Outcome of occupational asthma due to platinum salts after transferral to low-exposure areas

Abstract

Objective: To assess the health effects of transferral to low-exposure jobs on subjects with occupational asthma (OA). Methods: We performed a cross-sectional survey of 83 workers in 2 platinum (Pt) refineries and 2 catalyst production plants, all with diagnosed OA due to Pt salts. In all, 9 workers (group A; 11%) continued to be exposed at the time of examination, 16 subjects (group B; 19%) had been transferred to other workplaces within the production building, 39 subjects (group C; 47%) had been transferred to areas outside the building but inside the plant, and 19 subjects (group D; 23%) had left the plant. The median period from transferral to examination was 54 months (lower quartile 23 months, upper quartile 84 months, n = 74). Symptoms, skin-prick tests (SPT) with environmental allergens and Pt salt, total serum IgE, lung function, and bronchial hyperresponsiveness were assessed by standard procedures. Results: Asthma symptoms were reported by all subjects in the production area but by only 37 of 74 subjects (50%) after transferral, with no difference being found between groups B, C, and D. Both the proportion of subjects sensitized to Pt salts (100%, 88%, 67%, and 42% in groups A, B, C, and D, respectively) and the degree of sensitization were associated with exposure (P < 0.0002). Total IgE was higher in group A as compared with groups B, C, or D (P < 0.002). There was no association between bronchial hyperresponsiveness and exposure. Although no univariate difference in FEV₁ was found between the groups, regression analysis showed an association between FEV₁ and exposure (P < 0.002). In all, 13 subjects demonstrated a predicted FEV₁ value of <80% (22%, 6%, 10%, and 32% in groups A, B, C, and D, respectively). They were older (median 49 versus 37 years; P < 0.002) and had worked over longer periods in high-exposure areas in spite of symptoms (median 43 versus 10 months; P < 0.003). Fifteen subjects of groups C or D had been removed from areas B previously, eight of them due to respiratory symptoms. Conclusions: For the majority of subjects with OA due to Pt salts transfer to low exposure areas as defined in this study may not be associated with a more unfavorable outcome as compared with complete removal from exposure sources.