Exposure-effect relationship of platinum salt allergy in a catalyst production plant: Conclusions from a 5-year prospective cohort study

Background: There is a high incidence of occupational asthma and rhinitis c aused by platinum (Pt) salts in precious-metal refineries. Objective: We sought to assess exposure to Pt salts and the incidence of Pt salt allergy in a catalyst production plant. Methods: A 5-year prospective cohort study was performed in 159 catalyst pr oduction workers (94.6% of recruited), 50 craftsmen (92.6% of recruited), a nd 66 control subjects (76.7% of recruited) at yearly intervals. Subjects w ere assigned to exposure categories of high levels of Pt (n = 115), persist ently low levels of Pt (n = 51), intermittently low levels of Pt (n = 61), or no Pt (n = 48) after the initial survey according to job title and job l ocation. Skin prick test conversion from a negative response to a 4 mm or l arger wheal response with a 10(-2) mol/L hexachloroplatinic acid solution w as chosen as the outcome variable. Results: Exposure assessment of airborne Pt and Pt in the serum of workers demonstrated clear differences between exposure categories. The threshold l imit value of 2 mu g/m(3) for soluble Pt was exceeded in 3 (4%) of 78 measu rements. Thirteen subjects assigned to high exposure showed skin test conve rsion, and new allergic symptoms were associated with exposure. Among the h igh-exposure category, the incidence rate of skin prick test conversion was 5.9 per 100 person-years for newly employed subjects (n = 79) acid 2.1 per 100 person-years for those who had already been employed at the time of th e initial survey (n = 36). A predicting factor for skin test conversion in highly exposed subjects was smoking status (relative risk, 3.9; 95% confide nce interval, 1.6-9.7) but not atopy or bronchial hyperresponsiveness. Conclusion: Sensitization to Pt salts may develop in workers of catalyst pr oduction plants. Both the exposure to Pt salts and the incidence of Pt salt allergy were lower compared with reported data from precious-metal refiner ies.