ABSTRACT
The human population typically is exposed to radiation from a number of sources, both internal and external. These radiations arise primarily from the decay of potassium and ruthenium isotopes, as well as from the members of the uranium, thorium, and actinium decay chains. In addition, significant doses are delivered as a result of cosmic radiation arriving at the surface of the earth. Attention in the risk analysis community recently has been shifted from these sources, however, because of findings that geological sources of 222Rn (hereafter, radon) may produce risks larger than those produced by the other sources. A comparison of annual dose equivalent received from radon and other environmental sources reveals that radon in the air of homes yields roughly 20-30 mSv per year (with a quality factor of 20) in the United States, 1 whereas the others yield less than 1 mSv per year.2 Even if the whole body effective dose equivalent, rather than the dose equivalent alone, is used as the index of damage, radon yields 2 to 3 times the value noted for other radionuclides in the environment.
