What contaminants were present at levels greater than human-health benchmarks?
Radon, several trace elements (arsenic, boron, manganese, strontium, and uranium), nitrate, and fluoride were found individually at concentrations greater than human health benchmarks in about 1 to 7 percent of sampled wells nationally (using the higher of two proposed MCLs for radon). Pesticides, volatile organic compounds, several other trace elements were found at concentrations greater than human-health benchmarks in less than 1 percent of the sampled wells.
