Biomonitoring of exposure to metals and metalloids using toenail and fingernail sampling in individuals from artisanal gold mining areas in Mali

Artisanal gold mining can release metallic elements in the environment that can result in occupational and environmental exposures. This pilot study aimed to assess exposure to metals and metalloids from fingernail and toenail samples in artisanal gold mine workers, inhabitants of a mining and non-mining village in Mali. As it can be particularly challenging to collect and transport biological samples from remote areas, nail sample collection was tested as a potential choice for multielement biomonitoring. A convenience sampling of 315 individuals was performed equally distributed in each location group (105 per location) and stratified by populational group (male adults, female adults, and people <18 years). Toenail and fingernail samples were collected from each participant and twenty-one elements (aluminum (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), gallium (Ga), iron (Fe), lithium (Li), lead (Pb), manganese (Mn), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Th), uranium (u), vanadium (v) and zinc (Zn)) were quantified. Concentrations of 12 elements in fingernails and/or toenails were significantly higher in the mine worker group, in particular As, Co and Cu in both toenails and fingernails. In the mine worker group specifically, As concentrations in both fingernails and toenails were higher in males. Most metals also had a strong positive correlation overall. Both fingernails and toenails appear as interesting biomonitoring matrices for multielement exposure assessment with an impact of different variables, such as mining exposure and sex, on internal levels. The study also highlighted the importance of further human exposure assessment related to artisanal gold mining in Mali, including the identification of other environmental sources of exposure.