Mercury use in artisanal small-scale gold mining threatens human health: measures to describe and reduce the health risk

Steckling N. Mercury use in artisanal small-scale gold mining threatens human health: measures to describe and reduce the health risk. Bielefeld: Universität Bielefeld; 2016.**Background:** Mercury is used in more than 70 countries to extract gold in artisanal small-scale gold mining (ASGM). The application of mercury is simple and plays a key role in the livelihood for more than 16 million gold miners. Mercury is added to the crushed ore and builds an amalgam with the gold it contains. The amalgam is then smelted, the mercury evaporates, and gold remains. The amalgam smelting is the main source of mercury exposure in ASGM. ASGM is the largest anthropogenic source of global mercury pollution. The toxic metal poses a risk to the health of both the miners involved and the residents in the area, who do not work in ASGM. Mercury can be detected in critical quantities in the human bodies of both groups. The local threat aside, the mercury released is also of global concern due to its high transportability and persistence in the environment as well as its tendency to bioaccumulate. Mercury is neurotoxic and its harmful effects on the development of unborn children and infants are particularly alarming. Describing and reducing the health risk posed by the mercury used in ASGM are urgently needed measures, as demanded in the 2013 agreed Minamata Convention on Mercury. Objective and research questions: The overall objective of this thesis is to apply public health measures to describe the health risk due to the use of mercury in selected ASGM areas and to test the feasibility of a mercury-free extraction procedure using borax to reduce the risk. The main research question is: How to describe and reduce the human health risk of mercury used in ASGM? Four subquestions regard (I) the relevance of addressing different subgroups when attempting to describe and reduce the human health risk of mercury used in ASGM, (II) the mercury body burden in ASGM, (III) the health burden due to mercury exposure in ASGM, and (IV) a means of reducing the health risk due to the use of mercury in ASGM. The response to the research questions is included in the present synopsis and based on five published and peer-reviewed scientific papers. **Materials and methods:** This thesis comprises different materials and methods. The literature used was searched by applying narrative and systematic approaches (papers P1, P2, P3, P4, P5). P1 is a narrative review about children’s health and exposure to mercury. In P2 and P3, the mercury body burden was determined using human biomonitoring (HBM) data collected in Mongolia in 2008 (P2) and Zimbabwe in 2004 and 2006 (P3) and compared with the German HBM values, HBM I and II (P2, P3). Health effects attributable to mercury were analyzed for the sample from Zimbabwe using anamnestic data, neuropsychological testing, and clinical examination (P3). Cases of chronic mercury intoxication were identified and the sample prevalence determined and extrapolated to all of Zimbabwe (P3). The environmental burden of disease (EBD) was quantified in terms of disability-adjusted life years (DALYs) including primary, secondary, and modeled data (P3). Disease-specific and generic health state descriptions were developed which could be used to derive disability weights (DWs) for disease stages of the intoxication due to exposure to mercury in gold mining. Information about the health-related quality of life (HRQoL) and a comprehensive list of possible symptoms were gathered by expert elicitation. The list of symptoms was supplemented by a systematic literature search (P4). The feasibility of a mercury-free gold extraction method using borax was tested in a field project in Kadoma, Zimbabwe, in 2013 (P5). **Results:** Children are particularly vulnerable to mercury exposure. They might be exposed directly and indirectly to it from ASGM while several subgroups (pregnant and breastfeeding women, parents working as miners, etc.) play a role in the children’s exposure (P1). In the districts Bornuur and Jargalant, Mongolia, a sample of women of child-bearing age involved in mining or living in mining areas (P2), and in Kadoma, Zimbabwe (P3), a sample of adult and child male and female miners were investigated. Both samples showed raised mercury concentrations in human specimens above health-related exposure limit values. The analyses of health data showed a higher frequency of possibly mercury-related health effects in miners in comparison to controls (P3). The EBD in male and female adult and child miners in Zimbabwe in 2004 was high (total of 95,400 DALYs, 8 DALYs/1,000 population) while subgroup analyses identified males, particularly male children and young male adult workers, as the group with the highest burden (P3). The HRQoL of individuals with chronic metallic mercury vapor intoxication (CMMVI) caused by mercury exposure from ASGM can be substantially reduced by a number of health symptoms of varying severities (P4). In field testing, the application of a mercury-free gold extraction method using borax has been considered as feasible, what could reduce the health risk posed by mercury in ASGM (P5). **Discussion:** This thesis provides evidence to improve the understanding of the human health risk due the use of mercury in ASGM. The human health risk posed by mercury in ASGM can be described as considerable, subgroup-specific, and, indeed, reducible. The health risk is considerable given the particular risk of children (P1), the high mercury concentrations in specimens obtained from miners and not occupationally exposed residents in ASGM areas (P2, P3), the high prevalence of intoxications and EBD of miners (P3), the extensive range of possible health symptoms, and the reduced HRQoL due to mercury intoxication (P4). The health risk can be considered subgroup-specific for several reasons. These include the particular risk to children and the influence which the behavior of other subgroups has on the children’s exposure (P1), the human body burden detectable in miners and non-occupationally exposed residents in ASGM areas varying by sex and age (P2, P3), the prevalence of intoxications and EBD of intoxications in miners varying by sex and age (P3), and the extensive range of possible health symptoms which can but do not have to occur in individuals as a result of exposure to mercury (P3, P4). The health risk is reducible with regard to the fact that a mercury-free gold extraction method has been tested successfully (P5). Research of international literature reveals significant differences in mercury concentrations in human specimens of subgroups in ASGM areas. Combining HBM with health data is reasonable for identifying cases of chronic mercury intoxication, has also been done in samples of other countries. Based on the preliminary DALY estimates, chronic mercury intoxication from ASGM was integrated in the top 20 causes of the BoD in Zimbabwe in 2004 as estimated by the World Health Organization (WHO) in the GBD 2004 update. A national estimation of DALYs due the use of mercury in ASGM had not been investigated up to this point. Other DALY quantifications with focus on mercury are available, however, the research gaps for the use of mercury in ASGM (e.g., missing DWs) are mentioned in international literature. Results about the HRQoL of CMMVI enabled comparisons with the HRQoL of other health states investigated in other studies. The mercury-free gold extraction procedure using borax was identified as feasible in ASGM in Kadoma, Zimbabwe, and was also reported from other ASGM areas. However, a sustainable introduction needs follow-up implementation activi-ties. Further main limitations of this thesis are restricted literature search strategies, small sample sizes, and the reliance on assumptions and modeled data. The results of this thesis can be integrated into 8 of 9 steps of a human health risk analysis. Measures used to describe the risk should be applied in a health impact assessment (HIA) to monitor the success of a comprehensive introduction of a mercury-free extraction procedure. **Conclusions:** It is the conclusion of this thesis that the human health risk from mercury used in ASGM is considerable, subgroup-specific, and reducible. Various materials and methods were used, while some (e.g., estimation of DALYs and determination of HRQoL) had not been applied to this topic before. The relevance of different subgroups in the effort to describe and reduce the risk due to mercury from ASGM was identified. Some subgroups require attention most urgently either due to their particularly high vulnerability (fetuses and children), their influence on the exposure of others (e.g., pregnant women), or their particularly high EBD (young male gold miners). This thesis underlines the necessity to reduce the human health risk due to mercury in ASGM. The results of this thesis should be understood as an impetus to finding solutions for the continuing threat to human health from the use of mercury in ASGM

Comparing the self-reported health-related quality of life (HRQoL) of artisanal and small-scale gold miners and the urban population in Zimbabwe using the EuroQol (EQ-5D-3L+C) questionnaire: a cross-sectional study

BACKGROUND The role of artisanal and small-scale gold mining (ASGM) as a source of income is rapidly gaining importance in the economically difficult times in Zimbabwe. Besides limited epidemiological data, no data about the self-reported health-related quality of life (HRQoL) of artisanal and small-scale gold miners exist. The aim of the project was to access HRQoL of ASGM workers to improve the data base and compare the data to the urban Zimbabwean population. METHODS Data from 83 artisanal and small-scale gold miners in Kadoma, Zimbabwe was analysed. The HRQoL was assessed using the EuroQol dimensions (mobility, self-care, usual activities, pain/discomfort, anxiety/depression) accompanied by the cognition add-on questionnaire (EQ-5D-3L+C) and associated visual analogue scale (VAS). We described the EQ-5D dimensions and VAS values and computed health utility (HU) values using the Zimbabwean tariff. The proportions of miners reporting no problem in each EQ-5D dimension were compared with corresponding proportions reporting any problem (moderate or severe), and mean HU and VAS values were analysed across subgroups of the sample. To test differences between subgroups, Fisher's exact test was used and between urban and mining population, Student's t-test was used. RESULTS The reported health states of miners were homogenous, with a large amount (42%) reporting 'full health'. Mean (SD) VAS and HU values were 81.0 (17.5) and 0.896 (0.13), respectively. Subgroup analysis showed that miners with a lower education reported significantly more problems in the dimension of daily activities and miners with mercury contact had more problems in the dimensions of pain/discomfort and cognition. Comparison between mining and urban population showed that in the oldest age group, self-rated VAS values of miners were significantly higher than of their urban counterparts. CONCLUSIONS There were no significant differences in the HRQoL of mining and urban populations. However, the reason might be adverse health effects faced by the urban population that do not apply to rural mining areas. A higher education level of miners can improve the HRQoL, which is especially impaired by problems in the cognition dimension

Accidents, Injuries, and Safety among Artisanal and Small-Scale Gold Miners in Zimbabwe

Artisanal and small-scale gold mining (ASGM) employs 14-19 million people globally. There is limited research on accidents, injuries, and safety in Zimbabwe's ASGM. This study investigates the prevalence of accidents and injuries, as well as the associated risks and existing safety practices. A cross-sectional survey was conducted among artisanal and small-scale gold miners. Data from 401 participants were analyzed using descriptive statistics and regression analysis. The prevalence of accidents and injuries was 35.0% and 25.7%. Accidents associated with experiencing injuries included mine collapses and underground trappings. The major injury risk factors were digging, blasting, being male, being 18-35 years old, crushing, and the underground transportation of workers and materials. Injuries were reported highest among the miners working 16 to 24 h per day. Participants had heard about personal protective equipment (PPE). There was training and routine inspections mainly on PPE use. Mine owners and supervisors were reported as responsible for OSH, which was mainly PPE use. Practices including the use of wire winch ropes and escape routes were rare. There was ignorance on underground mine shaft support. The mining regulations that had the potential to introduce comprehensive safety controls were not adaptable. We recommend applicable health and safety regulations for Zimbabwe's ASGM

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

Health and Safety Risk Mitigation among Artisanal and Small-Scale Gold Miners in Zimbabwe

Artisanal and small-scale gold mining (ASGM) is often associated with no or compromised attention to health and safety. Although headlines of fatal accidents in Zimbabwe characterise ASGM, little attention is paid to prevention strategies. This study, therefore, explores health and safety risk mitigation in ASGM in Zimbabwe to inform prevention strategies. A qualitative design was used with focus group discussions and in-depth interviews. Data were analysed using thematic analysis, coding, and descriptive statistics. Reported factors contributing to compromised health and safety included immediate causes, workplace factors, ASM related factors, and contextual factors, with interconnectedness between the causal factors. In addition, factors related to ASGM were significant. For risk mitigation, formalisation, organisation of risk reduction, behaviour change, and enforcement of prevention strategies is proposed. A multi-causal analysis is recommended for risk assessment and accident investigation. A multi-stakeholder approach could be considered for risk mitigation including community and public health interventions. However, risk mitigation has been characterised by gaps and weaknesses such as lacking ASM policy, lack of capital, poor enforcement, negative perceptions, and non-compliance. Therefore, we recommend addressing the threats associated with health and safety mitigation to ensure health and safety protection in ASGM

Disability Weights for Chronic Mercury Intoxication Resulting from Gold Mining Activities: Results from an Online Pairwise Comparisons Survey

Steckling N, Devleesschauwer B, Winkelnkemper J, et al. Disability Weights for Chronic Mercury Intoxication Resulting from Gold Mining Activities: Results from an Online Pairwise Comparisons Survey. International Journal of Environmental Research and Public Health. 2017;14(1): 57

Disease profile and health-related quality of life (HRQoL) using the EuroQol (EQ-5D + C) questionnaire for chronic metallic mercury vapor intoxication

Steckling N, Plaß D, Bose-O’Reilly S, Kobal AB, Krämer A, Hornberg C. Disease profile and health-related quality of life (HRQoL) using the EuroQol (EQ-5D + C) questionnaire for chronic metallic mercury vapor intoxication. Health and Quality of Life Outcomes. 2015;13(1): 196.Background Toxic mercury is still being used today for example by workers mining gold, resulting in diverse health symptoms in users and individuals in proximity. A considerable burden of disease (BoD) can be assumed, while previous analyses were limited by data scarcity. Besides limited epidemiological data, neither data about the health-related quality of life (HRQoL) nor about the disease severity (disability weight, DW) is available. The aim of the project was to develop disease profiles of chronic metallic mercury vapor intoxication (CMMVI) by including the HRQoL to improve the data basis for BoD analyses of gold miners exposed to mercury. Methods Disease profiles comprising the disease label [a], differentiation into disease stages [b], description of the cause of exposure [c], a list of common symptoms [d], and an assessment of the HRQoL [e] were developed using expert elicitation and literature search. The HRQoL was assessed by experts using the five EuroQol dimensions accompanied by the cognition add-on questionnaire (EQ-5D + C). Results The ten sources used for the analyses (interview transcript, presentation, and eight literature reviews) identified more than 250 terms describing 85 distinguishable health effects of CMMVI. The analysis revealed 29 common symptoms that were frequently mentioned. Moderate and severe CMMVI cases differ regarding their symptoms and/or symptom severity and HRQoL, resulting in the EQ-5D + C-3L codes 121222 and 233333, respectively. Conclusions The profiles should be used to facilitate the ascertainment of CMMVI cases, to compare the HRQoL with other diseases, to derive DWs for improving BoD estimates, and to foster discussions about how to reduce the associated burden

Health-related quality of life (EQ-5D + C) among people living in artisanal and small-scale gold mining areas in Zimbabwe: a cross-sectional study

BACKGROUND In Zimbabwe, an estimated 500,000 people work in the sector of artisanal and small-scale gold mining (ASGM). Two million Zimbabweans are dependent on this sector. Using mercury is common to extract gold from ore. Long term exposure to mercury can cause various adverse health conditions including chronic mercury intoxication. The influence of these adverse health effects on the health-related quality of life (HRQoL) is still unknown. The aim of this study is to assess the HRQoL of people who identify themselves as miners, and to analyze potential influencing factors, such as age, years of working with mercury and health conditions caused by mercury exposure. METHODS This cross-sectional study assessed the HRQoL using the standardized EQ-5D + C (3 L) questionnaire and collected human specimens (blood, urine) of people living and possibly working in ASGM areas in Zimbabwe. Factors such as age, years of working with mercury and adverse health conditions possibly caused by mercury exposure were analyzed with regards to their influence on the HRQoL. RESULTS The 207 participants (82% male, mean age 38 years) reported 40 different health states. Of the study participants 42.5% reported to be in complete good health while 57.5% reported being unwell in different ways. Nine participants (4.3%) were identified with chronic mercury intoxication, whereas 92 participants (33.3%) had mercury levels above the \textquotedblAlert\textquotedbl threshold in at least one specimen. Having chronic mercury intoxication has a significant negative influence on the HRQoL, when taking into account age, gender and years of working with mercury. Cognitive problems were the most reported in the questionnaire, however, the association between this domain separately and the HRQoL was not verified. CONCLUSION This study shows that adverse health effects caused by chronic exposure to mercury, have a negative influence on the HRQoL among people living in ASGM areas

Analysis of the Mercury Distribution in Blood as a Potential Tool for Exposure Assessment - Results from Two Artisanal and Small-Scale Gold Mining Areas in Zimbabwe

People in artisanal and small-scale gold mining (ASGM) areas are frequently exposed to high levels of mercury (Hg). Hg analyses in urine and whole blood are the gold standard of biomonitoring, although this may not provide sufficient information about the source of exposure, e.g., due to the use of Hg for gold extraction or due to nutrition. To evaluate, whether the pharmacokinetic properties of individual Hg species may be useful for exposure assessment, we determined the Hg levels in different blood components from 199 participants. Therefore, whole blood was centrifuged on-site to yield erythrocytes and plasma. Globin was isolated from the erythrocytes by precipitation with ethyl acetate. Albumin was isolated from plasma by gradual precipitation with saturated ammonium sulfate solution. Hg levels in all samples were determined by using a direct Hg analyzer. Median Hg levels for whole blood, erythrocytes, and plasma were 2.7, 3.7, and 1.3 μg/l, respectively. In globin and albumin, median Hg levels were 10.3 and 7.9 μg/kg, respectively. The distribution of Hg was strongly correlated with whole blood Hg levels (p < 0.01) and the time between the last use of Hg and the date of the participation (p < 0.01). The results suggest that the distribution of Hg in blood is substantially affected by the extent and the frequency of the exposure to elemental Hg. Therefore, the analysis of Hg in erythrocytes and plasma may be a valuable tool for Hg exposure assessment in ASGM areas

Biomonitoring of arsenic, cadmium and lead in two artisanal and small-scale gold mining areas in Zimbabwe

People living and working in artisanal and small-scale gold mining (ASGM) areas are frequently exposed to elemental mercury (Hg), which is used for gold extraction. However, additional exposure to other toxic metals such as arsenic (As), cadmium (Cd) and lead (Pb) may result from mining-related activities and could be ingested via dust, water or food. In these areas, only limited biomonitoring data is available for toxic metals other than Hg. In particular, data about the exposure to As, Cd and Pb is unavailable for the Zimbabwean population. Therefore, we conducted a cross-sectional study in two ASGM areas in Zimbabwe to evaluate the internal exposure to these metals. In total, urine and blood samples from 207 people that identified themselves as miners were collected and analysed for As and Cd in urine as well as Pb in blood by GF-AAS. Median levels (interquartile ranges in μg/l) of As and Pb were 9.7 μg/l (4.0, 18.5) and 19.7 μg/l (12.5, 34.5), respectively. The 25th percentile and the median for Cd were below the limit of detection (0.5 μg/l); the 75th percentile was at 0.9 μg/l. The results were compared to reference values found for the general population in the USA and Germany, and a significant number of participants exceeded these values (As, 33 %; Cd, 27 %; Pb, 32 %), indicating a relevant exposure to toxic metals. Although not representative for the Zimbabwean population, our results demonstrate that the exposure to toxic metals is relevant for the public health in Zimbabwe and requires further investigation