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Pyrethroids Ubiquitous in California’s Urban Streams

(Beyond Pesticides, October 17, 2008) A study published in the September 15 issue of Environmental Science & Technology has found pyrethroid contamination in 100 percent of urban streams sampled. Synthetic Pyrethroids are one of the most widely used consumer pesticides, but recently they have been scrutinized for their resultant health and environmental effects. California is currently reevaluating certain pyrethroid-containing pesticides as a result of increasingly conclusive research.

Entitled “Statewide Investigation of the Role of Pyrethroid Pesticides in Sediment Toxicity in California’s Urban Waterways,” the research included California’s most urbanized regions, as well as the less developed North Coast and Lake Tahoe areas. Thirty creeks in eight regions were selected from 90 screened sites, and bioassays were conducted at two temperatures, 23 and 15 degrees Celsius. Researchers found 25 samples to be toxic at the higher temperature and all 30 at the lower, which is where pyrethroids are more toxic. “Bifenthrin was the pyrethroid of greatest toxicological concern, occurring in all 30 samples,” wrote the team, and the Los Angeles, Central Valley, and San Diego regions showed the most severe contamination. The sampling included analysis for 8 pyrethroids, 30 organochlorine pesticides, and piperonyl butoxide, which helps to make pyrethroids toxic at lower levels.

“It was really good that they did the temperature study,” said Kathryn Kuivila of the U.S. Geological Survey (USGS). The analysis confirmed that pyrethroids were the substance toxic to Hyalella azteca, the small shrimp used in the study. Kuivila and other researchers from USGS will present similar data from seven cities around the United States at a November meeting of the Society of Environmental Toxicology and Chemistry.

A similar study found pyrethroid toxicity in sediments in urban Texas streams. Co-author Jason Belden, Ph.D. said conditions between Texas and California are “different enough to indicate problems [with pyrethroids] across the country.”

Toxicologist Michael J. Lydy, Ph.D., said results like these could occur “any time you find a manicured yard, across the U.S.” This is just one of many reasons to convert public and private lawns and landscapes to organic management, which eliminates synthetic pesticides like pyrethroids. Visit our Lawns and Landscapes program page or our Alternatives fact sheets for tips on organic, Integrated Pest Management, and policy information.

Source: Environmental Science & Technology


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