Tiered aquatic risk refinement: Case study—at‐plant applications of granular chlorpyrifos to corn

Abstract

AbstractThe tools of risk assessment are important in the management of environmental risk from the use of agricultural chemicals. A tiered process of estimating and refining the risks from runoff to nontarget aquatic ecosystem is described. The methodology uses screening tools at the lower level of assessment and progresses to a probabilistic, geographically specific tool at the highest tier level. The tools are demonstrated by an analysis of the risks to aquatic ecosystems resulting from the use of granular chlorpyrifos on corn. Vegetative filter strips and reduced tillage were examined as potential best management practices to reduce runoff impact. In addition, data from outdoor microcosm experiments were used to refine toxicity endpoints. The combination of runoff reduction and endpoint refinement resulted in a two‐ to 16‐fold reduction in potential risk, based on 90th percentile endpoints. The results also located where more localized efforts in product stewardship, user education, potential field research, or more refined assessment may be beneficial. The simulation results are compared to field monitoring results.