Cross sectional and longitudinal study on selenium, glutathione peroxidase, smoking, and occupational exposure in coal miners

Objectives-To understand the variations of selenium (Se) concentration rela tive to changes in occupational exposure to coal dust, taking into account age and changes in smoking habits in miners surveyed twice, in 1990 and 199 4. To better understand the relation of Se concentration with glutathione p eroxidase activities (GSH-Px) in these miners. Methods-In 1994, blood samples were obtained from active (n=131) and retire d (n=40) miners without coal worker's pneumoconiosis, in whom Se concentrat ion was available at both surveys and in whom International Labour Organisa tion (ILO) profusion grade had not been changed. Active miners were exposed to high dust concentrations (n=48) or low dust concentrations (n=83). Mine rs were classified into three subgroups according to their estimated cumula tive exposure to dust, and into three subgroups according to their smoking habits. Results-Selenium concentration and GSH-Px activities were significantly low er in active than in retired miners (Se adjusted means: 62.6 v 72.2 ng/ml p =0.01). Moreover, Se concentration was lower in miners exposed to high comp ared with those exposed to low dust concentrations (adjusted means: 59.4 v 65.8). In miners exposed to high dust concentrations, Se concentration was significantly lower whereas erythrocyte GSH-Px activity was significantly h igher in the subgroup with estimated cumulative exposure >68 mg/m(3).y. In all miners, plasma GSH-Px activity was correlated with Se concentration (r= 0.22, p<0.005). The 4 year Se changes were negatively related to exposure t o high dust concentrations and positively related to change in exposure fro m high to retirement and to change from smoker to ex-smoker (p=0.01). Conclusion-The variations of Se concentration in relation to changes in occ upational exposure to coal dust and in smoking habits, and the close correl ation found between plasma Se concentration and GSH-Px activity suggest tha t both are required in antioxidant defence. These results agree well with t he hypothesis that the decrease in Se concentration reflects its use agains t reactive oxygen species generated by exposure to coal mine dust and by sm oking.