A community-based health survey for the time period between 1944 and 1995 was collected from 801 individuals who had lived downwind of the U.S. plutonium production facility located in Hanford, Washington. The results of the survey revealed high incidences of all cancers, including thyroid cancer. There were greater than expected numbers of central nervous system tumors and cancers that invaded the female reproductive system (e.g., cancers of the uterus, ovary, cervix, and breast). The authors argue that the greater-than-expected numbers found cannot be accounted for by selection bias alone. Comparisons of crude incidence rates, as well as of occurrence ratios between pairs of cancer types among Downwinders and reasonably similar populations, suggested that the excess neoplasms may be associated with radioactive contamination of food, water, soil, and/or air. In addition, a synergistic effect may exist with agricultural toxins. Previously neglected biophysical and physiological properties of internally lodged, long-lived 129I may be a significant etiological factor in the development of thyroid diseases, including cancer, and other malignancies in exposed populations.