Smarter Living: Chemical Index

Pyrethroid pesticides have the potential to harm the health of your family, pets, stream life, and beneficial insects.

What Are They?

Pyrethroids are a class of synthetic pesticides used widely in home insect-control products, including flea bombs, roach sprays, ant bait, flea-and-tick pet shampoos, and lice shampoos. The chemicals are also sprayed on crops. Although they are modeled after naturally occurring insecticides (pyrethrins) found in chrysanthemum flowers, pyrethroids are generally longer-lasting in the environment and are more toxic than their botanical cousins. Examples of pyrethroid pesticides include: cypermethrin, permethrin, deltamethrin, bifenthrin, and cyfluthrin.

Health Concerns

Pyrethroids are toxic to humans and dogs, and they can be particularly lethal to cats, bees, and fish and other water-dwelling creatures. In humans, the chemicals can harm the nervous system, and high amounts can cause headache, difficulty breathing, nausea, and vomiting. The Environmental Protection Agency (EPA) has found that one member of the pyrethroid class, permethrin, is "likely to be carcinogenic to humans."

The chemicals kill insects by blocking the transmission of messages in the nervous system. The human nervous system is less susceptible to these chemicals both because of our larger size and because humans and many other mammals have detox mechanisms to help rid the body of these chemicals. However, recent studies indicate that prenatal and infant exposure may lead to cognitive and developmental problems later on. Although dogs are able to detoxify these chemicals, cats are more susceptible and can suffer tremors, twitching, convulsions, and death if owners misuse pyrethroid-containing products.

Exposure

Using bug spray and other insecticidal products is the most common way that people come into contact with pyrethroids. The chemicals are found in roach, ant, and flying insect spray; flea bombs; roach traps and baits; pet tick-and-flea collars and shampoos; and lice and scabies shampoos for humans. People may breathe in the chemicals when spraying a product that kill flies or roaches or accidently ingest them after getting them on their hands or food. Young children are particularly at risk because they play on surfaces that may have been treated and frequently put their hands in their mouth. People can also absorb the chemicals through the skin while bathing a pet or from lice shampoos.

People also take in pyrethroids from eating conventionally grown fruits and vegetables. Children who regularly ate conventional produce were exposed continuously to pyrethroids in the diet punctuated by high exposures when pesticide products were used in the home, according to a 2009 study in the Journal of Exposure Science and Environmental Epidemiology.

Pyrethroids are also used for insect control in schools and restaurants, in mosquito-abatement programs, and on livestock.

Stay Safe

When it comes to pets, you can find less toxic treatments and chemical-free care at NRDC's GreenPaws Flea and Tick Products Directory. Use a flea comb to remove fleas and use pesticides as a last resort. With any pesticide, it’s important to read package labels, follow instructions, and use the least amount possible. Although cats are susceptible to pyrethroids, the chemicals are still used in cat treatments, so read labels before purchase.

Address roach and other pest,problems using integrated pest management (IPM) practices, which include promptly cleaning up food crumbs that attract insects, blocking entryways into your home, and using pesticides only when other methods have been exhausted. If you need professional help to safely eliminate household pests, refer to GreenShield and GreenPro for companies that use IPM methods.

One of the best ways to avoid pyrethroids in the diet is to eat organically grown produce.Levels of pesticides tend to be highest in the following types of produce: peaches, apples, nectarines, sweet bell peppers, celery, strawberries, cherries, pears, imported grapes, spinach, lettuce, and potatoes.

Remove lice with a nit comb rather than pesticide shampoos.

Sources

Read detailed information about the health effects of pyrethroids at the Agency for Toxic Substances and Disease Registry (ATSDR)'s Toxicological Profile for Pyrethrins and Pyrethroids.

Find out what chemicals are in your household insect-killers and other products at the U.S. Department of Health and Human Services’ Household Products Database.

Learn More

Read detailed information about the health effects of pyrethroids at the Agency for Toxic Substances and Disease Registry (ATSDR)'s Toxicological Profile for Pyrethrins and Pyrethroids.

Find out what chemicals are in your household insect-killers and other products at the U.S. Department of Health and Human Services’ Household Products Database.

last revised 12/27/2011

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