Evaluating agricultural pesticide use and risk for the Chesapeake Bay

Although agricultural pesticide use is suspected of being a major contributor to the risk of toxic contamination of the Chesapeake Bay, little information concerning the nature and extent of that risk is available. Such information is essential, however, for setting pesticide risk management priorities and for designing policies to reduce the risk of toxic pollution from agricultural sources.

To help meet the information needs of Bay region water quality Management, a model of agricultural pesticide risk is developed and used to assess pesticide risk in Virginia’s Chesapeake Bay Region. The information generated by the model includes: an inventory of which chemicals are used; where they are used; estimates of aggregate chemical use for counties and crops; and an evaluation of the potential adverse environmental effects of that use. This information is provided for both current (1990) and future (2000) pesticide risk.

An econometric model of land use in the Bay region is used to predict acreage in various crops to which pesticides will be applied in 1990 and 2000. Next, acreage estimates are combined with pesticide application rates to yield estimates of aggregate use of each pesticide. Finally, environmentally relevant characteristics of the pesticides (toxicity, persistence, mobility, etc.) are used to evaluate the potential environmental risk associated with that use.

The policy implications of this modeling are then explored. Particular attention is paid to the potential for targeting of pesticide risk management programs at chemicals, sub-regions, or production systems (i.e. crops) that represent the greatest risk of toxic contamination of the Chesapeake Bay.

Results indicate that while urbanization in the Chesapeake Bay region will reduce the amount of land devoted to crop production, the reduction in the acreage to which pesticides may be applied will not greatly reduce pesticide risk in the near future. The risk evaluation effort reveals that pesticide risk is highly concentrated in small subsets of the crops grown in the Bay region, of the pesticides used on those crops, and of the counties located in the region.