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Permethrin Facts
(Reregistration Eligibility Decision (RED) Fact Sheet)
EPA 738-F-06-012
June 2006
Contents
Permethrin Facts :
- Pesticide Reregistration
- Regulatory History
- Uses
- Health Effects
- Risks
- Risk Mitigation Regulatory Conclusion
- For More Information
- Appendix A: Amended Agricultural Use Patterns
Permethrin Home
Permethrin Reregistration Eligibility Decision (RED) (PDF, 195 pp, 3.2 MB, About PDF)
Pesticide Reregistration
All pesticides sold or distributed in the Unites States must be registered by the Environmental Protection Agency (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 considered 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 registers 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 the pesticide permethrin, case 2510.
Regulatory History
Permethrin was first registered and tolerances established in the United States in 1979 for use on cotton (April 29, 1979 44FR 24287). The registration was made conditional due to the need for additional toxicology and ecological effects data to fully evaluate carcinogenicity and aquatic risk, respectively. After additional toxicity data were reviewed, EPA concluded that permethrin was a weak carcinogen. Further, laboratory studies indicated that permethrin was highly toxic to fish and aquatic invertebrates; therefore, it was classified as Restricted Use pesticide (RUP) for the cotton use. From 1982 to 1989, an additional 55 + crop tolerances were approved for a wide variety of crops, including various fruits and vegetables, meat, milk and eggs.
In 1985 a Data Call-In (DCI) for ecological effects data for permethrin was issued. After evaluation of this data EPA concluded that the current RUP classification be maintained for all products for wide area agricultural uses (except livestock and premises uses) and outdoor wide area non-crop uses because of the possible adverse effects on aquatic organisms from spray drift and runoff. In 1988 a comprehensive DCI was issued requiring additional residue chemistry, environmental fate and toxicological data. In 1994 the producers of products containing permethrin for use on cotton requested voluntary cancellation of this use. From 1994 thru 2000 permethrin was subject to specific DCIs requesting data to assess agricultural and residential exposure, agricultural re-entry, and mosquito ULV products.
Uses
- Permethrin is registered for use on/in numerous food/feed crops, livestock and
livestock housing, modes of transportation, structures, buildings (including food
handling establishments), Public Health Mosquito abatement programs, and
numerous residential use sites including use in outdoor and indoor spaces, pets,
and clothing (impregnated and ready to use formulations).
- According to Agency data, approximately 2 million pounds of permethrin are
applied annually to agricultural, residential and public health uses sites. The
majority of permethrin, over 70%, is used in non-agricultural settings; 55% is
applied by professionals, 41% is applied by homeowners on residential areas, and
4% is applied on mosquito abatement areas.
- Permethrin is a restricted use pesticide for crop and wide area applications (i.e.,
nurseries, sod farms) due to high toxicity to aquatic organisms, except for wide
area mosquito adulticide use. It is a general use pesticide for residential and
industrial applications.
- Permethrin also has non-FIFRA pharmaceutical uses as a pediculicide for the treatment of head lice and scabies. The Food and Drug Administration (FDA) approves use of the pesticide-containing pharmaceutical under FFDCA.
Health Effects
Permethrin is a member of the pyrethroid class of pesticides. Similar to other pyrethroids, permethrin alters nerve function by modifying the normal biochemistry and physiology of nerve membrane sodium channels. However, EPA is not currently following a cumulative risk approach based on a common mechanism of toxicity for the pyrethroids. Although all pyrethroids interact with sodium channels, there are multiple types of sodium channels and it is currently unknown whether the pyrethroids have similar effects on all channels. Nor do we have a clear understanding of effects on key downstream neuronal function e.g., nerve excitability, nor do we understand how these key events interact to produce their compound specific patterns of neurotoxicity. There is ongoing research by the EPA’s Office of Research and Development and pyrethroid registrants to evaluate the differential biochemical and physiological actions of pyrethroids in mammals. This research is expected to be completed by 2007. When available, the Agency will consider this research and make a determination of common mechanism as a basis for assessing cumulative risk. Therefore, the human health risk assessment and RED document only considered the effects of permethrin.
Additionally, the Agency classified permethrin as “Likely to be Carcinogenic to Humans” by the oral route. This classification was based on two reproducible benign tumor types (lung and liver) in the mouse, equivocal evidence of carcinogenicity in Long- Evans rats, and supporting structural activity relationship information.
Risks
Dietary
- Acute, chronic non-cancer, and cancer dietary (food and drinking water) risks from permethrin were below the Agency’s level of concern (LOC).
Residential
- All non-cancer (dermal and inhalation) risks for individuals handling permethrin
products in a residential setting were below the Agency’s LOC. All cancer risk
estimates were also below the Agency’s LOC, except for the following scenario:
mixing/loading/applying the EC formulation via sponge to horses.
- The non-cancer post-application risk estimates for adults and youth aged children
exposed to an environment treated with permethrin were below the Agency’s
LOC; however, the risk estimate for toddlers exposed to permethrin treated indoor
surfaces (carpets) were above the Agency’s LOC. The cancer risk estimates for
adults exposed to indoor surfaces treated with permethrin from directed surface
sprays or total release foggers were also above the Agency’s LOC.
- The Agency considered post-application exposure to both outdoor residential misting systems and permethrin treated clothing. All scenarios were below the Agency’s non-cancer and cancer LOCs.
Aggregate Risks
- The acute aggregate risk non-cancer and cancer estimate from food and drinking
water does not exceed the Agency’s LOC.
- Aggregate short-term (1-30 days) non-cancer risk estimates, which include the contribution of risk from chronic dietary sources (food + drinking water) and short-term residential sources, exceeded the Agency’s LOC for toddlers exposed to permethrin through food and drinking water, and through post-application exposure during high contact activities on lawns and indoor surfaces. The risk driver for the aggregate non-cancer risk estimate was post-application exposure to permethrin on treated indoor surfaces (carpets).
- The aggregate cancer risk estimate exceeded the Agency’s LOC for adults
exposed to permethrin through food and drinking water, and through postapplication
exposure during high contact activity on lawns and indoor surfaces.
Similar to the non-cancer aggregate risk assessment, post-application exposure to
treated indoor carpets was the risk driver.
- All residential/recreational exposures are expected to be short-term in duration.
Therefore, no intermediate-term (1-6 months) or long-term (>6 months) aggregate
risk was assessed.
- EPA believes that the appropriate way to consider the pharmaceutical use of permethrin in its risk assessment is to examine the impact that the additional nonoccupational pesticide exposures would have to a pharmaceutical patient exposed to a related (or, in some cases, the same) compound. Based on a worse case scenario assessment, EPA estimates that the permethrin exposure a patient is expected to receive from a typical single application of a 1% and 5% permethrin pharmaceutical cream, respectively, is 450 to 2300 times greater than the combined exposure from the dietary and other non-occupational sources of permethrin. FDA has reviewed these estimates and determined that pesticide exposure in patients receiving treatment with a pharmaceutical permethrin drug product would fall within the expected range of exposure following treatment with permethrin drug product alone, and would not present an increased safety risk.
Occupational
- The majority of occupational handler risk estimates were below the Agency’s
non-cancer LOC at baseline personal protective equipment (PPE) (long-sleeve
shirt, long pants, no gloves, and no respirator). For all other scenarios where the
LOC was exceeded considering just baseline PPE, all occupational risk estimates
were below the Agency’s non-cancer LOC with additional PPE or engineering
controls.
- The estimated cancer risks for the majority of grower scenarios were also within
the negligible risk range (≤3 x 10-6) or less with baseline PPE and gloves.
However, a number of scenarios result in risk in the 10-5 to 10-6 range at this level
of PPE, and either require additional PPE before the cancer risk estimates were
below the negligible risk range, have no data available to estimate risk, or further
mitigation measures were not feasible.
- For all agricultural post-application scenarios assessed, the non-cancer risks do
not exceed the LOC (MOEs > 100) on the day of application, approximately 12
hours following application. Most of the post-application cancer risk estimated
for both hired hands and commercial/migratory farm workers were in the 10-5 to 10-7 range. The highest risk estimates, in the 10-4 range, were for conifer seed
cone harvesting and thinning of certain fruit trees.
- All non-cancer post-application exposure scenarios for military personnel and garment workers exposed to permethrin-impregnated battle dress or fabric, respectively, do not exceed the Agency’s LOC. Further, all of the postapplication cancer risk estimates for both populations were in the 10-6 range.
Ecological Risks
- Permethrin is highly toxic to both freshwater and estuarine aquatic organisms.
Most agricultural, public health, and down-the-drain scenarios modeled resulted
in exceedances in the acute risk quotient (RQ) for freshwater and estuarine fish,
invertebrates, and sediment organisms. The agricultural and public health
scenarios also showed the potential for chronic risks to estuarine and/or
freshwater organisms. Further, there is a potential concern for direct effects to a
variety of aquatic organisms.
- The acute and chronic RQs for terrestrial avian species are below the Agency’s
levels of concern. The acute RQs for terrestrial mammals were also below the
Agency’s acute LOCs; however, some chronic RQs exceeded the Agency’s LOC.
However, the Agency believes the chronic RQs for mammals are based on a
conservative estimate of toxicity, and therefore, may represent an overestimation of
risk.
- The potential for risk to terrestrial and aquatic plants from exposure to permethrin
cannot be assessed because toxicity data are not available. However, any toxicity
to plants would occur for reasons other than permethrin's insecticidal mode of
action because permethrin works as a neural toxin, and unlike insects, plants do
not have neural networks that could be affected.
- Permethrin toxicity data show that the compound is highly toxic to honeybees, as well as other beneficial insects.
Risk Mitigation
To address assessed risks of concern, the following mitigation measures will be implemented.
Residential Risk
- Discontinue use of sponge application method for formulations applied as
liquids. Ready to use (RTU) products, such as wipes and trigger pump sprays
will still be available for this use pattern.
- Discontinue use of all directed broadcast and crack and crevice sprays (i.e.,
low pressure handwand, backpack sprayer, cold fogger) on all residential indoor surfaces, except for aerosol sprays.
- Limit concentration of RTU aerosol consumer sprays to 0.5% ai of
permethrin. The Agency will consider products with higher
concentrations if the registrants for these products are able to
provide justification or data to the Agency which demonstrate that
little to no exposure will occur due to the specialized use of the
product.
- Limit concentration of RTU aerosol consumer sprays to 0.5% ai of
permethrin. The Agency will consider products with higher
concentrations if the registrants for these products are able to
provide justification or data to the Agency which demonstrate that
little to no exposure will occur due to the specialized use of the
product.
- Limit all total release fogger formulations to 0.25% ai of permethrin.
- The Agency will consider products with higher concentrations if
the registrants are able to provide justification or data that an
equivalent indoor surface residue of 2.4 μg/cm2, or less, will result
in a room size of 2000 ft3 or less.
- The Agency will consider products with higher concentrations if
the registrants are able to provide justification or data that an
equivalent indoor surface residue of 2.4 μg/cm2, or less, will result
in a room size of 2000 ft3 or less.
- Amend all liquid and wettable powder products registered for outdoor
residential use to either prohibit use in outdoor residential misting systems, or
provide specific use directions.
- Efficacy data for all finished pre-treated permethrin products, and wash-off data to support efficacy claims is required.
Occupational Risk
Handler
- Require wettable powder formulations to be packed in water soluble packaging.
- Require all aerial applications to be in closed cab aircraft.
- Discontinue the use of high pressure handwands in mushroom houses.
- Add PPE requirement to labels as follows:
- Wettable Powders- baseline PPE (long pants, long sleeved shirt, and shoes), and chemical-resistant gloves for mixers, loaders, and applicators.
- Emulsifiable Concentrations- baseline PPE and chemical-resistant gloves for mixers, loader, and applicators. Additional chemicalresistant apron is required for applicators performing animal dip applications.
- Dry Flowables- baseline PPE and chemical-resistant gloves.
- Dust- Double layer (coveralls over baseline PPE), chemical-resistant gloves, and a PF5 respirator for loaders and applicators.
- RTU Formulations- Baseline PPE and chemical-resistant gloves.
- Applicators of liquids via cold foggers and fog mister/generators.
- Require applicators to wear double layers, chemical-resistant gloves, and PF10 respirator.
Post-Application
- Increase REI for conifer cone seed harvesting to 30 days.
- Amend agricultural labels to include new use patterns (rate reductions, seasonal maximum reductions, and minimum retreatment intervals) identified for the selected crop uses specified Appendix A.
Ecological Risks
- Include standard pyrethroid specific spray drift language, including a 25 foot aquatic buffer zone for ground applications, 100-foot for aerial application, and 450 foot for ULV applications.
- Amend agricultural labels to include new use pattern (rate reductions, seasonal maximum reductions, and minimum retreatment interval) identified for the selected crop uses specified in Appendix A.
- Include the following statement in the environmental hazard section of the end
use products:
- This pesticide is highly toxic to bees exposed to direct treatment on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds while bees are actively visiting the treatment area.
- For all wide area mosquito abatement products:
- Remove 100 foot buffer zone restriction;
- Specify a maximum application rate of 0.007 lb ai/A per day or 0.18 lb ai/A per year.
- Specify minimum release height of 100 feet for fixed wing aircraft, and 75 feet for helicopter applications.
- Require droplet size <60 microns for aerial application, and <30 microns for ground application.
- Include stewardship language in the directions for use section of all products registered for outdoor use in residential areas.
Risk/Benefit Balance Analysis
The Agency also assessed the significance of permethrin use, and conducted a risk/benefit balancing analysis. Given the significance of the use of permethrin and the mitigated nature of the risks of permethrin, the Agency believes, on balance, that the benefits of permethrin outweigh the risks. With respect to the ecological risks, the Agency has reduced those risks by imposing various conditions that should reduce exposure of aquatic species to permethrin. With respect to the benefits, permethrin offers substantial benefits to users. In the agricultural area, permethrin provides a high benefit to the agricultural industry because of its broad label and 1 day PHI. According to comments received from various growers, the broad spectrum of pests that permethrin targets makes its use highly beneficial since the agricultural industry has been losing a number of insecticides, and the newer insecticides replacing them have chemistries that target specific insects and are narrow in their spectrum. Further, permethrin has a 1 day pre-harvest interval, which allows for effective pest control near harvest of registered crops. Also alternatives to permethrin, such as the fourth generation pyrethroids, may pose a greater risk to aquatic organisms because of their persistence in the environment.
For the public health use, permethrin is the most widely used mosquito adulticide in the United States because of its low cost, high efficacy, and low incidence of pest resistance. Although permethrin alternatives are comparably priced and are likely to be as effective as permethrin in many situations, they are not likely to universally substitute for all permethrin uses because of labeling constraints or resistance concerns. The Agency believes that the loss of permethrin would adversely affect the ability of mosquito abatement professionals to control mosquitoes in some situation, such as agricultural-urban interface and areas with known resistance to alternatives. With regard to the treatment of fabrics, permethrin is the only pesticide registered to pre-treat fabrics, which the AFPMB strongly supports as a method of preventing many diseases that might afflict military personnel in the field. On other uses, such as residential uses, where there may be a potential for ecological effects due to urban runoff, the Agency intends to identify steps which can be taken to allow a greater understanding of potential ecological risk from urban uses of pyrethroid as a whole during Registration Review.
Data Requirements
The Agency has identified data necessary to confirm the reregistration eligibility decision for permethrin. These studies are listed below and will be included in the generic DCI for this RED, which the Agency intends to issue at a future date.
Toxicology:
| 870.6300 | Developmental Neurotoxicity Study |
| 870.1300 | Acute Inhalation Toxicity Study |
Residue Chemistry:
| 860.1200 | Directions for Use |
| 860.1340 | Enforcement Analytical Method-Animals |
| 860.1380 | Storage Stability |
| 860.1500 | Magnitude of the Residue in Crop Plants (leaf lettuce, collards, and cabbage) |
Occupational Exposure
| 875.1200 | Dermal Exposure Indoors (ULV Cold Fogger) |
| 875.1400 | Inhalation Exposure Indoors (ULV Cold Fogger) |
Environmental Toxicology
| 850.1735 | Whole sediment acute toxicity for estuarine/marine invertebrates |
| 850.1740 | Whole sediment acute toxicity for estuarine/marine invertebrates |
| EPA/600/R-99/064 (ORD Study Method) | Chronic Freshwater Sediment Testing |
| EPA/600/R01/020 (ORD Study Method) | Chronic Estuarine/Marine Sediment Testing |
Regulatory Conclusion
The Agency has determined that permethrin containing products are eligible for reregistration provided that the risk mitigation measures are adopted and labels are amended to reflect these measures.
For More Information
Electronic copies of the Permethrin RED and all supporting documents are available in the public docket EPA-HQ-OPP-2004-0385 located on-line in the Federal Docket management System (FDMC) at http://www.regulations.gov.
For more information about EPA’s pesticide reregistration program, the Permethrin RED, or reregistration of individual products containing permethrin, please contact the Special Review and Reregistration Division (7508P), Office of Pesticide Programs, U.S. EPA, Washington, D.C. 20460, telephone 703-308-8000.
For information about the health affects of pesticides, or for assistance in recognizing and managing pesticide poisoning symptoms, please contact the National Pesticide Information Center (NPIC). Call toll-free 1-800-858-7378. The NPIC internet address is http://npic.orst.edu.
Appendix A: Amended Agricultural Use Patterns
|
Current Labels |
Mitigation Per the RED |
||||
Crop |
Max. Rate per application |
Minimum |
Seasonal Maximum Application Rate |
New |
New |
New |
Alfalfa |
0.2 |
14 |
0.2 per cutting |
0.2 |
30 |
0.2 per cutting |
Almonds |
0.4 |
3 |
2 |
0.25 |
10 |
0.75 |
Hazelnuts |
0.4 |
As needed |
1.6 |
0.25 |
10 |
0.75 |
Pistachios |
0.4 |
As needed |
1.6 |
0.3 |
10 |
0.9 |
Walnuts |
0.4 |
As needed |
1.6 |
0.25 |
10 |
0.75 |
Apples |
0.4 |
As needed |
0.6 |
0.25 |
10 |
0.5 |
Pears |
0.4 |
As needed |
0.8 |
0.25 |
10 |
0.65 |
Cherries |
0.2 |
As needed |
1.2 |
0.2 |
10 |
0.6 |
Peaches/Nectarines |
0.3 |
7 |
1.5 |
0.25 |
10 |
0.75 |
Artichokes |
0.3 |
As needed |
1.5 |
0.3 |
10 |
0.9 |
Asparagus |
0.1 |
As needed |
0.4 |
0.1 |
7 |
0.4 |
Avocados |
0.2 |
7 |
1.2 |
0.2 |
7 |
0.8 |
Broccoli |
0.2 |
As needed |
0.8 |
0.2 |
5 |
0.8 |
Brussels Sprouts |
0.2 |
As needed |
0.8 |
0.1 |
5 |
0.4 |
Cabbage |
0.2 |
5 |
1 |
0.2 |
5 |
0.4 (0.8 in HI) |
Cauliflower |
0.2 |
As needed |
0.8 |
0.1 |
5 |
0.4 (0.6 in HI) |
Cantaloupes |
0.2 |
7 |
1.6 |
0.2 |
7 |
0.8 (1.2 in HI) |
Cucumbers |
0.2 |
As needed |
1.6 |
0.2 |
7 |
1.2 |
Pumpkins |
0.2 |
As needed |
1.6 |
0.2 |
7 |
1.2 |
Squash (summer, winter) |
0.2 |
As needed |
1.6 |
0.2 |
7 |
1.2 |
Watermelon |
0.2 |
As needed |
1.6 |
0.2 |
7 |
1.2 |
Eggplant |
0.21 |
3 |
2 |
0.15 |
7 |
0.6 (1.0 in HI) |
Peppers, bell |
0.2 |
As needed |
1.6 |
0.2 |
5 |
0.8 |
Tomatoes |
0.2 |
5 |
1.2 |
0.2 |
7 |
0.6 (0.8 in HI) |
Celery |
0.2 |
As needed |
2 |
0.2 |
7 |
1.0 (1.2 in HI) |
Lettuce |
0.2 |
3 |
2 |
0.2 |
7 |
0.8 (1.2 in HI) |
Spinach |
0.2 |
As needed |
2 |
0.2 |
3 |
0.6 |
Collards |
0.2 |
As needed |
0.8 (0.4 in SC, GA, FL, WA) |
0.15 |
3 |
0.45 |
Greens, Turnip |
0.2 |
As needed |
0.8 (0.4 in SC, GA, FL, WA) |
0.15 |
3 |
0.45 |
Corn, Field |
0.2 |
6 |
0.6 |
0.15 |
7 |
0.45 |
Sweet Corn |
0.25 |
3 |
1.2 |
0.2 |
3 |
0.8 |
Garlic |
0.3 |
As needed |
2 |
0.2 |
10 |
0.8 |
Onions |
0.3 |
As needed |
2 |
0.3 |
7 |
1.0 |
Horseradish |
0.21 |
As needed |
0.6 |
0.15 |
10 |
0.45 |
Papaya |
0.4 |
7 |
1.2 |
0.15 |
10 |
0.75 |
Potatoes |
0.2 |
As needed |
1.6 |
0.2 |
10 |
0.8 |
Soybeans |
0.2 |
As needed |
0.4 |
0.2 |
10 |
0.4 |
 |
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