loading Liquids and         Potatoes                       0.1875  N/A1                   N/A1                         470    N/A1                   N/A1                       1,800
   Applying Sprays with a
   Groundboom Sprayer.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  N/A1                   N/A1                         350    N/A1                   N/A1                       1,400
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Liquids and         Pecans                          0.375  N/A1                   N/A1                         430    N/A1                   N/A1                         810
   Applying Sprays to Orchards with
   an Airblast Sprayer.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Wettable Powder     Potatoes                       0.1875  N/A1                   N/A1                         240    N/A1                   N/A1                       2,000
   (WSB) and Applying Sprays with a
   Groundboom Sprayer.
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 63181]]

                                     Sugar beets                      0.25  N/A1                   N/A1                         180    N/A1                   N/A1                       1,500
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Wettable Powder     Pecans                          0.375  N/A1                   N/A1                         290    N/A1                   N/A1                         820
   (WSB) and Applying Sprays to
   Orchards with an Airblast
   Sprayer.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Flagger Risk.......................
  Flagging Spray Applications......  Pecans                          0.375  120                    140                        6,200    140                    700                        7,000
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Potatoes                       0.1875  250                    270                       12,000    280                    1,400                     14,000
                                    ------------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Sugar beets                      0.25  190                    210                        9,400    210                    1,100                    11,000
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ There is no unit exposure for mixer/loader to add to the applying unit exposure until engineering controls.
\2\ Inhalation MOE is not of concern at the maximum application rate; therefore, an assessment of the typical application was not necessary.
a Note: Baseline unit exposure represents long pants, long sleeved shirt, no gloves, open cab tractor, and no respirator. Additional PPE includes double layer of clothing (50% protection
  factor for clothing), chemical resistant gloves, and a dust/mist respirator. Engineering controls include closed mixing/loading or water-soluble bag, single layer clothing, chemical
  resistant gloves, enclosed cab, enclosed cockpit, or enclosed truck (98% protection factor). Application rates are based on the maximum application rates listed on the TPTH labels, and on
  typical application rates reported by BEAD. Acres treated per day are from BEAD reports of the acres treated in one work day.
b Source: TPTH: HED Revised Risk Assessment for the Reregistration Eligibility Decision (RED) Document, September 21, 1999.

    Although the MOEs for mixing/loading wettable powder for aerial/
chemigation application were calculated to be less than 100, based on a
number of factors, the Agency determined in its reregistration
eligibility determination that the MOEs for the water soluble bag
formulation are acceptable. First, the results of the Agency's non-
cancer occupation risk assessment for this formulation (and similar
results in the occupational cancer risk assessment discussed below),
are not consistent with the Agency's experience that water soluble
packaging results in exposures comparable to the use of other
engineering controls such as closed mixing/loading systems for liquid
formulations, and is therefore a protective measure that the Agency
generally promotes. Second, the Agency believes that the significant
discrepancy observed between exposure from liquid formulations in
closed systems and water soluble bags for this chemical are due to the
failure of the TPTH water soluble bag study to replicate actual use
patterns on all three registered crop sites i.e., the study monitored
workers who handled only enough active ingredient to treat 5 acres,
modeling an airblast application scenario for pecan orchards which are
40 acres, rather than the 1,000 acres for aerial application to sugar
beets and potatoes.
    Results of the worker exposure study were thus, of necessity,
extrapolated to calculate risks from handling enough active ingredient
to evaluate larger acreages. However, the Agency does not believe,
under the circumstances present, that a linear extrapolation of
exposure from 5 acres to 1,000 acres is reliable. Consequently, while
the Agency believes that the study is appropriate to estimate exposures
based on treatment of 40 acres (i.e., airblast application on pecan
orchards), it does not believe that it is appropriate to use this same
study to estimate exposures based on treatment of 1,000 acres, and that
use of this study provides an overestimate of risk. Based on the
Agency's experience that water soluble packaging results in exposures
comparable to the use of other engineering controls such as closed
mixing/loading systems for liquid formulations, the Agency determined
in the RED that a new exposure study based on a larger treated acreage,
which was required with the issuance of the RED, will demonstrate that
the MOEs for the water soluble bag formulation are acceptable.
    2. Cancer risk assessment. The occupational cancer risk estimates
are summarized in Table 3 below. Under the Agency's non-dietary cancer
risk policy, cancer risks less than 1.0  x  10-6 (i.e., less
than a 1 in 1 million lifetime risk of excess cancer from TPTH
exposure) are generally considered acceptable, cancer risks greater
than 1  x  10-4 (i.e., more than a 1 in 10,000 lifetime risk
of excess cancer from TPTH exposure) are generally considered
unacceptable, whereas for cancer risks that fall between 1  x
10-6 and 1  x  10-4, the Agency's goal is to
bring these risks to 10-6 or less through mitigation if
feasible, although risks higher than 10-6 but less than
10-4 will generally be considered acceptable if measures to
mitigate these risks are not available and benefits of continuing use
are demonstrated. Mixing and loading wettable powder in water-soluble
bags for aerial/chemigation and for groundboom application on potatoes
was estimated at 1.5  x  10-4 for commercial applicators. As
noted above in Unit IV.E.1., the Agency believes that the deficiencies
in the exposure study used to model this formulation provide an
overestimate of exposure and risk for potatoes and sugarbeets. Most of
the other cancer risk estimates were greater than 1  x  10-6
but less than 1.0  x  10-4 (ranging from 1.1  x
10-6 to 9.1  x  10-5).

[[Page 63182]]

                                        TABLE 3.-- Summary of Occupational Handler Cancer Risk Estimate for TPTH
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Application                              Cancer Risk Estimate
          Exposure Scenario                     Crop           Rate (lb ai/-----------------------------------------------------------------------------
                                                                    A)             Baseline                   PPE               Engineering Controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mixer/Loader Risk...................
  Mixing/Loading Liquids for Aerial/  Pecans                          0.25  See Eng.                See Eng.                                      3.4E-6
   Chemigation Application.                                                 Control...............  Control...............
                                     -------------------------------------------------------------------------------------------------------------------
                                      Potatoes                       0.125  See Eng.                See Eng.                             6.3E-5 / 1.5E-6
                                                                            Control...............  Control...............
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  See Eng.                See Eng.                                      3.8E-5
                                                                            Control...............  Control...............
--------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Liquids for          Potatoes                       0.125  See Eng.                See Eng.                             6.1E-5 / 1.9E-6
   Groundboom Application.                                                  Control...............  Control...............
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  See Eng.                See Eng.                             3.7E-5 / 1.9E-6
                                                                            Control...............  Control...............
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Mixing/Loading Liquid for         Pecans                          0.25  See Eng.                See Eng.                                      1.0E-6
   Orchard Airblast Sprayer                                                 Control...............  Control...............
   Application
--------------------------------------------------------------------------------------------------------------------------------------------------------
  Mixing/Loading Wettable Powder      Pecans                          0.25  No Data Cont.           No Data Cont.                                 8.1E-6
 (WSB) for Aerial/Chemigation
 Application.
                                     -------------------------------------------------------------------------------------------------------------------
                                      Potatoes                       0.125  No Data Cont.           No Data Cont.                        1.5E-4 / 3.6E-6
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  See Eng.                See Eng.                                      9.1E-5
                                                                            Control...............  Control...............
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Mixing/Loading Wettable Powder    Potatoes                       0.125  See Eng.                See Eng.                             1.5E-4 / 4.6E-6
   (WSB) for Groundboom Application                                         Control...............  Control...............
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  See Eng.                See Eng.                             8.8E-5 / 4.6E-6
                                                                            Control...............  Control...............
--------------------------------------------------------------------------------------------------------------------------------------------------------

  Mixing/Loading Wettable Powder      Pecans                          0.25  See Eng.                See Eng.                                      2.4E-6
   (WSB) for Orchard Airblast                                               Control...............  Control...............
   Sprayer Application.
========================================================================================================================================================
Applicator Risk.....................
  Applying Sprays with a Fixed-Wing   Pecans                          0.25  No Data, See Eng.       No Data, See Eng.                             2.0E-6
   Aircraft.                                                                 Cont.                   Cont.
                                     -------------------------------------------------------------------------------------------------------------------
                                      Potatoes                       0.125  No Data, See Eng.       No Data, See Eng.                             3.8E-5
                                                                             Cont.                   Cont.
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  No Data, See Eng.       No Data, See Eng.                             2.3E-5
                                                                             Cont.                   Cont.
--------------------------------------------------------------------------------------------------------------------------------------------------------
  Applying Sprays with a Groundboom   Potatoes                       0.125  1.4E-4 / 4.3E-6         8.1E-5 / 2.5E-6                      3.5E-5 / 1.1E-6
   Sprayer
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  8.3E-5 / 4.3E-6         4.9E-5 / 2.5E-6                      2.1E-5 / 1.1E-6
--------------------------------------------------------------------------------------------------------------------------------------------------------
  Applying Sprays to Orchards with    Pecans                          0.25  4.4E-5                  2.5E-5                                        2.5E-6
   an Airblast Sprayer.
========================================================================================================================================================
Mixer/Loader/Applicator Risk........
  Mixing/Loading Liquids and          Potatoes                       0.125  N/A                     N/A                                           3.0E-6
   Applying Sprays with a Groundboom
   Sprayer.
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  N/A                     N/A                                           3.0E-6
--------------------------------------------------------------------------------------------------------------------------------------------------------

  Mixing/Loading Liquids and          Pecans                          0.25  N/A                     N/A                                           3.5E-6
   Applying Sprays to Orchards with
   an Airblast Sprayer.
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 63183]]

  Mixing/Loading Wettable Powder      Potatoes                       0.125  N/A                     N/A                                           5.7E-6
   (WSB) and Applying Sprays with a
   Groundboom Sprayer.
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  N/A                     N/A                                           5.7E-6
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Mixing/Loading Wettable Powder    Pecans                          0.25  N/A                     N/A                                           5.0E-6
   (WSB) and Applying Sprays to
   Orchards with an Airblast Sprayer
========================================================================================================================================================
Flagger Risk........................
    Flagging Spray Applications       Pecans                          0.25  4.5E-6                  3.4E-6                                        9.1E-8
                                     -------------------------------------------------------------------------------------------------------------------
                                      Potatoes                       0.125  3.4E-5                  2.5E-5                                        6.8E-7
                                     -------------------------------------------------------------------------------------------------------------------
                                      Sugar beets                    0.125  2.0E-5                  1.5E-5                                       4.1E-7
--------------------------------------------------------------------------------------------------------------------------------------------------------
aN/A--There is no unit exposure for mixer/loader to add to the applying unit exposure until engineering controls.
bBaseline unit exposure represents long pants, long sleeved shirt, no gloves, open cab tractor, and no respirator. Additional PPE includes double layer
  of clothing (50% protection factor for clothing), chemical resistant gloves, and a dust/mist respirator. Engineering controls include closed mixing/
  loading or water-soluble bag, single layer clothing, chemical resistant gloves, enclosed cab, enclosed cockpit, or enclosed truck (98% protection
  factor). Application rates are based on the maximum application rates listed on the TPTH labels, and on typical application rates reported by BEAD.
  Acres treated per day and number of exposures per year are based on data from BEAD. In cases where the number of acres treated or the number of
  exposures per year are different for commercial applicator and private grower, both estimates are presented, separated by a ``/'' in the following
  manner: commercial value / private grower value.
cSource: TPTH: HED Revised Risk Assessment for the Reregistration Eligibility Decision (RED) Document, September 21, 1999.

    3. Incident reports. The Agency reviewed the OPP Incident Data
System (IDS), Poison Control Center, California Department of Food and
Agriculture (replaced by the Department of Pesticide Regulation in
1991), and National Pesticide Telecommunications Network (NPTN)
databases for reported incident information for TPTH. Only seven cases
submitted to the IDS were identified; however, no documentation
confirming exposure or health effects were available. As a result, the
Agency has concluded that relatively few incidents of illness from
exposure to TPTH have been reported and no recommendations can be made
based on the few incident reports available [Ref. 2].

F. Post-Application Exposure and Risk Estimates

    The Agency determined there were three main categories of
activities which could result in the potential postapplication
exposures to individuals entering areas treated with TPTH [Ref. 17]:
     Harvesting pecans (although mechanically harvested, it is
a very dusty operation); Scouting and moving hand-set irrigation pipes
for potatoes and sugar beets; and
     Harvesting, sorting/packing, and brushing/washing potatoes
and sugar beets.
    None of these crop activities have been identified as scenarios
yielding potential chronic exposure (i.e.,  180 days of
exposure/year) concern.
    The postapplication exposure assessment for pecan harvesting was
based on a reentry study of pecan workers operating windrowing
equipment as part of pecan harvesting activities [Ref. 23]. Both dermal
and inhalation exposure monitoring were conducted. In addition, soil
and thatch samples were collected from the dripline beneath the treated
pecan trees (potential TPTH postapplication exposures were expected
from both the pecans and disturbances of the soil under trees). Both
the monitoring data, as well as the soil/thatch residue levels, were
used in the assessment.
    Soil and foliar dissipation data that were collected following
applications of TPTH to potatoes and peanuts [Ref. 24] were also used
for the postapplication exposure assessment for potatoes and sugar
beets (since potatoes and sugar beets both have similar application
rates and cultural techniques). TPTH did not appear to dissipate in the
soil; therefore, the highest daily mean level (1.36 parts per billion
TPTH) at one day post application was used in the assessment. The soil
level was used in conjunction with a soil/dermal transfer coefficient
of 3.9 ng/ppb/hr. The foliar dissipation curve is (log Y = -0.0573X + -
0.498), from the TPTH foliar dissipation study accepted by EPA in 1986
(Y = the dislodgeable foliar residue in g/cm2 and X
= the number of days after the application).
    The assumptions used in the calculations for occupational
postapplication risks include the following:
     Application rates used for the different postapplication
scenarios were:
    No rate required for pecan harvesting since the study provided
exposure values (g/kg/hr), making calculations based on an
application rate not necessary (the study application rate was 0.375 lb
ai/acre)
    For the harvesting and maintenance activities assessment, the non-
cancer calculations were completed using the maximum application rates
for specific crops recommended by the available TPTH labels. Typical
application rates were used in the calculations for the cancer
assessment.
     Transfer coefficients (Tc) were not used for pecan
harvesting estimates because the study provides exposure values
(g/kg/hr). For potato harvesting, a soil/dermal transfer
coefficient of 3.9 ng/ppb/hr was used, based on a study conducted by
the Medical University of South Carolina for the Agency's Hazard
Assessment Project [Ref. 24]. TPTH soil and foliar dissipation data.
For maintenance activities associated with potatoes and sugar beets,
the transfer coefficient was assumed to be 2,500 cm2/hr.

[[Page 63184]]

     Daily exposure is assumed to occur for 8 hours per day.
     The average body weight of 60 kg is used in the non-cancer
risk estimates (due to a developmental endpoint), while for cancer
estimates, 70 kg is used, representing a typical adult.
     Exposure frequency is estimated to be 40 days/year for
pecan harvesting, and 30 days/year for potato and sugar beet
maintenance activities and harvesting.
     Exposure duration is assumed to be 35 years. This
represents a typical working lifetime.
     Lifetime is assumed to be 70 years.
     Dermal absorption is assumed to be 10 percent for cancer
estimates because the Q1* is not based on a dermal study, as
in the handler assessment.
     The Q1* used in the cancer assessment is 1.83
(mg/kg/day)-1.

G. Occupational Postapplication Risk Characterization

    The postapplication risks are summarized in Tables 4-6 below. The
postapplication assessment indicates that for pecan harvesting, MOEs
exceed 100 on day zero after application, while cancer risk estimates
are greater than 1.0  x  10-4 until 7 days after the last
application at the Georgia site, and between 21 and 30 days after the
last application at the Texas site. However, pecan harvesting generally
occurs at least 21 days after TPTH application. As part of the
reregistration eligibility decision, TPTH labels have been amended to
require a minimum harvest interval of 30 days, thereby resulting in
MOEs over 100 and cancer risks of less than 1  x  10-4 for
pecan harvesters.
    As indicated in Table 5 below, MOEs for maintenance activities are
 100 on day zero after application for potatoes, and on the
second day after application for sugar beets. The cancer risk estimate
for maintenance activities was found to be less than 1.0  x
10-4 on the second day after application for both potatoes
and sugar beets. The MOE and cancer risk estimate for potato harvesting
do not exceed the Agency's level of concern on any day after
application (see Table 6). Since TPTH has a current REI of 48 hours for
all crops, postapplication risks for maintenance and harvesting
activities on sugar beets and potatoes are acceptable.

  Table 4.--Summary of Estimated Postapplication Risk Estimates Based on Residue Ratios During Pecan Harvesting
----------------------------------------------------------------------------------------------------------------
                                                          Soil/Thatch                   MOE
                                                            Residue    Residue --------------------- Cancer Risk
               Days After Last Treatment                 (g/   Ratiob                         Estimate
                                                              g)a                Dermal  Inhalation
----------------------------------------------------------------------------------------------------------------
Georgia................................................
  0....................................................          42.9    4.0        170        480       1.9E-04
  1....................................................          23.3    2.2        320        890       1.1E-04
  3....................................................            27    2.5        270        770       1.2E-04
  7....................................................          10.8    1.0        680       1900       4.9E-05
  14...................................................          11.7    1.1        630       1800       5.3E-05
  21...................................................            18    1.7        410       1200       8.1E-05
  30...................................................          18.4    1.7        400       1100       8.3E-05
  60...................................................          10.7    0.99       690       1900       4.8E-05
  90...................................................          10.9    1.01       680       1900       4.9E-05
  120..................................................           3.5    0.32      2100       5900       1.6E-05
----------------------------------------------------------------------------------------------------------------
Texas..................................................
  0....................................................           7.2    1.76       220       1100       1.4E-04
  1....................................................           7.4    1.80       220       1100       1.5E-04
  3....................................................           3.8    0.93       420       2100       7.6E-05
  7....................................................           6.4    1.56       250       1200       1.3E-04
  14...................................................           9.2    2.24       170        850       1.8E-04
  21...................................................           6.2    1.51       260       1300       1.2E-04
  30...................................................           4.2    1.02       380       1900       8.4E-05
  60...................................................           4.0    0.98       400       2000       8.0E-05
  90...................................................           3.1    0.76       520       2500       6.2E-05
  120..................................................           4.8    1.17       330       1600      9.6E-05
----------------------------------------------------------------------------------------------------------------
a Soil/thatch residues from pecan harvester exposure study (MRID #43557401).
b Residue ratios calculated by dividing the residue level on a given day by the residue level on the day
  exposure samples were collected (assumed to be 10.8 g/g for GA and 4.1 g/g for TX).

          Table 5.-- Summary of Postapplication Risk Estimates from TPTH During Maintenance Activities
----------------------------------------------------------------------------------------------------------------
                                     Potatoes Non-cancer    Sugar beets Non-    Potatoes and Sugar beets Cancera
                                    a (App. Rate: 0.1875   cancera (App. Rate:     (App. Rate: 0.125 lb ai/A)
                                          lb ai/A)            0.25 lb ai/A)    ---------------------------------
     Days After Last Treatment     --------------------------------------------
                                    DFRb (b (b(g/   Cancer Risk

                                      m>g/cm2)      MOE     m>g/cm2)      MOE         cm2)           Estimate

----------------------------------------------------------------------------------------------------------------
0.................................      0.084        100      0.112         80        0.056              1.2E-04
1.................................      0.074        120      0.099         91        0.049              1.1E-04
2.................................      0.065        140      0.087        100        0.043             9.3E-05
----------------------------------------------------------------------------------------------------------------
a The maximum application rates (0.1875 lb ai/A and 0.25 lb ai/A) were used for non-cancer assessment of
  potatoes and sugar beets, respectively. The typical application rate (0.125 lb ai/A) for both potatoes and
  sugar beets was used to estimate cancer risk.
b Dislodgeable foliar residue. Based on regression equation from study (MRID# 42507801) and using application
  rate indicated above, initial DFR of 4%, and a dissipation rate of 12% per day.

[[Page 63185]]

             Table 6.-- Summary of Postapplication Risk Estimates from TPTH During Potato Harvesting
----------------------------------------------------------------------------------------------------------------
                                                                    Non-cancer                   Cancer
                                                          ------------------------------------------------------
                Days After Last Treatmenta                   TRb (ppb                     TRb (ppb
                                                              TPTH)           MOE          TPTH)     Cancer Risk
----------------------------------------------------------------------------------------------------------------
Any Day..................................................         1.36       4,300,000         1.36      4.5E-9
----------------------------------------------------------------------------------------------------------------
a TPTH was not found to dissipate appreciably in soil; therefore, the above risks are applicable for any day
  after treatment.
b The transferrable residue was based on the highest daily average residue measured.

V. Summary of Benefits and Evaluation of Alternatives

A. Importance of Triphenyltin Hydroxide

    The Agency conducted a benefits assessment for TPTH by analyzing
the economic impact of cancellation on each of the three registered use
sites. Of the three sites for which TPTH is registered (pecans,
potatoes and sugarbeets), moderate economic impacts to pecan production
are anticipated if TPTH is not available for disease control. The
impact will be due to higher prices for the alternatives rather than
their reduced efficacy. More importantly, however, there is potential
for development of resistance from the use of the registered
alternatives which, as part of the triazole group of fungicides, share
a single site and similar mode of action, thereby increasing the risk
of resistance development over time in the absence of TPTH, which has a
different mode of action from the triazoles. For potatoes and
sugarbeets, minor economic impacts would result from TPTH cancellation,
although the cancellation of TPTH could adversely affect resistance
management programs relying on TPTH as an inexpensive contact fungicide
with a multi-site mode of action. Sugarbeet growers would also apply
greater amounts of an alternative fungicide (e.g. mancozeb), if TPTH
were not available, resulting in a negative impact on sugarbeet
integrated pest management (IPM) programs and greater overall
environmental pesticide loading.

B. Usage of Triphenyltin Hydroxide

    As already noted, TPTH is a non-systemic protectant foliar
fungicide registered for use on three sites: pecans, potatoes and
sugarbeets. The fungicide was also formerly registered for use on
carrots, peanuts and tobacco, and as an industrial preservative for
vinyl (PVC) electrical tubing. The exact mode of action of TPTH is not
clearly understood. Researchers indicate that TPTH inhibits oxidative
phosphorylation in fungal pathogens. The fungicide's inhibition of
other metabolic pathways has also been proposed [Ref. 25]. In addition
to disease control, TPTH is registered as a suppressant of Colorado
potato beetle populations on potatoes. The mode of action of TPTH
against the Colorado potato beetle has not been identified.
    TPTH use is limited to some extent by its phytotoxicity. The TPTH
label recommends that the fungicide not be applied in combination with
surfactants, spreaders, stickers or buffers to reduce the possibility
of phytotoxicity. A phytotoxic response occurs when applied alone at
the full label rate on potatoes [Ref. 26].
    The Agency estimates total usage of TPTH in the United States at
approximately 569,000 pounds of active ingredient per year [Ref. 27].
Pecans and sugarbeets represent the largest volume of use and highest
percent crop treated of the three use sites [Ref. 27].
    1. Pecans. TPTH is principally used to control scab, Cladosporium
effusum, the most important disease on pecans [Refs. 27 and 28]. TPTH
applications begin when leaves are unfolding and continue at 2 to 4
week intervals until the shucks begin to open. A maximum of 10
applications may be made per growing season, although the total amount
of TPTH which can be used in a given season is limited to 1.5 lbs
active ingredient per acre (ai/A) in Arizona and New Mexico, and all
areas west of Interstate 35 (I-35), and 2.25 lbs ai/A in all other
areas east of I-35. The difference in maximum seasonal application
rates is based on differences in climate which make disease pressures
greater in some areas relative to others [Ref. 2]. Scab infection
occurs on both foliage and nuts leading to lesion formation on nuts and
subsequent nut drop.
    In addition to scab, TPTH is registered to control other diseases
on pecans including: brown leaf spot (Cercospora fusca), downy spot
(Mycosphaerella caryigena), liver spot (Gnomonia nerviseda), powdery
mildew (Microsphaera alni), sooty mold (causal agent not identified)
and leaf blotch (Mycosphaerella dendroides).
    2. Potatoes. TPTH is used for control of early blight, Alternaria
solani, and late blight, Phytophthora infestans, of potatoes, primarily
in the upper Midwest potato growing region. The major states where TPTH
is used on potatoes include Minnesota, North Dakota, Wisconsin and
Colorado. Fungicide applications typically begin when plant disease
symptoms are first observed and continue as needed. Due to phytotoxic
concerns with applications of the fungicide at the full label rate of
0.19 lbs ai/A, TPTH is applied at 0.09 lbs ai/A in combination with
another fungicide, typically mancozeb at 1 lb a.i./A. Two to three
TPTH/mancozeb applications are usually made per growing season [Ref.
27]. A maximum of 0.56 lbs ai/A of TPTH can be applied in a given
season (or the equivalent of three applications at the maximum labeled
use rate).
    TPTH plays a role in potato IPM programs in the upper Midwest.
University plant pathologists have developed IPM programs incorporating
the use of TPTH, thereby allowing growers to reduce the total amount
and number of fungicide applications to potatoes per growing season.
    TPTH is also registered as a suppressant of Colorado potato beetle
(CPB) populations. Research by Hare, Logan and Wright [Ref. 29]
indicated that applications of TPTH reduced CPB larval densities. The
researchers concluded that applications of TPTH may enable potato
growers to reduce the total number of insecticides necessary for
control of CPB. However, applying TPTH at the rate reported to suppress
CPB may not be acceptable due to applications of the fungicide
resulting in a phytotoxic response to many commercially desirable
varieties. Thus, the Agency does not consider TPTH to be a viable pest
control option for control of CPB.
    3. Sugarbeets. TPTH is used in North Dakota, Minnesota and West
Texas to control Cercospora leaf spot, Cercospora beticola, on
sugarbeets [Ref. 30]. If the disease is not adequately controlled,
fungal infection results in defoliation and subsequent yield losses.
    TPTH applications begin when environmental conditions conducive for
Cercospora leafspot infection appear or when infection is first
observed.

[[Page 63186]]

Growers typically apply up to four TPTH applications with the rate
varying between the maximum and minimum labeled rate [Ref. 31]. The
current maximum labeled seasonal use rate is 0.5 lbs ai/A in all states
(or two applications at the maximum labeled use rate) except Minnesota,
North Dakota, and Michigan, where the maximum seasonal use allowed is
0.75 lbs ai/A (or three applications at the maximum labeled use rate).
Use of TPTH at the highest labeled rate has been necessary in some
states in recent years due to TPTH tolerance.

C. Alternatives Assessment

    1. Pecans. Several potential alternative fungicides are registered
for pecans including: azoxystrobin, benomyl, copper compounds, dodine,
fenarimol, fenbuconazole, propaconazole, sulfur, thiophanate methyl,
and ziram. TPTH is a protectant fungicide having a multi-site mode of
action which controls all dominant fungal diseases (such as scab, downy
spot, brown leaf spot, powdery mildew, liver spot, and leaf blotch) of
pecans. No alternative fungicide is claimed to control all of the
diseases listed on labels as being controlled by TPTH [Ref. 32].
    Published data were not available for the Agency to determine the
efficacy of TPTH compared to registered alternatives for control of
scab. Due to this lack of data, the Agency spoke with experts familiar
with scab to determine pecan yield impacts without the use of TPTH.
Based on expert input, it appears that pecan diseases can be controlled
using registered alternatives, but production costs will increase. The
experts also claimed that the pecan growers are already on the verge of
bankruptcy, and if the production costs were to increase, then many
small pecan growers may be forced out of business. All experts believed
that in the absence of TPTH, propaconazole and fenbuconazole would be
used for scab control. In the southern states, pecans are sprayed
approximately 6-8 times per year with different fungicides (mostly
TPTH, propaconazole and fenbuconazole). The researchers estimated that
replacing TPTH with propaconazole and fenbuconazole will not impact the
yield but pecan production costs will be increased due to higher
fungicide costs. In addition, since propaconazole and fenbuconazole
belong to the triazole group of fungicides, their extensive use may
result in pest resistance due to their similar modes of action [Ref.
27].
    During 1999, azoxystrobin was also registered for use on pecan
against scab. Azoxystrobin is very effective in controlling scab and
possibly other diseases but growers may not use it extensively due to
its higher cost per acre. The rest of the registered alternative
fungicides appear to have limited viability for the control of pecan
diseases. The scab pathogen has developed resistance against benomyl
and thiophanate-methyl. Applications of dodine result in a phytotoxic
response by several pecan varieties [Refs. 33 and 34]. Some states
suggest that the use of dodine be restricted to certain varieties or be
used only during the pre-pollination period [Ref. 35]. Applications of
copper or sulfur may result in a phytotoxic response by pecan foliage
at high temperatures. No data are available to determine the efficacy
of fenarimol for control of scab. Based on a communication with a
university plant pathologist, fenarimol is less efficacious than TPTH
[Ref. 30].
    Cultural controls are practiced to reduce scab infection. These
include pruning the tree for better air circulation and the use of
resistant varieties [Refs. 36, 37 and 38]. However, these non-chemical
controls alone cannot provide acceptable control of scab.
    2. Potatoes. TPTH is registered for control of early blight,
Alternaria solani, and late blight, Phytophthora infestans. Registered
alternative fungicides to TPTH for control of early and/or late blight
include those that are protective (chlorothalonil, copper compounds,
metalaxyl, and the ethylene bisdithiocarbamates (EBDCs), such as
mancozeb, maneb, and metiram) and those with protective, systemic and
curative properties (azoxystrobin, cymoxanil, dimethemorph, metalaxyl).
    Growers use TPTH in the late season to control pathogen sporulation
to prevent tuber blight phase of the disease. Recently registered
fungicides (azoxystrobin, dimethemorph, and cymoxanil) also have
antisporulation activity against the late blight pathogen. However,
TPTH is preferred due to its lower per acre treatment costs, reasonable
efficacy and because it has a different mode of action than the other
registered alternatives, diminishing the likelihood of resistance
development [Refs. 27 and 32].
    Chlorothalonil, mancozeb and azoxystrobin are also effective in
controlling early blight disease on potatoes. Based on three field
studies, EPA concluded that combinations of TPTH/mancozeb fungicide
applications provide either equal or greater efficacy than any other
fungicide application for control of early blight [Refs. 39, 40 and
41]. However, a statistical analysis of the data indicates that there
were no significant differences when comparing mancozeb/TPTH to
mancozeb treatments in terms of yield. Thus, the Agency believes that
if TPTH were not available, growers could use mancozeb at 0.80 to 1.60
lbs ai/A without any decrease in efficacy in the upper Midwest potato
growing region. Other secondary alternatives (chlorothalonil, maneb and
metiram) could also be used without any decrease in efficacy. The
Agency is aware that the unavailability of TPTH might affect potato IPM
programs. This may result in growers applying greater amounts of other
fungicides (chlorothalonil and EBDCs) during the potato growing season
than if TPTH use were allowed to continue.
    Cultural controls are practiced to reduce fungal infection. These
include: (1) Planting tolerant and/or resistant varieties and (2)
supplying adequate fertilizer and water to maintain plant vigor and
reduced susceptibility to fungal infection [Ref. 42]. However,
fungicides are still needed for acceptable disease control.
    3. Sugarbeets. The most viable alternatives to TPTH are
tetraconazole (currently only available under an emergency exemption)
and mancozeb. If TPTH were no longer registered there could be two
possible scenarios: (1) Mancozeb and tetraconazole (under an emergency
exemption or full registration) are available, and (2) mancozeb alone
is available. If mancozeb and tetraconazole are available, sugarbeet
growers will use them in alternation to achieve a comparable disease
control [Ref. 43]. Tetraconazole is a locally systemic fungicide and is
more efficacious than TPTH or mancozeb in controlling the pest. Using a
combination of tetraconazole and mancozeb, the growers are not likely
to suffer any yield loss. The Agency is currently reviewing an
application for registration of tetraconazole, which could be granted
within the coming year. start
    If both TPTH and tetraconazole were not available, then the growers
would have no choice but to use mancozeb alone. Based on two
comparative performance studies the Agency estimates sugarbeet growers
would most likely use mancozeb without a decrease in efficacy if the
spraying frequencies are doubled [Ref. 44]. The Agency estimates that
seven mancozeb applications would be needed compared to a total of four
with TPTH. This increased number of applications and the higher
application rate of using EBDC fungicides would lead to an increase in
the pesticide load on sugarbeets of about 10 lbs a.i./A, resulting in a
negative impact on

[[Page 63187]]

sugarbeet IPM programs. Exclusive reliance on a single fungicide could
also result in resistance development and impede the ability of farmers
to manage resistance through use of multiple fungicides with different
modes of action [Ref. 32].
    Other registered fungicides on sugarbeets include benomyl,
thiophanate-methyl and thiabendazole, and copper compounds. These
fungicide are not considered viable alternatives due to the development
of Cercospora leafspot isolates resistant to these fungicides [Ref.
45]. Cercospora leafspot resistance to TPTH has not occurred in the
United States but has been reported in Greece where there has been
extensive and exclusive use of the fungicide on sugarbeets [Ref. 25].
    Cultural practices can mitigate disease incidence, but none of the
practices can provide commercially acceptable control without the use
of fungicides. These non-chemical control practices include the
planting of resistant varieties and long crop rotations [Ref. 36].

VI. Agency Evaluations of Comments to the PD 1

A. Public Comments and Agency Responses to the Toxicological Concerns
contained in the PD 1

    Although no comments relating to the carcinogenicity or inhalation
toxicity were received in response to the PD 1, the Agency did receive
a number of comments relating to the toxicity and immunotoxicity of
TPTH. A summary of these comments and the Agency's responses follow.
    1. Comment. The American Civil Liberties Union (ACLU) commented
that they take strong exception to any action that merely requires
warning labels directed at pregnant or fertile women. In addition, they
believe that labeling is not an adequate or appropriate substitute for
regulating toxic exposures and does not protect the reproductive health
of male workers.
    Response. In the Registration Standard, the Agency required several
measures designed to minimize risks from exposure to TPTH while
additional studies were conducted to clarify the exact nature of the
developmental effects. To alert female pesticide applicators about the
potential for teratogenic effects, a label statement indicating that
``TPTH causes birth defects in laboratory animals and that exposure
during pregnancy should be avoided'' was required for all TPTH
products. In addition, the Agency imposed additional regulatory
requirements including protective clothing which must be worn by all
persons handling TPTH (i.e., impermeable gloves, long pants, long-
sleeved shirt, hat and boots) and appropriate respiratory protection.
Since the Registration Standard was issued, the registrant has
voluntarily required closed mixing/loading systems for aerial
applications, adoption of mechanical transfer systems for all liquid
formulations and packaging of the wettable powder formulation in water
soluble packets. These requirements are equally protective of male and
female pesticide applicators handling pesticide products containing
TPTH. Secondly, the Registration Standard also requires the
classification of TPTH as a restricted use pesticide, which provides
greater controls to ensure proper pesticide handling and use. The
Agency believes that these restrictions will effectively minimize risks
to female and male applicators by reducing the potential for exposure.
    2. Comment. American Hoechst Corporation disagrees with the
Agency's position that TPTH produces teratogenic effects and that a
NOAEL has not been determined in the two previously reviewed rat
teratogenicity studies [Refs. 5 and 46]. American Hoechst and M&T
Chemicals had the rat teratology study by Battelle Columbus
Laboratories [Ref. 3] peer reviewed by two independent sources and
submitted the results of those reviews. One reviewer found that 2.8 mg/
kg/day was clearly a NOAEL for teratogenicity while the second reviewer
was unable to identify a no effect level from the data available. In
addition, American Hoechst submitted the results of a teratology study
of triphenyltin fluoride (TPTF) that had been previously submitted to
EPA. The NOAEL for this study was 3.0 mg/kg/day.
    Response. The submissions from American Hoechst Corporation do not
satisfactorily eliminate concerns regarding the teratogenicity of TPTH
because no new information was presented to the Agency. Although these
studies provided sufficient data to assure that TPTH is not teratogenic
in rats at dose levels up to and including 8.0 mg/kg/day, these studies
did result in developmental and maternal toxicity. Second, the
registrant did not provide new information indicating that a NOAEL
exists in the two rat studies. Third, the teratology study with TPTF
also indicated hydroureter as a fetal lesion. The initial reviewer of
this study classified this compound as a teratogen.
    3. Comment. American Hoechst Corporation commented that the PD 1
failed to note that guidelines for immunotoxicity have not been
established by the Agency. The notice also failed to note two
immunotoxicity studies submitted to the Agency in January 1983. The
registrants concluded that the first study, conducted with male mice
dosed at 2.5 mg/kg/day for 10 days produced no indication of
immunosuppressive effect as indicated by a reduction of spleen or
thymus weights. The second study was a 14-day subchronic study. They
concluded that the immunological status of mice receiving TPTH was not
impaired until doses administered were overtly toxic as indicated by
loss of body weight or mortality. The NOAEL for immunotoxicity was 5
mg/kg/day.
    Response. The Agency acknowledges that guidelines for
immunotoxicity testing were not available at the time of the PD 1. EPA
reviewed both studies referenced by American Hoescht Corporation in
developing the TPTH Registration Standard. In the first study, only a
single dose of TPTH was made. The Agency concludes that this study does
not adequately determine whether TPTH can affect the thymus. The Agency
believes the second study did not demonstrate a definite NOAEL for
TPTH. A decrease in spleen weight occurred at the lowest dose tested
(2.5 mg/kg/day). The study also showed a consistent increase in
response to T-dependent antigen. In addition, decreased leukocyte
counts were observed at all dosage levels of TPTH, except at 10 mg/kg/
day. Based on the results of these studies, the Agency required
additional data in the Registration Standard, which were assessed as
part of the TPTH Registration Eligibility Decision.
    A single comment relating to the reproductive effects toxicity of
TPTH was received in response to the PD 1. A summary of this comment
and the Agency's response follows.
    Comment. The ACLU also commented that the Agency has not given
equal priority to potential testicular effects associated with exposure
of males to TPTH.
    Response. In the PD 1, the Agency stated its concerns regarding
data suggesting that TPTH may produce decreased testicular weights in
laboratory animals. As discussed above, Hoechst-Celanese Corporation
submitted a rat two-generation reproduction study in which there were
no specific effects of TPTH on the actual reproductive performance of
the test animals. Based on the results of this study, the Agency's
concern regarding adverse reproductive effects has been rebutted by the
TPTH registrants.
    A single comment relating to the toxicity to non-target organisms
of

[[Page 63188]]

TPTH was received in response to the PD 1. A summary of this comment
and the Agency's response follows.
    Comment. One pecan grower noted that grazing cattle in TPTH-treated
pecan groves did not adversely affect the cattle or other nontarget
organisms.
    Response. The registered labels for the use of TPTH on pecans has a
restriction against the grazing of livestock in treated areas.
Therefore, this practice is in violation of FIFRA. It should also be
noted that grazing cattle in treated areas can result in residues in
meat and milk, thereby contributing to human dietary exposure and risk.

B. Public Comments and Agency Responses to the Occupational and
Residential Exposure Discussion Contained in the PD 1

    Comments relating to exposure to TPTH were received in response to
the PD 1. A summary of those comments and the Agency's responses
follow.
    1. Comment. There has been some concern from EPA about exposure,
but 85 to 90 percent of the spray operations in Georgia are made from
an air-conditioned tractor cab or enclosed cab.
    Response. The Agency has taken enclosed cabs into account in its
revised risk assessment. Since EPA issued the PD 1, all TPTH labels
were amended to require closed cab tractors during application to
registered crops.
    2. Comment. It is very rare to find a woman involved in a pecan
spray operation.
    Response. The Agency is concerned about exposure to men as well as
women from exposure to TPTH. In the absence of data, the Agency assumes
that TPTH exposure to both male and female workers may potentially
result in developmental effects, even though it is not known whether
exposure to males results in developmental effects because male animals
were not included in the developmental toxicity studies. The Agency
believes that this is a reasonable assumption because data are
available for other chemicals indicating that adverse developmental
effects can occur with males. In addition, the Agency is also concerned
about carcinogenicity, inhalation toxicity and immunotoxicity which
clearly affected both males and females in the laboratory studies.
    3. Comment. An aerial applicator noted that mixer/loaders are
equipped with rubber gloves, goggles, a respirator, long-sleeved
shirts, long pants and boots which essentially eliminates the
possibility of dermal contact. In addition, the pilot himself has no
exposure due to the fact that he makes each spray pass to the up wind
side staying clear of the swath he made in the previous pass.
    Response. Several worker exposure studies are available indicating
that exposure does occur to workers even with the use of protective
clothing and equipment. Even with state-of-the-art protective clothing
and equipment, worker exposure to TPTH does occur. With the new
mitigation measures in place and reduction in application rates, these
exposures are no longer expected to result in unreasonable risk to
workers. Aerial applicators are also required to be in enclosed
cockpits when applying TPTH. EPA data do not support anecdotal
assertions that pilots who make spray passes up wind avoid any
pesticide exposure.
    4. Comment. Aerial applicators apply about 75% of the fungicides to
sugarbeets in Minnesota and North Dakota. These applicators are
schooled in the safe application of pesticides. All field marking is
done automatically and no people are in the field for this purpose
during application. Ground boom sprayers are pulled with tractors with
closed cabs and in most cases, air conditioned cabs which further
reduces applicator exposure.
    Response. The Agency has incorporated relevant protective measures,
such as use of enclosed cabs and protective clothing in its revised
risk assessment.

C. Public Comments and Agency Responses to the Benefits and Evaluation
of Alternatives Contained in the PD 1

    Over 490 comments to the TPTH PD1 were received and reviewed by the
Agency for information useful to the assessment of fungicidal benefits
of TPTH applications. Useful information includes that on efficacy, use
practices, alternative control measures, economic impact, and extent of
usage. The majority of the comments were endorsements of the benefits
of TPTH for agricultural production. However, no data were submitted to
support the benefits of TPTH in these testimonial comments. Responses
to comments providing information on the benefits to TPTH are listed
below.
    1. Comment. Several sugarbeet grower groups commented on the
comparative efficacy of mancozeb and TPTH for control of Cercospora
leafspot. These groups stated that if TPTH were not available, greater
amounts of mancozeb would be needed for disease control.
    Response. The Agency agrees that additional mancozeb applications
would be needed in the absence of TPTH for control of Cercospora
leafspot. This information has been included in the sugarbeet site
analysis.
    2. Comment. The University of Georgia, College of Agriculture,
Cooperative Extension Service, submitted information on both chemical
and cultural control methods to reduce scab epidemics on pecans. The
comment stated that scab is the major pecan disease in the state.
Infection results in a decrease in nut weight and quality. The comment
also mentioned that TPTH is the material that provides effective
control of scab and other minor diseases on pecans. The low cost of the
fungicide also makes TPTH a popular fungicide for pecan disease
control.
    The comment discussed the use of resistant varieties for control of
scab. Most of the old resistant varieties found in pecan groves today
were introduced because of their resistance to scab. However, the scab
fungus has been able to overcome this resistance resulting in an
increase in scab infection. The introduction of new pecan varieties
does not provide acceptable scab resistance. The development of
resistance by the scab fungus to introduced pecan varieties and the
limited amount of available pecan germplasm indicate that varietal
resistance may not be an acceptable method of control.
    The comment also addressed registered alternative fungicides to
TPTH, specifically benzimidazole fungicides (benomyl and thiophanate-
methyl) and dodine. Applications of dodine result in a phytotoxic
response to many pecan varieties. Pecan phytotoxicity to dodine was
also addressed by several other comments from both the university and
pecan grower community. Scab resistance to benzimidazole fungicides has
been reported in several pecan orchards. Pest resistance has resulted
in the failure of this class of fungicides to control scab.
    Response. The Agency acknowledges the importance of TPTH for
control of pecan scab and the lack of comparable chemical and non-
chemical methods of scab control. This information was reflected in the
pecan site analysis.
    3. Comment. The North Dakota State University/University of
Minnesota Cooperative Extension Service submitted data on the
comparative performance of mancozeb and TPTH for control of Cercospora
leafspot and subsequent yield effects on sugarbeets. The conclusions
presented in the data indicated that TPTH was the most efficacious
fungicide for control of Cercospora leafspot compared to EBDCs and an
untreated control.
    Response. The data provide a trend indicating that TPTH is a more

[[Page 63189]]

efficacious fungicide in terms of disease severity, total yields and
recoverable sugar. However, these differences were not consistently
statistically different. Thus, the Agency concludes sugarbeet growers
could replace TPTH with mancozeb without facing a significant
difference in marketable yields.

VII. Risk/Benefit Analysis

A. Summary of Risk

    EPA has evaluated the risk posed by TPTH to workers mixing, loading
and applying the pesticide to pecans, sugarbeets and potatoes.
Developmental toxicity MOE estimates are greater than 100 for mixer/
loaders using the flowable concentrate formulation, with the exception
of applications to sugar beets at the maximum application rate with
aerial/chemigation application (MOE of 84), based on conservative
assumptions and a developmental NOAEL based on the highest dose tested,
since no LOAEL was established. MOEs for mixer/loaders for the wettable
powder formulation in water soluble bags for aerial/chemigation
application are less than 100 (ranging from 33 to 82); however, the
Agency believes these MOEs are actually over 100 given deficiencies in
the exposure study used to model this formulation (see discussion in
Unit IV.E. of this preamble). MOEs for applicators and harvesters are
all greater than 100.
    The cancer risks to mixer/loaders range from 1.0  x
10-6 to 6.3  x  10-5 for mixing/loading the
liquid formulation, and range from 2.4  x  10-6 to 1.5  x
10-4 for mixing/loading the wettable powder formulation in
water soluble bags (WSBs). The estimated risk for the wettable powder
in WSBs for aerial/chemigation application is considered to be an
overestimate of the actual risk (see Unit IV.E. of this preamble).
Thus, mixer/loader cancer risks for all use scenarios are believed to
be less than 1.0  x  10-4. Cancer risks for TPTH applicators
range from 1.1  x  10-6 to 3.8  x  10-5. Cancer
risks are less than 1.0  x  10-4 after 21 days and for pecan
harvesters are less than 1.0  x  10-4 for post-application
maintenance activities after 48 hours.

B. Summary of Benefits

    If TPTH were unavailable, growers would have to use greater
quantities of alternative fungicides. Some of these may not provide as
effective control as TPTH. Reliance on available alternatives, without
the ability to rotate in TPTH treatments, could also result in an
increased likelihood of resistance development. Additional possible
disadvantages of using alternative fungicides include phytotoxicity,
limited availability due to local restrictions, and higher cost.
Unavailability of TPTH could also result in increased use of EBDC
fungicides, which are used at shorter intervals than TPTH and at higher
rates, resulting in a higher overall volume of pesticide use and
environmental loading.

C. Conclusions

    Based on its risk and benefits assessment, the Agency has concluded
that the risks associated with the use of TPTH in accordance with
current label restrictions are not unreasonable. Therefore, benefits
provided from the use of TPTH outweigh the risks.

VIII. Agency's Decision Regarding Special Review

    EPA has concluded that the risks of TPTH are outweighed by the
benefits of continued use. EPA proposes to terminate the Special Review
examining the developmental toxicity of TPTH to workers. Label
modifications highlighting teratogenic risks and requiring protective
gear and the adoption of engineering controls (use of water soluble
packs, closed mixing/loading systems, and mechanical transfer systems)
have significantly reduced worker exposure to TPTH. The availability of
dermal developmental data and data on dermal absorption have enabled
the Agency to refine the 1985 risk assessment used in the PD 1, which
assumed 100% dermal absorption and minimal worker protection. The risks
associated with exposure to TPTH are thus considered to be outweighed
by the benefits derived from its use. The Agency believes that exposure
to TPTH does not pose an unreasonable risk to workers or the general
public under currently labeled use conditions, which include
classification as a Restricted Use Pesticide, engineering controls and
protective clothing requirements.

IX. Bibliography

    1. U.S. Environmental Protection Agency (USEPA). Triphenyltin
Hydroxide Pesticide Registration Standard and Guidance Document,
September 1984.
    2. U.S. Environmental Protection Agency. Reregistration
Eligibility Decision (RED): Triphenyltin Hydroxide (TPTH), November
1999.
    3. U.S. Environmental Protection Agency. Triphenyltin Hydroxide:
Toxicology Branch Chapter for the RED, Memorandum from John Doherty
to Angel Chiri, March 22, 1999.
    4. Rodwell, D. (1987). An Embryotoxicity Study in Rabbits with
Tri-phenyltin Hydroxide: Laboratory Project No. WIL-39012.
Unpublished study prepared by WIL Research Laboratories. 308 p.
(MRID 40104801).
    5. Carlton, B.D.; Connell, M.M. (1981). Final Report on
Evaluation of the Teratogenicity of Triphenyltin Hydroxide (TPTH) in
the Sprague-Dawley Rat: Project No. NO723-0200. (Unpublished study
received Mar 2, 1982 under 148-689; prepared by Battelle, submitted
by Thompson-Hayward Chemical Co., Kansas City, KS.; CDL:070696-A)
(MRID 00094903).
    6. Kavlock, Robert J. Triphenyltin Hydroxide Developmental
Toxicology Study, EPA, Health Effects Research Laboratory, RTP,
March 28, 1985.
    7. Bates, D. (1985). A Teratology Study in Rats with
Triphenyltin Hydroxide: Final Report: Project No. WIL-39011.
Unpublished study prepared by WIL Research Laboratories, Inc. 371 p.
(MRID 00144489).
    8. Tasker, E. (1985). One Generation Teratology and Reproductive
Study in Rats with Triphenyltin Hydroxide: Project No: WIL-39013:
Final Rept. Unpublished study prepared by WIL Research Laboratories,
Inc. 443 p. (MRID 00142878).
    9. American Hoechst Corp. (1986). A Dietary Two-generation
Reproduction Study in Rats with Triphenyltin Hydroxide: Final
Report: Project No. WIL-39022. Unpublished study prepared by WIL
Research Laboratories. 2,815 p. (MRID 00162655).
    10. Carlton, B.D.; Howard, M. (1982). Final Report on the
Evaluation of the Teratogenicity of Triphenyltin Hydroxide (TPTH) in
the Syrian Golden Hamster: Project No. NO723-0100. (Unpublished
study received Mar 2, 1982 under 148-689; prepared by Battelle,
submitted by Thompson-Hayward Chemical Co., Kansas City, KS.;
CDL:070697-A) (MRID 00094904).
    11. Miller, Victor. Memorandum to Louis Kerestesy and Eric
Ferris and Susan Lewis (all USEPA). Peer Review of Triphenyltin
Hydroxide (TPTH), Tox. Chemical No. 896E. January 9, 1991.
    12. Nemec, M. (1993). A Developmental Toxicity Study of
Triphenyltin Hydroxide (TPTH) Administered Dermally in Rabbits:
Final Report: Lab Project Number: WIL-160012. Unpublished study
prepared by WIL Research Labs, Inc. 493 p. (MRID 42909101).
    13. Tennekes, H.; Horst, K.; Luetkemeier, H.; et al. (1989).
TPTH Technical (Code: HOE 029664 of ZD97 0004) Chronic Toxicity/
Oncogenicity: 104-week Feeding Study in Rats: Laboratory Project ID
No. 046980. Unpublished study prepared by Research & Consulting Co.
AG. in cooperation with Experimental Pathology Services, ANAWA
Laboratories AG and Cytotest Cell Research GmbH & Co. KG. 2116 p.
(MRID 41085702).
    14. Tennekes, H.; Horst, K.; Luetkemeier, H.; et al. (1989).
TPTH Technical (Code: HOE 029664 of ZD97 0004) Oncogenicity: 80-week
Feeding Study in Mice: Laboratory Project ID No. 047002. Unpublished
study prepared by Research & Consulting Co. AG in cooperation with
Experimental Pathology Services and ANAWA Laboratories AG and CCR.
1428 p. (MRID 41085701).
    15. U.S. Environmental Protection Agency. Peer Review of
Triphenyltin Hydroxide (TPTH), Memorandum from Roy Sjoblad to Jack
Housenger, 1990.
    16. Doherty, John and Copley, Marion. Memorandum to Jack
Housenger (USEPA) and Cynthia Giles-Parker (USEPA).

[[Page 63190]]

Triphyltin Hydroxide: HED Peer Review Committee verification of the
inclusion of rat pituitary data for quantitative carcinogenic risk
assessment. June 29, 1992.
    17. U.S. Environmental Protection Agency. TPTH (Triphenyltin
Hydroxide): HED Revised Risk Assessment for the Reregistration
Eligibility Decision (RED) Document, Memorandum from Sarah Levy to
Loan Phan, September 21, 1999.
    18. U.S. Environmental Protection Agency. Triphenyltin Hydroxide
(TPTH)--Report of the Hazard Identification Assessment Review
Committee, Memorandum from John Doherty and Jess Rowland to
Christina Scheltema, November 13, 1998.
    19. U.S. Environmental Protection Agency (USEPA). Federal
Register Notice (61 FR 36298). July 10, 1996.
    20. U.S. Environmental Protection Agency, Revised Occupational
and Residential Exposure Assessment and Recommendations for the
Reregistration Eligibility Decision Document for Triphenyltin
Hydroxide (TPTH), Memorandum from Kelly O'Rourke to Sarah Law,
September 14, 1999.
    21. Bookbinder, M. (1995). Exposure of Workers Mixing/Loading
Super-Tin 80WP (Triphenyltin Hydroxide: TPTH) Fungicide for
Application to Pecan Groves in Georgia: (Final Report): Lab Project
Number: AA930104. Unpublished study prepared by American
Agricultural Services, Inc. and Griffin Corp. Chemical Services. 602
p. (MRID 43599401).
    22. Lewis, Paul and Scheltema, Christina. Memorandum to Jude
Andreasen (USEPA). Revised Occupational Risk Assessment for the Use
of TPTH on Pecans. March 6, 1997.
    23. Bookbinder, M. (1994). Exposure of Workers During Reentry
into Pecan Groves Treated with Super-Tin 80WP (Triphenyltin
Hydroxide: TPTH) Fungicide: Final Report: Lab Project Number:
AA930102: AA930103. Unpublished study prepared by American
Agricultural Services, Inc. and Case Consulting Labs, Inc. 1000 p.
(MRID 43557401).
    24. U.S. Environmental Protection Agency. Review of Reentry Data
Submission to Support the Reregistration of Triphenyltin Hydroxide
(TPTH), Memorandum from Jeff Evans to Eric Feris, March 1, 1993.
    25. Chrysayi-Tokousbalides, M. and Giannopolitis, C.N. 1981.
Cross-resistance in Cercospora beticola to triphenyltin and
oligomycin. Plant Disease 65:267-268.
    26. Stevenson, W. 1992. University of Wisconsin. Personal
communication to P.I. Lewis (USEPA). March 9, 1992.
    27. U.S. Environmental Protection Agency. Triphenyltin Hydroxide
(TPTH) Benefits Analysis, Memorandum from Tara Chand-Goyal and John
Faulkner to Robert McNally/Loan Phan, August 15, 1999.
    28. Latham, H.A. and Hammond, J.M. 1983. Control of Cladosporium
caryigenum on pecan leaves and nut shucks with propaconazole (CGA-
64250). Plant Disease 67:1136-1139.
    29. Hare, J.D.; Logan, P.A.; and Wright, R.J. 1983. Suppression
of Colorado potato beetle, Leptinotarsa decemlineata, (Say)
(Coleoptera: Chrysomelidae) Populations with Antifeedant Fungicides.
Environmental Entomology. 12:1470-77.
    30. White, L.V. Griffin Corporation. 1991. Personal
communication to J. Lamb. Jellinek, Schwartz, Connolly, Freshman,
Inc. August 16, 1991.
    31. Jones, R. 1992. University of Minnesota. Personal
communication to P.I. Lewis. USEPA. March 25, 1992.
    32. U.S. Environmental Protection Agency. Review of Supplemental
Information (Letters, Faxes and E-Mails from the Growers, Commodity
Groups and University Researchers) to Update TPTH Benefits Based on
Fungicide Resistance Management on Pecans, Potatoes, and Sugarbeets,
Memorandum from Tara Chand-Goyal to Nancy Zahedi/Robert McNally,
November 1999.
    33. Brown, S. Crocker, T.F., Ellis, H.C., and Hadden, J. (1991).
Georgia pecan spray guide. The University of Georgia. Cooperative
Extension Service. College of Agriculture.
    34. McVay, J.R. Estes, P. Gazaway, W.S., Patterson, M.G. J.W.
Everest and W.D. Goff. (1991). 1991 Commercial Pecan Insect, Disease
and Weed Control Recommendations. Alabama Cooperative Extension
Service. Auburn University, Auburn, AL. Circular ANR-27.
    35. Littrell, R.H. and Betrand, P.F. (1981). Management of Pecan
Fruit and Foliar Diseases and Fungicides. Plant Disease 65:769-774.
    36. Horne, C.W., Amador, J.M., Johnson, J.D., McCoy, N.L.,
Philley, G.L., Lee, T.A., Kaufman, H.W., Jones, R.K., Barnes, L.W.
and Black, M.C. (1988). Texas Plant Disease Handbook. B-1140.
College Station, TX.
    37. Amling, H.J. Everest, J.W. Goff, W.D. McVay, J.R. (1984).
Pecan Production. Alabama Cooperative Extension Service. Circular
ANR-54. Auburn University, Auburn, AL.
    38. Latham, A.J. Carden, E.L., and McDaniel, N.R. (1988).
Highlights of Agricultural Research. 35:10. Alabama Agricultural
Experiment Station. Auburn University, Auburn, AL.
    39. Stevenson, W.R. and Gilson, F.A. (1982). Control of potato
early and late blight with foliar fungicide sprays, 1981. Fungicide
and Nematicide Test Results. 37:157.
    40. Stevenson, W.R., James, R.V., and Stewart, J.S. (1991).
Wisconsin Vegetable Disease Trials--1990. University of Wisconsin.
    41. Stevenson, W.R., Stewart, J., Pscheidt, J., and Sanderson,
P. (1986). Evaluation of foliar sprays for control of potato early
blight, 1985. Fungicide and Nematicide Tests. 41:105.
    42. Binning, L.K. et al. (1991). Commercial Vegetable Production
in Wisconsin. University of Wisconsin. Madison, WI.
    43. Lamey, H.A. (1999). Department of Plant Pathology, North
Dakota State University, Fargo, ND. Personal communications to Tara
Chand-Goyal (USEPA) in October and November, 1999.
    44. Ely, C. (1985). Covington and Burling. Washington, DC.
Comments on behalf of American Hoechst Corporation, Duphar, Griffin
Corporation, M&T Chemical Inc., and Wesley Industries, Inc. in
Response to the Notice of Special Review for Pesticide Products
Containing Triphenyltin Hydroxide (TPTH).
    45. Lamey, H.A. (1991). North Dakota Plant Disease Control
Guide. NDSU Extension Service. Fargo, ND.
    46. Ravert, J.; Parke, G.S.E. (1976). Investigation of
Teratogenic and Toxic Potential of Technical Triphenyltin Hydroxide:
Laboratory No. 6E-524. (Unpublished study received Oct 18, 1979
under 148-689; prepared by Cannon Laboratories, Inc., submitted by
Thompson-Hayward Chemical Co., Kansas City, KS; CDL:099051-A) (MRID
00086547).

List of Subjects

    Environmental protection.

    Dated: September 20, 2000.
Susan H. Wayland,
Acting Assistant Administrator for Prevention, Pesticides, and Toxic
Substances.
[FR Doc. 00-27036 Filed 10-19-00; 8:45 am]
BILLING CODE 6560-50-F
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