Permethrin Facts
(Reregistration Eligibility Decision (RED) Fact
Sheet)
EPA 738-F-06-012
June 2006
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 (LOG).
Residential
• All non-cancer (dermal and inhalation) risks for individuals handling permethrin products in a
residential setting were below the Agency's LOG. All cancer risk estimates were also below the
Agency's LOG, 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 LOG; however, the risk
estimate for toddlers exposed to permethrin treated indoor surfaces (carpets) were above the
Agency's LOG. 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
LOG.
• 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 LOG.
• 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 LOG 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 LOG 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 LOG
at baseline personal protective equipment (PPE) (long-sleeve shirt, long pants, no gloves, and
no respirator). For all other scenarios where the LOG was exceeded considering just baseline
PPE, all occupational risk estimates were below the Agency's non-cancer LOG 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
LOG (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 LOG. 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 LOG. 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.
o 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.
o 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 ug/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:
o Wettable Powders- baseline PPE (long pants, long sleeved shirt, and shoes), and
chemical-resistant gloves for mixers, loaders, and applicators.
o Emulsifiable Concentrations- baseline PPE and chemical-resistant gloves for mixers,
loader, and applicators. Additional chemicalresistant apron is required for applicators
performing animal dip applications.
o Dry Flowables- baseline PPE and chemical-resistant gloves.
o Dust- Double layer (coveralls over baseline PPE), chemical-resistant gloves, and a PF5
respirator for loaders and applicators.
o RTU Formulations- Baseline PPE and chemical-resistant gloves.
o 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:
o 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:
o Remove 100 foot buffer zone restriction;
o Specify a maximum application rate of 0.007 Ib ai/A per day or 0.18 Ib ai/A per year.
o Specify minimum release height of 100 feet for fixed wing aircraft, and 75 feet for
helicopter applications.
o 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
Whole sediment acute toxicity for estuarine/marine
invertebrates
Whole sediment acute toxicity for estuarine/marine
invertebrates
Freshwater Sediment
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.regulatlons.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, of for assistance in recognizing and managing
pesticide poisoning symptoms, please contact the National Pesticide Information Center (NPIC). Call
toll-free 1-800-858-7378, from 6:30 am to 4:30 am Pacific Time, or 9:30 am to 7:30 pm Easter
Standard Time, seven days a week. The NPIC internet address is http://npic.orst.edu.
Appendix A: Amended Agricultural Use Patterns
Crop
Alfalfa
Almonds
Hazelnuts
Pistachios
Walnuts
Apples
Pears
Current Labels
Mitigation Per the
Max. Rate Minimum Seasonal New New
per retreatment Maximum Maximum Minimum
application interval Application rate per retreatment
! RED
New
Seasonal
Maximum
(Ib ai/A) (days) Rate application interval Application
(Ib ai/A)
^—
0.2 14
0.4
3
0.2 per
cutting
2
(Ib ai/A) (days) Rate
0.2
0.25
0.4 As needed 1.6 0.25
0.4
0.4
As needed
As needed
1.6
1.6
0.4 As needed 0.6
0.4
As needed
0.8
0.3
0.25
0.25
0.25
(0.4
dormant
30
10
10
10
10
10
10
(Ib ai/A)
0.2 per
cutting
0.75
0.75
0.9
0.75
0.5
0.65
-------
Cherries
Peaches/Nectarines
Artichokes
Asparagus
Avocados
Broccoli
Brussels Sprouts
Cabbage
Cauliflower
Cantaloupes
Cucumbers
0.2
As needed
1.2
only)
0.2
0.3 7 1.5 0.25
1 1
0.3
0.1
0.2
0.2
0.2
As needed
As needed
7
As needed
As needed
0.2 5
0.2
0.2
0.2
As needed
7
As needed
1.5
0.4
1.2
0.8
0.8
1
0.8
1.6
1.6
0.3
0.1
0.2
0.2
0.1
0.2
0.1
0.2
0.2
10
10
10
7
7
5
5
5
5
7
7
0.6
0.75
0.9
0.4
0.8
0.8
0.4
0.4 (0.8 in
HI)
0.4 (0.6 in
HI)
0.8 (1.2 in
HI)
1.2
-------
Pumpkins
Squash (summer,
winter)
Watermelon
Eggplant
Peppers, bell
Tomatoes
Celery
Lettuce
Spinach
Collards
Greens, Turnip
0.2
0.2
0.2
0.21
0.2
0.2
0.2
0.2
0.2
0.2
0.2
As needed
As needed
As needed
3
As needed
5
As needed
3
As needed
As needed
As needed
1.6
1.6
1.6
2
1.6
1.2
2
2
2
0.8 (0.4 in
SC, GA, FL,
WA)
0.8 (0.4 in
0.2
0.2
0.2
0.15
0.2
0.2
0.2
0.2
0.2
0.15
0.15
SC, GA, FL,
7
7
7
7
5
7
7
7
3
3
3
1.2
1.2
1.2
0.6 (1.0 in
HI)
0.8
0.6 (0.8 in
HI)
1.0 (1.2 in
HI)
0.8 (1.2 in
HI)
0.6
0.45
0.45
-------
Corn, Field
Sweet Corn
Garlic
Onions
Horseradish
Papaya
Potatoes
Soybeans
0.2
6
0.25 3
1
0.3
0.3
0.21
0.4
0.2
As needed
As needed
As needed
7
As needed
WA)
0.6
0.15
1.2 0.2
1
2
2
0.6
1.2
1.6
0.2
0.3
0.15
0.15
0.2
0.2 As needed 0.4 0.2
7
3
10
7
10
10
10
10
0.45
0.8
0.8
1.0
0.45
0.75
0.8
0.4
------- |