United States
Environmental Protection
Agency
Prevention, Pesticides
and Toxic Substances
(7508C)
EPA738-F-00-008
September 2000
Coumaphos Facts
EPA has reassessed the risks of coumaphos and reached a Reregistration Eligibility Decision
(RED) on the uses of coumaphos where a decision was deferred in the 1996 Coumaphos RED. In
1996, a reregistration decision was only reached for the dip vat use by the U.S. Department of
Agriculture. In this RED Addendum, EPA has determined that if the risk mitigation measures for this
organophosphate (OP) pesticide are adopted, coumaphos fits into its own "risk cup"-- its individual,
aggregate risks are within acceptable levels. Coumaphos also is eligible for reregistration, pending a full
reassessment of the cumulative risk from all OPs.
Used on livestock (beef and dairy cattle,
horses, goats, sheep and swine) and swine
bedding for the control of arthropod pests,
coumaphos residues in food and drinking water
do not pose risk concerns. With mitigation
limiting exposure to workers who handle this
pesticide, coumaphos fits into its own "risk
cup." With other mitigation measures,
groundwater sources of drinking water could be
further protected from potential pesticide
contamination.
EPA's next step under the Food Quality
Protection Act (FQPA) is to complete a
cumulative risk assessment and risk
management decision encompassing all the OP
pesticides, which share a common mechanism
of toxicity. The interim decision on coumaphos
cannot be considered final until this cumulative
assessment is complete. Further risk mitigation
may be warranted at that time.
EPA is reviewing the OP pesticides to
determine whether they meet current health and
safety standards. Older OPs need decisions about their eligibility for reregistration under FIFRA. OPs
with residues in food, drinking water, and other non-occupational exposures also must be reassessed to
make sure they meet the new FQPA safety standard.
The OP Pilot Public Participation Process
The organophosphates are a group of
related pesticides that affect the functioning of the
nervous system. They are among EPA's highest
priority for review under the Food Quality Protection
Act.
EPA is encouraging the public to
participate in the review of the OP pesticides.
Through a six-phased pilot public participation
process, the Agency is releasing for review and
comment its preliminary and revised scientific risk
assessments for individual OPs. (Please contact
the OP Docket, telephone 703-305-5805, or see
EPA's web site, www.epa.gov/pesticides/op.)
EPA is exchanging information with
stakeholders and the public about the OPs, their
uses, and risks through Technical Briefings,
stakeholder meetings, and other fora. USDA is
coordinating input from growers and other OP
pesticide users.
Based on current information from
interested stakeholders and the public, EPA is
making interim risk management decisions for
individual OP pesticides, and will make final
decisions through a cumulative OP assessment.
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The coumaphos registration eligibility decision was made through the OP pilot public
participation process, which increases transparency and maximizes stakeholder involvement in EPA's
development of risk assessments and risk management decisions. EPA worked extensively with
affected parties to reach the decisions presented in this interim decision document, which concludes the
OP pilot process for coumaphos.
Uses
An insecticide/acaricide, coumaphos is used to control flies, ticks, and mites, among other
arthropod pests on livestock and swine bedding. Predominant use is on beef cattle.
Coumaphos is an important tool in the USDA Cattle Fever Tick Eradication Program (dip vat
treatment) to prevent the reintroduction of equine and bovine piroplasmosis into the U.S.
Emergency exemptions exist for coumaphos use in bee hives to control varroa mites and small
hive beetles.
Estimated annual domestic use is very low- approximately 71,000 pounds of active ingredient
per year.
Health Effects
Risks
Coumaphos can cause cholinesterase inhibition in humans; that is, it can overstimulate the
nervous system causing nausea, dizziness, confusion, and at very high exposures (e.g., accidents
or major spills), respiratory paralysis and death.
Dietary exposures from eating commodities treated with coumaphos are not of concern for the
entire U.S. population, including infants and children. Drinking water is not a significant source
of exposure.
Coumaphos is not registered for use in residential areas, therefore residential risks were not
assessed.
Risks are of concern for workers who mix, load, and apply coumaphos to livestock and swine
bedding.
Environmental risks were not reassessed because the Agency has no reason to believe the
conclusions would change since the 1996 RED was issued.
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Risk Mitigation
In order to support a reregistation eligibility decision for coumaphos, the following risk
mitigation measures are necessary:
• To mitigate risks to workers:
For dip vat use:
Restrict the use of the 42% flowable product to U.S. Department of Agriculture
(USDA-APfflS) staff enrolled in the USD A-APHIS cholinesterase monitoring
program.
For spray uses:
• Maintain the current use restriction limiting the number of animals an individual can treat
using hand-held sprayers to 100 head per day at the maximum application rate and
move this restriction to a more prominent place on the labels.
For dust uses:
Prohibit the use of mechanical dusters as a method of application for coumaphos
technical, all manufacturing-use products and all end-use products;
Require the use of a dust/mist respirator and a chemical-resistant apron; and
• Limit the number of animals an individual may treat using a shaker can to 25 head per
day and the swine bedding area to be treated to 1,000 sq. ft. per day.
To further mitigate any potential ground water contamination:
• Restrict the disposal of bioremediated coumaphos spent solution from dip vat
operations to shallow, concrete-lined evaporation ponds.
• To reflect the uses currently supported by the technical registrant:
Restrict the formulation of coumaphos products for use on beef cattle, dairy cattle,
horses, swine and swine bedding use only.
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Next Steps
Numerous opportunities for public comment were offered as this decision was being
developed. The Coumaphos RED Addendum therefore is issued in final (see
www.epa.gov/REDs/ or www.epa.gov/pesticides/op), without a formal public comment
period. The docket remains open, however, and any comments submitted in the future will be
placed in this public docket.
To effect risk mitigation as quickly as possible, time frames for making the changes described in
the Coumaphos RED Addendum are shorter than those in a usual RED. All labels need to be
amended to include the above mitigation and submitted to the Agency within 90 days after
issuance of this RED Addendum.
When the cumulative risk assessment for all organophosphate pesticides is completed, EPA will
issue its final tolerance reassessment decision for coumaphos and may request further risk
mitigation measures. The Agency expects to revoke six tolerances for residues in meat, fat, and
meat byproducts of goats and sheep, because the technical registrant no longer supports these
uses and will request voluntary cancellation of these uses. For all OPs, raising and/or
establishing tolerances will be considered once a cumulative assessment is completed.
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