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 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
• Mercury from ASGM is responsible for 37% of the global emissions of mercury and is the largest single source of air and water mercury.
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? Effect(s) observed
Yard et al. (2012) Peru Neurologic, kidney dysfunction, digestive system disorder
Harari et al. (2012) Ecuador Tremor
Tomicic et al. (2011) Burkina Faso Neurologic
Bose-O’Reilly et al. (2010) Indonesia
Mercury intoxication (based on a merger of medical score and biomonitoring results)
Gardner et al. (2011) BrazilHigher prevalence of anti-nuclear autoantibodies (ANA) and anti-nucleolar autoantibodies (ANoA) compared to control (i.e., immunological effect)
Bose-O’Reilly et al. (2008)
IndonesiaZimbabwe
Mercury intoxication (based on a merger of medical score and biomonitoring results) found in children
Silva et al. (2004) Brazil High prevalence of detectable ANA and ANoA compared to controls
Drake et al. (2001) VenezuelaIncrease in NAG (protein in urine considered evidence of preclinical, nonspecific damage to proximal tubule of kidney)
Source: Gibb & O’Leary 2014
Health effects AMONG those indirectly exposed TO ASgm
Individuals not directly engaged in ASGM but living in ASGM communities or communities near ASGM
StudyWhere
conducted?
Effect(s) observed
Nyland et al. (2011) Brazil Immunologic effect (higher prevalence of ANA and ANoA compared to controls)
Tian et al. (2010) ChinaUrinary mercury associated with urinary β2-microglobulin and N-acetyl-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 GuianaNeurologic effects seen in mothers, no major effects observed in children
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 effectsSource: Gibb & O’Leary 2014
Urinary mercury concentrations AMONG those working or living in
asgm communities
0
100
200
300
400
500
600
700
800
900
Study Author and Year
Uri
nary
Merc
ury
(µ
g/g
-Cr)
neurologic signskidney effects
Hurtado et al. 2006
• 50 µg/L has been associated with kidney damage• 100 µg/L is associated with neurologic effects
Mean urinary mercury levels of various exposure groups
Mean & range of hair mercury concentrations of female residents
of ASGM communities
Hacon et al. 2000
Barbosa et al. 1998
Barbosa et al. 1998
Malm et al. 2010
Pinheiro et al. 2005
Pinheiro et al. 2005
Cordier et al. 1998
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
1.128.11
14.0811.4
8.259.39
1.6
Study
Hair
Merc
ury
(µ
g/g
)
PTWI
Mean & range of hair mercury Concentrations of children and infants of
asgm communities
Dorea
et a
l. 20
12
Dorea
et a
l. 20
12
Dorea
et a
l. 20
12
Barbo
sa e
t a.
199
8
Barbo
sa e
t a.
199
8
Malm
et a
l. 20
10
Pinhe
iro e
t al. 2
007
(M)
Pinhe
iro e
t al. 2
007
(F)
Grand
jean
et al. 1
999
Grand
jean
et al. 1
999
Grand
jean
et al. 1
999
Cordier
et a
l. 19
98
Count
er e
t al.
2005
Umba
ngta
lad
et a
l. 20
07
Umba
ngta
lad
et a
l. 20
07
Mur
phy et
al.
2008
0
10
20
30
40
50
60
70
80
4.0 1.9 3.87.3
10.8 8.6
16.113.411.9
25.4
17.7
2.56.0
1.0 0.9 3.4
Study
Hair
Merc
ury
(µ
g/g
)
AIR MEASUREMENTS AT ASGM OPERATIONS IN VENEZUELA &
PERUDrake et al. 2001 (Venezuela)
• Range: 0.1-6,315 µg/m³
• Mean: 183 µg/m³
• 20% of the measurements (N=61) were above 50 µg/m³
Concentration at which
health effect is reported to
occur
Health effect
WHO (2000) 15 µg/m3
Renal tubular effects &
changes in plasma enzymes
WHO (2000) 30 µg/m3 Tremor
Hurtado et al. 2006 (Peru)
Amalgam smelter
• Range: 530-4,440 µg/m³
• Mean: 2,423.3 µg/m³
• N=6
Working and/or living in quimbaletes
• Range: 12-55 µg/m³
• Mean: 30.5 µg/m³
• N=6
Living in artisanal mining town
• Range: 3-23 µg/m³
• 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]
CountryQuality of
Data*
ASGM Mercury Use (tons) % of total
Hg applied to
concentrate
amalgamation
% of total Hg applied to whole
ore amalgamati
on
Emission
Factor
Year of
most recent
data
Mean air
emission (tons)
Min Mean Max
Bolivia 4 84.0 120.0156.
025 75 0.38 2012 45.000
Brazil 4 31.5 45.0 58.5 50 50 0.50 2007 22.500Chile 2 1.0 4.0 7.0 50 50 0.50 2009 2.000Colombia
3 90.0 180.0270.
017 83 0.33 2012 60.000
Ecuador 3 25.0 50.0 75.0 20 80 0.35 2007 17.500French Guiana
3 3.8 7.5 11.3 100 0 0.75 2008 5.625
Paraguay
1 0.1 0.3 0.5 100 0 0.75 2012 0.225
Peru 4 49.0 70.0 91.0 25 75 0.38 2010 26.25Venezuela
3 7.5 15.0 22.5 25 75 0.38 2005 5.625
*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.