Quantitative goals for a Rn-222 multimedia mitigation plan

The U.S. Environmental Protection Agency's revised proposed Rn-222 in drink ing 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 impleme ntation of a multimedia mitigation plan. If states or water suppliers choos e to comply with the alternate maximum contaminant level, the health risk r eduction achieved by multimedia mitigation programs must be equal to or gre ater than the health risk reduction that would be achieved by compliance wi th the maximum contaminant level rather than the alternate maximum contamin ant level. We have developed a method to determine quantitative goals for m itigating existing homes and building new Rn-222-resistant homes to achieve a health risk reduction to the public equivalent to the health risk differ ential 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 N orth Carolina, and it was concluded that, over time, the health risk reduct ion achievable from alternate maximum contaminant level compliance and the implementation of a multimedia mitigation program would be much greater tha n from compliance with the maximum contaminant level.