Flea Poisons: The Danger to Humans

EPA Believes Risks Are Acceptable; Others Aren’t so Sure

By Jillian Olsen | December 16, 2008

A few drops of a pyrethroid-based flea and tick treatment can knock out pests for a whole month — this is potent stuff. So what happens when your child hugs a dog recently treated with Sergeant’s Gold? Or when you pet a cat’s head after applying Hartz UltraGuard Plus drops? What are the risks?

Acceptable, says the Environmental Protection Agency (EPA). But not everyone agrees. “This is really an example of how public human health is not being protected in our current system of pesticide review,” asserted Miriam Rotkin-Ellman, a scientist with the Natural Resources Defense Council (NRDC).

The NRDC published a list this year of chemicals commonly found in flea and tick treatments, ranked according to how safe they are for humans. Permethrin, an active ingredient in products like K9 Advantix and Bio Spot Spot On Flea and Tick Control for Dogs, is classified under the most toxic category by NRDC because the EPA says it is “likely to be carcinogenic to humans” if ingested orally.

The labels on these products warn consumers of the risks they’re accepting. “Harmful if swallowed or absorbed through skin,” reads the label on Sergeant’s Gold Flea and Tick Squeeze-On for Dogs. The label on Bio Spot instructs users to “Avoid contact with skin or clothing. Wash thoroughly with soap and water after handling.”

Children come into close contact with pets, making powerful flea and tick treatments potentially hazardous. Credit: Rich Parsons.

The EPA, which regulates these spot on pet products, has previously expressed concern over the potential risks they may pose to people. In particular, tests revealed a possible danger to toddlers who play with treated pets. An EPA assessment of Sergeant’s cyphenothrin spot on products in 2006 concluded that “toddler exposure from dermal (hug) and hand-to-mouth activities to treated companion animals continues to be of concern.” Similar testing of Hartz’s d-phenothrin products in May 2008 found the same risk.

But both these assessments were revised shortly after the original conclusions, EPA representatives said. The original cyphenothrin tests had overestimated the amount of product commonly applied to the pet, and when calculations were done for a smaller dose, the margin of safety was acceptable, explained Marion Johnson, branch chief of the EPA’s Office of Pesticide Programs registration division. A more refined test of the d-phenothrin products likewise “resolved the risk for toddler hand-to-mouth exposure,” EPA officials said via e-mail.

But the NRDC isn’t comforted. “It’s definitely very alarming to us,” Rotkin-Ellman said. “The more we look into these products, the more we find examples of how the risk assessments fall short of protecting human health.”