OCCURRENCE AND POTENTIAL HUMAN-HEALTH SIGNIFICANCE OF SYNTHETIC ORGANIC CONTAMINANTS IN SOURCES OF DRINKING WATER

摘要

The sustainability of drinking-water supplies is greatly influenced by water-quality constraints—some well-characterized and some that are poorly understood. The key question about many current and potential sources of drinking water is not the adequacy of supply, but whether the water delivered to consumers is safe to drink. Answers to this question have exploded beyond regulated contaminants, which have maximum contaminant levels (MCL), to include consideration of the possible significance of hundreds of additional contaminants that have been detected in streams and ground water, including ambient waters, source water and treated water. Since about 1990, knowledge about the occurrence of a wide range of synthetic organic contaminants (hereinafter referred to as organic contaminants) in streams and ground water has expanded rapidly as a result of improved analytical capabilities (increased number of contaminants and lower detection levels), improved understanding of contaminant sources and transport and their inclusion in water-quality assessments. The U.S. Geological Survey’s National Water Quality Assessment Program and Toxic Substances Hydrology Program have developed national-scale1,2 or reconnaissance assessments of the occurrence of more than 300 organic contaminants (many with no drinking water standards or guidelines) in streams and ground water. The method detection or reporting levels for most contaminants ranged from 0.01 to 0.5 μg/L. Findings provide a broad perspective on the extent and nature of contaminants that may occur in current or potential drinking-water sources of different types and in different land-use settings.