United States
Environmental Protection
Agency
Prevention, Pesticides
and Toxic Substances
(7508C)
EPA738-F-00-014
February 2001
Phorate Facts
EPA has assessed the risks of phorate and reached an Interim Reregistration Eligibility
Decision (ERED) for this organophosphate (OP) pesticide. Phorate is eligible for reregistration,
pending a full reassessment of the cumulative risk from OPs.
Used primarily on a variety of field
agricultural crops, phorate residues from food alone
do not exceed the Agency's level of concern.
However, for dietary risk from drinking water, based
on modeling (SCI-GROW), the maximum estimated
-concentrations of phorate and metabolites (sulfoxide
and sulfone) in groundwater are slightly greater than
the Agency's Drinking Water Level of Comparison
(DWLOC) for chronic drinking water exposure.
Also, the estimated concentrations of phorate and.its
metabolites in surface water slightly exceed EPA's
DWLOC for acute exposure. However, the
conservative nature of the food assessment together
with extensive risk mitigation proposed hi this
document lead the Agency to believe that the dietary
risk from food and drinking water exposure for
phorate and its degradates will be below the
Agency's level of concern following implementation
of mitigation-measures. Phorate has no residential
uses. With the implementation of certain risk
mitigation measures, phorate's worker and ecological
risks also will be below levels of concern for
reregistration.
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.
EPA's next step under the Food Quality Protection Act (FQPA) is to complete a cumulative
risk assessment and risk management decision encompassing the OP pesticides, which share a
common mechanism of toxicity. The interim decision on phorate cannot be considered final until this
cumulative assessment is complete. Further risk mitigation may be warranted at that time.
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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 phorate interim decision was made through the OP pilot pubHc 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
phorate.
Uses
Phorate is an insecticide/nematicide used to control various insects such as the Mexican bean
beetle, corn roptworm, mites, European corn borers, wireworms, white grubs, cornleaf aphids,
seedcom beetles, leafminers, thrips, black cutworms, leaflioppers, white flies, nematodes,
southern corn rootworm, flea beetle larvae, psyllids, wireworms, Colorado potato beetle, lygus,
chinchbug nymphs, Banks grass mites, seedcorn maggots, sugar beet root maggot, sugar beet
leafhopper, grasshoppers, and Hessian Fly. Phorate is used on potatoes, corn (fresh, sweet,
field)), peanuts, cotton, sugarcane, wheat (spring/winter), soybeans, beans, sorghum, sugar
beets, lilies (field grown), daffodils, and radishes grown for seed.
An estimated 3 million pounds of phorate are produced annually. Crops with the highest usage
with reference to pounds produced are corn (46%), potatoes (21%) and cotton (13%).
Almost 2.5 million acres are treated annually. Crops with the highest percentage of acres
treated include potatoes (20%), fresh sweet corn (10%) and peanuts (9%). Most of the usage
is in FL, WI, CA, GA, MS, AL, TX, ID, MT, and MI.
There are no residential uses for phorate.
Health Effects
Phorate 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.
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Risks
Acute and chronic dietary risks from food alone do not exceed the Agency's level of concern,
however, for dietary risk from drinking water, the maximum estimated concentrations of
phorate and metabolites (sulfoxide and sulfone) in groundwater and surface water slightly
exceed EPA's level of concern.
Worker risks are of concern for the mixer/loader/applicator when using open bags, open cab
ground equipment and minimum Personal Protective Equipment. Aerial applicators and
flaggers (without engineering controls) also have risks above EPA's level of concern.
Ecological risks are also of concern to the Agency. Risks to birds, fish, and mammals are high.
Study results indicate that ingestion of phorate poses acute and chronic risks to birds.
Additionally several bird kills, some involving large numbers of birds, have been reported and
linked to the use of phorate on winter wheat. Fall application seems to pose a particular risk
because during winter, degradation and downward movement is expected to be slow. As a
result, in the following spring, concentrations of phorate and its metabolites can occur at
hazardous levels in pools on the soil surface. Acute and chronic risks to aquatic organisms
resulting from surface run-off to rivers, streams and coastal areas is high based on study results.
Additionally, a few fish kill incidents have been reported and indirectly linked to phorate. Risks
to mammals may result from agricultural use, based- on study results. Phorate is moderately to
highly toxic to honey bees on an acute basis.
Risk Mitigation
In order to support a reregjstration eligibility decision for phorate, the following risk mitigation
measures listed below are necessary. Although most of the mitigation measures are directed to a
specific risk scenario (worker risk, ecological risk, or drinking water concern), some measures will
reduce risk in more than one area of concern:
To mitigate risks to agricultural workers:
Require the use of engineering controls such as enclosed loading and enclosed application
systems and use of closed cabs.
Phase out open bag use.
Prohibit aerial application.
Prohibit use of phorate on peanuts at pegging.
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Prohibit use on wheat.
Require soil incorporation.
Allow sidedress use on cotton only in Arizona and California..
Allow only one application per season.
EPA believes that a more thorough assessment of exposure to re-entry workers is needed. The
Agency is requiring efficacy data and additional agricultural practice data to help define if any
activities could result in post application exposure. Pending review of the efficacy data, EPA
believes that application rates should be reduced up to 25 % unless the studies show that the
reduced rates are not efficacious. After reviewing the additional agricultural practice data, EPA
also reserves the right to require guideline 132-1 (foliar residue dissipation study) and 133-3
(dermal exposure upon reentry study) data. In the interim, the reentry intervals will remain
unchanged since several of the uses are preplant.
To mitigate ecological risks the following label modifications are required:
"Environmental Hazards: This pesticide is very highly toxic to fish and wildlife. Do not apply
directly to water, or to areas where surface water is present or to intertidal areas below the
mean high-water mark Runoff may be hazardous to aquatic organisms in neighboring areas.
Do not contaminate water when disposing of equipment wastewater or rinsate. Birds and
...mammals may be killed if granules are not properly covered with soil in all areas of the treated
field and in loading areas."
"Do not apply in wet soil conditions that may prevent the equipment from covering pesticide
granules."
Under some conditions phorate may have a high potential for runoff into surface water for
several days post application. Do not apply in the following situations:
"Frequently flooded areas"
"Areas where intense or sustained rainfall is forecasted to occur within 48 hours"
Use Best Management Practices for minimizing surface runoff in tiie following areas:
"Poorly draining or wet soils with readily visible slopes toward adjacent surface water"
"Areas over-laying extremely shallow ground water"
"Areas with in-field canals or ditches that drain to surface water"
"Areas not separated from adjacent surface waters with vegetated filter strips"
"Areas over-laying tile drainage systems that drain to surface water"
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When used on credible soils, best management practices for rninimizing runoff should be
employed. Consult your local soil conservation service for recommendations in your use area
In particular, where highly erodible land (HEL) is adjacent to aquatic bodies, a 66 foot
buffer/setback area should be left in grass or other natural vegetation.
Do not apply within 50 feet of any drinking water well to minimize potential contamination.
Do not wash, load, or empty application equipment near any well, as this practice is a potential
source of ground water contamination.
Next Steps
Numerous opportunities for public comment were offered as this decision was being
developed. The phorate RED 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
When the cumulative risk assessment for all organophosphate pesticides is completed, EPA
will issue its final tolerance reassessment decision for phorate and may request further risk
mitigation measures. The Agency will revoke 21 tolerances and amend 7 tolerances for
phorate now. For all OPs, raising and/or establishing tolerances will be considered once a
cumulative assessment is completed.
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