Spatial, Temporal, and Dietary Variables Associated with Elevated Mercury Exposure in Peruvian Riverine Communities Upstream and Downstream of Artisanal and Small-Scale Gold Mining

Abstract

Artisanal and small-scale gold mining (ASGM) is a primary contributor to global mercury and its rapid expansion raises concern for human exposure. Non-occupational exposure risks are presumed to be strongly tied to environmental contamination; however, the relationship between environmental and human mercury exposure, how exposure has changed over time, and risk factors beyond fish consumption are not well understood in ASGM settings. In Peruvian riverine communities (n = 12), where ASGM has increased 4–6 fold over the past decade, we provide a large-scale assessment of the connection between environmental and human mercury exposure by comparing total mercury contents in human hair (2-cm segment, n = 231) to locally caught fish tissue, analyzing temporal exposure in women of child bearing age (WCBA, 15–49 years, n = 46) over one year, and evaluating general mercury exposure risks including fish and non-fish dietary items through household surveys and linear mixed models. Calculations of an individual’s oral reference dose using the total mercury content in locally-sourced fish underestimated the observed mercury exposure for individuals in many communities. This discrepancy was particularly evident in communities upstream of ASGM, where mercury levels in river fish, water, and sediment measurements from a previous study were low, yet hair mercury was chronically elevated. Hair from 86% of individuals and 77% of children exceeded a USEPA (U.S. Environmental Protection Agency) provisional level (1.2 µg/g) that could result in child developmental impairment. Chronically elevated mercury exposure was observed in the temporal analysis in WCBA. If the most recent exposure exceeded the USEPA level, there was a 97% probability that the individual exceeded that level 8–10 months of the previous year. Frequent household consumption of some fruits (tomato, banana) and grains (quinoa) was significantly associated with 29–75% reductions in hair mercury. Collectively, these data demonstrate that communities located hundreds of kilometers from ASGM are vulnerable to chronically elevated mercury exposure. Furthermore, unexpected associations with fish mercury contents and non-fish dietary intake highlight the need for more in-depth analyses of exposure regimes to identify the most vulnerable populations and to establish potential interventions.

Predictors of mitochondrial DNA copy number and damage in a mercury‐exposed rural Peruvian population near artisanal and small‐scale gold mining: An exploratory study

“…The lack of a direct impact of Hg exposure on mtDNA CN or damage is the first report of effect or lack thereof in a human population. We note that the potential for interactive effects with genotoxicants (as has been observed in laboratory models: Wyatt et al, 2017a, b) or with dietary limitations (as in the current study) remains important. The average lesion values for some groups in this study are in the range of 0.4-0.6 lesions/10 kb, compared to previously reported values of 0.75/10 kb for patients with Friedreich's ataxia (Haugen et al, 2010), and 0.17/10 kb for veterans with Gulf War Illness (Chen et al, 2017).…”

“…In addition, the study is limited in its ability to distinguish long‐term and acute Hg exposure as hair measurements represent a time‐integrated measurement corresponding to roughly 2 months prior to collection. Hair samples from this region were demonstrated to be predictive of chronic exposure(Wyatt et al, ); however, acute Hg exposure is likely exclusive to gold miners, which constitute just two study participants. The half‐life of MeHg in blood is approximately 2 months, which is well reflected in our study, since it is approximately the time captured in the hair samples that we obtained (Smith and Farris, ; Yaginuma‐Sakurai et al, ).…”

Elevated Hair Mercury Levels Are Associated With Neurodevelopmental Deficits in Children Living Near Artisanal and Small‐Scale Gold Mining in Peru

“…All but one of the native children had hair mercury levels greater than the U.S. NRC reference value. This is likely a consequence of the high fish consumption documented in native communities in Madre de Dios (Wyatt et al, 2017) and the wider Amazon region (e.g., Farias et al, 2006; Piperata et al, 2013; Roche et al, 2011).…”

“…Second, the region is considered one of the world's most biodiverse, containing a number of important ecological parks and preserves, including Manu National Park and the Tambopata Reserve. Third, ASGM activities are now known to have contributed to mercury contamination events and high levels of methylmercury in waterways, fish tissue, and resident's blood and hair (Ashe, 2012; Diringer et al, 2015; Gonzalez et al, 2019; Hurtado et al, 2006; Weinhouse et al, 2017; Wyatt et al, 2017; Yard et al, 2012), even among individual living hundreds of miles from active mining (Wyatt et al, 2017).…”

“…Limited surveillance of mercury contamination in Madre de Dios has suggested that the communities living near small‐scale gold mining operations may be at risk of health impacts from mercury exposures (Ashe, 2012; Diringer et al, 2015; Wyatt et al, 2017; Yard et al, 2012). Indeed, a number of studies of riverine communities in the Brazilian Amazon suggest mercury exposures in the region may be of a sufficient magnitude to cause subtle neurologic, motor, and somoatosensory deficits in adults (Dolbec et al, 2000; Lebel et al, 1996, 1998; Peplow & Augustine, 2014; Yokoo et al, 2003) and neurodevelopmental delays in infants (Dórea et al, 2012; Marques et al, 2016).…”