FOR IMMEDIATE RELEASE
July 1, 2004

CONTACT: Jim Tobin
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Tadpoles Exposed to Pesticide Atrazine Fare Worse at Lower Concentrations than Higher
Study in Environmental Health Perspectives Finds Counterintuitive Patterns in Rates of Survival

[RESEARCH TRIANGLE PARK, NC] Tadpoles exposed to atrazine, the most commonly used pesticide in the United States, were more likely to die after 30 days' exposure to lower concentrations than after exposure for the same time period to higher concentrations, according to a study published today in the July issue of the peer-reviewed journal Environmental Health Perspectives (EHP). The study on four species of frogs found counterintuitive patterns in rates of survivorship—with the exception of two types of more mature tadpoles, survival was significantly lower for all animals exposed to 3 parts per billion (ppb) than for those exposed to either 30 or 100 ppb.

The U.S. Environmental Protection Agency (EPA) set a safe drinking water standard of 3 ppb for atrazine. In October 2003, the EPA reapproved atrazine for use in the United States after an environmental review. Most earlier studies on the pesticide evaluated the shorter-term impact of contaminants at relatively high concentrations. This study evaluated lower-level concentrations for an extended period of time.

The researchers exposed tadpoles of four species of frogs -- spring peepers, American toads, green frogs, and wood frogs -- at early and late developmental stages to commercial preparations of atrazine. Importantly, some survival patterns only became apparent after more than three weeks of exposure. "Given the pattern of significantly reduced survival at low concentrations, the results of our study suggest that low-level testing is imperative when considering contaminant exposure of amphibians. Not only are these results contrary to traditional thinking, but they also occur at ecologically relevant levels," the study authors write.

"Given that atrazine is typically applied in the spring, when these animals are also in their larval stages, the experiment may well reflect a likely real world scenario," said Dr. Jim Burkhart, science editor for EHP. "This is the first study to find these sorts of surprising mortality patterns for atrazine. It is not, however, the first study to find surprising results occurring at low levels of exposure to a chemical, which reflects the complexity of this sort of research."

The study authors are Sara I. Storrs and Joseph M. Kiesecker of the Department of Biology at Pennsylvania State University. The article is available for free at http://ehp.niehs.nih.gov/docs/2004/6821/abstract.html.

EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP became an Open Access journal in January 2004. More information is available online at http://www.ehponline.org/.

Editor's note: Working media can register to receive press releases via e-mail by visiting http://www.ehponline.org/press/, calling 919-653-2582, or e-mailing ehpmedia@brogan.com.