Mercury Exposure and Health Impacts among Individuals in the Artisanal and Small-Scale Gold Mining Community: A Comprehensive Review

Table 1. Health effects observed in ASGM areas.
Reference (country of origin) Study population Observed effects
Abbreviations: ANA, antinuclear autoantibodies; ANoA, anti-nucleolar autoantibodies; GM, geometric mean; IFN interferon; IL, interleukin; NAG, N-acetyl-β-D-glucoaminidase; TNF, tumor necrosis factor.
Studies that included persons occupationally exposed to Hg from ASGM    
Yard et al. 2012 (Peru) 103 people living in a gold mining area, including 35 who had direct contact with Hg at least once per month. > 50% reported headache, mood swings, or muscle weakness. Previous medical diagnoses included digestive system disorder (n = 20), kidney dysfunction (n = 9), and nervous system disorders (n = 4). Participants reporting kidney dysfunction had higher urine total Hg concentrations (GM = 12.0 μg/g-creatinine) than those not reporting kidney dysfunction (GM = 5.1 μg/g-creatinine; p < 0.05). Urinary Hg concentrations were significantly (p < 0.05) higher among people who heated amalgam compared with those who never heated amalgam.
Harari et al. 2012 (Ecuador) 200 gold miners; 37 gold merchants; 72 referents. Tremor was found to be associated with blood and urinary Hg. Elimination of Hg appeared to be modified by a polymorphism. The gold merchants had the highest blood and urinary Hg because they burned amalgam on a daily basis.
Tomicic et al. 2011 (Burkina Faso) 93 gold workers; 779 workers related to gold mining activities. Nearly half of the 93 workers considered most susceptible to Hg exposure reported ≥ 5 symptoms possibly related to Hg exposure (frequent headaches, sleep disorder, dizziness/fits of giddiness, wounds/irritation of mouth, unusual tiredness, walking difficulty, trembling, pins and needles/tingling in hands or feet, vision disorder, persistent cough, thoracic pain, rhinitis). Gold ore dealers were found to have higher urine Hg than ore washers; dealers heated Hg an average of 13.2 times per day compared with individuals not dealing gold who heated Hg 7.8 times per day.
Bose-O’Reilly et al. 2010a (Indonesia) Group 1: 21 Sulawesi residents (control group); Group 2: 66 Kalimantan residents living in an exposed area with no occupational exposure; Group 3: 18 Sulawesi residents living in an exposed area with no occupational exposure; Group 4: 30 Kalimantan Hg workers—panning, but no smelting; Group 5: 17 Sulawesi, Hg workers—panning, but no smelting; Group 6: 69 Kalimantan Hg workers—smelting; Group 7: 60 Sulawesi, Hg worker–smelting. A determination of Hg intoxication was based on a merging of medical score and biomonitoring results. The following rates of intoxication were observed: Group 1: 0%; Group 2: 31:8%; Group 3: 16.7%; Group 4: 43.3%; Group 5: 23.5%; Group 6: 62.3%; Group 7: 41.6%. Hg-exposed workers showed typical symptoms of Hg intoxication, such as movement disorders (ataxia, tremor, dysdiadochokinesia, etc.).
Gardner et al. 2010 (Brazil) 98 gold miners in Rio Rato (Para state); 91 emerald miners (Goias state); 57 diamond miners (Goias state). Hg-exposed gold miners had higher prevalence of detectable ANA and ANoA as compared with diamond and emerald miners with no occupational Hg exposure. Hg-exposed gold miners with detectable ANA or ANoA in serum had significantly higher serum concentrations of the proinflammatory cytokines IL-1β, TNF-α, and IFN-γ as compared with diamond and emerald miners. The authors concluded that the results suggest that Hg increases autoimmune dysfunction and systemic inflammation.
Bose-O’Reilly et al. 2008 (Indonesia, Zimbabwe) 80 children working with Hg (51 Indonesia, 29 Zimbabwe); 36 children living in Hg-exposed areas (22 Indonesia, 14 Zimbabwe); 50 [control group (31 Indonesia, 19 Zimbabwe)]. 8% of children working with Hg in Indonesia were considered Hg intoxicated. 29% of children living in Hg-exposed areas in Zimbabwe were considered intoxicated. 55% of children working with Hg in Zimbabwe were considered intoxicated. None of the control children were considered intoxicated. Chronic Hg intoxication is a combination of severe and specific symptoms and raised Hg levels in biomarkers.

Silva et al. 2004;


98 (54 currently working in a gold mine) in Rio Rato, a gold mining community in the mid-Tapajos watershed; 140 in Jacareacanga, a riverine settlement on the mid-Tapajos River (no current occupational exposure; elevated MeHg in fish consumed); 98 in Tabatinga, a riverine community in the lower Amazon (no occupational exposure; low MeHg in fish). There was a high prevalence of detectable ANA (54.1%) and ANoA (40.8%) in Rio Rato miners (≥ 1:10 serum dilution). The prevalence was lower in Jacareancanga (10.7% ANA and 18% ANoA) and much lower in Tabatinga (7.1% ANA and 2.0% ANoA).
Drake et al. 2001 (Venezuela) 21 small-scale gold miners. 3 had detectable NAG, a biological marker of preclinical, nonspecific damage to the kidney’s proximal tubule cells in excess of reference values.
Drasch et al. 2001 (Philippines) 102 occupationally exposed ball-millers and amalgam-smelters; 63 Mt. Diwata residents, environmentally exposed; 100 individuals residing downstream in Monkayo; 42 Davao residents (control group). Workers reported fatigue, tremor, memory problems, restlessness, weight loss, metallic taste, and disturbances in sleeping. Diagnosis of Hg intoxication in the workers was significantly higher in the downstream community, in the Mt. Diwata nonoccupational group, and in the workers compared with the control group. Median concentrations of Hg in blood, urine, and hair among the workers were significantly different from the concentrations found in the control group.
Studies of persons not engaged in gold mining but living in areas affected by ASGM    
Nyland et al. 2011 (Brazil) 232 persons living in the Lower Tapajós River Basin in the Brazilian Amazon, an area with a history of Hg use in small-scale gold mining. Elevated titers of Hg in blood and plasma were associated with ANA but not with ANoA. Pro-inflammatory and antinflammatory interleukins and IL-17 were increased with MeHg exposure but were decreased in the subset of the population with elevated ANA. The authors concluded that the data indicate an immunotoxic or immunomodulatory effect of MeHg in the range of exposures found in this population but suggest that there may be a specific phenotype of MeHg susceptibility.
Tian et al. 2009 (China) 203 persons living in an area contaminated with Hg due to gold extraction; 191 persons from a control area. Urinary Hg was significantly correlated with β2-microglobulin and NAG.
Alves et al. 2006 (Brazil) 105 adults in seven riverine communities (104 consumed fish daily); six riverine communities were along the mid-Rio Negro; one was located along the tributary Rio Cuiuni; 105 controls (volunteer donors at a blood bank); fish species high in MeHg were consumed more frequently by the riverine population (45.5%) than by controls (18.8%). Mean hair Hg of the riverines (34.5 ppm) was significantly higher than controls (1.0 ppm). Positive serum ANA was more frequently observed in riverine fish-eaters (12.4%) than controls (2.9%). There was, however, no significant association between hair Hg and ANA.
Cordier et al. 2002 (French Guiana) 156 children and their 104 mothers in Upper Maroni communities (high Hg exposure); 69 children and their 51 mothers in Camponi (medium Hg exposure); 153 children and their 115 mothers in Awala (low Hg exposure). (Hg exposure was the result of gold mining activity.) No major neurological signs were observed in the children examined. After adjusting for potential confounders, a dose-dependent association was observed between maternal hair Hg level and increased deep tendon reflexes, poorer coordination of legs, and decreased performance in the Standard-Binet Copying score, which measures visuospatial organization.
Harada et al. 2001 (Brazil) 132 fishermen and their families (n = 182) in three fishing villages along the Tapajos River. General sensory disturbance was observed in 16 of 50 subjects (32%) whose hair Hg was > 20 ppm. Several subjects were diagnosed with Minamata disease.
Akagi et al. 2000 (Philippines) 162 school­children in a community of Mindanao where gold is processed. Predominant findings among the children were gingival discoloration, adenopathy, underweight, and dermatologic abnormalities.
Grandjean et al. 1999 (Brazil) 351 school­children between 7 and 12 years of age in four villages along the Tapajos River basin downstream from a gold mining area; 135 mothers of 252 children were examined; hair samples obtained from 113 mothers of 222 children were examined. Neuropsychological tests of motor function, attention, and visuospatial performance showed decrements with increasing hair Hg concentrations.
Lebel et al. 1998 (Brazil) 91 adult inhabitants living 250 km downstream from the most extensive gold mining fields in Brazil. The villagers were not exposed to Hg vapor. The area was accessible only by water. Near visual contrast sensitivity and manual dexterity, adjusted for age, decreased significantly with increasing hair Hg levels. There was a tendency for muscular fatigue to increase and muscular strength to decrease in women. Hair Hg levels were significantly higher for persons who presented disorganized movements on an alternating movement task and for persons with restricted visual fields. Hair Hg concentrations were < 50 μg/g.