Answer to Question #943 Submitted to "Ask the Experts"

Q

Have any adverse health impacts been reported anywhere in the world due to excessive natural radiation?

A

The only conclusive adverse health effect from natural radiation has been the reported increase of lung cancers in underground miners exposed to radon. Sources of natural radiation include cosmic radiation from space, terrestrial radionuclides in the earth, and cosmogenic radionuclides, such as ³H and ¹⁴C, that are created by cosmic radiation in the atmosphere. The National Council on Radiation Protection and Measurements (NCRP) Report No. 94, "Exposure of the Population in the United States and Canada from Natural Background Radiation," 1987, is a useful reference. The radon of most concern is ²²²Rn, which is a radioactive gas. It is a decay product of ²³⁸U and ²²⁶Ra which are mined at various locations throughout the world. Because ²²²Rn has a half-life of 3.8 days, it can accumulate in the air of the mines. The solid decay products of ²²²Rn, which may become attached to dust or smoke particles, are inhaled by the miners. As these decay products undergo further decay, a radioactive dose is deposed in the lungs and pulmonary tissues. It is believed that this radioactive exposure leads to the increased number of lung cancers seen in these underground miners. Estimates of the increased cancer risk to the underground miners from radon can be found on the U.S. Environmental Protection Agency Web site. John Jacobus, M.S., CHP