Drinking-water contribution to natural background radiation.

The average concentrations of naturally occurring radionuclides in drinking water are estimated from recent measurements and are used to estimate the annual effective dose equivalent associated with drinking water due to the different radionuclides. The annual effective dose equivalents are determined from the annual intake of these radionuclides using dosimetric information based on ICRP Publication 30 dosimetric models and cohort analysis considering risk coefficients developed by the U.S. Environmental Protection Agency using data from the report of the Biological Effects of Ionizing Radiation Committee (BEIR III) of the National Academy of Sciences. The resulting contribution from drinking water sources to the annual effective dose equivalent is in the range of 0.002 to 0.05 mSv/y (0.2-5 mrem/yr) for those using community drinking water supplies (approximately 216 million people in the United States). The contribution to the annual effective dose equivalent from 222Rn dissolved in water is in the range of 0.8-30 mu Sv/y (0.08-3 mrem/yr) based on the inhalation pathway following the release of 222Rn from drinking water.