Answer to Question #206 Submitted to "Ask the Experts"

Q

Do senior citizens or infants face greater health risks from radiation?

A

Radiation risk is, in general, inversely proportional to age for both deterministic and stochastic effects. In children, interference with growth and development is a deterministic effect. These effects obviously do not occur in adults; thus children are more sensitive. Sensitivity to other deterministic effects (acute radiation syndromes, cataract, immunosupression, etc.) is essentially independent of age. An exception occurs from exposure in utero; the young embryo is more sensitive than the term fetus. Some old animal data suggested that LD-50 (a measure of lethality) declines in the elderly. Risk of stochastic effects declines with age. For genetic effects, the risk disappears in postmenopausal females and declines in older males because they are less likely to father additional children. For cancer, the latent period between exposure and frank appearance of disease is years to decades. Thus, the period at risk is the remainder of the life span of the exposed individual. Individuals who are older at the time of exposure are more likely to die from intercurrent disease before the radiation-induced cancer is expressed. S. Julian Gibbs, DDS, Ph.D. Professor of Radiology