Description

Resmethrin is a synthetically produced pesticide in the pyrethroid family, used for control of flying and crawling insects in homes, greenhouses, indoor landscapes, mushroom houses, industrial sites, stored product insects and for mosquito control. It is also used for fabric protection, pet sprays and shampoos, and applied to horses or in horse stables.

Resmethrin is a synthetic derivative of naturally occurring pyrethrins, derived from pyrethrum, an extract from the flowers of chrysanthemum. It is not a natural or “organic” alternative to pesticides. Though it is considered to have very low toxicity to most people and pets, it can cause some health effects (see Possible Health Effects, below). Care should be taken to keep pregnant woman and infants from being exposed.

Resmethrin is often used in aerosol formulations. Resmethrin has been used in the U.S. East Coast fight against mosquitoes potentially carrying the West Nile Virus.

Health Effects

Immediate Health Effects

If SWALLOWED, resmethrin is Not Available
If ABSORBED THROUGH SKIN, resmethrin is Not Available
If INHALED (SNIFFED OR BREATHED IN), resmethrin is Not Available

Longterm or Delayed Health Effects

This chemical may cause cancer. It is considered a Possible Carcinogen by the World Health Organization, the U.S. Environmental Protection Agency, or another agency.
Allergen
Neurotoxin = Can harm brain and central nervous system
Asthma Trigger
Development Toxicant = Can interfere with normal development of a fetus or child

Other

Considered to have very low toxicity to most people, dogs, cats and other mammals, but may cause skin and eye irritation, such as itching, burning, in some people.
Neurological effects, including dizziness, incoordination, headache, twitching, loss of bladder control, seizures, numbness, tingling sensations. These symptoms are unlikely at the relatively low doses generally used.
Effects on the liver or thyroid have been noted in animal studies.
Respiratory effects and allergy symptoms, including stuffy or runny nose, scratchy throat, especially for individuals suffering from allergies.
Developmental toxicity: Resmethrin decreased the survival and weight of rat pups born to exposed female rats in animal studies and is listed by the State of California as known to cause developmental toxicity.

How Exposures Occur

During and Immediately After Spraying Outdoors

Resmethrin is used in residential neighborhoods for eliminating mosquitoes that may carry the West Nile Virus. Children may be exposed if they remain outdoors during application or if they touch anything outdoors immediately after spraying.

During or Immediately After Spraying Indoors

Children may inhale resmethrin when it is sprayed indoors, or they may touch and subsequently ingest resmethrin that has fallen on objects within the home. Resmethrin may also enter homes through open windows.

Pet Sprays or Shampoos

Children may be exposed to resmethrin if they play with pets immediately after the application of flea and tick shampoos and sprays.

Solutions

How to detect resmethrin

Read labels to determine if resmethrin is in products in your home or check PAN’s Pesticide Database for a list of brands and products containing this pesticide. If you hire a professional exterminator, ask for safety information,such as a Material Safety Data Sheet (MSDS), for the products used.
Resmethrin breaks down into a smelly byproduct, phenylacetic acid, which binds strongly to textiles and dissipates slowly, smelling of urine.

How to minimize exposure to resmethrin

Avoid Exposure: Ask your neighbors for notification when they spray permethrin and other pesticides outdoors. Bring in pets, laundry, toys, and other outdoor equipment.
-Cover outdoor tables and ornamental fish ponds.
-Remain inside while spraying takes place, close windows and doors and turn off your air conditioning (or set it to circulate indoor air) before spraying begins.
-Keep children inside at least one hour after spraying.
-Avoid direct contact with surfaces that are still wet from pesticide spraying.
Wash skin and clothing exposed to resmethrin with soap and water.
Avoid Spraying: If for any reason a person wishes their property to be excluded from mosquito spraying, contact your local Town Clerk, County Executive and your County Legislator for proper procedures. Resmethrin is a Restricted Use Pesticide and should only be applied by certified personnel.

Alternatives

Choose least-toxic pest control methods, such as Integrated Pest Management, for your home garden, lawn and shrubs. Prevent insects from entry into homes: Repair or install window and door screens; remove standing water outdoors (in roof gutters, old tires, buckets and wading pools) and repair leaky plumbing; seal trash containers.
Instead of using insect repellents containing resmethrin, wear protective clothing outdoors, with long sleeves and pant legs. Inspect for ticks after outdoor activities. In regions where Lyme disease and West Nile virus have been identified, use of an insect repellent may be necessary. Spray clothing rather than skin. Inspect for ticks when returning indoors.
Reduce mosquito breeding habitats by removing standing pools of water such as leaning roof gutters, old tires, buckets, and regularly changing the water in wading pools. Repair or install window and door screens to keep mosquitoes from getting into your home.
See How To Keep Mosquitos From Biting for more tips on preventing and avoiding mosquito bites.

For More information

Books, articles, factsheets and reports

Scourge and Mosquito Control Information Sheet. New York State Department of Health, Information for Consumers.

http://www.health.state.ny.us/nysdoh/pest/scourge.htm

For Your Information: Synthetic Pyrethroids for Mosquito Control. U.S. Environmental Protection Agency, Prevention Pesticides, and Toxic Substances, April 17, 2002.

http://www.epa.gov/pesticides/factsheets/pyrethroids4mosquitos.htm

Pesticides & Mosquito Control. U.S. Environmental Protection Agency, Office of Pesticide Programs, February 2001.

http://www.epa.gov/pesticides/factsheets/mosquitocontrol.htm

OVERKILL: Why Pesticide Spraying for West Nile Virus May Cause More Harm Than Good. Toxics Action Center and Maine Environmental Policy Institute, July 2001

http://www.meepi.org/wnv/mass.htm