268 - Efficacy of the Hair Biomarker for Methylmercury Exposure Monitoring for Peruvian Communities near ASGM

Total mercury content (THg) in hair is an accepted biomarker for chronic dietary methylmercury (MeHg) exposure. However, for communities near artisanal and small-scale gold mining (ASGM), the potential for exogenous contamination of hair with inorganic mercury has led to recommendations for alternative (and potentially more costly) biomarkers of MeHg exposure for public health monitoring in the ASGM context. In some regions, such as the Peruvian Amazon, MeHg exposure monitoring is not widely implemented. Instead, public health officials rely only on urine THg, an exposure biomarker for inorganic Hg and not MeHg. The guidance that discourages the hair biomarker for ASGM communities is largely based on studies that focused on occupationally exposed individuals, rather than cohorts representative of community populations near ASGM activity. Here, we sought to validate the efficacy of hair THg for public health monitoring of MeHg exposures for populations living in ASGM communities. We quantified both THg and MeHg contents in hair from a representative subset of participants (N=287) in a large, population-level mercury exposure assessment in the ASGM region in Madre de Dios (MDD), Peru. We compared population MeHg-THg correlations and %MeHg values with demographic variables including community location, sex, occupation, and nativity. We observed that hair MeHg-THg correlations were high (r >0.7) for all communities, regardless of location or nativity. Specifically, for individuals within ASGM communities, 81% (121 of 150 total) had hair THg predominantly in the form of MeHg (i.e., >66% of THg) and reflective of dietary exposure to mercury. Furthermore, for individuals with hair THg exceeding the U.S. EPA threshold (1.0 ug/g), 88 out of 106 (83%) had MeHg as the predominant form. As a result, had urine THg solely been used for mercury exposure monitoring, approximately 59% of the ASGM population would have been misclassified as having low mercury exposure. Our results support the use of hair THg for monitoring of MeHg exposure of populations in ASGM settings where alternative biomarkers of MeHg exposure are not feasible.