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.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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



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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

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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


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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


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