Diet choices determine mercury exposure risks for people living in gold mining regions of Peru

Abstract

Artisanal and small-scale gold mining (ASGM) is the largest global anthropogenic mercury (Hg) source and is widespread in the Peruvian Amazon. Consuming Hg-laden foods exposes people to this potent neurotoxin. While numerous studies have examined fish Hg content near ASGM, Hg accumulation in other commonly consumed animal- and plant-based foods from terrestrial environments is often overlooked. In this study, we aim to address understudied dietary Hg exposures. To understand Hg exposure from food staples in the Peruvian Amazon, we measured total and methyl Hg in local crops, fish, chicken meat, chicken feathers, and eggs from ASGM-impacted and upstream (reference) communities. Diet surveys were used to estimate probable weekly Hg intake from each food. Fish and chicken stable carbon and nitrogen isotope signatures were analyzed to evaluate trophic magnification. Though few crops exceeded food safety recommendations, rice methyl Hg proportions were high (84%). Trophic level was an expected key predictor of fish Hg content. 81% (17 of 21) of local carnivorous fish exceeded WHO and USEPA recommendations. Compared to upstream communities, mining-impacted communities demonstrated elevated total Hg in crops (1.55 (IQR: 0.60-3.03) μg/kg upstream versus 3.38 (IQR: 1.62-11.58) in mining areas), chicken meats (2.69 (IQR: BDL-9.96) μg/kg versus 19.68 (IQR: 6.33-48.1)), and feathers (91.20 (IQR: 39.19-216.13) μg/kg versus 329.99 (IQR: 173.22-464.99)). Chicken meats from mining areas exhibited over double the methyl Hg concentrations of those upstream. Methyl Hg fractions in chicken muscle tissue averaged 93%. Egg whites and livers exceeded Hg recommendations most frequently. Proximity to mining, but not trophic position, was a predictor of chicken Hg content. Our results demonstrate that terrestrial and aquatic foods can accumulate Hg from mining activity, introducing additional human Hg exposure routes. However, locally sourced carnivorous fish was the largest contributor to an estimated three-fold exceedance of the provisional tolerable weekly Hg intake.