IS OCCUPATIONALLY INDUCED EXPOSURE TO RADIATION A RISK FACTOR FOR THYROID-NODULE FORMATION

The prevalence of thyroid nodules was studied with ultrasonography in a group of male hospital workers (n = 44) who had been exposed occupat ionally to x-rays. This group was compared with a group of nonexposed workers (n = 88) who were age- and sex-matched with the exposed worker s. Thyroid nodules were detected in 18 (41%) of the exposed workers, c ompared with 11 (13%) of the nonexposed controls. Both groups were sub divided with respect to age (i.e., 30-39 y, 40-49 y, 50-59 y), and the re was a higher and significant relative risk for thyroid nodule forma tion in the exposed group. We also divided the groups into subgroups a ccording to levels of exposure (i.e., nonexposed, exposed for < 20 y, and exposed for > 20 y), and a significant result was obtained with th e linear-trend chi-square test. The preliminary results of our study s uggest that occupationally induced exposure to radiation may be a risk factor for thyroid nodule formation.