EPIDEMIOLOGIC-STUDY OF TIME AND SPACE CLUSTERING OF 4 CASES OF CHOROIDAL MALIGNANT-MELANOMA

Objective: To identify common risk factors that might be associated wi th a cluster of 4 cases of choroidal malignant melanoma that occurred in a manufacturing plant between 1982 and 1985. Design: Survey of chor oidal malignant melanoma cases in Caddo and Bossier parishes during th e same time frame. Methods: We identified 4 additional individuals wit h choroidal malignant melanoma first diagnosed during the study period . Characteristics of the workplace were examined and a questionnaire w as administered to all subjects to ascertain exposures to putative car cinogens and to putative risk factors for intraocular malignant melano ma. Observed and expected incidence rates were calculated. Results: Th e overall incidence of intraocular malignant melanoma for the 2 parish es during the 4-year period was 0.56 cases per 100 000 population per year, similar to the expected rates for this population. The incidence rate for the manufacturing plant employees was 16.5 cases per 100 000 per year. The mean age at diagnosis for workers at the plant was 38.7 years compared with 69.2 years for nonplant employees. Conclusions: T he close occurrence of manufacturing plant cases in time and space and the younger age of the people are consistent with a cluster of intrao cular melanoma cases. No specific risk factors were found in the workp lace environment to impute a causal association.