Exposure to pesticides can trigger genotoxic and mutagenic processes through different pathways. However, epidemiological studies are scarce, and further work is needed to find biomarkers sensitive to the health of exposed populations. Considering that there are few evaluations of soybean farmers, the aim of this study was to assess the effects of human exposure to complex mixtures of pesticides. The alkaline comet assay modified with restriction enzyme (hOGG1: human 8-oxoguanine DNA glycosylase) was used to detect oxidised guanine, and compared with the buccal micronucleus cytome assay, global methylation, haematological parameters, biochemical analyses (serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, gamma-glutamyl-transferase and butyrylcholinesterase), and particle-induced X-ray emission (PIXE) for the analysis of inorganic elements. Farm workers (n = 137) exposed to different types of pesticides were compared with a non-exposed reference group (control; n = 83). Results of the enzyme-modified comet assay suggest oxidation of guanine in DNA generated by pesticides exposure. It was observed that DNA damage (comet assay and micronucleus test) was significantly increased in exposed individuals compared to the unexposed group. The micronucleus test demonstrated elimination of nuclear material by budding, defective cytokinesis and dead cells. Occupationally exposed individuals also showed genomic hypermethylation of DNA, which correlated with micronucleus frequency. No differences were detected regarding the haematological and biochemical parameters. Finally, significantly higher concentrations of Al and P were observed in the urine of the soybean farmers. DNA damage could be a consequence of the ability of the complex mixture, including Al and P, to cause oxidative damage. These data indicate that persistent genetic instability associated with hypermethylation of DNA in soybean workers after long-term exposure to a low-level to pesticides mixtures may be critical for the development of adverse health effects such as cancer.
Tobacco farming is an important economic income in Brazil, although it has been challenged as regard the occupational exposure to both pesticides and nicotine endured by farmers. Chronic occupational exposure to complex mixtures can lead to health hazardous. We examined genomic instability and epigenetic changes in tobacco farmers occupationally exposed to pesticide mixtures and nicotine at tobacco fields. DNA damage was assessed by alkaline comet assay in blood cells. Genomic DNA was isolated, and telomere length was measured using quantitative polymerase chain reaction assay. We measured 5-methyl-2'-deoxycytidine, a marker of global DNA methylation, and p16 promoter methylation. The oxidative profile was evaluated by trolox equivalent antioxidant capacity and lipid peroxidation (thiobarbituric acid reactive substances) in serum. Exposure parameters, plasma cotinine and inorganic element levels, were also measured. DNA damage was significantly elevated for farmers in relation to unexposed group (P < 0.001; Mann-Whitney test) and positively associated with years of exposure. Inverse relationship between DNA damage and total equivalent antioxidant activity was demonstrated for exposed and unexposed groups. Exposed group showed significantly shorter telomeres (P < 0.001; unpaired t-test) and DNA hypomethylation (P < 0.001; unpaired t-test), as well as p16 hypermethylation (P = 0.003; Mann-Whitney test). Lipid peroxidation was increased for exposed group in relation to unexposed one (P = 0.02; Mann-Whitney test) and presented a positive correlation with global DNA methylation (P = 0.0264). Farmers have increased plasma cotinine levels (P < 0.001) and inorganic elements (phosphorus, sulphur and chlorine) in relation to unexposed group. Elevated oxidative stress levels due to chronic occupational pesticide mixtures and nicotine exposure in tobacco farmers were associated with higher DNA damage, shorter telomeres and altered DNA methylation. Telomere-accelerated attrition due to exposure may be potential intermediate step before a disease state.
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