Occupational human exposure to mercury in artisanal small-scale gold mining communities of Colombia

•Mercury exposure (blood, urine and hair) in 238 ASGM miners was assessed in Colombia.•A 55% of the miners (n = 131) had Hg/methylmercury values in hair above EPA threshold.•Mercury levels in amalgam burners were 6 to 8-fold higher than all other miners.•Fish intake, burning and manipulate amalgam were significant indicators of Hg exposure.•Exposure to Hg clearly depend on different processing activities carried out in ASGM.