`[Federal Register Volume 65, Number 204 (Friday, October 20, 2000)]
[Notices]
[Pages 63174-63190]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-27036]



[[Page 63173]]

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Part IV





Environmental Protection Agency





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Triphenyltin Hydroxide; Proposed Determination To Terminate Special 
Review; Notice

  Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / 
Notices  

[[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: 
[email protected].

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: ``[email protected],'' 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 Canceraa (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

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Hydroxide Pesticide Registration Standard and Guidance Document, 
September 1984.
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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).
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Toxicology Study, EPA, Health Effects Research Laboratory, RTP, 
March 28, 1985.
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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).
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Report: Project No. WIL-39022. Unpublished study prepared by WIL 
Research Laboratories. 2,815 p. (MRID 00162655).
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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).
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Ferris and Susan Lewis (all USEPA). Peer Review of Triphenyltin 
Hydroxide (TPTH), Tox. Chemical No. 896E. January 9, 1991.
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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).
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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).
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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.
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Hydroxide): HED Revised Risk Assessment for the Reregistration 
Eligibility Decision (RED) Document, Memorandum from Sarah Levy to 
Loan Phan, September 21, 1999.
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(TPTH)--Report of the Hazard Identification Assessment Review 
Committee, Memorandum from John Doherty and Jess Rowland to 
Christina Scheltema, November 13, 1998.
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Register Notice (61 FR 36298). July 10, 1996.
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and Residential Exposure Assessment and Recommendations for the 
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September 14, 1999.
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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).
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Andreasen (USEPA). Revised Occupational Risk Assessment for the Use 
of TPTH on Pecans. March 6, 1997.
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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).
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Submission to Support the Reregistration of Triphenyltin Hydroxide 
(TPTH), Memorandum from Jeff Evans to Eric Feris, March 1, 1993.
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Cross-resistance in Cercospora beticola to triphenyltin and 
oligomycin. Plant Disease 65:267-268.
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communication to P.I. Lewis (USEPA). March 9, 1992.
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(TPTH) Benefits Analysis, Memorandum from Tara Chand-Goyal and John 
Faulkner to Robert McNally/Loan Phan, August 15, 1999.
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caryigenum on pecan leaves and nut shucks with propaconazole (CGA-
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of Colorado potato beetle, Leptinotarsa decemlineata, (Say) 
(Coleoptera: Chrysomelidae) Populations with Antifeedant Fungicides. 
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communication to J. Lamb. Jellinek, Schwartz, Connolly, Freshman, 
Inc. August 16, 1991.
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communication to P.I. Lewis. USEPA. March 25, 1992.
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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.
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Extension Service. College of Agriculture.
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Pecan Production. Alabama Cooperative Extension Service. Circular 
ANR-54. Auburn University, Auburn, AL.
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Highlights of Agricultural Research. 35:10. Alabama Agricultural 
Experiment Station. Auburn University, Auburn, AL.
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early and late blight with foliar fungicide sprays, 1981. Fungicide 
and Nematicide Test Results. 37:157.
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Wisconsin Vegetable Disease Trials--1990. University of Wisconsin.
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P. (1986). Evaluation of foliar sprays for control of potato early 
blight, 1985. Fungicide and Nematicide Tests. 41:105.
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in Wisconsin. University of Wisconsin. Madison, WI.
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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).
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Guide. NDSU Extension Service. Fargo, ND.
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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 
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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`