Genetic damage in environmentally exposed populations to open-pit coal mining residues: Analysis of buccal micronucleus cytome (BMN-cyt) assay and alkaline, Endo III and FPG high-throughput comet assay

Abstract

DNA and chromosomal damage in individuals occupationally exposed to coal mining residues have repeatedly been reported in lymphocytes and epithelial cells, suggesting a systemic exposure-response in which generation of oxidative damage may play a major role. Nevertheless, the understanding of this mechanism is still incomplete, particularly in regard to environmental exposures. This study aimed to evaluate DNA damage using the cytome assay (BMN-cyt) in buccal cells and its relation to primary and oxidative DNA damage in lymphocytes, assessed by the high-throughput alkaline and modified (FPG-ENDO III) Comet assay in individuals with environmental exposure to coal mining residues in northern Colombia. Considering metals from coal mining activities as the main source of reactive oxygen species (ROS) generation, the concentrations of inorganic elements in blood samples was also assessed. The analysis revealed that frequencies of BMN-cyt parameters related to DNA damage (micronuclei), cytokinesis (binucleated cells) and cell death (condensed chromatin, karyorrhexis, pyknosis and karyolysis) were significantly higher in individuals that were environmentally exposed to coal compared to the unexposed group. The level of % Tail DNA in the alkaline and the modified Comet assay was 4.0 and 4.3 times higher among exposed individuals than in unexposed controls respectively. Increased MN frequencies in buccal cells were correlated with increased %Tail DNA in alkaline and FPG Comet assay. Additionally, exposed individuals had higher concentrations of Cr, Ni, Mn, and Br in the blood compared to unexposed controls. %Tail DNA in alkaline Comet assay was highly correlated with Al, Mn, and Br concentrations, while %Tail DNA in the FPG Comet assay correlated with Mn levels. These results suggest that oxidative damage, particularly purine oxidation, may play an essential role in DNA damage in individuals exposed to coal residues and that some inorganic elements are related to this effect.