High Weedkiller Levels Found in River Checks

Atrazine, the second most widely used weedkiller in the country, is showing up in some streams and rivers at levels high enough to potentially harm amphibians, fish and aquatic ecosystems, according to the findings of an extensive Environmental Protection Agency database that has not been made public.

The analysis -- conducted by the chemical's manufacturer, Syngenta Crop Protection -- suggests that atrazine has entered streams and rivers in the Midwest at a rate that could harm those ecosystems, several scientific experts said. In two Missouri watersheds, the level of atrazine spiked to reach a "level of concern" in both 2004 and 2005, according to the EPA, and an Indiana watershed exceeded the threshold in 2005.

Much of the data on atrazine levels has remained private because Syngenta's survey of 40 U.S. watersheds was done in connection with the EPA's 2006 decision to renew its approval of the pesticide. The Washington Post obtained the documents from the Natural Resources News Service, a District-based nonprofit group focused on environmental issues.

Atrazine has been linked to sexual abnormalities in frogs and fish in several scientific studies, but the EPA ruled in September that the evidence was not sufficiently compelling to restrict use of the pesticide. EPA spokeswoman Jennifer Wood said the agency "has concluded that atrazine does not adversely affect gonadal development in frogs, based on a thorough review of 19 laboratory and field studies, including studies submitted by [Syngenta] and others in the public literature."

The pesticide is popular among corn and sorghum farmers despite the controversy because it is inexpensive and blocks photosynthesis, thus killing plants to which it is applied.

"It works and it's inexpensive, and that's what farmers love," said Tim Pastoor, head of toxicology at Syngenta. "It's magic for them. It's like the aspirin of crop protection."

EPA officials and independent experts spent last week in meetings in Arlington, debating the "ecological significance" of atrazine water contamination, according to agency documents. The results of the deliberations -- the monitoring data was plugged into computer models to estimate the effects on ecosystems -- will be published in several weeks and will help determine how EPA officials regulate the pesticide in the future.

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