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Urban Insecticide Use Linked to Decline of Delta Ecosystem

(Beyond Pesticides, July 17, 2009) High levels of pyrethroid pesticides in the Sacramento-San Joaquin River Delta, the number one river system on America’s Most Endangered Rivers List of 2009, has been linked to heavy urbanization in the region. Leading a study to understand the collapse of the delta’s ecosystem, University of California-Berkeley toxicologist Donald Weston, Ph.D. found that these pesticides most likely reached the river from urban storm drains, collecting household pesticide disposal and runoff from lawns of 1.4 million residents in the Sacramento region.

Five years ago, a study by Dr. Weston and his colleague Michael J. Lydy, Ph.D of Southern Illinois University in Carbondale found that synthetic phyrethroids were collecting in river and creek sediments at levels that are toxic to bottom dwelling fish. Current research holds that there are enough pyrethroids to kill tiny shrimp, which are said to be the first link in the aquatic food chain.

Pyrethroids are synthetic versions of pyrethrin, a natural insecticide found in certain species of chrysanthemum. It initially came on the market as a ‘safer’ alternative to the heavily regulated and highly toxic organophosphates, such as diazinon and chlorypyrifos. Despite the fact that there are plenty of effective pest control methods that are not nearly as toxic, it is now one of the most popular class of household pesticides, making appearances in the form of powders and sprays to control mosquitoes, fleas, flies, and cockroaches. This high-volume use of pyrethroid pesticides is cause for concern to consumers as it has been linked to serious chronic health problems. They are classified as possible human carcinogens and suspected endocrine disruptors, and have been found lingering in the dust at daycare centers. Pyrethroids, however, are particularly dangerous to aquatic life even at the same concentrations used to fend off mosquitoes.

Common pyrethroid-based pesticides include: Bifenthrin, Cyfluthrin, Cypermenthrin, Deltamethrin, Fenvalerate, Permethrin, Resmethrin, Sumithrin, and Tetramethrin.

Unlike pyrethrins, synthetic pyrethroids are designed to last longer in the sunlight, and can remain toxic in soil for months, where they can easily make their way into the watershed through storm drains. Contamination may also be caused by the dumping of unused pesticides down sink drains, as Dr. Weston’s study shows that Sacramento’s regional wastewater treatment plant is the single largest source of pyrethroid pollution in the Delta.

Dr. Weston’s study was presented to the Central Valley Regional Water Quality Control Board in Rancho Cordova. The board plans to list much of the area’s waterways as “impaired” due to the high levels of pyrethroid pesticides. This, hopefully, could bring about new usage rules and a ban on some products that contain pyrethroids. For more information on less toxic alternatives to pyrethroids, refer to our factsheets on the web.

Source: The Sacramento Bee


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