Assessing occupational mercury exposures and behaviours of artisanal and small-scale gold miners in Burkina Faso using passive mercury vapour badges

•Measures occupational exposure to mercury vapour in artisanal and small-scale gold mining.•Uses passive mercury vapour monitors, an economic alternative to biomonitoring.•Extremely high levels of mercury exposure detected that exceed guideline values.•Area air sampling with LUMEX supports the exposure levels measured by the passive samplers.•Pertinent as a possible monitoring approach for Minamata Convention compliance.

Artisanal and small-scale gold mining (ASGM) is a crucial economic activity in Burkina Faso, however it is associated with significant mercury exposure and health concerns. The aim of the present study was to assess the level of mercury (Hg) vapour exposures and occupational behaviours at a representative site using Hg vapour monitor badges and questionnaires. To our knowledge this is the first time that personal exposure to Hg vapour during ASGM activities has been reported. The study population were ASGM workers who completed a questionnaire (n=100) or participated with an occupational exposure assessment using commercially available passive Hg vapour samplers (n=44). Occupational exposure to Hg was high during open-air burn events with a time weighted average (TWA) exposure of 7026±6857 µg/m3 for burners, and 1412±2870 µg/m3 for bystanders. Most (82%) of the people present at the burn exceeded the Permissible Exposure Limit (PEL) of 100 µg/m3, and 11% exceeded the level considered to be Immediately Dangerous to Life and Health (IDLH) of 10,000 µg/m3. Even control workers who were not present at the burn exceeded the PEL (24%), likely due to legacy Hg contamination producing latent Hg releases to the atmosphere. Similarly, 86% of the miners at the burn and 59% of control workers had an 8-h TWA that exceeded the Recommended Exposures Limit (REL). Several occupational behaviours that may contribute to Hg exposures were documented. This study corroborates previous studies suggesting that Hg exposure during amalgam burning is very high, and demonstrates the plausibility of using passive vapour monitoring badges rather than costly and logistically difficult biomonitoring methods. Mercury reduction and elimination interventions are strongly needed to reduce Hg exposure in ASGM communities, particularly as countries come into compliance with the Minamata Convention.