ORIGINAL PAPER Alterations in antioxidant defense system of workers chronically exposed to arsenic, cadmium and mercury from coal flying ash Lulzim Zeneli • Ankica Sekovanic ´ • Majlinda Ajvazi • Leonard Kurti • Nexhat Daci Ó Springer Science+Business Media Dordrecht 2015 Abstract Humans are exposed to different stress factors that are responsible for over-production of reactive oxygen species. Exposure to heavy metals is one of these factors. The aim of the study was to analyze the effect of chronic exposure to heavy metals through coal flying ash on the efficiency of antioxidative defensive mechanisms, represented by the activity of superoxide dismutase, glutathione peroxidase and ascorbic acid. Nonessential elements such as arsenic and mercury levels showed a significant increase (p [ 0.001) in the power plant workers rather than in the control subjects. There were no significant differ- ences of blood cadmium between power plant workers and control subjects. We found a significant positive correlation (p \ 0.05) between BAs/SZn (r = 0.211), BAs/BSe (r = 0.287), BCd/SCu (r = 0.32) and BHg/ BSe (r = 0.263) in the plant workers. Red blood cell antioxidant enzymes and plasma ascorbic acid were significantly lower in power plants workers than in the control group (p \ 0.002). We can conclude that levels of mercury, arsenic and cadmium in blood, despite their concentration within the reference values, significantly affect plasma ascorbic acid concentration, superoxide dismutase and glutathione peroxidase activity, which are able to increase the risk of oxidative stress. Keywords Blood Á Trace elements Á Antioxidant Á Correlation Á PP workers Abbreviations ROS Reactive oxygen species GPx Gluthatione peroxidase SOD Superoxide dismutase CAT Catalase BMe Blood Me SMe Serum Me PP Power plant C-index Covalent index I-index Ionic index Introduction Metal and metalloid elements such as cadmium (Cd), arsenic (As) and mercury (Hg) are the most abundant toxic metals in the environment. Their common sources are diverse including natural and anthropogenic pro- cesses such as combustion of coal and mineral oil, smelters, and mining. (Phillips et al. 2003; Patra et al. 2005, 2007). Animals, including humans, generally get L. Zeneli (&) Á L. Kurti Faculty of Medicine, Institute of Biochemistry, University of Prishtina, 10000 Prishina, Republic of Kosovo e-mail: lzeneli@gmail.com A. Sekovanic ´ Institute of Medical Research and Occupational Health, Zagreb, Croatia M. Ajvazi Á N. Daci Department of Chemistry, University of Prishtina, Prishina, Republic of Kosovo 123 Environ Geochem Health DOI 10.1007/s10653-015-9683-2