The burden of chronic mercury intoxication in artisanal small-scale gold mining in Zimbabwe: data availability and preliminary estimates

Abstract

BackgroundArtisanal small-scale gold mining (ASGM) is a poverty-driven activity practiced in over 70 countries worldwide. Zimbabwe is amongst the top ten countries using large quantities of mercury to extract gold from ore. This analysis was performed to check data availability and derive a preliminary estimate of disability-adjusted life years (DALYs) due to mercury use in ASGM in Zimbabwe.MethodsCases of chronic mercury intoxication were identified following an algorithm using mercury-related health effects and mercury in human specimens. The sample prevalence amongst miners and controls (surveyed by the United Nations Industrial Development Organization in 2004 and the University of Munich in 2006) was determined and extrapolated to the entire population of Zimbabwe. Further epidemiological and demographic data were taken from the literature and missing data modeled with DisMod II to quantify DALYs using the methods from the Global Burden of Disease (GBD) 2004 update published by the World Health Organization (WHO). While there was no disability weight (DW) available indicating the relative disease severity of chronic mercury intoxication, the DW of a comparable disease was assigned by following the criteria 1) chronic condition, 2) triggered by a substance, and 3) causing similar health symptoms.ResultsMiners showed a sample prevalence of 72% while controls showed no cases of chronic mercury intoxication. Data availability is very limited why it was necessary to model data and make assumptions about the number of exposed population, the definition of chronic mercury intoxication, DW, and epidemiology. If these assumptions hold, the extrapolation would result in around 95,400 DALYs in Zimbabwe’s total population in 2004.ConclusionsThis analysis provides a preliminary quantification of the mercury-related health burden from ASGM based on the limited data available. If the determined assumptions hold, chronic mercury intoxication is likely to have been one of the top 20 hazards for population health in Zimbabwe in 2004 when comparing with more than 130 categories of diseases and injuries quantified in the WHO’s GBD 2004 update. Improving data quality would allow more accurate estimates. However, the results highlight the need to reduce a burden which could be entirely avoided.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-069X-13-111) contains supplementary material, which is available to authorized users.

Global Burden of Disease of Mercury Used in Artisanal Small-Scale Gold Mining

“…The diagnostic tool developed by Drasch et al 14 has previously been applied to samples of gold miners in Indonesia, 16,17 Tanzania, 29 Philippines, 14 and Zimbabwe. 18 For the current analysis, raw data from these studies were pooled and reanalyzed in the new built primary dataset. The analysis was based on urine samples, and the essential indicators of the diagnostic tool 30 were applied ( Table 2).…”

“…This assumption was made based on the published research as summarized previously. 18 Therefore, only the morbidity partdthe YLDsdis calculated and added to zero YLLs to express DALYs.…”

“…50 Prevalence. Earlier analyses of the primary data 14,15,17,18,29 yielded diverging prevalence estimates, because an extensive diagnostic tool 14 was used rather than the essential indicators 30 and combined with mercury concentrations in blood, hair and urine rather than, as was done in this analysis, focusing on urine samples. It was decided to focus on urine data to only consider exposures to mercury vapor.…”

“…The burden was estimated at about 95,400 disability-adjusted life years (DALYs) using an incidence-based approach and a approximative disability weight (DW). 18 Pure Earth and Green Cross Switzerland 19 assumed a global ASGM BoD of 1.5 million DALYs as a rough estimate. Besides the generally limited database, a missing DW, a factor needed for DALY quantification, hampered the calculation of more valid estimates.…”

Signs and symptoms of mercury-exposed gold miners

“…Symptoms of severe damage of the brain (cerebellum) such as ataxia, tremor and movement disorders were found in the mining communities. In 70% of the amalgam burners in Kadoma a Hg intoxication was diagnosed" [37]. 4.…”