Arsenic and herbicide degradates in Iowa rural private drinking water wells

Studies of long-term exposure to high arsenic concentrations in drinking water report increased risks for skin, lung and cardiovascular disorders. Few toxicity studies are available on herbicide degradates, which are emerging water contaminants. Federal surveillance programs document widespread arsenic occurrence in Midwestern aquifers tapped for drinking water; herbicide degradates are also being detected. EPA regulates arsenic in public water; many herbicide compounds are reduced or removed during public drinking water treatment. Private drinking water wells are not regulated. Study question: Are rural private well water users at a high risk of exposure to arsenic and herbicide degradates in their drinking water? To collect baseline data on occurrence and concentration of arsenic and degradates of commonly used herbicides in Iowa rural private wells, we conducted a three year (2006–08) study of 475 rural wells. Each well was sampled once in a seasonal framework; well owners completed a well construction/site survey. Forty-seven percent of wells had detectable arsenic (0.001 mg/L: MDL); 8.7% of wells had arsenic at or above EPA's MCL for public water (0.01 mg/L). The range of detectable arsenic was 0.001–0.160 mg/L. Acetanilide herbicide degradates were found in 45% of wells. Regression analyses of possible factors related to contaminant concentrations (well construction characteristics, water chemistry, aquifer characteristics, water use) are planned. A public health information program aimed at reducing or removing arsenic and herbicide degradates from private drinking water, including well construction and water treatment options, will be designed for dissemination to rural residents.