Much attention has been given to groundwater contamination due to the release of hazardous constituents from treatment and disposal facilities. Since some of the constituents entered groundwater aquifers in much shorter times than had been calculated, regulatory agencies have become concerned that hazardous constituents may be escaping from units not currently regulated under hazardous waste management programs. One of the major concerns of regulators is that unlined earthen surface impoundments in industrial wastewater treatment trains may be leaking heavy metals such as chromium and other hazardous constituents into the groundwater. The Environmental Protection Agency is moving toward bringing such impoundments under the Resource Conservation and Recovery Act (RCRA) regulations. In addition, EPA is now proposing to list hexavalent chromium as a hazardous air pollutant due to its possible release from the mist of cooling towers, citing hexavalent chromium's potent carcinogenicity as the primary concern. While such a listing would primarily affect worker exposure, leakage of chromium from surface impoundments could enter groundwater sources and carry exposures far beyond industrial facilities.