Blood antioxidant status in coal dust-induced respiratory disorders: A longitudinal evaluation of multiple biomarkers

To investigate the involvement of oxidative stress in coal dust-induced respiratory disorders, red brood cell and serum antioxidants in 66 coal miners were related to 5-year changes in coal workers' pneumoconiosis (CWP), chronic bronchitis, and lung function decrease (n = 40). Reduced (GSH) and oxidized (GSSG) glutathione concentrations, glutathione peroxidase (Gpx), glutathione-S-transferase (GST), superoxide dismutase (SOD), and catalase activities were measured in erythrocytes and vitamin A, Vitamin E and iron were determined in serum. Changes in CWP were determined by chest radiography, chronic bronchitis was determined from a validated questionnaire and lung function decline was calculated by linear regression for a 10 year interval before blood sampling. SOD activity was increased in miners with progression of CWP (2308 +/- 156 vs 1703 +/- 155 U g(-1) Hb, p < 0.05), and GSH was reduced in those with chronic bronchitis at follow-up (3.53 +/- 0.16 vs 4.05 +/- 0.09 mmol g(-1) Hb, p < 0.01). Stepwise discriminant analysis showed that for both pneumoconiotic and non-pneumoconiotic respiratory disease in this cohort, increased enzymatic antioxidants (i.e. Gpx, Catalase, SOD) were high risk factors, while increased 'non-enzymatic' antioxidants (i.e. vitamin E, GSH) indicated reduced risk. GST activity showed discriminative power in two ways, i.e. decreased activity in those at risk for CWP, but increased in those with rapid decline in FEV(1). We conclude that the multiple marker approach applied here shows the relevance of interpretation of total 'antioxidant status' versus single antioxidant measurements in health screening of individuals at risk for respiratory impairments.