Naturally occurring radionuclides in drinking water: An exercise in risk benefit analysis.

The scientific background information describing the occurrence, measurement, health effects, treatment technology, risk assessment and economic consequences of the presence of naturally occurring radionuclides in drinking water are described for 60,000 public drinking water supplies. The relevant data for the occurrence of radium, uranium and radon in drinking water supplies are discussed and analysed. Radon is of importance because it is released in the process of taking showers and baths and in washing dishes and clothes. Its progeny is then inhaled, leading to the risk of lung cancer. Radium and uranium can both cause bone cancer. The range of average occurrence of natural radioactivity in drinking water is as follows:(226)Ra, 0.3 to 0.8 pCi L(-1);(228)Ra, 0.4 to 1.0 pCi L(-1); uranium, 0.3 to 2.0 pCi L(-1) and(222)Rn, 500 to 600 pCi L(-1). The estimated lifetime risks due to the mean groundwater concentrations of naturally occurring radionuclides are:(226)Ra and(228Ra), 1.0 10(-5); uranium, 2.0 × 10(-6) and radon, 4.0 × 10(-4). The cost to reduce total radium levels to 5.0 pCi L(-1) is about $9 million. An equivalent expenditure would be required to reduce radon levels to about 4,000 pCi L(-1), or uranium levels to about 100 pCi L(-1). The problem of maximizing the total mortality and the reduction per unit dollar outlay per unit dollar cost for the uranium/radon case is examined.