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The Matsigenka people living traditional lifestyles in remote areas of the Amazon rely on a fish-based diet that exposes them to methylmercury (MeHg) at levels that have been associated with decreased IQ scores. In this study, the association between Hg levels and working memory was explored using the framework of the Multicomponent Model. Working memory tasks were modified to fit the culture and language of the Matsigenka when needed and included measures for verbal storage (Word Span) visuospatial storage (Corsi Block Task) and a measure of executive functions, the Self-Ordered Pointing Task (SOPT). An innovation of the Trail Making Tests A & B (TMT A & B) was pilot tested as another potential measure of executive functions. The mean hair Hg levels of 30 participants, ages 12 to 55 years, from three different communities (Maizal, Cacaotal and Yomibato) was 7.0 ppm (sd = 2.40), well above the World Health Organization (WHO) limit for hair of 2.0 ppm and ranged from 1.8 to 14.2 ppm, with 98% of a broader sample of 152 individuals exceeding the WHO limit. Hair Hg levels showed significant associations with cognitive performance, but the degree varied in magnitude according to the type of task. Hg levels were negatively associated with executive functioning performance (SOPT errors), while Hg levels and years of education predicted visuospatial performance (Corsi Block accuracy). Education was the only predictor of Word Span accuracy. The results show that Hg exposure is negatively associated with working memory performance when there is an increased reliance on executive functioning. Based on our findings and the review of the experimental research, we suggest that the SOPT and the Corsi Block have the potential to be alternatives to general intelligence tests when studying remote groups with extensive cultural differences.

Artificial lake expansion and high mercury loading synergistically increase mercury contamination risk from gold mining., Artisanal and small-scale gold mining (ASGM) is the largest global source of anthropogenic mercury emissions. However, little is known about how effectively mercury released from ASGM is converted into the bioavailable form of methylmercury in ASGM-altered landscapes. Through examination of ASGM-impacted river basins in Peru, we show that lake area in heavily mined watersheds has increased by 670% between 1985 and 2018 and that lakes in this area convert mercury into methylmercury at net rates five to seven times greater than rivers. These results suggest that synergistic increases in lake area and mercury loading associated with ASGM are substantially increasing exposure risk for people and wildlife. Similarly, marked increases in lake area in other ASGM hot spots suggest that “hydroscape” (hydrological landscape) alteration is an important and previously unrecognized component of mercury risk from ASGM.

Gold shops in artisanal and small-scale gold mining communities represent major point sources of airborne mercury pollution. Concentrations of elemental mercury (Hg0) emitted by these shops can be determined using a portable atomic absorbance spectrometer (AAS) with Zeeman correction. These measured Hg0 concentrations can then be correlated to position as determined by a hand-held GPS unit, and the resulting data mapped using a Geographic Information System (GIS). A detailed method for obtaining and analyzing data collected near gold shops in Mazuko, Peru is provided. Maps generated using this method were employed to identify point sources of Hg0 contamination originating from gold shops in ASGM communities and were shared with local city managers to assist in urban planning.•A detailed method is provided to collect and process data, ultimately generating a map that allows for the screening of a community to identify point sources of Hg0 contamination.•Raw data is provided, as well as a video detailing data processing and mapping using a common spreadsheet program and an open-source GIS.•The generated map can be used for determining areas where people may be exposed to elevated Hg0 concentrations and/or occupational mercury vapor exposure, targeted enforcement, or outreach to limit Hg0 pollution., Graphical abstract Image, graphical abstract

Artisanal gold mining in Amazon forests and rivers has been reported in all Amazonian countries. Amazon mining has a wide range of negative effects and severe environmental and social consequences. Given that the activity in the region is mostly illegal, there are few studies published in the scientific literature on recovery of areas degraded by gold mining. This study conducts an experimental reforestation project aimed to evaluate soil degradation and explore the seedling survivorship and early growth of 51 tropical tree species in gold mined areas at 5 study sites distributed across the Madre de Dios region, in the Peruvian Amazon. The study evaluates the effect of biochar amendments on the survivorship and growth of 51 tropical species. The study also analyzes the influence of species wood density on seedling performance one year after planting. In order to inform further restoration plantation strategies, species were chosen with the end goals of timber production, biodiversity enhancement, and soil restoration. Site degradation, soil properties and mercury levels were analyzed in degraded areas and paired reference forest patches. Soils after gold mining are found to be highly degraded, with soil C being nearly absent, cation content greatly decreased, and loss of fine sediment. Soil mercury levels were found below national and international environmental quality standards. A positive correlation and a statistically significant relationship were found between survivorship and wood density. This reveals that the higher the wood density of the species, the higher the survival percentage. Growth and overall performance of mid, and especially low wood density species were significantly increased by biochar additions, while no effect was recorded on high wood density species growth. The study provides guidance on the post-ASGM restoration potential for 51 common and useful tree species and gives practitioners recommendations for combinations of species and fertilization treatments to optimize restoration designs.

In the Brazilian Amazon, where the majority of Yanomami villages are settled, mercury (Hg) exposure due to artisanal small-scale gold mining (ASGM) has been reported since the 1980s. This study assessed mercury exposure in the Yanomami reserve and whether the level of contamination was related to the ASGM geographical location. It was conducted using a cross-sectional study of 19 villages. Direct interviews were performed and hair samples were used as a bioindicator of Hg exposure. The Prevalence-Ratio (PR) was estimated as an indicator of association between ASGM geographical locations and human exposure to mercury. Mercury levels (239 hair samples) ranged between 0.4 and 22.1 μg·g−1 and presented substantial differences amongst the villages. In the Waikas-Aracaça region, where current ASGM was reported, we observed the highest Hg concentrations (median = 15.5 μg·g−1). Almost all participants presented with hair-Hg levels >6 μg·g−1 (prevalence = 92.3%). In the Paapiu region, we observed the lowest concentrations (median = 3.2 μg·g−1; prevalence = 6.7%). Our findings showed that the Waikas Ye’kuana and Waikas Aracaca villages presented with 4.4 (PR = 4.4; Confidence Interval (CI) 95% = 2.2–9.0) and 14.0 (PR = 14.0; CI 95% = 7.9–24.9) times higher prevalence of hair-Hg concentration, respectively, compared with Paapiu. Considering seasonal variation of Hg-exposure, the lowest concentrations were observed during the wet season (June–September) and the highest in the dry season (December–April). Our study suggests that there is an association between mercury exposure and ASGM geographical locations.