WASHINGTON 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. The Washington Post obtained the documents from the Natural Resources News Service, a Washington, D.C.-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 its use. 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."
Atrazine 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.
The federal government first approved atrazine in the 1950s, but it came under increased scrutiny in the late 1990s after Tyrone B. Hayes, a professor of integrative biology at the University of California at Berkeley, did a series of studies first for chemical companies and then on his own that indicated that tiny amounts of the pesticide de-masculinized tadpoles of African clawed frogs. The European Union declared it a harmful "endocrine disrupter" and banned it as of 2005, but the EPA decided to allow its continued use after determining that the agency lacked a standard test for measuring the hormone-disrupting effects of chemicals.
Instead, EPA officials and company representatives agreed on a plan to monitor atrazine levels in "40 of the most vulnerable watersheds in the country," said Jim Jones, deputy assistant administrator for the EPA's Office of Prevention, Pesticides, and Toxic Substances.
Syngenta has collected more than 10,000 samples since 2004, Pastoor said, taking readings at least every four days at each site.
Jones said there are limits on what details of the Syngenta survey can be released to the public the company claims some of the data is proprietary information, and anyone who requests the information must pledge not to share it with competing pesticide companies but the monitoring system is protecting the public's health. "It obviously makes it more challenging for us, but we're operating under a statute," Jones said. "We're following the law."
Nancy Golden, a biologist and toxicologist at the U.S. Fish and Wildlife Service who studies how chemicals affect aquatic creatures, said fish exposed to as little as 0.5 parts per billion of atrazine in the lab demonstrate behavioral problems. At higher levels, they experience stunted growth. The levels of atrazine in 2004 in the two Missouri sites were more than 100 times the 0.5 parts per billion concentration, the Syngenta data show.
Golden said the data documented "atrazine levels that are sustained at pretty high levels for several weeks. That's definitely a cause for concern."
Peter deFur, a biologist at Virginia Commonwealth University, said "chronic low-level exposure" to atrazine can harm aquatic life. "I don't think low levels of atrazine exposures are safe," deFur said.
Charles Scott, field supervisor for the Fish and Wildlife Service's Missouri Ecological Services Field Office, said high levels of atrazine in northeastern Missouri could potentially affect several endangered and threatened species, including the pallid sturgeon, the Higgins' eye mussel, the fat pocketbook mussel and the decurrent false aster, a wetland plant. "It has a lot of biological impacts," Scott said of the pesticide.
The EPA has asked Syngenta to do additional monitoring at the two sites in northeastern Missouri where atrazine concentrations significantly exceeded 10 parts per billion, the level at which the agency believes it can have an impact on aquatic systems. In these two watersheds, concentrations reached more than 50 parts per billion for days at a time.
Wood, the EPA spokeswoman, said the Indiana watershed did not trigger the agency's level of concern in 2006 and the company will be monitoring it for another year.
Pastoor, who noted that atrazine's effect of stunting plant growth is reversed as soon as the pesticide is taken away, said the fact that two watersheds showed high levels of exposure "doesn't mean there's a problem there. It just means there's a yellow flag that says you should take a look."
The two sites in question, he added, were prone to excessive runoff because they have an impervious clay soil that channels runoff into waterways, the land is sloped, and one of the farmers working the land had cleared much of the vegetation. Syngenta sales agents and local corn growers are trying to reform the practices of the farmer in question.
"We anticipate that site will significantly improve," Pastoor said.
Hayes, who stopped working as a contractor for a coalition of chemical companies years ago and is now one of atrazine's most vocal opponents, said he does not think the federal government is surveying the pesticide enough in light of its pervasive influence.
"What's most disturbing about the information you're talking about is all that EPA requires Syngenta to do is monitor atrazine in a few key sites," Hayes said. "Industry's been allowed to have such a huge hand in the regulation of atrazine."