Pesticide appearing in watershed

Five years ago, the Environmental Protection Agency moved to phase out homeowner sales of diazinon, a popular lawn insecticide that posed human health risks and had shown up at elevated levels in Seattle-area streams.

As diazinon has disappeared from retail shelves, many Puget Sound homeowners have turned to carbaryl, a chemical that federal sampling now detects in the Seattle watershed of Thornton Creek.

Carbaryl, sold under the brand name Sevin, is toxic to aquatic bugs that are an important source of food for fish and birds, and its presence in the waterway was flagged this week in an analysis released by the Washington Toxics Coalition, which has been campaigning to reduce pesticide use in the Puget Sound region.

"We're just chasing our tails when people just move to another toxic pesticide," said Philip Dickey, a coalition scientist who co-authored the study.

Chemical-company officials say that carbaryl has been in widespread use for more than a half century, and proved to be a safe and effective chemical against a wide range of pests. Bayer CropScience, maker of Sevin, calls it "one of the most environmentally responsible pesticides you can use."

"We take stewardship of our products very seriously, and we believe that our carbaryl products pose no undue risk to homeowners, farm workers, wildlife or the environment," said Greg Coffey, a spokesman for Bayer CropScience.

As a water pollutant, carbaryl appeared to be of little concern through the late '90s, when diazinon — then the biggest-selling Seattle-area insecticide — was showing up in area streams. During that time, U.S. Geological Survey sampling of Thornton Creek rarely detected carbaryl.

But in 2002, the diazinon phase-out took hold, and sales of carbaryl soared more than tenfold at several retail chains tracked by King County officials. Also that year, carbaryl began to be detected more frequently in Thornton Creek.

National Academy of Science guidelines recommend that aquatic carbaryl levels not exceed 0.02 parts per billion. At Thornton Creek in 2002, four of the water samples tested by the U.S. Geological Survey detected carbaryl at levels ranging from 0.054 parts per billion to 0.48 parts per billion.

Since 2002, five other water samples tested for carbaryl at levels that exceeded the National Academy of Science's guidelines, according to preliminary data released by the U.S. Geological Survey.

Carbaryl's detection in Thornton Creek frustrates David Galvin, King County hazardous-waste program manger, who has been pitching gentler alternative lawn-care methods to area homeowners.

"I was disappointed to see this," he said. "I think the natural reaction for most homeowners is to reach for the next product on the shelf."

Carbaryl, like diazinon, is a neurotoxin that acts on an insect's nervous system. It is now under an extended federal safety review expected to be completed as early as 2006. In a preliminary move last year, the EPA curtailed the use of some carbaryl products used around homes, and noted "concern" about exposures as adults do yard work or children play on carbaryl-treated lawns.

The U.S. Fish and Wildlife Service, in a letter to the EPA earlier this year, said it was concerned about carbaryl's risks to threatened and endangered species, and noted "a growing body of literature" about the chronic effects of carbaryl on aquatic organisms.

Carbaryl is just one of several chemicals marketed for bug control in homes and gardens. In recent years, some manufacturers have heavily promoted other insecticides that contain pyrethroids, chemicals that also can be toxic to aquatic life.

Since 2002, King County officials have been unable to track Puget Sound pesticide-sales trends. That's because the company that once sold the information to the county no longer provides it, according to Galvin.

Hal Bernton: 206-464-2581 or hbernton@seattletimes.com