United States
Environmental Protection
Agency
Prevention, Pesticides
and Toxic Substances
(7508C)
EPA738-F-01-O06
February 2002
Chlorpyrifos Facts
EPA has assessed the risks of chlorpyrifos and reached an Interim Reregistration Eligibility
Decision (IRED) for this organophosphate (OP) pesticide. Provided that risk mitigation measures are
adopted, chlorpyrifos fits into its own "risk cup"- its individual, aggregate risks are within acceptable
levels. Chlorpyrifos also is eligible for reregistration, pending a full reassessment of the cumulative
risk from all OPs.
Used on a variety of food and feed crops,
golf courses, as a non-structural wood treatment, and
as an adult mosquitocide, chlorpyrifos residues in
food and drinking water do not pose risk concerns.
With mitigation eliminating virtually all homeowner
uses, chlorpyrifos fits into its own "risk cup." With
other mitigation measures, chlorpyrifos worker and
ecological risks also will be below levels of concern
for reregistration.
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 chlorpyrifos cannot be considered final
until this cumulative assessment is complete.
Further risk mitigation may be warranted at that
time.
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 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 chlorpyrifos 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
chlorpyrifos.
Uses
Chlorpyrifos is an organophosphate insecticide, acaricide and miticide used to control foliage
and soil-borne insect pests on a variety of food and feed crops.
Approximately 10 million pounds are applied annually in agricultural settings. The largest
agricultural market for chlorpyrifos in terms of total pounds ai is corn (~5.5 million).
Health Effects
Risks
Chlorpyrifos 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 food crops treated with chlorpyrifos are below the level of
concern for the entire U.S. population, including infants and children. Drinking water risk
estimates based on screening models and monitoring data from both ground and surface water
for acute and chronic exposures are generally not of concern.
In June, 2000, the Agency entered into an agreement with the technical registrants to
eliminate virtually all homeowner uses, except ant and roach baits in child resistent
packaging.
Residential postapplication exposures may occur after termiticide use in residential structures.
To mitigate risks from this use, the technical registrants agreed in June 2000 to limit
termiticide treatments to 0.5% solution, and cancel all postconstruction uses. Pre-construction
use will remain until 2005, unless acceptable exposure data are submitted that show that
residential postapplication risks from this use are not a concern.
Occupational exposure to chlorpyrifos is of concern to the Agency. Exposures of concern
include mixing/loading liquids for aerial/chemigation and groundboom application, mixing
wettable powder fov groundboom application, aerial application, and application by backpack
sprayer, high-pressure handwand, and hand-held sprayer or duster. Generally, these risks can
be mitigated by a combination of additional personal protective equipment and engineering
controls, and by reductions in application rates. Additionally, the Agricultural Handler Task
Force will be developing exposure data to better characterize the risk from certain uses (e.g.,
applying granulars by air).
X
If
-------
Risk quotients indicate that a single application of chlorpyrifos poses risks to small mammals,
birds, fish and aquatic invertebrate species for nearly all registered outdoor uses. Multiple
applications increase the risks to wildlife and prolong exposures to toxic concentrations. To
address these risks, a number of measures including reduced application rates, increased
retreatment intervals, reduced seasonal maximum amounts applied per acre, and no-spray
setback zones around water bodies will be needed.
Risk Mitigation
In order to support a reregistration eligibility decision for chlorpyrifos, the following risk
mitigation measures are necessary:
To mitigate risks to agricultural workers PPE consisting of double layers, chemical resistant
gloves, chemical resistant shoes plus socks, chemical resistant headgear for overhead
exposure, chemical resistant apron when cleaning and mixing or loading and a dust/mist
respirator are required for the following scenarios: mixing/loading liquids for groundboom
and airblast application, loading granulars for ground application, tractor drawn granular
spreader, and low pressure handwand.
engineering controls are required for the following scenarions: mixing wettable powder for
groundboom application (water soluble packaging), mixing wettable powder for airblast
application (water soluble packaging), and aerial application of sprays (enclosed cockpit).
There are still some occupational risk scenarios that are still below the target MOE of 100,
even with all feasible PPE or engineering controls. The risk assessments for these uses will
be refined with additional data.
To mitigate ecological risks the technical registrants have agreed to label amendments which
include the use of buffer zones to protect water quality, fish and wildlife, reductions in
application rates, number of applications per season, seasonal maximum amounts applied, and
increases hi the minimum intervals for retreatment.
The mitigation measures prescribed in the IRED along with mitigation that is already being
implemented as a result of the June, 2000, Memorandum of Agreement, will reduce risk to
both terrestrial and aquatic species. For example, many of the reported incidents of wildlife
mortality associated with chlorpyrifos use were related to residential lawn and termite uses
and use on golf courses. The residential uses have been eliminated, the termiticide use is
being phased out, and the application rate on golf courses has been reduced from 4 to 1
Ib/ai/A. Additionally, no-spray buffers around surface water bodies, as well as rate
reductions for agricultural uses will be implemented as a result of this IRED and will further
reduce the environmental burden of chlorpyrifos.
Hi
«
-------
Next Steps
Numerous opportunities for public comment were offered as this decision was being
developed. In addition, the chlorpyrifos IRED has been issued with a public comment period
(see www.epa.gov/REDs/ or www.epa.gov/pesticides/op ).
When the cumulative risk assessment for all organophosphate pesticides is completed, EPA
will issue its final tolerance reassessment decision for chlorpyrifos and may request further
risk mitigation measures. The Agency will revoke the tomato tolerance and amend the grape
and apple tolerances for chlorpyrifos. For all OPs, raising and/or establishing tolerances will
be considered once a cumulative assessment is completed.
------- |