Occupationally related tumors in tar refinery workers

Abstract

Background: The study comprised 606 workers with tar-induced dermatosis employed in a German tar refinery. During the period from 1946 to 1996 they were recognized as having an occupational disease.

Objective: The aim of this study was to characterize the histologic findings and the localization of the occupational dermatosis and to determine the latency period of the carcinomas from the beginning of exposure in the tar refinery to the first occurrence of malignant skin tumors. Furthermore, the study aimed to check whether other skin changes were frequently diagnosed in addition to known tar-induced tumors.

Methods: The data were collected retrospectively from the documents of the Employer's Liability Insurance Association.

Results: Surgical removal of 4754 skin tumors was documented up to the end of 1996 in the study. In 90% of cases the histologic diagnosis was confirmed. Among other conditions, this yielded 2490 precancerous stages, 380 squamous cell carcinomas, 218 basal cell carcinomas, and 182 keratoacanthomas. The skin tumors were found mainly in the facial area, as well as on the forearms and hands. Latency from the first exposure in the tar refinery until manifestation of tar-induced dermatosis covered a period of 57 years.

Conclusion: In comparison to the general population, the ratio of squamous cell to basal cell carcinomas was shifted toward the squamous cell carcinomas (1.7:1). Sunlight is known to be a cofactor in the pathogenesis of keratosis, squamous cell carcinomas, and basal cell carcinomas. However, the difference in location of these tumors shows that the role sunlight plays in the pathogenesis of precancerous lesions and squamous cell carcinomas may be overvalued. The latency period from the beginning of exposure to the manifestation of squamous cell carcinomas could not be evaluated because of an intervention bias as a result of preventive excisions of precancerous lesions. The frequent occurrence of keratoacanthomas (in 18.7% of the workers) and the early age at which this disease became manifest relative to the general population (median, 55 years) indicate that employment in a tar refinery can primarily or secondarily cause keratoacanthomas.