According to a new study by the U.S. Geological Survey, Trace Elements and Radon in Groundwater Across the United States, 1992-2003, about 20% of untreated water samples from public, private and monitoring wells contain concentrations of at least one trace element, such as arsenic, manganese and uranium, at levels of potential health concern.
These findings are based on over 5,000 samples collected primarily from public and private wells nationwide. This study is part of efforts by the U.S. Geological Survey's National Water-Quality Assessment Program to monitor the quality of the nation's groundwater and surface water.
Human health benchmarks used in this study include U.S. Environmental Protection Agency Maximum Contaminant Levels for regulated contaminants and Health Based Screening Levels (HBSLs) for unregulated contaminants. HBSLs are unenforceable contaminant threshold guidelines developed by the USGS in collaboration with EPA, and the New Jersey Department of Environmental Protection and Oregon Health Sciences University.
The major findings of the new study include:
- Arsenic, uranium, and manganese, were the trace elements in groundwater that most frequently exceeded USEPA human-health benchmarks.
- Climate and land use are important factors in trace element distribution.
- Basic geology and geochemistry of water samples helps to predict occurrence of trace elements in groundwater.
- The effects of mixtures of trace elements are poorly understood and could cause further health concerns.
More information about the USGS and its national water quality assessment program can be accessed at USGS.gov.