Quantitative goals for a 222Rn multimedia mitigation plan

The U.S. Environmental Protection Agency's revised proposed 222Rn in drinking water regulation gives states or individual community water systems the option of compliance with the maximum contaminant level or compliance with the higher, alternate maximum contaminant level accompanied by the implementation of a multimedia mitigation plan. If states or water suppliers choose to comply with the alternate maximum contaminant level, the health risk reduction achieved by multimedia mitigation programs must be equal to or greater than the health risk reduction that would be achieved by compliance with the maximum contaminant level rather than the alternate maximum contaminant level. We have developed a method to determine quantitative goals for mitigating existing homes and building new 222Rn-resistant homes to achieve a health risk reduction to the public equivalent to the health risk differential between alternate maximum contaminant level and maximum contaminant level compliance. This method can be applied to an entire state, a portion of a state, or to an individual water supplier. The method was applied to North Carolina, and it was concluded that, over time, the health risk reduction achievable from alternate maximum contaminant level compliance and the implementation of a multimedia mitigation program would be much greater than from compliance with the maximum contaminant level.