Mercury exposure and health impacts among individuals in the artisanal & small-scale gold mining (ASGM) community Herman Gibb, PhD, MPH Gibb Epidemiology Consulting Arlington, VA, USA Different forms of mercury • Elemental mercury • Inorganic mercury (e.g., mercuric nitrate, mercuric chloride, mercurous chloride, mercuric sulfide, mercuric acetate) • Organic mercury (e.g., methylmercury, ethylmercury) Biomarkers of mercury • Hair (methylmercury) • Blood (all forms of mercury) • Urine (elemental and inorganic mercury) Mad as a hatter • In the 19th and 20th Centuries, inorganic mercury (mercuric nitrate) was used in the production of felt for hats. The hatters were exposed to mercury vapor from a reaction that released volatile free mercury. • As early as 1829, adverse health symptoms including mental confusion, emotional disturbances, and muscular weakness were reported among hatters. • A U.S. Public Health Service estimated that in 1934, 80% of American hat makers had mercurial tremors – what the workers referred to as “the shakes.” • The term “mad as a hatter” is associated with the syndrome. The minamata incident • One of the most severe incidents of mercury poisoning occurred in Minamata, Japan, when a local company dumped what is estimated to have been 27 tons of methylmercury into Minamata Bay over a period of 1932-1968. • The methylmercury accumulated in shellfish and fish. • Consumption of the fish and shellfish resulted in the deaths of cats, dogs, pigs, and humans. What became known as Minamata disease is a neurologic syndrome caused by severe mercury poisoning. • Children born to mothers who consumed the fish and shellfish were born with severe congenital deformities. Minamata Disease Symptoms: • Ataxia • Numbness in the hands and feet • General muscle weakness • Narrowing in the field of vision • Damage to hearing and speech Extreme cases: • Insanity • Paralysis • Coma • Death The minamata convention • The Convention is an international treaty designed to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. • The treaty was developed under the aegis of the United Nations Environment Programme. • The Convention was opened for signature in October 2013 in Minamata, Japan. • There are now 102 signatories (countries) to the Convention. The minamata convention • Article 7 and Annex C of the Convention address artisanal and small-scale gold mining (ASGM) and the development of national plans for ASGM. The Convention calls for nations to gather health data, train health care workers, and raise awareness in regard to ASGM activity. • All countries in South America are signatories of the Convention with the exception of Suriname. How and why is mercury used in asgm? • Mercury forms an amalgam with the ore. • Mercury is heated and vaporizes leaving the gold behind. • The method is cheaper than other methods, can be done by one person and is quick and easy. UNEP 2012 UNEP 2012 How big is the problem? • Mercury from ASGM is responsible for 37% of the global emissions of mercury and is the largest single source of air and water mercury. • Mercury vapors in the air around amalgam burning sites can be alarmingly high and almost always exceeds the WHO limit for public exposure of 1.0 µg/m³. UNEP 2013 How widespread is the problem? • Approximately 15 million people, including approximately 3 million women and children, participate in the ASGM industry in 70 countries. • These 70 countries are found primarily in East and Southeast Asia, Sub-Saharan Africa & South America. UNEP 2013 Health effects among those engaged in ASgm Study Where conducted? Yard et al. (2012) Peru Harari et al. (2012) Ecuador Tomicic et al. (2011) Burkina Faso Bose-O’Reilly et al. (2010) Indonesia Effect(s) observed Neurologic, kidney dysfunction, digestive system disorder Tremor Neurologic Mercury intoxication (based on a merger of medical score and biomonitoring results) Higher prevalence of anti-nuclear autoantibodies (ANA) and anti-nucleolar autoantibodies (ANoA) compared to control (i.e., immunological effect) Gardner et al. (2011) Brazil Bose-O’Reilly et al. (2008) Indonesia Zimbabwe Silva et al. (2004) Brazil High prevalence of detectable ANA and ANoA compared to controls Drake et al. (2001) Venezuela Increase in NAG (protein in urine considered evidence of preclinical, nonspecific damage to proximal tubule of kidney) Source: Gibb & O’Leary 2014 Mercury intoxication (based on a merger of medical score and biomonitoring results) found in children Health effects AMONG those indirectly exposed TO ASgm Individuals not directly engaged in ASGM but living in ASGM communities or communities near ASGM Study Where conducted? Nyland et al. (2011) Brazil Immunologic effect (higher prevalence of ANA and ANoA compared to controls) Tian et al. (2010) China Urinary mercury associated with urinary β2-microglobulin and Nacetyl-β-D-glucosaminidase (NAG) (biomarkers of preclinical kidney effects) Alves et al. (2006) Brazil Immunologic effect (higher prevalence of ANA among riverine fish eaters compared to controls) Cordier et al. (2002) French Guiana Harada et al. (2001) Brazil Sensory disturbance; several subjects were diagnosed with Minimata disease Akagi et al. (2000) Philippines Gingival discoloration, adenopathy, underweight, and dermatologic abnormalities found in children Grandjean et al. (1999) Brazil Neurologic effects Lebel et al. (1998) Brazil Neurologic effects Source: Gibb & O’Leary 2014 Effect(s) observed Neurologic effects seen in mothers, no major effects observed in children Urinary mercury concentrations AMONG those working or living in asgm communities 900 800 Urinary Mercury (µg/g-Cr) 700 600 500 400 300 200 100 neurologic signs kidney effects 0 Study Author and Year Hurtado et al. 2006 Mean urinary mercury levels of various exposure groups • 50 µg/L has been associated with kidney damage • 100 µg/L is associated with neurologic effects Mean & range of hair mercury concentrations of female residents of ASGM communities 100 95 90 85 80 75 Hair Mercury (µg/g) 70 65 60 55 50 45 40 35 30 25 20 14.08 15 11.4 10 5 1.12 8.11 9.39 8.25 1.6 0 Hacon et al. 2000 Barbosa et al. 1998 Barbosa et al. Malm et al. 2010 Pinheiro et al. 1998 2005 Study Pinheiro et al. 2005 Cordier et al. 1998 PTWI Mean & range of hair mercury Concentrations of children and infants of asgm communities 80 Hair Mercury (µg/g) 70 60 50 40 30 25.4 20 10 16.1 4.0 1.9 3.8 7.3 10.8 13.4 11.9 17.7 8.6 2.5 0 Study 6.0 1.0 0.9 3.4 AIR MEASUREMENTS AT ASGM OPERATIONS IN VENEZUELA & PERU Drake et al. 2001 (Venezuela) Hurtado et al. 2006 (Peru) • Range: 0.1-6,315 µg/m³ Amalgam smelter • Mean: 183 µg/m³ • Range: 530-4,440 µg/m³ • 20% of the measurements (N=61) were above 50 µg/m³ • Mean: 2,423.3 µg/m³ Concentration at which health effect is reported to occur WHO (2000) WHO (2000) 15 µg/m3 • N=6 Working and/or living in quimbaletes Health effect • Range: 12-55 µg/m³ • Mean: 30.5 µg/m³ Renal tubular effects & changes in plasma enzymes • N=6 Living in artisanal mining town • Range: 3-23 µg/m³ 30 µg/m3 Tremor • Mean: 11.8 µg/m³ • N=5 ASGM Mercury consumption and associated emissions In south america [Adapted from UNEP (2013) Technical Background Report for the Global Mercury Assessment] ASGM Mercury Use (tons) % of total Hg applied to concentrate amalgamation % of total Hg applied to whole ore amalgamation Emission Factor Year of most recent data Mean air emission (tons) Quality of Data* Min Mean Max Bolivia 4 84.0 120.0 156.0 25 75 0.38 2012 45.000 Brazil Chile 4 2 31.5 1.0 45.0 4.0 58.5 7.0 50 50 50 50 0.50 0.50 2007 2009 22.500 2.000 Colombia 3 90.0 180.0 270.0 17 83 0.33 2012 60.000 Ecuador French Guiana Paraguay Peru 3 25.0 50.0 75.0 20 80 0.35 2007 17.500 3 3.8 7.5 11.3 100 0 0.75 2008 5.625 1 4 0.1 49.0 0.3 70.0 0.5 91.0 100 25 0 75 0.75 0.38 2012 2010 0.225 26.25 Venezuela 3 7.5 15.0 22.5 25 75 0.38 2005 5.625 Country *Quality of Data: Worst (1) to Best (4) Summary 1. The problem of mercury emissions from ASGM is widespread – ASGM occurs in 70 countries and is responsible for 37% of the global emissions of mercury 2. Health effects associated with ASGM have been reported in at least 10 countries on 3 continents. These effects are primarily neurologic, kidney, and immunologic. 3. Urinary mercury concentrations in ASGM communities are significantly elevated above concentrations associated with health effects. 4. Hair mercury concentrations in women living in or near ASGM communities are significantly elevated above the hair mercury concentrations associated with WHO’s Provisional Tolerable Weekly Intake. 5. Hair mercury concentrations in children living in or near ASGM communities are elevated above those of other fish eating populations. 6. Brazil has the most gold miners in South America (estimated 500,000), but the amount of mercury emissions (tons released) is estimated to be higher in Bolivia, Colombia, and Peru.