Assessment of Radiation Dose and Effects from Radon and Its Progeny in Energy-Efficient Homes

Abstract

Radon and its short-lived daughters present in indoor air are currently estimated to be responsible for dose equivalents of ∼ 30 mSv/yr (3 rem/yr) to small portions of the respiratory tract. Linear extrapolation from the dose-response values of uranium miners heavily exposed to the same nuclides would suggest that the majority of lung cancers in the nonsmoking population are caused by environmental ²²²Rn. Such projections cause major concern since both the high linear energy transfer of the alpha radiation involved and the amount of radiation delivered to the critical tissue, which cannot be considered low at environmental exposure levels, speak against beneficial threshold effects in this case. Higher indoor radon concentrations and shifts in the disequilibrium of the short-lived daughters in energy-efficient homes, caused mostly by reduced air exchange rates, will lead to a severalfold increase of lung cancer incidence from radon. Based on the above assumption, ∼100 additional lung cancer death/yr. million will result from an increase in radionuclide concentrations in indoor air. In situations where soil or building materials contain elevated radium levels, living in energy-efficient houses may be as dangerous as heavy smoking. Possible means of reducing indoor radon levels in existing buildings range from diffusion barriers to heat exchangers. The latter devices allow high air exchange rates, which also reduce other critical indoor pollutants. Judged by the standards of the nuclear industry, the costs of reducing exposure to radon and its daughters are very low ($3000 U.S./person. Sv).