The impact of pesticide use on groundwater in North Carolina

A North Carolina study revealed that certain pesticides have impacted groundwater above health-based standards in vulnerable areas. Ninety-seven shallow, surficial aquifer-monitoring wells were sampled at least twice. Sites for the monitoring wells were chosen based on an evaluation with the Pesticide DRASTIC model and a known record of pesticide use. Where possible, areas of greater risk were intentionally selected. Twenty-three pesticides or pesticide degradates were detected in 26 of the 97 wells. Nine of the pesticides or degradates are no longer registered for use; two of these chemicals, dibromochloropropane and methylene chloride, were found in excess of health-based guidance levels (HBGL) or state groundwater quality standards (GWQS). Of the registered pesticides or their degradates, the herbicides dichlorprop and simazine and the insecticide isomers BHC-alpha and BHC-delta were in excess of HBGL. The herbicide atrazine was detected at 83% of its GWQS. The U.S. Environmental Protection Agency (USEPA) Pesticides and Groundwater State Management Plans will be required for atrazine and simazine to be sold and used, which will provide additional protection to public health and the environment. Pesticide DRASTIC ratings or soil-leaching potential values and the proportion of wells were unrelated to pesticide detections