Mercury Exposures in Informal Gold Miners and Relatives in Southern Peru

Mercury pollution in Peru: geographic distribution, health hazards, and sustainable removal technologies

Peru is one of the great gold producers worldwide. However, a significant portion of the gold produced in Peru derives from artisanal small-scale gold mining (ASGM) in the Andes and Amazon. In ASGM, gold amalgamation with mercury (Hg) is a critical procedure to refine gold through the formation of Au-Hg alloys. Due to the rudimentary and improvised techniques conducted by small-scale and informal miners, Hg contamination has become of great concern and is strictly associated with ASGM. Multiple studies have evidenced notably high concentrations of Hg in consumable fish species, rivers, sediments, and air in locations where ASGM is one of the main sources of income to local communities and is carried out aggressively. In the present review, we have conducted a systematic search for national and international literature reporting the concentration and distribution of Hg pollution across environmental compartments, biota, and human samples in Peru. The results and data retrieved from the articles were quantitatively and qualitatively analyzed, and the distribution of Hg across environmental compartments was visualized through a geographic information system. Additionally, we reviewed the use of adsorption techniques as alternatives to treat Hg⁰ vapor from the gold shop and smelter flues, one of the main sources of hazardous levels of Hg exposure.

Dried blood spots to characterize mercury speciation and exposure in a Colombian artisanal and small-scale gold mining community

The artisanal and small-scale gold mining (ASGM) sector uses the most mercury (Hg) worldwide. Despite health concerns associated with high Hg exposures in these communities, ASGM sites are often situated in resource limited and remote regions which challenge traditional human biomonitoring approaches. To help overcome such challenges, here we report on the development of a high-quality method to characterize chemical speciation of Hg in dried blood spots (DBS), and then apply this method to assess Hg exposures in people sampled from an ASGM community (Pueblito Mejia) and a nearby town (Barranco de Loba) in Colombia. We collected DBS and urine samples from 35 individuals in 2018, and used these to assess occupational (DBS inorganic Hg (InHg) and urine total Hg (THg) measures) and environmental (DBS methylmercury (MeHg) measures) exposure of participants to different forms of Hg. The accuracy and precision of the DBS-based measures generally met assay performance guideline. In study participants, the mean concentrations of DBS MeHg, InHg, and THg, and urine THg were 1.9, 4.1, 6.0, and 3.1 μg/L, respectively. For 37% of the participants, DBS THg values exceeded the 5 μg/L 'alert level' proposed by the German HBM Commission. About 60% of the blood Hg was in the InHg form thus exemplifying a need to speciate Hg in blood sampled from ASGM sites to better understand the contributions of environmental and occupational exposure sources. This study demonstrates the feasibility of using DBS for Hg speciation exposure assessments in remote and resource-limited areas such as ASGM communities.

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

Children living near artisanal and small-scale gold mining (ASGM) are at risk of exposure to mercury, a neurotoxicant. It is not certain whether such exposures are harming development, as they occur in underresourced contexts entwined with other stressors, such as malnutrition and enteric infection. This study sought to investigate the association between hair-mercury levels and visual-motor, cognitive, and physical development among children living near ASGM in the Peruvian Amazon. Total hair-mercury levels were measured in 164 children ages 5-12 living in Madre de Dios, Peru. Primary outcomes included Visual-Motor Integration assessed via the Beery-VMI Developmental Test, General Cognitive Ability assessed via the Batería-III Woodcock-Munoz (Spanish-language Woodcock-Johnson Tests of Cognitive Abilities), and Physical Health assessed via anthropometry/hemoglobin counts. Mean (SD) hair-mercury level was 2.06 (2.43) μg/g. Fifty-four children (32.9%) had hair-mercury levels above the World Health Organization reference level of 2.0 μg/g. After controlling for sex, child age, maternal education, and family socioeconomic status, each one unit increase in log hair-mercury level was associated with a 1.01 unit decrease in Visual-Motor Integration (95%CI: -2.06, 0.05, p = 0.061), a 2.59 unit decrease in General Cognitive Ability (95%CI: -4.52, -0.66, p = 0.012), and a 2.43 unit decrease in Physical Health (95%CI: -5.34, 0.49, p = 0.096). After adjustment for covariates, children with hair-mercury levels exceeding the World Health Organization reference level scored 4.68 IQ points lower in Cognitive Ability than their peers. Mercury exposures related to ASGM may be harming child development in the Peruvian Amazon. Children in this region may benefit from intervention to reach their full developmental potential.

Heavy metal pollution caused by small-scale metal ore mining activities: A case study from a polymetallic mine in South China

Although metal ore mining activities are well known as an important source of heavy metals, soil pollution caused by small-scale mining activities has long been overlooked. This study investigated the pollution of surface soils in an area surrounding a recently abandoned small-scale polymetallic mining district in Guangdong province of south China. A total of 13 tailing samples, 145 surface soil samples, and 29 water samples were collected, and the concentrations of major heavy metals, including Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Pb, and Se, were determined. The results show that the tailings contained high levels of heavy metals, with Cu, Zn, As, Cd, and Pb occurring in the ranges of 739-4.15 × 10³, 1.81 × 10³-5.00 × 10³, 118-1.26 × 10³, 8.14-57.7, and 1.23 × 10³-6.99 × 10³ mg/kg, respectively. Heavy metals also occurred at high concentrations in the mine drainages (15.4-17.9 mg/L for Cu, 21.1-29.3 mg/L for Zn, 0.553-0.770 mg/L for Cd, and 1.17-2.57 mg/L for Pb), particularly those with pH below 3. The mean contents of Cu, Zn, As, Cd, and Pb in the surface soils of local farmlands were up to 7 times higher than the corresponding background values, and results of multivariate statistical analysis clearly indicate that Cu, Zn, Cd, and Pb were largely contributed by the mining activities. The surface soils from farmlands surrounding the mining district were moderately to seriously polluted, while the potential ecological risk of heavy metal pollution was extremely high. It was estimated that the input fluxes from the mining district to the surrounding farmlands were approximately 17.1, 59.2, 0.311, and 93.8 kg/ha/yr for Cu, Zn, Cd, and Pb, respectively, which probably occurred through transport of fine tailings by wind and runoff, and mine drainage as well. These findings indicate the significant need for proper containment of the mine tailings at small-scale metal ore mines.

Global Burden of Disease of Mercury Used in Artisanal Small-Scale Gold Mining

BACKGROUND

Artisanal small-scale gold mining (ASGM) is the world's largest anthropogenic source of mercury emission. Gold miners are highly exposed to metallic mercury and suffer occupational mercury intoxication. The global disease burden as a result of this exposure is largely unknown because the informal character of ASGM restricts the availability of reliable data.

OBJECTIVE

To estimate the prevalence of occupational mercury intoxication and the disability-adjusted life years (DALYs) attributable to chronic metallic mercury vapor intoxication (CMMVI) among ASGM gold miners globally and in selected countries.

METHODS

Estimates of the number of artisanal small-scale gold (ASG) miners were extracted from reviews supplemented by a literature search. Prevalence of moderate CMMVI among miners was determined by compiling a dataset of available studies that assessed frequency of intoxication in gold miners using a standardized diagnostic tool and biomonitoring data on mercury in urine. Severe cases of CMMVI were not included because it was assumed that these persons can no longer be employed as miners. Cases in workers' families and communities were not considered. Years lived with disability as a result of CMMVI among ASG miners were quantified by multiplying the number of prevalent cases of CMMVI by the appropriate disability weight. No deaths are expected to result from CMMVI and therefore years of life lost were not calculated. Disease burden was calculated by multiplying the prevalence rate with the number of miners for each country and the disability weight. Sensitivity analyses were performed using different assumptions on the number of miners and the intoxication prevalence rate.

FINDINGS

Globally, 14-19 million workers are employed as ASG miners. Based on human biomonitoring data, between 25% and 33% of these miners-3.3-6.5 million miners globally-suffer from moderate CMMVI. The resulting global burden of disease is estimated to range from 1.22 (uncertainty interval [UI] 0.87-1.61) to 2.39 (UI 1.69-3.14) million DALYs.

CONCLUSIONS

This study presents the first global and country-based estimates of disease burden caused by mercury intoxication in ASGM. Data availability and quality limit the results, and the total disease burden is likely undercounted. Despite these limitations, the data clearly indicate that mercury intoxication in ASG miners is a major, largely neglected global health problem.

Human health risk assessment of mercury vapor around artisanal small-scale gold mining area, Palu city, Central Sulawesi, Indonesia

Emissions of elemental mercury, Hg(0), from artisanal small-scale gold mining activities accounted for 37% of total global Hg(0) emissions in 2010. People who live near gold-mining areas may be exposed to high concentrations of Hg(0). Here, we assessed the human health risk due to Hg(0) exposure among residents of Palu city (Central Sulawesi Province, Indonesia). The area around the city has more than 60t of gold reserves, and the nearby Poboya area is the most active gold-mining site in Indonesia. Owing to its geography, the city experiences alternating land and sea breezes. Sampling was done over a period of 3 years (from 2010 Aug. to 2012 Dec.) intermittently with a passive sampler for Hg(0), a portable handheld mercury analyzer, and a mercury analyzer in four areas of the city and in the Poboya gold-processing area, as well as wind speeds and directions in one area of the city. The 24-h average concentration, wind speed, and wind direction data show that the ambient air in both the gold-processing area and the city was always covered by high concentration of mercury vapor. The Hg(0) concentration in the city was higher at night than in the daytime, owing to the effect of land breezes. These results indicate that the inhabitants of the city were always exposed to high concentrations of Hg(0). The average daytime point-sample Hg(0) concentrations in the city, as measured with a handheld mercury analyzer over 3 days in July 2011, ranged from 2096 to 3299ngm(-3). In comparison, the average daytime Hg(0) concentration in the Poboya gold-processing area was 12,782ngm(-3). All of these concentrations are substantially higher than the World Health Organization air-quality guideline for annual average Hg exposure (1000ngm(-3)). We used the point-sample concentrations to calculate hazard quotient ratios by means of a probabilistic risk assessment method. The results indicated that 93% of the sample population overall was at risk (hazard quotient ratio ≥1 and cut off at the 95th percentile value of the sample population) of mercury toxicity, that is, damage to the central nervous system due to chronic exposure. The corresponding percentages for the northern, central, southern, and western areas of the city were 83%, 84%, 95%, and 95%, respectively. Our results indicate that the residents of Palu city are at serious risk from exposure to high concentrations of atmospheric Hg(0).

Metal concentration in water, sediment and four fish species from Lake Titicaca reveals a large-scale environmental concern

Although intensive mining activity and urban sewage discharge are major sources of metal inputs to Lake Titicaca, the risk posed by metal pollution to wildlife and human populations has been poorly studied. In this study we compared the concentrations of Cu, Zn, Cd, Hg, Pb, Co, and Fe in water, sediment, and two tissues (liver and muscle) of four fish species (Odontesthes bonariensis, Orestias luteus, Orestias agassii, and Trichomycterus rivulatus) across important fishery areas in Lake Titicaca. The concentration of Pb in water at the discharge sites of the main rivers and of most elements, with the exception of Co and Fe, in all fish collected in this study exceeded the safety thresholds established by international legislation. The highest metal concentrations were observed in benthopelagic species, and liver tissue was identified as the main depository for all metals with the exception of mercury. The metal bioaccumulation pattern in fish was weakly related to the metal concentrations in the environment with the exception of Hg at the most polluted location, partly explained by the different metabolic role of essential and non-essential elements and the influence of other factors such as species' ecology and individual traits in the bioaccumulation of most metals. As metal pollution extended across the study area and high metal concentrations were detected in all four fish species, we urge the authorities to enforce legislation for water and fish consumption and to evaluate the effects of metal pollution on fish health.

A review of mercury exposure among artisanal small-scale gold miners in developing countries

PURPOSE

Extraction of gold using mercury has been a way out of poverty for millions of people in developing countries. Artisanal small-scale gold mining (ASGM) has expanded during the last decades and is often carried out under primitive conditions. Thus, workers in this industry may be exposed to high levels of mercury and suffer from toxic effects from mercury exposure. The objective of this review was to provide an outline of the studies available on elemental mercury exposure among artisanal small-scale gold miners.

METHODS

Searching the PubMed and Embase databases, 26 studies with a total of 3,005 exposed subjects and 442 controls across 14 different developing countries were found. Urine mercury levels were used as biomarkers of exposure.

RESULTS

In general, the urine mercury levels were elevated and a considerable proportion of workers had urine mercury levels above existing guidelines. Exposed subjects were stratified into residents, miners, millers, smelters, and refiners, who by work task content were expected to be increasingly exposed to mercury. This group order did show a clear trend of increasing mercury levels. Mercury levels differed substantially between studies. Possible explanations include dissimilarities in gold extraction methods, use of protective devices, and selection of participants.

CONCLUSIONS

This review provides evidence that artisanal gold miners and residents of the mining sites are exposed to mercury vapour to an extent where acute and long-term toxic effects of mercury are likely. Interventions aimed at reducing exposure and emission of mercury from ASGM are needed.

Mercury exposure among artisanal gold miners in Madre de Dios, Peru: a cross-sectional study

INTRODUCTION

Exposure to mercury, a toxic metal, occurs primarily from inhaling mercury vapors or consuming methylmercury-contaminated fish. One third of all anthropogenic mercury emissions worldwide are from artisanal gold mining, which uses mercury to extract gold. Although recent reports suggest that the Madre de Dios region in Peru (with >30,000 artisanal miners) has extensive mercury contamination, residents had never been assessed for mercury exposure. Thus, our objective was to quantify mercury exposure among residents of an artisanal mining town in Madre de Dios and to assess risk factors for exposure.

METHODS

We conducted a cross-sectional assessment of 103 residents of an artisanal gold mining town in July 2010. Each participant provided a urine and blood sample and completed a questionnaire assessing potential exposures and health outcomes. We calculated geometric mean (GM) urine total mercury and blood methylmercury concentrations and compared log-transformed concentrations between subgroups using linear regression.

RESULTS

One third (34.0 %) of participants were gold miners. All participants had detectable urine total mercury (GM, 5.5 μg/g creatinine; range, 0.7-151 μg/g creatinine) and 91 % had detectable blood methylmercury (GM, 2.7 μg/L; range, 0.6-10 μg/L); 13 participants (13 %) reported having kidney dysfunction or a neurological disorder. Urine total mercury concentrations were higher among people who heated gold-mercury amalgams compared with people who never heated amalgams (p < 0.05); methylmercury concentrations were higher among fish consumers compared with nonfish consumers (p < 0.05).

CONCLUSION

Our findings suggest that mercury exposure may be widespread in Huaypetue.

Health assessment of artisanal gold miners in Indonesia

Small scale miners use mercury to extract gold from ore in many countries. An environmental and health assessment was performed in Indonesia in two regions, Galangan in Central Kalimantan and Talawaan in Northern Sulawesi. The environmental assessment showed severe mercury contamination of the sediments, and increased mercury levels in local fish. For the health investigation 281 volunteers were recruited and examined by a standardized questionnaire, a neurological examination and neuro-psychological tests. A medical score was used consisting of significant factors of mercury intoxication. Mercury exposed workers showed typical symptoms of mercury intoxication, such as movement disorders (ataxia, tremor, dysdiadochokinesia, etc.). Blood, urine and hair samples were taken from any participant and analyzed for mercury. The mercury concentration in the biomonitors was high, partly extreme high in the working population, increased in the population living in the same habitat and low in the control group. By a standard protocol which includes a combination of threshold values of mercury in the biomonitors and a medical sum score the diagnosis of chronic mercury intoxication was made for highly burdened workers (amalgam smelters) in 55% in Sulawesi and in 62% in Kalimantan. Less exposed mineral processors and the general population in the mining areas were also intoxicated to a high percentage.

Health assessment of artisanal gold miners in Tanzania

In 2003 UNIDO (United Nations Industrial Development Organization) conducted an environmental and health assessment in a small-scale mining area in Tanzania. BGS (British Geological Survey) performed the environmental assessment. The Institute of Forensic Medicine - University of Munich performed the health assessment. The results of the medical, neurological and neuro-psychological examination of 180 participants from the affected area of Rwamagasa and 31 controls were analyzed. Urine, blood and hair samples were analyzed to detect the level of mercury body burden. Mercury concentrations in the bio-monitors urine, blood and hair were statistically significantly higher in the exposed population from Rwamagasa compared to the control group from Katoro. Only amalgam burners showed mercury levels above the toxicological threshold limits. A speciation of mercury in hair indicated that mainly elemental mercury vapor contributed to the high body burden of the artisanal miners. 104 amalgam-burners, the most exposed population group, were examined. 25 of these workers were found to be intoxicated. Small-scale mining is a serious health hazard for amalgam burners. Reduction of the exposure is essential to prevent further damage.

Human mercury exposure and adverse health effects in the Amazon: a review

This paper examines issues of human mercury (Hg) exposure and adverse health effects throughout the Amazon region. An extensive review was conducted using bibliographic indexes as well as secondary sources. There are several sources of Hg (mining, deforestation, reservoirs), and exposure takes place through inhalation or from fish consumption. There is a wide range of exposure, with mean hair-Hg levels above 15 microg/g in several Amazonian communities, placing them among the highest reported levels in the world today. Dietary Hg intake has been estimated in the vicinity of 1-2 microg/kg/day, considerably higher than the USEPA RfD of 0.1 microg/kg/day or the World Health Organization recommendation of 0.23 microg/kg/day. Neurobehavioral deficits and, in some cases, clinical signs have been reported both for adults and children in relation to Hg exposure in several Amazonian countries. There is also some evidence of cytogenetic damage, immune alterations, and cardiovascular toxicity. Since fish provide a highly nutritious food source, there is an urgent need to find realistic and feasible solutions that will reduce exposure and toxic risk, while maintaining healthy traditional dietary habits and preserving this unique biodiversity.