The Impact of Flea & Tick Products on Our Waterways

*image context at bottom of page

Flea treatment products have been found in wastewater, sometimes at concentrations that are toxic to sensitive aquatic species. Recent studies have found that these products make their way from indoor drains in homes and pet clinics to the wastewater collection system. They ultimately end up in creeks, rivers, lakes, estuaries, and the San Francisco Bay because wastewater treatment plants are not capable of fully removing these toxic chemicals. Fipronil and imidacloprid – chemicals commonly found in flea and tick spot treatments – have been found in urban runoff and undiluted wastewater effluent at concentrations above toxicity thresholds for sensitive aquatic species.


So how do flea and tick products reach the Bay? Harmful pesticides from these treatments can end up in our local waterways when you do the following.


  • Bathe a pet which has been treated with topical tick and flea products: Contrary to manufacturer labels, spot-on products do wash off during bathing. These pesticides wash off your pet and are discharged directly into our wastewater system.
  • Wash items that come into contact with a treated pet: Scientific studies indicate that chemicals from indoor flea control (including spot-ons, collars, sprays, and foggers) can wipe off on your hands, clothing, and furniture and travel throughout your home – as shown in the image above. 
  • Apply outdoor flea and tick sprays: Chemicals from outdoor flea and tick sprays get washed away by storm runoff into our storm drains. This chemical-laced water then flows directly into local waterways without ever passing through a water treatment facility.


*The photos above are part of a study where researchers incorporated a fluorescent dye into the spot treatment to photograph the spread. Photographs are reprinted from Bigelow Dyk, M., et al. (2012). Fate and distribution of fipronil on companion animals and in their indoor residences following spot-on flea treatments, Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes, 47(10): 913-924. Reprinted by permission Taylor & Francis LLC.