Epidemiologic clues to the cause of melanoma.

An intensive search found that 146 cases of cutaneous or ocular melanoma had occurred among residents of Lane County, Oregon, from 1958 through 1972. Of these cases, 35 led to death. Countywide, increasing incidence rates were corroborated by increasing death rates for both sexes. Risk of disease was highest in a moist, flat residential area near the intersection of two rivers in the county's urban portion and in its agricultural area. The incidence pattern strongly suggested local cycles in subcounty units. Although overall melanoma risk was higher in urban areas, an apparent widespread rural epidemic was identified, beginning abruptly in 1965 and lasting several years. If similar geographic and temporal characteristics can be identified in other localities, the search for an etiologic agent could focus on a smaller range of possibilities.