Smarter Living: Chemical Index
Flea and Tick Pesticide
The insecticide propoxur, used in pet flea and tick collars, is a known human carcinogen and is toxic to the nervous system.
Propoxur interferes with an essential enzyme, acetylcholinesterase, which normally controls messaging between nerve cells. It kills fleas and ticks by inducing spasmodic overexcitation of the nervous system. In large doses, it can harm or kill cats, dogs and, in extreme poisoning cases, humans. At lower levels of exposure, propoxur can cause a variety of symptoms, many of which can mimic common illnesses; these include nausea, vomiting, diarrhea, wheezing, sweating and tearing eyes. More severe poisoning can cause muscle twitching, drooling, seizures, respiratory paralysis and death.
Young children are also particularly vulnerable to TCVP and other pesticides because their bodies and brains are still developing, and chemicals that interfere with the nervous system during development may cause long-term or permanent damage. Some recent research indicates that exposure to this type of pesticide can impair children's neurological development, resulting in pervasive disorders that may include delays in motor development and attention deficit/ hyperactivity disorder.
Where it is Found
Propoxur is used in pet flea and tick collars. Flea and tick collars can leave a high level of pesticide residue on a pet's fur, posing a health risk to adults and children who play with the pet. Children are especially vulnerable, as they may be more likely to spend extended time in close contact with pets, or put their hands in their mouths after petting an animal.
Give your pet regular baths with a pesticide-free pet shampoo, and use a flea comb between baths.
Launder your pet's bedding in hot water, and vacuum carpets regularly to eliminate flea eggs that could be hidden there.
If you do need to use a chemical flea-control product, choose the safest options as suggested in our GreenPaws Product Directory. Those generally dispensed as a pill usually contain the least toxic chemicals, and they don't leave a residue on your pet or in your home.
Check the label. Avoid flea collars that list propoxur, tetrachlorvinphos, amitraz or carbaryl (recently cancelled for use in flea collars) as active ingredients. Instead, opt for products whose labels list lufenuron, spinosad, methoprene, or pyriproxyfen. These are common and effective insect growth regulators.
Americans spend more than $1 billion each year on flea- and tick-control products for their pets. Over the years, NRDC has helped remove six of the most toxic chemicals from these products, but two of them—tetrachlorvinphos and propoxur—are still in use. The Environmental Protection Agency (EPA) should step in to ban these dangerous products nationwide. Retailers should help keep pets and families safe by pulling products that contain these dangerous substances from their shelves. You can help by going to GreenPaws.org to tell stores to protect our kids from dangerous products.
Rauh, V.A., Garfinkel, R., Perera, F.P., et al. "Impact of Prenatal Chlorpyrifos Exposure on Neurodevelopment in the First 3 Years of Life Among Inner-City Children." Pediatrics, December 2006 (Vol. 118, No. 6), pp 1845–1859.
Robin M. Whyatt, et al. "Prenatal Insecticide Exposures and Birth Weight and Length among an Urban Minority Cohort." Environmental Health Perspectives. July 2004. (Vol 112, No. 10) pp 1125-1132)
U.S. EPA. Reregistration Eligibility Decision: Propoxur. EPA 738-R-97-009. U.S. EPA (2006). Organophosphate Cumulative Risk Assessment
NRDC, Poison on Pets II (PDF), April 2009,
last revised 12/28/2011