United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508C)
EPA-738-F-00-019
March 2001
R.E.D. FACTS
Pesticide
Reregistration
Trial late
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 (FQPA) 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 2695,
triallate.
Use Profile
Triallate is a pre-emergent herbicide federally registered, but restricted to use
in CO, ID, KS, MN, MT, NE, NY ND, OR, SD, UT, WA, and WY on barley,
lentils, peas (dried and succulent), triticale, wheat, and canary grass. The Agency
has found that all currently registered uses of triallate, except canary grass, are
eligible for reregistration, provided specified changes are made to the label. Canary
grass is not being supported by the registrant for reregistration and the tolerance has
been revoked. In addition, since completion of the RED, a tolerance has recently
been established for a new use of triallate on sugar beets.
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Regulatory
History
On average, about 2.3 million pounds of triallate are applied annually on 2.1
million acres. Depending on the crop, triallate formulations may be applied before
or after planting, either by ground or aerial equipment. Application is typically
made either in the fall or in the spring, before targeted weed species germinate.
Triallate was first registered as a herbicide in the U.S. in 1961. Because
triallate is a List B chemical, no Registration Standard was prepared. A Data Call-
in (DCI) was issued in 1991 requiring the submission of additional data on product
and residue chemistry, toxicity environmental fate, and ecological effects. In 1993
and 1994, two additional DCIs were issued requiring the submission of a female
mouse oncogenicity study at higher dose levels and a developmental neurotoxicity
study.
Human Health
Assessment
Toxicity
Triallate is a herbicide in the class of thiocarbamates, which includes
pebulate, molinate, EPTC, butylate, vernolate, and cycloate. As with other
chemicals in this class, neurotoxicity is the major toxic effect; however, other toxic
effects, including carcinogenicity were also observed in toxicology studies for this
compound.
Toxicity categories, which range from I (most toxic) to IV (least toxic), show
that triallate has a low order of acute oral (Toxicity Category HI); dermal (Toxicity
Category IV); and inhalation (Toxicity Category IV) toxicity. In primary irritation
studies, triallate produces slight irritation to the eye (Toxicity Category HI) and skin
(Toxicity Category IV), and is a skin sensitizer.
Triallate is classified as a Group C chemical (possible human carcinogen),
based on hepatocellular carcinomas in male mice, with a positive trend and
borderline significance in female mice, and increased incidence of renal tubular cell
adenomas in rats.
Cumulative Risk
In accordance with the FQPA, the Agency is examining whether and to what
extent some or all organophosphorous and carbamate (including, but not limited to,
methyl carbamate, N-methyl carbamate, thiocarbamate, and dithiocarbamate)
pesticides may share a common mechanism of toxicity. In contrast to other
carbamates, the Agency has a less fully developed understanding of whether the
thiocarbamates share a common mechanism of toxicity with other cholinesterase-
inhibiting or carcinogenic chemicals. As a result, the Agency has not determined if it
would be appropriate to include them in a cumulative risk assessment with other
such chemicals (e.g., the organophosphorous and carbamate pesticides).
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Therefore, for the purposes of this risk assessment, the Agency has assumed that
triallate does not share a common mechanism of toxicity with cholinesterase-
inhibiting chemicals.
Dietary Risks
Overall acute and chronic dietary (food only) risks associated with triallate
use on all registered use sites, including the proposed use of triallate on sugar beets,
are not of concern to the Agency. Acute and chronic drinking water concentrations
were also estimated to evaluate the contribution of drinking water to dietary risk.
These drinking water estimates are based on ground and surface water computer
models that predict concentrations for both parent triallate and the metabolite
TCPSA. Aggregating both food and drinking water acute and chronic (non-
cancer) risks, the dietary exposures are not of concern to the Agency.
Triallate is classified as a Group C chemical (possible human carcinogen).
Based on a linear low-dose (Qi*) approach for human cancer risk characterization,
the cancer dietary risk is 7.1 x 10"8, which is less than EPA's target of 1 x 10"6 (1 in
1 million) and, therefore, is not of concern to the Agency.
Although chronic (cancer) dietary (food only) risk is not of concern to the
Agency, aggregating the cancer dietary risk (food) with model estimated drinking
water concentrations is of concern. To address this, the registrant initiated a surface
water monitoring program to measure parent triallate and metabolite TCPSA in high
use areas with vulnerable soil conditions.
Tolerances
Tolerances [refer to 40 CFR 180.314 (c)] or maximum residue limits are
summarized below:
• Revoke 1 tolerance (lentils hay), since it is no longer considered a significant
livestock feed item.
• Add 3 new tolerances (barley hay; wheat forage; wheat hay), due to changes
toOPPTSGLN860.1000.
• The tolerance for peas will apply to lentils.
All other tolerances are to be increased, except barley grain, which will
remain the same.
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Worker Risks
There are potential occupational exposures to pesticide handlers and to
workers when applying triallate. For mixers/loaders, applicators, and flaggers, risks
for all exposure scenarios are not of concern with either personal protective
equipment (PPE) (i.e., gloves and dust/mist filtering respirators) or engineering
controls (enclosed cockpits and trucks). The addition of some of these protective
measures are necessary to reduce cancer risk to handlers.
Significant exposure to triallate during harvesting, or any other late season
activity, is not likely since triallate is applied pre-emergence. Therefore, post-
application exposure is not expected, provided that the current 12-hour restricted-
entry interval (RET) is observed.
Environmental
Assessment
Risk Mitigation
Ecological Risks
The use of triallate is not likely to pose significant risk to birds, fish, large
mammals, reptiles or nontarget insects. Levels of concern are slightly exceeded for
endangered small mammals; however, this risk is dependent upon ingestion of large
amounts of contaminated insects or seed in the diet. Levels of concern for acute
risk, based on water modeling results, are slightly exceeded for endangered aquatic
invertebrates. However, because the habitat of endangered aquatic organisms
where triallate is registered are not likely to be exposed to the high modeled
concentrations of triallate, effects to endangered aquatic invertebrates are not
expected. Additionally, levels of concern for acute risk are exceeded for terrestrial
and semiaquatic plants. Although risks to plants are greater than the level of
concern, the overall ecological risk associated with the use of triallate is low;
therefore, no additional mitigation measures to reduce estimated ecological risks are
necessary.
In order to support a RED for triallate, some risk mitigation measures are
necessary and must be implemented. To address aggregate cancer dietary risk
concerns (food and water), the registrant initiated a surface water monitoring
program to measure parent triallate and metabolite TCPSA in high use areas with
vulnerable soil conditions. A final report of this study is expected in late 2002.
Interim results indicate that surface drinking water concentrations are not of concern
to the Agency.
There are also potential occupational exposures to pesticide handlers and to
workers when applying triallate. For mixers/loaders, applicators, and flaggers, risks
for all exposure scenarios are mitigated with either personal protective equipment
(PPE) (i.e., chemical resistant gloves and dust/mist filtering respirators) or
engineering controls (i.e., enclosed cockpits and trucks).
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Additional Data
Required
EPA is requiring the following additional generic studies for triallate to
confirm its regulatory assessments and conclusions: discussion of formation of
impurities; stability to normal and elevated temperatures, metals, and metal ions;
pH; UV/Visible absorption; partition coefficient; crop field trials (wheat hay);
processed food/feed (barley); field accumulation in rotational crops; aquatic
invertebrate life-cycle (21 day); aquatic plant growth; and surface drinking water
monitoring.
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.
Product Labeling All triallate end-use products must comply with EPA's current pesticide
Changes product labeling requirements, with the risk mitigation measures discussed above,
Red U i red anc^uses no l°n§er eligible for reregistration should be excluded. For a
comprehensive list of labeling requirements, please see the triallate RED document.
Regulatory
Conclusion
The Agency has found that all currently registered uses of triallate, except
canary grass, are eligible for reregistration, provided specified changes are made to
the label. The use of eligible triallate products in accordance with labeling specified
in this RED will not pose unreasonable adverse effects to humans or the
environment. These products will be reregistered once the required confirmatory
generic data, product specific data, CSFs, and revised labeling are received and
accepted by EPA. Products which contain active ingredients in addition to triallate
will be reregistered when all of their other active ingredients also are eligible for
reregistration.
For More
Information
EPA is requesting public comments on the Reregistration Eligibility Decision
(RED) document for triallate during a 60-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 OPP Public
Regulatory Docket (7502C), US EPA, Ariel Rios Building, 1200 Pennsylvania
Avenue NW, Washington, DC 20460; telephone 703-305-5805.
Electronic copies of the RED and this fact sheet are available on the Internet.
See htt|x/yww\^ep£LgQy/REDs or
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Printed copies of the RED and fact sheet can be obtained from EPA's
National Service Center for Environmental Publications (EPA/NSCEP), PO Box
42419, Cincinnati, OH 45242-2419; telephone 1-800-490-9198; fax 513-489-
8695.
Following the comment period, the triallate RED document also will be
available from the National Technical Information Service (NTIS), 5285 Port Royal
Road, Springfield, VA 22161; telephone 1-800-553-6847, or 703-605-6000.
For more information about EPA's pesticide reregistration program, the
triallate RED, or reregistration of individual products containing triallate, 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 1-800-
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. Their internet address is
htto ://ace. orst. edu/info/nptn/.
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