Some flea control products can have environmental effects, traces of pesticides in San Francisco Bay

SAN FRANCISCO (KGO) – Some popular flea control products can be responsible for dragging traces of pesticides into San Francisco Bay. The amounts are very low, according to a new study, but experts say the bay’s ecosystem may be at risk.

Americans spend more than a billion dollars annually keeping fleas and ticks away from their pets. Many pet owners use spot-on topical treatments that require just a few drops on the pet’s neck to kill fleas and ticks for a month. But some of these products contain a pesticide called fipronil, and that shows up where it shouldn’t be, in the sediment at the bottom of San Francisco Bay.

Rebecca Sutton is part of a regional program with the San Francisco Estuary Institute that monitors the bay’s water quality. Sutton and other scientists fear that fipronil could be harmful to tiny creatures on the bottom of the bay. According to Sutton, “this is the basis of our food web. So if these creatures have an impact, it could go off and harm our fish and wildlife.”

Sutton’s team believes fipronil got into the bay through the use of pesticides outdoors. They used sales data from Fipronil products to identify a potential source.

Jennifer Teerlink of the California Department of Pesticide Regulation says the concentration of fipronil used in flea treatments “is high enough … compared to many other products that go down the drain” to be worth further research.

Spot-on flea control products use the natural oil on your pet’s skin to help spread the pesticide around their body. Photos from a UC Riverside study show how fipronil spreads after use.

According to Sutton, “These chemicals get into our hands when we pet our pets, put on our clothes and bedding. So when we wash our hands or wash our clothes, it all goes down the drain.”

Sutton’s team tested wastewater flowing in and out of eight sewage treatment plants around the bay and found fipronil in all of them. She says, “The treatment did not remove significant amounts of these pesticides, even in our most modern facilities.”

Researchers say the pesticide is flowing into the bay.

The amount of fipronil found in wastewater is tiny, roughly the equivalent of a drug tablet in an Olympic swimming pool. But even at this level, it is above the Environmental Protection Agency guidelines for freshwater streams and creeks. There are no guidelines for salt water.

Another new study focused on washing dogs treated with fipronil. Researchers from the California Department of Pesticide Regulation washed 34 dogs for up to 28 days after flea treatment. Then they tested the water to see how much pesticide drained off.

Teerlink says all water samples contained fibronil, and the study concluded, “Pesticides wash off the animals during routine bathing in concentrations high enough to be significant for overall wastewater pollution.”

The researchers say more studies are needed on fipronil and other flea and tick pesticides that may end up in the bay. They will do more testing this summer.

One way to potentially reduce pesticides on your pet’s fur is to use oral flea treatments, which are now available for dogs and cats, but you need to go to a veterinarian to get them. Experts say frequent vacuuming and washing of pet litter can often eliminate the need for flea pesticides.

For more information on research from the San Francisco Estuary Institute, click here.

Not all topical flea treatments contain fipronil, but many popular products do. One of the leading manufacturers is Frontline. The parent company sent this statement: Fipronil is an active ingredient that is used around the world in a wide variety of formulations for many different uses, including pesticides to protect crops and turf, and pet products. There are more than 130 registered Fipronil products in the state of California. Fipronil is used very differently for topical pet products than it is used for agricultural pesticides, including different formulations and methods of administration.

When evaluating the treatment and control of fleas and ticks, for example in dogs and cats, topical products containing fipronil are subjected to a rigorous evaluation of safety, effectiveness and quality; and regulators around the world review and approve its use.

The cited studies do not identify any direct causal relationship with pets as a source of contamination. And as the studies show, more research is needed to better understand this situation.

We remain committed to addressing issues that threaten animals’ ability to live healthier and happier lives, including the sustainability of the environment in which they live.

Courtesy photo: Melinda Bigelow Dyk, Yu Liu, Zhenshan Chen, Helen Vega & Robert I. Krieger (2012)
The fate and distribution of fipronil in pets and in their interiors
After spot-on flea treatments
Journal of Environmental Sciences and Health, Part B:
Pesticides, Food Spills, and Agricultural Waste, 47:10, 913-924.
Reprinted with permission from Taylor & Francis, LLC (
Click here to read the article.

Written and produced by Jennifer Olney

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