Influence of free radicals on cardiovascular risk due to occupational exposure to mercury

This study was designed to investigate the relation between occupational exposure to mercury and cardiovascular risk, as well as free radicals. The study subjects included 30 male workers exposed to mercury from a fluorescent lamp plant in Alexandria after exclusion of 12 workers with conditions that may bias the results. A matched control group of 20 male subjects were selected from a food industrial plant. The participants were subjected to interview, clinical examination, electrocardiography and R-R deep breathing variability test as a measure of cardiac autonomic function. Spot urine and venous blood samples were collected to measure mercury levels. Free radicals related markers were measured in serum namely lipid peroxide, superoxide dismutase (SOD) activity, catalase activity and glutathione S-transferase. Results showed significant longer electrocardiographic Q-Tc interval, which is corrected to heart rate, in exposed workers than in controls (p=0.002). The R-R deep breathing variability indices were significantly increased among exposed workers in comparison to controls (maximal variation (MV) ratio, p=0.024 & MV rate, p=0.019). The mercury levels in both urine and blood of exposed workers were significantly higher than controls (p<0.0001), with mean levels exceeding the permissible limits. Free radicals related markers revealed significant higher level of lipid peroxide, as well as significant lower levels of SOD activity, catalase activity and glutathione S-transferase among exposed workers than among controls (p<0.0001 for all). Independent relations were observed between Q-Tc and lipid peroxide, and between MV rate and SOD and catalase activities among exposed workers after adjustment for the confounders by multivariate regression analyses. These findings may suspect a cardiac autonomic dysfunction probably related to free radicals in mercury exposed workers. Also, it may through light on some preventive implications.