63174 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

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.

SUMMARY: This Notice sets forth EPA’s

preliminary determination regarding the

continued registration of pesticide

products containing triphenyltin

hydroxide (TPTH) and sets forth the

Agency’s assessment of the risks and

benefits associated with pesticidal uses

of TPTH. On January 9, 1985, the

Agency issued a Notice of Special

Review of pesticide products containing

triphenyltin hydroxide based on

developmental toxicity (teratogenicity)

concerns (50 FR 1107). Although not a

subject of the Special Review, the

Agency also cited concerns for

reproductive toxicity, carcinogenicity,

immunotoxicity, inhalation toxicity and

adverse effects to non-target organisms

in the Position Document 1. Due to

voluntary actions by the registrants that

have reduced worker exposure to TPTH,

as well as additional data that refine the

risk assessment, EPA has determined

that the risks of using TPTH are

substantially lower than when the

Special Review was initiated in 1985.

This Notice proposes to terminate the

triphenyltin hydroxide Special Review

based on the Agency’s determination

that the benefits of TPTH use outweigh

the risks.

DATES: Comments, data and information

relevant to the Agency’s proposed

decision, identified by the docket

control number [OPP–30000/42A], must

be received on or before November 20,

2000.

ADDRESSES: Comments may be

submitted by mail, electronically, or in

person. Please follow the detailed

instructions for each method as

provided in Unit I. of the

SUPPLEMENTARY INFORMATION. To ensure

proper receipt by EPA, it is imperative

that you identify docket control number

OPP–30000/42A in the subject line on

the first page of your response.

FOR FURTHER INFORMATION CONTACT: Phil

Budig, Special Review and

Reregistration Division (7508C), Office

of Pesticide Programs, Environmental

Protection Agency, 1200 Pennsylvania

Ave., NW., Washington, DC 20460.

Telephone (703) 308–8029; e-mail

address: budig.phil@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does This Action Apply to Me?

You may be affected by this action if

you are a pesticide registrant with

registered products which contain

triphenyltin hydroxide as an active

ingredient, or if you are an agricultural

producer or a mixer, loader or

applicator using products containing

triphenyltin hydroxide as an active

ingredient. Since other entities may also

be interested, the Agency has not

attempted to describe all the specific

entities that may be affected by this

action. If you have any questions

regarding the applicability of this action

to a particular entity, consult the person

listed under FOR FURTHER INFORMATION

CONTACT.

B. How Can I Get Additional

Information, Including Copies of

Support Documents

1. Electronically. You may obtain

electronic copies of this document, and

certain other related documents that

might be available electronically, from

the EPA Internet Home Page at http://

www.epa.gov/. To access this

document, on the Home Page select

‘‘Laws and Regulations,’’ ‘‘Regulations

and Proposed Rules,’’ and then look up

the entry for this document under the

‘‘Federal Register—Environmental

Documents.’’ You can also go directly to

the Federal Register listings at http://

www.epa.gov/fedrgstr/.

2. In person. The Agency has

established an official record for this

action under docket control number

OPP–30000/42A. The official record

consists of the documents specifically

referenced in this action, any public

comments received during an applicable

comment period, and other information

related to this action, including any

information claimed as Confidential

Business Information (CBI). This official

record includes the documents that are

physically located in the docket, as well

as the documents that are referenced in

those documents. The public version of

the official record does not include any

information claimed as CBI. The public

version of the official record, which

includes printed, paper versions of any

electronic comments submitted during

an applicable comment period, is

available for inspection in the Public

Information and Records Integrity

Branch (PIRIB), Rm. 119, Crystal Mall

#2, 1921 Jefferson Davis Hwy.,

Arlington, VA, from 8:30 a.m. to 4 p.m.,

Monday through Friday, excluding legal

holidays. The PIRIB telephone number

is (703) 305–5805.

3. By mail. You may request copies of

this document and supporting

documents by writing to: Public

Information and Records Integrity

Branch, Information Resources and

Services Division (7502C), Office of

Pesticide Programs, Environmental

Protection Agency, 1200 Pennsylvania

Ave., NW., Washington, DC 20460. Be

sure to include docket control number

[OPP–30000/42A] in your request.

C. How and to Whom Do I Submit

Comments?

You may submit comments through

the mail, in person, or electronically. To

ensure proper receipt by EPA, it is

imperative that you identify docket

control number OPP–30000/42A in the

subject line on the first page of your

response.

1. By mail. Submit your comments in

triplicate to: Public Information and

Records Integrity Branch (PIRIB),

Information Resources and Services

Division (7502C), Office of Pesticide

Programs (OPP), Environmental

Protection Agency, 1200 Pennsylvania

Ave., NW., Washington, DC 20460.

2. In person or by courier. Deliver

your comments to: Public Information

and Records Integrity Branch (PIRIB),

Information Resources and Services

Division (7502C), Office of Pesticide

Programs (OPP), Environmental

Protection Agency, Rm. 119, Crystal

Mall #2, 1921 Jefferson Davis Hwy.,

Arlington, VA. The PIRIB is open from

8:30 a.m. to 4 p.m., Monday through

Friday, excluding legal holidays. The

PIRIB telephone number is (703) 305–

5805.

3. Electronically. You may submit

your comments electronically by e-mail

to: ‘‘opp-docket@epa.gov,’’ or you can

submit a computer disk as described

above. Do not submit any information

electronically that you consider to be

CBI. Avoid the use of special characters

and any form of encryption. Electronic

submissions will be accepted in

WordPerfect 6.1/8.0 or ASCII file

format. All comments in electronic form

must be identified by docket control

number OPP–30000/42A. Electronic

comments may also be filed online at

many Federal Depository Libraries.

D. How Should I Handle CBI That I

Want to Submit to the Agency?

Do not submit any information

electronically that you consider to be

CBI. You may claim information that

you submit in response to this

document as confidential by marking

any part or all of that information as

CBI. Information so marked will not be

disclosed except in accordance with

procedures set forth in 40 CFR part 2.

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

63176 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

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 runoff 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-observedadverse-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

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

Exposure

Routes

Exposure DurationDose (mg/kg/

day) Effect Study UncertaintyFactor Comment

Dermal ........ Short-term (1–

7 days)

NOAEL 3.0 No effect observed at the

highest dose

tested

Dermal developmental toxicity

(rabbit)

100 Route-specific study; MOE based on

UF for inter-species (10x) extrapolation and intra-species variability

(10x)

Dermal ........ Intermediateterm (1

week to several mos)

NOAEL 3.0 No effect observed at the

highest dose

tested

Dermal developmental toxicity

(rabbit)

100 Route-specific study; MOE based on

UF for inter-species (10x) extrapolation and intra-species variability

(10x)

Inhalation .... Any time periodNOAEL 0.092a Death following

lung lesions

Subchronic inhalation study

(rat)

100 Route-specific study; MOE based on

UF for inter-species (10x) extrapolation, intra-species variability (10x)

Dermal & Inhalation.Cancer Risk Oral Q1* 1.83

mg/kg/day-1

Probable human

carcinogen

Oral cancer rat

and mouse

studies showing pituitary,

testicular, and

liver tumors.

NA A dermal absorption of 10% should be

used. Based on comparison between

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)

63178 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

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

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

Exposure Scenario Crop Application

Rate (lb ai/A)

Dermal Short- and Intermediate-Term

(MOE = 100)

Inhalation (MOE = 100)

Baseline PPE

Engineering

Controls

Baseline PPE

Engineering

Controls

Mixer/Loader Risk.

Mixing/Loading Liquids

for Aerial/Chemigation

Application.

Pecans 0.375 See Eng.

Control ...........

See Eng.

Control ...........

140 See Eng.

Control ...........

See Eng.

Control ...........

520

Potatoes 0.1875 See Eng.

Control ...........

See Eng.

Control ...........

110 See Eng.

Control ...........

See Eng.

Control ...........

410

Sugar

beets

0.25 See Eng.

Control ...........

See Eng.

Control ...........

84 See Eng.

Control ...........

See Eng. .......

Control ...........

310

Sugar

beets

0.125 (Typ) See Eng.

Control ...........

See Eng.

Control ...........

170 See Eng.

Control ...........

See Eng.

Control ...........

N/A2

Mixing/Loading Liquids

for Groundboom Application.

Potatoes 0.1875 See Eng.

Control ...........

See Eng.

Control ...........

740 See Eng.

Control ...........

See Eng.

Control ...........

2,800

Sugar

beets

0.25 See Eng.

Control ...........

See Eng.

Control ...........

560 See Eng.

Control ...........

See Eng.

Control ...........

2,100

Mixing/Loading Liquid

for Orchard Airblast

Sprayer Application.

Pecans 0.375 See Eng.

Control ...........

See Eng.

Control ...........

1400 See Eng.

Control ...........

See Eng.

Control ...........

5,200

Mixing/Loading Wettable

Powder (WSB) for

Aerial/Chemigation

Application.

Pecans 0.375 See Eng.

Control ...........

See Eng.

Control ...........

55 See Eng.

Control ...........

See Eng.

Control ...........

600

Pecans 0.25 (Typ) See Eng.

Control ...........

See Eng.

Control ...........

82 See Eng.

Control ...........

See Eng.

Control ...........

N/A2

Potatoes 0.1875 See Eng.

Control ...........

See Eng.

Control ...........

44 See Eng. ControlSee Eng.

Control ...........

480

63180 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

TABLE 2.— SUMMARY OF OCCUPATIONAL HANDLER DERMAL AND INHALATION NON-CANCER RISK ESTIMATES—Continued

Exposure Scenario Crop Application

Rate (lb ai/A)

Dermal Short- and Intermediate-Term

(MOE = 100)

Inhalation (MOE = 100)

Baseline PPE

Engineering

Controls

Baseline PPE

Engineering

Controls

Potatoes 0.125 (Typ) See Eng.

Control ...........

See Eng.

Control ...........

65 See Eng.

Control ...........

See Eng.

Control ...........

N/A2

Sugar

beets

0.25 See Eng.

Control ...........

See Eng.

Control ...........

33 See Eng.

Control ...........

See Eng.

Control ...........

360

Sugar

beets

0.125 (Typ) See Eng.

Control ...........

See Eng.

Control ...........

65 See Eng.

Control ...........

See Eng.

Control ...........

N/A2

Mixing/Loading Wettable

Powder (WSB) for

Groundboom Application.

Potatoes 0.1875 See Eng.

Control ...........

See Eng.

Control ...........

290 See Eng.

Control ...........

See Eng.

Control ...........

3,200

Sugar

beets

0.25 See Eng.

Control ...........

See Eng.

Control ...........

220 See Eng.

Control ...........

See Eng.

Control ...........

2,400

Mixing/Loading Wettable

Powder for Orchard

Airblast Sprayer Application.

Pecans 0.375 See Eng.

Control ...........

See Eng.

Control ...........

550 See Eng.

Control ...........

See Eng.

Control ...........

6,000

Applicator Risk.

Applying Sprays with a

Fixed-Wing Aircraft.

Pecans 0.375 No Data, See

Eng. Cont.

No Data, See

Eng. Cont.

240 No Data, See

Eng. Cont.

No Data, See

Eng. Cont.

630

Potatoes 0.1875 No Data, See

Eng. Cont.

No Data, See

Eng. Cont.

190 No Data, See

Eng. Cont.

No Data, See

Eng. Cont.

510

Sugar

beets

0.25 No Data, See

Eng. Cont.

No Data, See

Eng. Cont.

140 No Data, See

Eng. Cont.

No Data, See

Eng. Cont.

380

Applying Sprays with a

Groundboom Sprayer.

Potatoes 0.1875 460 580 1,300 310 1,500 5,300

Sugar

beets

0.25 340 440 960 230 1,100 4,000

Applying Sprays to Orchards with an Airblast Sprayer.Pecans 0.375 33 55 630 95 480 950

Pecans 0.25 (Typ) 50 82 950 140 720 1,400

Mixer/Loader/Applicator

Risk.

Mixing/Loading Liquids

and Applying Sprays

with a Groundboom

Sprayer.

Potatoes 0.1875 N/A1 N/A1 470 N/A1 N/A1 1,800

Sugar

beets

0.25 N/A1 N/A1 350 N/A1 N/A1 1,400

Mixing/Loading Liquids

and Applying Sprays

to Orchards with an

Airblast Sprayer.

Pecans 0.375 N/A1 N/A1 430 N/A1 N/A1 810

Mixing/Loading Wettable

Powder (WSB) and

Applying Sprays with

a Groundboom Sprayer.

Potatoes 0.1875 N/A1 N/A1 240 N/A1 N/A1 2,000

Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices 63181

TABLE 2.— SUMMARY OF OCCUPATIONAL HANDLER DERMAL AND INHALATION NON-CANCER RISK ESTIMATES—Continued

Exposure Scenario Crop Application

Rate (lb ai/A)

Dermal Short- and Intermediate-Term

(MOE = 100)

Inhalation (MOE = 100)

Baseline PPE

Engineering

Controls

Baseline PPE

Engineering

Controls

Sugar

beets

0.25 N/A1 N/A1 180 N/A1 N/A1 1,500

Mixing/Loading Wettable

Powder (WSB) and

Applying Sprays to

Orchards with an Airblast Sprayer.

Pecans 0.375 N/A1 N/A1 290 N/A1 N/A1 820

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. bSource: 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 × 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 ×

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 × 10-6 and 1 × 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 × 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 × 10-6 but less than 1.0 × 10-4

(ranging from 1.1 × 10-6 to 9.1 × 10-5).

63182 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

TABLE 3.— SUMMARY OF OCCUPATIONAL HANDLER CANCER RISK ESTIMATE FOR TPTH

Exposure Scenario Crop

Application

Rate (lb ai/

A)

Cancer Risk Estimate

Baseline PPE Engineering Controls

Mixer/Loader Risk.

Mixing/Loading Liquids for Aerial/

Chemigation Application.

Pecans 0.25 See Eng.

Control ............

See Eng.

Control ......................

3.4E-6

Potatoes 0.125 See Eng.

Control ............

See Eng.

Control ......................

6.3E-5 / 1.5E-6

Sugar

beets

0.125 See Eng.

Control ............

See Eng.

Control ......................

3.8E-5

Mixing/Loading Liquids for Groundboom

Application.

Potatoes 0.125 See Eng.

Control ............

See Eng.

Control ......................

6.1E-5 / 1.9E-6

Sugar

beets

0.125 See Eng.

Control ............

See Eng.

Control ......................

3.7E-5 / 1.9E-6

Mixing/Loading Liquid for Orchard Airblast Sprayer ApplicationPecans 0.25 See Eng.

Control ............

See Eng.

Control ......................

1.0E-6

Mixing/Loading Wettable Powder

(WSB) for Aerial/Chemigation Application.

Pecans 0.25 No Data Cont. No Data Cont. 8.1E-6

Potatoes 0.125 No Data Cont. No Data Cont. 1.5E-4 / 3.6E-6

Sugar

beets

0.125 See Eng.

Control ............

See Eng.

Control ......................

9.1E-5

Mixing/Loading Wettable Powder

(WSB) for Groundboom Application

Potatoes 0.125 See Eng.

Control ............

See Eng.

Control ......................

1.5E-4 / 4.6E-6

Sugar

beets

0.125 See Eng.

Control ............

See Eng.

Control ......................

8.8E-5 / 4.6E-6

Mixing/Loading Wettable Powder (WSB)

for Orchard Airblast Sprayer Application.

Pecans 0.25 See Eng.

Control ............

See Eng.

Control ......................

2.4E-6

Applicator Risk.

Applying Sprays with a Fixed-Wing Aircraft.Pecans 0.25 No Data, See

Eng. Cont.

No Data, See Eng.

Cont.

2.0E-6

Potatoes 0.125 No Data, See

Eng. Cont.

No Data, See Eng.

Cont.

3.8E-5

Sugar

beets

0.125 No Data, See

Eng. Cont.

No Data, See Eng.

Cont.

2.3E-5

Applying Sprays with a Groundboom

Sprayer

Potatoes 0.125 1.4E-4 / 4.3E-6 8.1E-5 / 2.5E-6 3.5E-5 / 1.1E-6

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 an Airblast Sprayer.Pecans 0.25 4.4E-5 2.5E-5 2.5E-6

Mixer/Loader/Applicator Risk.

Mixing/Loading Liquids and Applying

Sprays with a Groundboom Sprayer.

Potatoes 0.125 N/A N/A 3.0E-6

Sugar

beets

0.125 N/A N/A 3.0E-6

Mixing/Loading Liquids and Applying

Sprays to Orchards with an Airblast

Sprayer.

Pecans 0.25 N/A N/A 3.5E-6

Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices 63183

TABLE 3.— SUMMARY OF OCCUPATIONAL HANDLER CANCER RISK ESTIMATE FOR TPTH—Continued

Exposure Scenario Crop

Application

Rate (lb ai/

A)

Cancer Risk Estimate

Baseline PPE Engineering Controls

Mixing/Loading Wettable Powder (WSB)

and Applying Sprays with a

Groundboom Sprayer.

Potatoes 0.125 N/A N/A 5.7E-6

Sugar

beets

0.125 N/A N/A 5.7E-6

Mixing/Loading Wettable Powder

(WSB) and Applying Sprays to Orchards with an Airblast Sprayer

Pecans 0.25 N/A N/A 5.0E-6

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 μg/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 (μg/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 (μg/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.

63184 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

• 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

× 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 × 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 × 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

Days After Last Treatment

Soil/Thatch

Residue

(μg/g)a

Residue

Ratiob

MOE

Cancer Risk

Estimate 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 μg/g for GA and 4.1 μg/g for TX).

TABLE 5.— SUMMARY OF POSTAPPLICATION RISK ESTIMATES FROM TPTH DURING MAINTENANCE ACTIVITIES

Days After Last Treatment

Potatoes Noncancer a (App.

Rate: 0.1875

lb ai/A)

Sugar beets

Non-cancera

(App. Rate:

0.25 lb ai/A)

Potatoes and Sugar

beets Cancera (App.

Rate: 0.125 lb ai/A)

DFRb

(μg/

cm2)

MOE

DFRb

(μg/

cm2)

MOE

DFRb(μg/

cm2)

Cancer Risk

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.

Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices 63185

TABLE 6.— SUMMARY OF POSTAPPLICATION RISK ESTIMATES FROM TPTH DURING POTATO HARVESTING

Days After Last Treatmenta

Non-cancer Cancer

TRb (ppb

TPTH) MOE TRb (ppbTPTH) 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 nonsystemic 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.

63186 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

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 nonchemical 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

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

63188 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

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 airconditioned 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 thiophanatemethyl) 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

Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices 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 × 10-6 to 6.3 × 10-5 for

mixing/loading the liquid formulation,

and range from 2.4 × 10-6 to 1.5 × 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

× 10-4. Cancer risks for TPTH applicators

range from 1.1 × 10-6 to 3.8 × 10-5.

Cancer risks are less than 1.0 × 10-4 after

21 days and for pecan harvesters are less

than 1.0 × 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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Registration Standard and Guidance

Document, September 1984.

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Reregistration Eligibility Decision (RED):

Triphenyltin Hydroxide (TPTH), November

1999.

3. U.S. Environmental Protection Agency.

Triphenyltin Hydroxide: Toxicology Branch

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4. Rodwell, D. (1987). An Embryotoxicity

Study in Rabbits with Tri-phenyltin

Hydroxide: Laboratory Project No. WIL–

39012. Unpublished study prepared by WIL

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5. Carlton, B.D.; Connell, M.M. (1981).

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(TPTH) in the Sprague-Dawley Rat: Project

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prepared by Battelle, submitted by

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RTP, March 28, 1985.

7. Bates, D. (1985). A Teratology Study in

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study prepared by WIL Research

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study received Mar 2, 1982 under 148–689;

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Kerestesy and Eric Ferris and Susan Lewis

(all USEPA). Peer Review of Triphenyltin

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January 9, 1991.

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H.; et al. (1989). TPTH Technical (Code: HOE

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Feeding Study in Mice: Laboratory Project ID

No. 047002. Unpublished study prepared by

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with Experimental Pathology Services and

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63190 Federal Register / Vol. 65, No. 204 / Friday, October 20, 2000 / Notices

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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(USEPA). Federal Register Notice (61 FR

36298). July 10, 1996.

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(MRID 43599401).

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23. Bookbinder, M. (1994). Exposure of

Workers During Reentry into Pecan Groves

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(1982). Control of potato early and late blight

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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