Presentations

Anthropogenic chemicals are widely used in agriculture to increase crop yields and prevent crop damage by pests. Chemicals of concern in groundwater include fertilizers (primarily nitrate) and pesticides (insecticides, herbicides, fungicides, nermaticides, rodenticides, etc). In 2000, U.S. farmers used approximately 12 million tons of nitrogen and applied more than 1.2 billion pounds of pesticides (active ingredient). There are more than 20,000 pesticide products registered for use in the U.S. Protecting groundwaters from contamination by agricultural chemicals has proven to be difficult. Nitrate contamination of shallow groundwater is a widespread problem in agricultural regions within the U.S.; in fact nitrate is the most widespread groundwater contaminant in the country. Nitrate (an inorganic ion) is not readily attenuated and is very mobile in groundwater. Pesticides are synthetic organic chemicals and are attenuated to some degree by degradation and sorption to soil. However some commonly used pesticides are highly toxic and known carcinogens. Fertilizer use is not regulated at the state or federal level. However the U.S. EPA, pursuant to the SDWA has established a maximum contaminant level of 10 mg/l for public drinking water supplies. A suite of best management practices (BMPs) have been developed to prevent or minimize leaching of fertilizers to the underlying water table and to streams. The effectiveness of these BMPs, with respect to the design and application/maintenance is not clear. The U.S. EPA is responsible for regulating the sale and use of pesticides. EPA?s authority is derived from the Federal Insecticide, Rodenticide, and Fungicide Act (FIFRA). Under FIFRA, EPA is responsible for registering or licensing pesticide products for use in the U.S. Registration decisions are based on assessments of affects on human health and the environment and require strict adherence to label direction. Pesticide use that is not in accordance with label directions is subject to civil and/or criminal penalties. FIFRA regulations are typically implemented through State Departments of Agriculture. Maximum contaminant levels have also been established for some pesticides. Many states have statutorily authorized classification systems for groundwater. Classification is typically based on existing and future potential uses and provides a basis for assigning groundwater standards. Agricultural use is a common classification and many states have promulgated agricultural use standards which may include standards for nitrogen and selected pesticides. Other approaches that have been utilized to minimize or mitigate groundwater contamination from agricultural chemicals include differential management, which, in the case of agricultural chemicals attempts to identify and map areas, soil types and hydrogeologic conditions which result in high vulnerability to contamination from agricultural practices. Based on recent data from around the U.S. it is clear that regulatory, voluntary and programmatic efforts to reduce nitrate contamination have not been as successful as intended. It is time for the agricultural community working with State and Federal government agencies to take a new look at current regulations and practices, assess the effectiveness and explore new approaches.