Agricultural pesticide use in estuarine drainage areas: a preliminary summary for selected pesticides

This report summarizes the agricultural application of a group of 28 commonly applied pesticides in the 78 estuarine drainage areas (EDAs) contained in the National Oceanic and Atmospheric Administrations (NOAA) National Estuarine Inventory (NEI). The estimates of pesticide use are taken from a data base developed as part of a joint NOAA/Environmental Protection Agency (EPA) project to assess pesticide use, runoff, and potential impact in the Nation's estuaries. The pesticide use estimates are circa 1982 and are based on county use estimates taken from the National Pesticide Use Inventory compiled by Resources for the Future (RFF). EPA's Office of Marine and Estuarine Protection provided support for the development of the data base. The primary purpose of this project is to identify estuaries most at risk due to agricultural pesticide use. Two experimental approaches are taken in this report to assess the potential impact of these pesticides. The first accounts for the varying toxicity of the 28 pesticides to estuarine organisms. The second approach develops quantitative measure that can be used to compare and rank estuarine systems with respect to the amount of pesticides applied per unit area of cropland. An analysis of the relative toxicities of the pesticides to aquatic organisms and additional supporting information (for example, a discussion of each pesticide's half-life in the environment, bioconcentration potential, mode of action, and EPA regulatory status) is also included to provide a more complete picture of the use and potential impact of these pesticides. Because the use estimates are based on typical application rates and assumptions about the percent of crop receiving treatment, estimates for specific pesticide/crop combinations for a particular area may be an over-or underestimate. However, taken over an entire estuarine drainage area the estimates portray the differences in general patterns of use among estuarine systems and coastal regions.