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

Abstract

Objectives-To understand the variations of selenium (Se) concentration relative to changes in occupational exposure to coal dust, taking into account age and changes in smoking habits in miners surveyed twice, in 1990 and 1994. To better understand the relation of Se concentration with glutathione peroxidase activities (GSHPx) in these miners. Methods-In 1994, blood samples were obtained from active (n=131) and retired (n=40) miners without coal worker's pneumoconiosis, in whom Se concentration was available at both surveys and in whom International Labour Organisation (ILO) profusion grade had not been changed. Active miners were exposed to high dust concentrations (n=48) or low dust concentrations (n=83). Miners were classified into three subgroups according to their estimated cumulative exposure to dust, and into three subgroups according to their smoking habits. Results-Selenium concentration and GSH-Px activities were significantly lower 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 compared 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 higher 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 to high dust concentrations and positively related to change in exposure from 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 occupational exposure to coal dust and in smoking habits, and the close correlation found between plasma Se concentration and GSH-Px activity suggest that both are required in antioxidant defence. These results agree well with the hypothesis that the decrease in Se concentration reflects its use against reactive oxygen species generated by exposure to coal mine dust and by smoking. (Occup Environ Med 2001;58:239-245)

Systemic Oxidative Stress Promoted by Emissions of Particulate Matter is Attenuated by Antioxidant Supplementation

“…SOD activity was also inhibited in all groups examined and a similar response was also found in other studies involving coal mining workers [10,13]. On the other hand, rats exposed sub-chronically to a mine ambience showed SOD and GPx induction at the first week followed by SOD inhibition at the fourth week of exposure [22].…”

“…The first finding regarding coal extraction, was a systemic OS present in the blood or workers directly or indirectly exposed to PM emissions related to coal mining [1], in general accordance to the related literature [10,13,16]. More importantly, they also revealed that people living in the vicinity (ca.…”

“…GPx showed decreased activity in all exposed groups, also resembling the profile found in underground workers exposed to coal extraction [1], as in individuals exposed to SHSR incineration [2]. Similarly, Nadif and collaborators [13] found lower GPx activity in the blood from active miners compared to retired ones. GR activity showed decreased values only in subjects directly exposed (34.7%) compared to controls, which were recovered to control values after the antioxidant intervention.…”

“…Catalase activity was increased in directly exposed coal miners, but only underground workers showed decreased GPx activity. In this regard, GPx inhibition seems to be consistent with chronic exposure to airborne contaminants [10,13], which will consequently render higher hydroperoxide levels inside the cells. In the presence of transition metal ions, such as ferrous or cuprous ions, H 2 O 2 is converted to the most deleterious radical hydroxyl (HO • ), via the Fenton reaction [6].…”

“…Such prooxidant/antioxidant imbalance was already detected in the blood of subjects chronically exposed to coal dusts, provoking enhanced lipoperoxidation in plasma [9,10] together with a decline in antioxidants such as reduced glutathione [11], and antioxidant enzymes such as superoxide dismutase, glutathione peroxidase and glutathione S-transferase [10][11][12][13].…”