United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508C)
EPA-738-F-99-014
November 1999
&ERA R.E.D. FACTS
Pesticide
Reregistration
Use Profile
Triphenyltin Hydroxide
All pesticides sold or distributed in the United States must be registered by
EPA, based on scientific studies showing that they can be used without posing
unreasonable risks to people or the environment. Because of advances in scientific
knowledge, the law requires that pesticides which were first registered before
November 1,1984, be reregistered to ensure that they meet today's more stringent
standards.
In evaluating pesticides for reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human health and
environmental effects of each pesticide. To implement provisions of the Food
Quality Protection Act of 1996, EPA considers the special sensitivity of infants and
children to pesticides, as well as aggregate exposure of the public to pesticide
residues from all sources, and the cumulative effects of pesticides and other
compounds with common mechanisms of toxicity The Agency develops any
mitigation measures or regulatory controls needed to effectively reduce each
pesticide's risks. EPA then reregisters pesticides that meet the safety standard of
the FQPA and can be used without posing unreasonable risks to human health or
the environment.
When a pesticide is eligible for reregistration, EPA explains the basis for its
decision in a Reregistration Eligibility Decision (RED) document This fact sheet
summarizes the information in the RED document for reregistration case 0099,
triphenyltin hydroxide (TPTH).
TPTH is a non-systemic foliar fungicide used to control early and late blight
on potatoes; leaf spot on sugar beets; and scab, brown leaf spot and other diseases
on pecans. It is only registered for use on these three crops. There are no
residential, public health or other non-food uses of TPTH.
TPTH comes in liquid and wettable powder (in water soluble packaging)
formulations, and its use is restricted to certified applicators. TPTH is applied by
ground equipment, chemigation, airblast spray, and aircraft. TPTH labels require
mechanical transfer for liquids, and a closed mixing/loading system for aerial
applications. Handlers are required to wear coveralls, waterproof gloves, chemical
resistant footwear, protective eyewear, chemical resistant headgear for overhead
exposure, and chemical resistant apron when cleaning equipment, mixing, or
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Regulatory
History
loading. These protective measures may be reduced or modified as specified by
the Worker Protection Standard (WPS) when closed systems or enclosed cabs are
used.
TPTH was first registered as a pesticide in the U.S. in 1971. EPA issued a
Registration Standard for TPTH in September, 1984 (PB85248797) that classified
TPTH as a restricted use pesticide (RUP) due to acute and developmental toxicity
concerns; imposed label warnings regarding developmental toxicity and potential
adverse ecological effects; established a 24-hour reentry period; required additional
data; and announced the Agency's intent to initiate a Special Review of TPTH. In
January 1985, the Agency issued a Position Document (PD 1) initiating the Special
Review of TPTH, based on potential developmental toxicity risks to mixers, loaders
and applicators. In 1988, EPA issued a Data Call-in for studies on
immunotoxicity reproductive and inhalation toxicity, and carcinogenicity EPA also
issued a Reregistration Standard Update in 1992 to require additional data for
reregistration purposes. In March 1992, TPTH was classified as a BZ carcinogen
(probable human carcinogen).
Currently, there are 16 TPTH products registered to four companies. There
are also 10 Special Local Needs (or FIFRA section 24(c) registrations) for
products containing TPTH.
Human Health
Assessment
Toxicity
In studies using laboratory animals, TPTH generally has been shown to have
high acute oral, dermal and inhalation toxicity It is an irritant to the eye and is not a
skin sensitizer. Toxicity Categories, which range from 1 (most toxic) to 4 (least
toxic), were n (oral), n (dermal), and I (inhalation).
TPTH belongs to a class of chemicals (organotins) known to be
immunotoxic. TPTH is considered to be a developmental toxicant, although it is not
considered to have mutagenic/genetic toxicity properties. It is carcinogenic both in
the rat (inducing pituitary and testicular tumors) and in the mouse (inducing liver
tumors), and is classified as a 62, possible human carcinogen by all routes of
exposure (oral, dermal and inhalation).
Dietary Exposure
People may be exposed to residues of TPTH through the diet Tolerances or
maximum residue limits have been established for TPTH (please see 40 CFR
180.236). EPA has reassessed the TPTH tolerances and found that most are
acceptable, one must be reassigned, and new tolerances must be established for
sugar beet tops and livestock commodities.
Currently there are no Codex Maximum Residue Limits (MRLs) established
for residues of TPTH in/on plant or animal commodities.
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EPA has assessed the dietary risk posed by TPTH.
For females 13+ years old, the population of concern for acute dietary
risk assessment, exposure from all current TPTH tolerances represents less than
35% of the acute PAD (population adjusted dose, or the acute Reference Dose
(RfD), the amount believed not to cause adverse effects from one day consumption,
adjusted to reflect a 3x FQPA Safety Factor). The exposure level of the most
highly exposed subgroup, females 20+ years old, not nursing or pregnant,
represents 34% of the acute PAD. Therefore, it appears that acute dietary risk is
not of concern.
For the general U.S. population and four subgroups, exposure from all
current TPTH tolerances represent less than 5% of the chronic PAD (population
adjusted dose, or the chronic Reference Dose (RfD), the amount believed not to
cause adverse effects if consumed daily over a 70-year lifetime, adjusted to reflect a
1 Ox FQPA Safety Factor). The exposure level of the U.S. population, including
infants and children, represents 2% of the chronic PAD. Therefore, it appears that
chronic non-cancer dietary risk is minimal
For the general U.S. population, however, it appears chronic cancer
dietary risk is a concern. For the U.S. population, based on exposure from all
current TPTH tolerances, the chronic cancer dietary risk estimate is 1.0 x 10"6 from
food alone (generally, cancer dietary risk estimates that include food and drinking
water exposures less than 1.0 x 10"6 are not of concern). However, the cancer
dietary risk estimate is primarily driven by sugar beet tops (the main feed item of the
three registered crop uses), and the resulting residues found in meat and milk. Since
there is a feeding restriction on TPTH products, the dietary risk assessment is likely
to overestimate actual exposure from sugar beet tops.
Based on the Agency's modeling estimates, potential exposure to TPTH
residues in drinking water derived from surface water (through spray drift or run-
off) results in aggregate dietary risk (food and drinking water exposures) that
exceeds the Agency's levels of concern for both chronic non-cancer and chronic
cancer dietary risk.
Occupational and Residential Exposure
There are no residential or other non-occupational uses of TPTH currently
registered, so only occupational exposures were assessed. Based on current use
patterns, handlers (mixers, loaders, and applicators) may be exposed to TPTH
during and after normal use. Since 1985, the TPTH labels have been modified to
include engineering controls (mechanical transfer systems for mixing/loading liquid
formulations, closed systems for aerial applications, and water soluble packaging)
and personal protective equipment (respirators and chemical resistant protective
clothing).
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Despite these protective measures, margins of exposure (MOEs) and cancer
risk estimates remain unacceptable, primarily for mixers/loaders of the wettable
powder formulation (in water soluble bags), and pecan harvesters who reenter
treated fields.
Human Risk Assessment
TFIH generally is of high acute toxicity causes developmental effects in
animal studies and has been classified as a Group BZ, probable human carcinogen
Only three food crop uses (pecans, potatoes, sugar beets) are registered. Non-
cancer dietary risk from exposure to TPTH residues in foods is low However, the
cancer risk posed to the general population may pose concerns, especially when
aggregated with surface water source drinking water exposures; modeling estimates
of TPTH concentrations in surface water exceed Drinking Water Levels of Concern
(DWLOCs). Because of TPTH's soil binding qualities, however, and buffer zones
implemented to mitigate ecological risks (discussed below), EPA does not believe
TPTH residues will concentrate in water at levels of dietary concern. The Agency
is calling in additional fate data to verify its conclusion; based on these studies, EPA
will determined whether water monitoring is warranted In addition, since there is
an enforceable feeding restriction on TPTH labels against feeding sugar beet tops to
livestock, it is likely that the Agency's estimates of dietary exposure from sugar beet
tops overestimate potential risk
Of greater concern is the risk posed to TPTH handlers, particularly
mixers/loaders/applicators, and field workers who come into contact with treated
crops following application of this pesticide. Exposure and risk to workers will be
mitigated by the use of personal protective equipment (PPE) required by the
Worker Protection Standard (WPS) and prior measures as a result of TPTH
Special Review negotiations, supplemented by closed cab application as required
by this RED. Post-application reentry workers on pecan fields will be required to
observe a 30-day pre-harvest interval.
Based on this assessment, the wettable powder formulation poses
unreasonable risk. However, the results of the Agency's occupational (non-cancer
and cancer) risk assessment for this formulation 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. 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 (acres treated) on all three registered crop sites.
Therefore, to support this formulation and to refine the risk estimates for wettable
powder in water soluble bags for groundboom and aerial/chemigation application
on the larger acreages representative of actual use, the Agency will call in a new,
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confirmatory exposure study on the wettable powder formulation. The Agency
believes that a new worker exposure study based on a larger treated acreage will
demonstrate that the MOEs for the water soluble bag formulation are acceptable.
In addition, for workers, cancer risk estimates are in the 10"5 to 10"6 range,
taking into account certain personal protective equipment and engineering controls.
Under EPA's Non-Dietary Cancer Risk Policy, the Agency considers risks of 10"6
or lower not to be of concern and carefully examines risks in the range of 1 Cr4 to
10"6 to seek ways of reducing risks prior to reregistration. For most worker
scenarios, cancer risks cannot be feasibly mitigated to 10"6 short of cancellation.
Based on a benefits assessment conducted for the TPTH Special Review the
Agency has determined that TPTH's continuing role as a resistance management
tool for pecans, potatoes and sugar beets warrants continued availability of the
fungicide, and that TPTH has benefits that outweigh the risks from use. In addition,
reductions in the total amount of TPTH that can be used in a given season
(implemented to mitigate ecological risks) will ensure that worker exposures will not
increase beyond current levels.
FQPA Considerations
Tolerances with amendments and changes specified in the RED document
meet the FQPA safety standard for the general population. EPA's water modeling
indicates potential dietary concerns from residues in drinking water (surface water
source). However, because of TPTH's soil binding qualities, and buffer zones that
will be required on TPTH labels, the Agency does not believe TPTH will reach
water at levels of dietary concern. The Agency is requiring additional data to verify
its conclusion; based on these studies, EPA will determine whether water
monitoring is required
Aggregate risk assessment for TPTH considered risks from TPTH treated
food and residues in drinking water (based on modeling). There are no residential
uses of TPTH registered, so only dietary (food and drinking water) risk was
assessed.
For risk assessment purposes, the Agency has not assumed that TPTH has a
common mechanism of toxicity with any other chemical(s).
Environmental Environmental Fate
Assessment Data submitted for reregistration show that TPTH binds strongly to soil, is
stable to photolysis, and resistant to photo degradation and hydrolysis. Because of
its soil binding qualities, TPTH is not expected to leach to groundwater. However,
TPTH could reach surface water through spray drift and run-off, where the fate of
the TPTH parent compound and its degradates are uncertain, as data is lacking on
important fate qualities of these metabolites. The registrants will submit aerobic and
anaerobic aquatic metabolism studies, a field dissipation study, an aerobic soil
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metabolism study, and batch equilibrium studies so that the Agency can better
evaluate the fate of TPTH and its degradates in soil and water. In addition, buffer
zones from water bodies will minimize the opportunity for spray drift and run-off
into water.
Ecological Effects
TPTH is moderately toxic to avian and mammalian species and exceeds
acute and chronic LOCs. For a single application of TPTH, acute avian LOCs
were exceeded for endangered species for all crops. The avian chronic level of
concern is exceeded at all registered maximum application rates.
For multiple broadcast applications of liquid products, mammalian acute
levels of concern are not exceeded at maximum application rates for any crop.
However, the mammalian chronic LOG is exceeded at all registered maximum
application rates for all food uses.
TPTH is very highly toxic to freshwater and marine/estuarine organisms.
Exposure assessments were conducted using Tier n level modeling with
PRZM/EXAMS. The RQs calculated from the modeling results show that acute
and chronic LOCs for freshwater fish are exceeded.
High acute and chronic LOCs for freshwater invertebrates are exceeded for
the pecan use pattern. Also, acute restricted use, endangered species and chronic
LOCs for freshwater invertebrates were exceeded for the potato and sugar beet
use patterns.
High acute risk LOCs for estuarine/marine fish are exceeded for the pecan
use pattern. Also, endangered species LOCs for estuarine/marine fish were
exceeded for the potato and sugar beet use patterns. High acute, restricted use and
endangered species LOCs for estuarine/marine invertebrates are exceeded for all
use patterns.
The exposure and risk to these nontarget species will be mitigated by
reductions in the maximum seasonal use amounts currently allowed on TPTH labels.
The registrants have agreed to reduce the maximum seasonal use rates on all three
crop sites, which will reduce exposure to nontarget organisms. In addition, the
addition of buffer zones to labels will protect aquatic species.
Risk Mitidation Since the initiation of the TPTH Special Review in 1985, the registrants have
voluntarily taken actions to reduce worker exposures to TPTH. These actions
include deletion of TPTH use on carrots, peanuts and tobacco; requiring closed
mixing/loading systems for aerial applications; requiring use of closed cab tractors
by applicators of the flowable concentrate formulation; addition of protective
clothing requirements to labels; adoption of mechanical transfer systems for liquid
formulations; and packaging of the wettable powder in water soluble bags.
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Additional Data
Required
To lessen the risks to human health and the environment identified in the
TPTH RED, EPA is requiring the following additional risk mitigation measures:
N The maximum seasonal use on pecans may not exceed 24 ounces ai/acre in areas
and states that are west of Interstate 35 (e.g., Arizona, New Mexico, and some
areas of Oklahoma and Texas). In all other areas and states (east of Interstate 35)
the maximum seasonal use on pecans may not exceed 36 ounces ai/acre. High
humidity east of Interstate 35 favors disease development in pecans, requiring
higher seasonal use amounts.
N The maximum seasonal use on potatoes must be reduced to 9 ounces ai/acre in
all states.
N The maximum seasonal use on sugar beets must be reduced to 8 ounces ai/acre in
all states EXCEPT Minnesota, North Dakota, and Michigan.
N Labels will require a buffer zone of 100 feet from water bodies for ground
applications, and a buffer zone of 300 feet from water bodies for aerial applications.
EPA is requiring the following additional generic studies for TPTH to confirm
its regulatory assessments and conclusions:
N 81-8: Acute neurotoxicity/rat
N 82-7: Subchronic neurotoxicity/rat
N Special Study: Developmental immunotoxicology neurotoxicity study
N 171-4: Independent laboratory validation (for animal method) and radio
validation (plant and animal method)
N 171 -4m: Multiresidue testing
N 171-4e: Storage stability
N 231 and 232: Dermal and inhalation exposure; wettable powder (in water
soluble bags) formulation
N 72-4a: Fish early life stage toxicity test (sheepshead minnow)
N 72-4b: Aquatic invertebrate life cycle (mysid)
N 122-2: Aquatic plant growth
N 163 -1: Sediment and soil absorption/desorption for parent and degradates
N 164-1: Field dissipation study
N 162-1: Aerobic soil metabolism
N 162-4: Aerobic aquatic metabolism
N 162-3: Anaerobic aquatic metabolism
The Agency also is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of Formula
(CSFs), and revised labeling for reregistration
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Product Labeling
Changes
Required
Regulatory
Conclusion
For More
Information
All TFIH end-use products must comply with EPA's current pesticide
product labeling requirements and with the following measures. For a
comprehensive list of labeling requirements, please see the TPTH RED document.
N Applicators (ground and aerial) will be in enclosed cabs.
N The pre-harvest interval (PHI) for pecan use will be 30 days.
N The maximum seasonal use on pecans may not exceed 24 ounces ai/acre in areas
and states that are west of Interstate 35 (e.g., Arizona, New Mexico, and some
areas of Oklahoma and Texas). In all other areas and states (east of Interstate 35)
the maximum seasonal use on pecans may not exceed 36 ounces ai/acre.
N The maximum seasonal use on potatoes must be reduced to 9 ounces ai/acre in
all states.
N The maximum seasonal use on sugar beets must be reduced to 8 ounces ai/acre in
all states EXCEPT Minnesota, North Dakota, and Michigan.
N A buffer zone of 100 feet from water bodies is required for ground applications.
N A buffer zone of 300 feet from water bodies is required for aerial applications.
The use of currently registered products containing TPTH in accordance with
approved labeling will not pose unreasonable risks or adverse effects to humans or
the environment. Therefore, all uses of these products are eligible for reregistration
The registrants have agreed to amend labels reflecting worker and
environmental risk mitigation measures for use in the 2000 growing season
However, full re-registeration of products containing TPTH will not be completed
until the required product-specific data and revised Confidential Statements of
Formula are received and accepted by EPA.
EPA is requesting public comments on the Reregistration Eligibility Decision
(RED) document for TPTH during a 90-day time period, as announced in a Notice
of Availability published in the Federal Register. To obtain a copy of the RED
document or to submit written comments, please contact the Pesticide Docket,
Public Information and Records Integrity Branch, Information Resources and
Services Division (7502C), Office of Pesticide Programs (OPP), US EPA,
Washington, DC 20460, telephone (703) 305-5805.
Electronic copies of the RED and this fact sheet are available on the Internet.
See http://www.epa.gov/REDs.
Printed copies of the RED and fact sheet can be obtained from EPA's
National Service Center for Environmental Publications (EPA/NSCEP), P.O. Box
42419, Cincinnati, OH 45242-2419, telephone (800) 490-9198; fax
(513)489-8695.
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Following the comment period, the TPTH RED document will also be
available from the National Technical Information Service (NTIS), 5285 Port Royal
Road, Springfield, VA 22161, telephone (800) 553-6847, or (703) 605-6000.
For more information about EPA's pesticide reregistration program, the
TPTH RED, or reregistration of individual products containing TPTH, please
contact the Special Review and Reregistration Division (7508C), OPP, US EPA,
Washington, DC 20460, telephone (703) 308-8000.
For information about the health effects of pesticides, or for assistance in
recognizing and managing pesticide poisoning symptoms, please contact the
National Pesticide Telecommunications Network (NPTN). Call toll-free
(800) 858-7378, from 6:30 am to 4:30 pm Pacific Time, or 9:30 am to 7:30 pm
Eastern Standard Time, seven days a week. The NPTN internet address is
ace.orst.edu/info/nptn.
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