(Beyond Pesticides, December 13, 2011) Despite opposition from Lake Tahoe water providers and environmental groups, the Lahontan Regional Water Quality Control Board (LRWQCB) voted last week to allow the use of pesticides to control invasive species like Asian clams and the underwater plants Eurasian watermilfoil and curly leaf pondweed. For years, the rules regulating pesticide use in Lake Tahoe limited their use to below detectable levels, creating a “de facto prohibition,” explains Mary Fiore-Wagner, an environmental scientist with the LRWQCB. The decision to allow the use of pesticides in the lake now rests in the hands of California State Water Resources Control Board.
Carl Young, interim executive director of the League to Save Lake Tahoe/Keep Tahoe Blue, told the Associated Press that the plan poses a threat to the lake’s water quality and the public’s health, and he’s concerned visitors and residents could be exposed to pesticides through Tahoe’s fish and drinking water. The League is urging regulators to use non-chemical methods, including bottom barriers that involve the use of large mats to starve the species of sunlight and oxygen. The aquatic plants can be managed through mechanical harvesting.
The U.S. Army Corps of Engineers estimates economic impacts from introductions of new aquatic invasive species at $417.5 million over 50 years. It cites property values and lost tourism spending as the largest impacts. Asian clams were brought to the U.S. in the 1920’s for food and have become a nuisance in Lake Tahoe. Because of their nutrient-rich waste, they are blamed for contributing to cloudiness in of the lake’s famously clear water. The nonnative plant species, Eurasian watermilfoil and curly leaf pondweed, are considered a problem because they could clog intakes for the region’s water supply system. Despite these concerns, the head of the local water supply association still opposes the use of pesticides.
Greg Reed, Board Chairman of Tahoe Water Suppliers Associations, told the Tahoe Daily Tribune that he is “very concerned” about the impacts aquatic pesticides could have on drinking water at Lake Tahoe. He told the newspaper that he was “appreciated of water board staff’s efforts to diminish any effects of pesticide use on water quality,” but said, “The possibility of contaminated water is a frightening one.” Many water providers draw drinking water directly from the lake and would be unable to filter out any pesticides that reach their intake pipes, Mr. Reed added. The Tahoe Water Suppliers Associations unsuccessfully lobbied the LRWQCB to impose a five-year moratorium on any chemical use on projects at Lake Tahoe, giving more time to study potential adverse impacts.
Pesticides that are likely to be used to control these species include copper sulfate (Asian clams) and glyphosate (Eurasian watermilfoil and curly leaf pondweed). Copper sulfate is an irritant and is linked to adverse reproductive effects and organ damage. Glyphosate, the active ingredient in RoundUp and its aquatic counterpart Rodeo, is linked to non-Hodgkin’s lymphoma, neurotoxicity, adverse reproductive effects, and organ damage. As expected, both copper and glyphosate have been shown in the scientific literature to have adverse impacts on aquatic ecosystems.
“I think honestly this is coming down to human health issues,” Carl Young told the Associated Press. “They can say all they want that [pesticides] won’t harm people, but it’s poison and it can kill things.”
Take Action: Before pesticides can be used in Lake Tahoe, the California State Water Resources Control Board and then the Environmental Protection Agency must weigh in. Beyond Pesticides will update this story when the public comment period opens in California.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.