POTENTIAL PUBLIC HEALTH IMPLICATIONS OF EXPOSURE TO ARSENIC FROM PRIVATE DRINKING WATER WELLS IN THE UNITED STATES

Arsenic exposures and health effects have been the subject of a large number of public health studies in recent years. There has been significant controversy over the dose levels at which adverse health effects may occur as well as numerous local or regional studies of arsenic concentrations in drinking water sources. This paper addresses the potential exposures to contaminants in the drinking water of millions of Americans supplied via private (domestic) drinking water wells. There are several aspects to the public health issue of arsenic in private drinking water wells that are very much interrelated. These questions are; What is the water concentration or exposure dose at which adverse health effects may occur, and Where are the wells or aquifer systems that have arsenic concentrations of public health concern.

The public health evaluation of contaminant exposures via drinking water is based on the calculation of an exposure dose from contaminant concentrations and ingestion rates, and comparison of the calculated dose with doses expected to cause some health endpoint. Concentration and location data from specific private wells are essentially non-existent (although some states do maintain records of well permits, etc.) A recent study by the United States Geological Survey which compiled and assessed water quality data on private wells identified arsenic, atrazine, and nitrate as contaminants that are widely present in private wells at concentrations of potential public health concern. This presentation will focus on the distribution and potential health effects from exposure to arsenic.

Potential exposure doses of arsenic are calculated using the frequency distributions of measured arsenic concentrations in major aquifer systems that are significant sources for private wells. Although arsenic exposure produces a number of adverse health effects, hyperpigmentation and keratosis of the skin seem to be the most sensitive endpoints (occur at the lowest doses). Comparison of the resulting probability distributions of potential exposure doses compared with doses likely to produce these health conditions indicates that adverse health effects from arsenic exposure are unlikely for the vast majority of Americans obtaining water from private wells.