Occupational and environmental mercury exposure among small-scale gold miners in the Talensi–Nabdam District of Ghana's Upper East region

Abstract

Mercury use in small-scale gold mining is ubiquitous across Ghana but little is known about the extent to which such activities have contaminated community residents and miners. Here, occupational exposures to elemental mercury (via urine sampling) and dietary exposures to methylmercury (via hair sampling) were assessed among 120 participants recruited from a mining community located in the Talensi–Nabdam District of Ghana's Upper East region during summer 2009. More than one-fifth of the participants had moderately high levels of urinary mercury (> 10 μg/L) and 5% had urine mercury levels that exceeded the WHO guideline value of 50 μg/L. When participants were stratified according to occupation, those active in the mining industry had the highest mercury levels. Specifically, individuals that burned amalgam had urine mercury levels (median: 43.8 μg/L; mean ± SD: 171.1 ± 296.5 μg/L; n = 5) significantly higher than median values measured in mechanical operators (11.6 μg/L, n = 4), concession managers/owners (5.6 μg/L, n = 11), excavators that blast and chisel ore (4.9 μg/L, n = 33), individuals that sift and grind crushed ore (2.2 μg/L, n = 47), support workers (0.5 μg/L, n = 14), and those with no role in the mining sector (2.5 μg/L, n = 6). There was a significant positive Spearman correlation between fish consumption and hair mercury levels (r = 0.30) but not with urine mercury (r = 0.18) though further studies are needed to document which types of fish are consumed as well as portion sizes. Given that 200,000 people in Ghana are involved in the small-scale gold mining industry and that the numbers are expected to grow in Ghana and many other regions of the world, elucidating mercury exposure pathways in such communities is important to help shape policies and behaviors that may minimize health risks.