WASHINGTON — Pesticides linked to cancer, birth defects and neurological disorders contaminate almost all of the nation’s rivers and streams and most fish found in them, but seldom at concentrations likely to affect people, government scientists said Friday. Though the pesticides were less common in ground water, the U.S. Geological Survey’s study of data between 1992 and 2001 found them present in streams in both urban and agricultural areas at concentrations that could affect aquatic life or fish-eating wildlife. Robert Hirsch, the USGS associate director for water, said that “while the use of pesticides has resulted in a wide range of benefits to control weeds, insects, and other pests, including increased food production and reduction of insect-borne disease, their use also raises questions about possible effects on the environment, including water quality.” About 40 pesticides of 100 that were studied accounted for most of the findings in water, fish and sediment. Three herbicides used mainly on farms, atrazine, metolachlor, and cyanazine, were the most frequently detected in agricultural streams. Three herbicides used commonly in cities, simazine, prometon, and tebuthiuron, showed up more often in urban streams. The pesticides also showed up more than 90 percent of […]