United States.
Environmental Protection
Agency
Prevention, Pesticides
and Toxic Substances
(7508C)
EPA 738-F-02-005
June 2002
Terbufos Facts
EPA has assessed the risks of terbufos and reached an Interim Reregistration Eligibility
Decision (IRED) for this organophosphate (OP) pesticide. Provided that risk mitigation measures are
adopted, terbufos fits into its own "risk cup"-- its individual, aggregate risks are within acceptable
levels. Terbufos also is eligible for reregistration, pending a full reassessment of the cumulative risk
from all OPs. .
Used on com, sorghum, and sugar beets,
terbufos residues in food and drinking water do not
pose risk concerns with the implementation of certain
risk mitigation measures. Terbufos has no
residential uses. With other risk reduction measures,
terbufos's worker and ecological risks also will be
substantially reduced.
EPA's next step under the Food Quality
Protection Act (FQPA) is to consider the cumulative
risks of the OP pesticides, which share a common
mechanism of toxicity. The interim decision on
terbufos cannot be considered final until this
consideration of OP risks 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 FFDCA safety
standard, effected by the FQPA of 1996.
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 after considering the cumulative risks of
the OPs.
The terbufos interim 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 terbufos.
-------
Uses
An insecticide, terbufos is used to control insects in corn, sorghum, and sugar beets. The
major use is on corn to control soil insects such as; corn rootworm, wireworm, white grubs,
seedcorn maggots, billbugs, and nematodes.
According to Agency figures, annual domestic use is approximately 7.5 million pounds of
active ingredient per year. Roughly 87% is used on corn.
Health Effects
Terbufos 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.
Risks
• Dietary exposures from eating food crops treated with terbufos are below the level of concern
for the entire U.S. population, including infants and children. Drinking water, however, is a
significant source of exposure.
• EPA also has risk concerns for workers who load, and/or apply terbufos. For the Counter 15G
formulation, there are risk concerns for both scenarios on each crop, whereas, the Counter
20CR formulation in open bags only presents risk concerns for the loading scenario. There are
no risk concerns for 20CR in lock-n-load containers.
• Terbufos presents high acute risks to non-target terrestrial wildlife species. Terbufos is the
leading cause offish kill incidents reported to EPA for any pesticide applied to corn, and ranks
fourth in fish kill incidents reported to EPA for any pesticide applied to any crop. From 1976
to present, 96 fish kill incidents involving terbufos were reported to the Agency.
Benefits
The benefits of terbufos on corn were estimated using a comparative product performance
assessment. This assessment aimed at quantifying, to the extent possible, the benefits derived from
the use of terbufos on corn primarily for control of corn rootworm.
• The benefits assessment concluded that under most conditions the alternative insecticides
produced similar or greater yields than fields where terbufos was used.
• Terbufos did show an advantage over the alternative insecticides in controlling billbugs in
North Carolina, corn rootworm in the Northeast, and some secondary corn pests.
2 ,
-------
Risk Mitigation
In order to support a reregistration eligibility decision for terbufos, the following risk
mitigation measures are necessary:
• To mitigate risks to agricultural workers:
• Require the use of a closed loading system for the North Carolina Special Local Needs
registration of Counter 20CR.
Require that the Counter 15G label be amended to indicate that applications must be
made using enclosed cab tractors.
Reduce the application rate on sorghum from 1.96 Ibs. active ingredient (a.i.) per acre
to 1.7 Ibs. a.i. per acre.
• To mitigate drinking water and ecological risks:
• Require a 55% reduction in sales of terbufos by 2008, based on 2000 sales figures.
Require a 500 ft. vegetative buffer between treated area and surface water on
neighboring land
Require a 500 ft vegetative buffer between a standpipe drain outlet and surface water
on neighboring land.
• Require a 66 ft. setback between the treated area and entry points to surface water
bodies on non-highly credible soils.
• Require a 300 foot setback between me treated area and entry points to surface water
bodies on highly credible soils.
• Require a 66 ft. setback between treated area and standpipes on terraced fields as well
as 66 ft. vegetative buffer between the tile outlet and surface water bodies
Restrict loading, rinsing, and washing equipment within 300 ft. from surface water
bodies or within 50 ft. from wells unless conducted on an impervious surface.
Remove the "over the top" application on corn for European corn borer control. ,
Require placing granules for banded applications on corn in a 7 inch band over the
row, in front of the press wheel, and incorporated into the topi inch of soil.
-------
To prevent the flow of rainfall down planted rows, the label text will be required to
read "To prevent channeling of surface water run-off, adjust the planter row-cleaners
appropriately to prevent rows lower in .height than adjacent soil".
Next Steps
For this IRED there will be a 60 day comment period before the document is finalized (see
www.epa.gov/pesticides/reregistration/status.htrn. or www.epa.gov/pesticides/op ). In
addition, the docket remains open and any comments submitted in the future will be placed in
this public docket.
When EPA has considered the cumulative risks of the OP pesticides, the Agency will issue its
final tolerance reassessment decision for terbufos and may request further risk mitigation
measures. The Agency will revoke 1 tolerance for terbufos, now. For all OPs, EPA will
consider raising and/or establishing tolerances once the cumulative risks of the OPs have been
considered.
------- |