Mercury exposure in female artisanal small-scale gold miners (ASGM) in Mongolia: An analysis of human biomonitoring (HBM) data from 2008

Background: Many poor in developing countries have turned to artisanal small-scale gold mining (ASGM) in an attempt to improve their situation. However, the mercury used to extract gold from ore is discharged in vaporized form into the environment, where it poses a hazard for human health. Methods: As part of an environmental epidemiological study in Mongolia to evaluate the burden of environmental mercury contamination urine, blood and hair samples were collected from residents of areas with or without mercury contamination. A total of 200 blood, urine and hair samples were analyzed for mercury and divided into three subgroups according to mercury content: (1) occupational exposure (high/medium); (2) environmental exposure (low); and (3) no exposure. Internal mercury distributions of the subgroups were compared using the Kruskal-Wallis and Mann-Whitney U-test. The Chi-square test and likelihood ratio proportion were used to compare the findings with threshold limits. Results: The highest values and greatest differences were seen in the urine samples (p<0.001, Kruskal-Wallis). The occupational group showing the highest exposure with a median mercury level of 4.36 mu g/l (control group: 0.10 mu g/l, p<0.001), 7.18 mu g/g creatinine and 12 results above the threshold limit HBM I (Human Biomonitoring I). Even participants from the low-exposure subgroup showed elevated mercury levels (median 2.88 mu g/l urine and 2.98 mu g/g creatinine, p<0.001), with 10 individuals above the HBM I threshold limits. Discussion: The body burden resulting from the use of mercury in artisanal gold mining is high not only in the miners themselves, an increased mercury hazard was also found for inhabitants of mining areas who were not actively involved in mining. Public health support measures are urgently needed to alleviate the situation.