Yes.
Permethrin is a mosquito insecticide commonly sprayed in residential areas in Colorado and counties and can be toxic at high concentrations of pets.
The chemical is also found in some dog flea collars and is approved for use in low concentration products – usually diluted with water or oil to 1/100 pound of 1/100 pound. Fort Collins, Loveland, Longmont and Bloomfield are one of the field-wide communities contracted with a mosquito management company that regularly uses 30% permethrin mixtures, no more than 0.007 pounds per acre.
Exposure to permethrin can cause dogs and cats to behave strangely, pump their ears or roll on the ground.
Cats are particularly sensitive to chemicals. Exposure to concentrations above 45% may affect its nervous system and lead to death. The Fort Collins City website recommends bringing pets indoors in fog.
Cities and counties usually spray permethrin in July and August as West Nile virus levels rise.
See the full list of sources below.
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refer to:
Mosquito-controlled synthetic pyrethroids from the U.S. Environmental Protection Agency, visiting in July 2025. Source link
VDCI’s Colorado client, VDCI Mosquito Management, visited in July 2025. Source link
Products for managing mosquito population management, VDCI Mosquito Management, visited July 2025. Source link
Aqua-Perm X-UL 30-30, Specimen Tag, Visited July 2025. Source link
National Pesticide Information Center, General Information of Permethrin, Visited in July 2025. Source link
Toxicology of dipermethrin in cats, Australian Veterinary Journal, January 2008. Source link
West Nile Virus, Fort Collins City, visited in July 2025. Source link
West Nile Virus and Mosquito Control Frequently Asked Questions, Colorado State University Extension, Visited in July 2025. Source link
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Tyler has been reporting in Colorado's environmental, cultural and local governments for the past three years. Recently, he spent Boulder Weekly employee journalists and photographers, where he covered the rapidly growing Longmont city…more Tyler Hickman