An outbreak of chromium ulcer in a manufacturing plant

On May 23, 1989, managers of a manufacturing plant requested an investigation of an outbreak of hand ulceration and skin discoloration among workers. The plant has manufactured kitchen ranges for 30 years and employs approximately 633 hourly workers. The affected employees worked in the enamel department, where metallic range tops are coated with a "ground coat" or sprayed with an enamel coloring, and then baked in ovens at 1200F. Our evaluation included physical examinations, environmental sampling, and a questionnaire eliciting information concerning skin ulceration job history, demographics, and use of protective practices. We identified 10 enamel department workers (13.5%) who developed chromium ulcers between January 1st and June 30th, 1988. Ulcers were found on hands, forearms, periumbilical area and/or axillae. Within the enamel department, workers who handled conveyer hooks used to suspend range tops as they passed through the oven were at greatest risk (rate ratio (RR) = 12.44, 95% confidence interval (CI) = 2.90-53.35). Workers who wore gloves were protected from developing ulcers (RR = 0.08, 95% CI = 0.01-0.60). Normally, trivalent chromium (Cr+3) does not cause skin ulcers unless it is oxidized to hezavalent chromium Cr+6). The enamel used contained only Cr+3, not Cr+6, but analysis of hooks that had passed through the oven revealed Cr+6 on their surface. A mechanical failure of the oven resulted in the formation of sharp edges of the parts and consequently causing the abrasion of exposed skin. We believe Cr+3 was converted to Cr+6 during the baking process which associated with the mechanical failure of the oven causing this outbreak.