Does the Honey Bee "Risk Cup" Runneth Over? Estimating Aggregate Exposures for Assessing Pesticide Risks to Honey Bees in Agroecosystems.

Honey bees (Apis mellifera) are uniquely vulnerable to nontarget pesticide impacts because, as ubiquitous managed pollinators, they are deliberately transported into areas where crops are grown with pesticides. Moreover, attributes making them excellent managed pollinators, including large long-lived colonies and complex behavior, also make them challenging subjects for toxicity bioassays. For over 150 years, improvements in formulation and delivery of pesticides, increasing their environmental and temporal presence, have had unintended consequences for honey bees. Since 1996, the Environmental Protection Agency has used "aggregate risk"--exposure risks to all possible sources--to set tolerances; once a "risk cup" is filled, no new pesticide or use can be approved unless risks are reduced elsewhere. The EPA now recommends a modeling approach for aggregating all exposure risks for bees, with differential lifestage sensitivity and exposure probabilities. Thus, the honey bee is the first insect with its own "risk cup"--a technological innovation that may not have unintended consequences for this beleaguered beneficial species.