Groundwater vulnerability to pesticides varies geographically, depending on soil characteristics, pesticide application rates, and the persistence and toxicity of the pesticides used. Areas such as central Nebraska, with sandy, highly leachable soils and high application rates of toxic or persistent pesticides, generally have high vulnerability ratings. ERS Farm Resource Regions appearing to be most vulnerable include the Mississippi Portal, Eastern Uplands, and Southern Seaboard regions. Commonly found agricultural pesticides in surface and ground water include atrazine, metolachlor, and alachlor. The possibility of pathogens contaminating water supplies is attracting increased attention.
Bacteria are the largest source of impairment in estuaries , and the second leading cause in rivers.
Potential sources include inadequately treated human waste, wildlife, and animal feeding operations. Animal waste contains pathogens that pose a threat to human health. Several diseases from micro-organisms in livestock waste can be contracted through direct contact with contaminated water, consumption of contaminated drinking water, or consumption of contaminated shellfish. Bacterial, rickettsial, viral, fungal, and parasitic diseases are potentially transmissible from livestock to humans. Fortunately, proper animal management practices and water treatment minimize the risk most of these pathogens pose to human health.