North Carolina

 This report summarizes the available pesticide data for surface waters in the Santee River Basin and coastal drainages (SANT) study area, as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Data from the U.S. Environmental Protection Agency Storage and Retrieval (STORET) database and data collected by the USGS in the SANT NAWQA study area were assessed. A description of the study area is followed by an estimate of pesticide application data. Detected pesticides and their reported maximum concentrations are summarized. Pesticide concentrations are compared with applicable water-quality standards. Seasonality of pesticide concentrations in surface water in the SANT NAWQA study area also is assessed.

Significant Findings

• Twenty-eight pesticides were detected at surface-water stations in the STORET database between 1973-93: 5 herbicides and 23 insecticides.

• Thirty-six pesticides were detected at the SANT NAWQA stations from February 1996 through January 1997: 25 herbicides and 11 insecticides.

• At the SANT NAWQA stations, the percentage of insecticides detected was greater at an urban site (31 percent) than at an agricultural site (15 percent).

• Water-quality criteria for protection of aquatic life and (or) human health were exceeded by 16 insecticides (carbaryl, chlordane, chlorpyrifos, o,p-DDT, p,p-DDT, diazinon, dieldrin, guthion, heptachlor epoxide, lindane, malathion, methoxychlor, mirex, parathion, pentachlorophenol, and toxaphene).

• Several pesticides detected at the SANT NAWQA stations showed seasonal variability in concentrations: atrazine, chlorpyrifos, deethylatrazine, metolachlor, prometon, simazine, and tebuthiuron

Are those concentrations harmful?

In general, most concentrations were below Federal water-quality criteria. However, 16 pesticides had concentrations that exceeded aquatic life or human health criteria (tables 1 and 2). At stations in the STORET database, maximum concentrations of chlordane, o,p-DDT, p,p-DDT, diazinon, dieldrin, guthion, heptachlor epoxide, lindane, methoxychlor, mirex, parathion, and toxaphene exceeded criteria to protect aquatic life. The maximum lindane concentration also exceeded the lifetime health advisory level (HAL) and maximum contaminant level (MCL). The maximum pentachlorophenol concentration exceeded the MCL. In the SANT NAWQA database, carbaryl, chlorpyrifos, diazinon, dieldrin, malathion, and parathion all exceeded the criteria to protect aquatic life.

At sustained high concentrations, these pesticides may be harmful to aquatic organisms. The HAL and MCL are standards for finished drinking water. Surface water provided 86 percent of the public water supply in the SANT study area in 1990 (Hughes, 1994). Although pesticide concentrations in streams may occasionally exceed these standards, water collected by water utilities is treated before it is released for public consumption, and the concentration is likely to decrease as a result of treatment.

State study shows widespread pesticide contamination in ground water

 Residues are from legal use

http://www.ibiblio.org/arc/ground_water.htm

http://www.ibiblio.org/arc/pestgroundwater.htm