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.