A methodology to assess the risk of an existing pesticide and potential future pesticides in regulatory decision-making

When a pesticide is banned, in an effort to reduce pesticide-related risk to the public, substitute pesticide(s) with different risks would likely replace the risk from the banned pesticide. This paper provides a framework that may be used as a regulatory decision support tool in studying the effect of banning a pesticide at the national level. A risk analysis of the prevailing pesticide and the potential substitute pesticide(s) must be separately performed and compared before a decision to ban the pesticide is adopted. In this study, an ordinal logistic regression model is developed using 21 pesticides and 99 watersheds to relate pesticide distribution in surface waters with chemical property, watershed property, and pesticide use. The model is used to predict substitute pesticide residue distributions in streams for evaluating intermediate drinking water risks before and after potential ban of atrazine. About 80% of atrazine will likely be replaced by 2,4-D, bromoxynil, dicamba, and nicosulfuron. We found that banning atrazine will increase the risk from these substitute pesticides, but the cumulative risk from atrazine and the substitutes actually decreased slightly after the ban. Atrazine is a potential carcinogenic pesticide and the prospect that its substitues are non-carcinogenic and pose less threat to the public warrants further attention. This study provides a scientific framework for decision-making and policy implementation related to banning a pesticide of concern