served by a water utility. One risk reduction technique is public education programs to encourage radon mitigation from indoor air. The previously conducted education and outreach programs reviewed by the committee were largely unsuccessful; therefore, the committee concluded that public education and outreach programs alone would be insufficient to achieve a measurable reduction in health risk.

A multimedia mitigation program will reduce radon risks in indoor air in lieu of reduction to the MCL in drinking water. The specific design of each community water utility's program will depend on many factors. At the same time, complicated risk-reduction programs like those discussed here have many potential difficulties. For example, for water utilities that provide water that contains radon at levels between the MCL and the AMCL, the feasibility of using a multimedia mitigation program will depend on whether there are homes with relatively high indoor radon concentrations. Only in those homes is it feasible to reduce the air concentration sufficiently such that an expensive, large-scale water mitigation program in the region is not needed to satisfy the multimedia program requirements. The key issue is determining how many buildings must have air mitigation systems to obtain a reduction in public risk equal to that which could be achieved by reducing radon in the water supplied to the community. Moreover, air monitoring programs will be needed to identify the homes whose indoor air must be mitigated and effective outreach programs will be needed to educate the public about the need to modify these homes to reduce indoor radon so that the water utility can demonstrate the risk reduction needed for compliance. Finally, consideration needs to be given to how the costs of mitigation of private homes will be apportioned among homeowners and the water utilities or state government.

Another potential problem is the present-day scarcity of trained personnel (particularly in the water utilities) that could design or maintain home air mitigation systems and carry out the tests needed to ensure continued performance of these systems.

Finally, the committee recognizes that the reduction in risk by multimedia programs will not be distributed equally among the public. The mitigation of indoor-air radon in a small number of homes means risk reduction among only a few people who had high initial risk, rather than a uniform risk reduction for a whole population served by the water utility.

The various analyses conducted allowed the committee to estimate the risk and annual number of fatalities caused by radon in water and to compare it with the risk caused by radon in air. The figure presented here summarizes the cancer risk posed by inhaling radon in air (with and without the addition of radon from using water in the home) and the risk posed by drinking water that contains dissolved radon. Specifically, in 1998 in the United States, there will be about 160,000 deaths from lung cancer, mainly as a result of smoking tobacco. Of those, about 19,000 are estimated to result from inhaling radon gas in the home;

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