Long-Term Environmental Methylmercury Exposure Is Associated with Peripheral Neuropathy and Cognitive Impairment among an Amazon Indigenous Population

Abstract

Widespread contamination of the Amazon basin with mercury has been reported to occur since at least the mid-80s due to heavy gold mining activity. Although initial studies have indicated that this may lead to deleterious neurological consequences to the indigenous populations living in the region, further research is needed to better characterize the neurological burden of such long-term exposure. With this aim, a cross-sectional exploratory study has been conducted with the Yanomami indigenous population residing in a northern Amazon region. All participants underwent a structured interview; detailed neurological examination, including assessment for cognitive, motor, coordination, and sensory functions; and laboratorial testing for serum hemoglobin, blood glucose, and methylmercury levels in hair samples. This study enrolled 154 individuals of 30.9 ± 16.8 years of age, of which 56.1% were female. Mean methylmercury levels in hair were 3.9 ± 1.7 µg/g. Methylmercury levels in hair > 6.0 µg/g were found in 10.3%. Among participants with hair methylmercury levels ≥ 6.0 μg/g, the prevalences of peripheral neuropathy and reduced cognitive performance were, respectively, 78.8% (95%CI 15–177%, p = 0.010) and 95.9% (95%CI 16–230.8%, p = 0.012) higher than those of individuals with lower levels. These results suggest that chronic mercury exposure may lead to significant and potentially irreversible neurotoxicity to Yanomami population living in the northern Amazon basin.

The GSTP1 rs1695 Polymorphism Is Associated with Mercury Levels and Neurodevelopmental Delay in Indigenous Munduruku Children from the Brazilian Amazon

“…People who live close to areas invaded by ASGM, mostly Amazonian indigenous peoples, are threatened by its harmful effects and are at risk of developing several health issues [ 8 , 9 , 10 ]. By causing neuropsychiatric damage, Hg exposure resulting from this activity has a direct impact on people’s quality of life [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. A recent study showed a tendency of worse mental health indicators in Munduruku indigenous people with elevated levels (≥6.0 µg/g) of MeHg exposure [ 11 ].…”