The U.S. Environmental Protection Agency stands at the center of a storm over the re-registration of atrazine, one of the most widely used herbicides in the world. Atrazine is being reviewed as part of EPA’s ongoing program to evaluate older pesticides to ensure that they meet current health and environmental safety standards; the agency’s review entails a comprehensive reassessment of existing restrictions on the use of the herbicide. Recent scientific reports have suggested that atrazine disrupts the hormonal systems of certain amphibians, and may be linked to worldwide population declines among these species. These studies have been challenged by other scientists, however, who claim that the evidence of such effects is inconclusive.

The scientific controversy over atrazine highlights the importance of emerging scientific understanding—and uncertainty—about the effects of so-called “endocrine disrupting” chemicals. Under the best of circumstances, these chemical effects are vexingly complex, and the causal links behind them are poorly understood. The EPA’s decision on atrazine is an important one, signaling the agency’s approach to regulation and policymaking in this arena; it could mark a further divergence between U.S. policies and those of European countries. The European Union decided in October 2003 not to allow re - registration of atrazine and a sister product, simazine.

Regulatory decisions about atrazine in the U.S. and other countries will have significant strategic implications for agrochemical companies. Syngenta has the greatest exposure to such decisions, since many of its products, including its fastest growing herbicide product, LUMAX, combine atrazine with other active ingredients. Monsanto, Bayer, Dupont, and Dow also market, to varying degrees, products containing atrazine. Further restriction of atrazine would bring even greater market dominance to glyphosate herbicides such as Monsanto's Round Up, but at the cost of losing one of the most effective chemical tools for managing the evolution of resistance to glyphosate.