Silicosis prevalence and exposure-response relations in South African goldminers

The impact of environmental conditions on non-communicable diseases in sub-Saharan Africa: A scoping review of epidemiologic evidence

Background

The burden of non-communicable diseases (NCDs) in sub-Saharan Africa (SSA) is increasing. Environmental conditions such as heavy metals and air pollution have been linked with the incidence and mortality of chronic diseases such as cancer, as well as cardiovascular and respiratory diseases. We aimed to scope the current state of evidence on the impact of environmental conditions on NCDs in SSA.

Methods

We conducted a scoping review to identify environmental conditions linked with NCDs in SSA by identifying studies published from January 1986 through February 2023. We searched African Index Medicus, Ovid Medline, Scopus, Web of Science, and Greenfile. Using the PICOS study selection criteria, we identified studies conducted in SSA focussed on physical environmental exposures and incidence, prevalence, and mortality of NCDs. We included only epidemiologic or quantitative studies.

Results

We identified 6754 articles from electronic database searches; only 36 met our inclusion criteria and were qualitatively synthesised. Two studies were conducted in multiple SSA countries, while 34 were conducted across ten countries in SSA. Air pollution (58.3%) was the most common type of environmental exposure reported, followed by exposure to dust (19.4%), meteorological variables (13.8%), heavy metals (2.7%), soil radioactivity (2.7%), and neighbourhood greenness (2.7%). The examined NCDs included respiratory diseases (69.4%), cancer (2.7%), stroke (5.5%), diabetes (2.7%), and two or more chronic diseases (19.4%). The study results suggest an association between environmental exposures and NCDs, particularly for respiratory diseases. Only seven studies found a null association between environmental conditions and chronic diseases.

Conclusions

There is a growing body of research on environmental conditions and chronic diseases in the SSA region. Although some cities in SSA have started implementing environmental monitoring and control measures, there remain high levels of environmental pollution. Investment can focus on improving environmental control measures and disease surveillance.

How We Treat Drug-Susceptible Pulmonary Tuberculosis: A Practical Guide for Clinicians

Tuberculosis (TB) remains one of the leading causes of morbidity and mortality worldwide and pulmonary TB (PTB) is the main variant responsible for fueling transmission of the infection. Effective treatment of drug-susceptible (DS) TB is crucial to avoid the emergence of Mycobacterium tuberculosis-resistant strains. In this narrative review, through a fictional suggestive case of DS PTB, we guide the reader in a step-by-step commentary to provide an updated review of current evidence in the management of TB, from diagnosis to post-treatment follow-up. World Health Organization and Centre for Diseases Control (CDC) guidelines for TB, as well as the updated literature, were used to support this manuscript.

The prevalences and levels of occupational exposure to dusts and/or fibres (silica, asbestos and coal): A systematic review and meta-analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury

BACKGROUND

The World Health Organization (WHO) and the International Labour Organization (ILO) are developing joint estimates of the work-related burden of disease and injury (WHO/ILO Joint Estimates), with contributions from a large number of individual experts. Evidence from human, animal and mechanistic data suggests that occupational exposure to dusts and/or fibres (silica, asbestos and coal dust) causes pneumoconiosis. In this paper, we present a systematic review and meta-analysis of the prevalences and levels of occupational exposure to silica, asbestos and coal dust. These estimates of prevalences and levels will serve as input data for estimating (if feasible) the number of deaths and disability-adjusted life years that are attributable to occupational exposure to silica, asbestos and coal dust, for the development of the WHO/ILO Joint Estimates.

OBJECTIVES

We aimed to systematically review and meta-analyse estimates of the prevalences and levels of occupational exposure to silica, asbestos and coal dust among working-age (≥ 15 years) workers.

DATA SOURCES

We searched electronic academic databases for potentially relevant records from published and unpublished studies, including Ovid Medline, PubMed, EMBASE, and CISDOC. We also searched electronic grey literature databases, Internet search engines and organizational websites; hand-searched reference lists of previous systematic reviews and included study records; and consulted additional experts.

STUDY ELIGIBILITY AND CRITERIA

We included working-age (≥ 15 years) workers in the formal and informal economy in any WHO and/or ILO Member State but excluded children (< 15 years) and unpaid domestic workers. We included all study types with objective dust or fibre measurements, published between 1960 and 2018, that directly or indirectly reported an estimate of the prevalence and/or level of occupational exposure to silica, asbestos and/or coal dust.

STUDY APPRAISAL AND SYNTHESIS METHODS

At least two review authors independently screened titles and abstracts against the eligibility criteria at a first stage and full texts of potentially eligible records at a second stage, then data were extracted from qualifying studies. We combined prevalence estimates by industrial sector (ISIC-4 2-digit level with additional merging within Mining, Manufacturing and Construction) using random-effects meta-analysis. Two or more review authors assessed the risk of bias and all available authors assessed the quality of evidence, using the ROB-SPEO tool and QoE-SPEO approach developed specifically for the WHO/ILO Joint Estimates.

RESULTS

Eighty-eight studies (82 cross-sectional studies and 6 longitudinal studies) met the inclusion criteria, comprising > 2.4 million measurements covering 23 countries from all WHO regions (Africa, Americas, Eastern Mediterranean, South-East Asia, Europe, and Western Pacific). The target population in all 88 included studies was from major ISCO groups 3 (Technicians and Associate Professionals), 6 (Skilled Agricultural, Forestry and Fishery Workers), 7 (Craft and Related Trades Workers), 8 (Plant and Machine Operators and Assemblers), and 9 (Elementary Occupations), hereafter called manual workers. Most studies were performed in Construction, Manufacturing and Mining. For occupational exposure to silica, 65 studies (61 cross-sectional studies and 4 longitudinal studies) were included with > 2.3 million measurements collected in 22 countries in all six WHO regions. For occupational exposure to asbestos, 18 studies (17 cross-sectional studies and 1 longitudinal) were included with > 20,000 measurements collected in eight countries in five WHO regions (no data for Africa). For occupational exposure to coal dust, eight studies (all cross-sectional) were included comprising > 100,000 samples in six countries in five WHO regions (no data for Eastern Mediterranean). Occupational exposure to silica, asbestos and coal dust was assessed with personal or stationary active filter sampling; for silica and asbestos, gravimetric assessment was followed by technical analysis. Risk of bias profiles varied between the bodies of evidence looking at asbestos, silica and coal dust, as well as between industrial sectors. However, risk of bias was generally highest for the domain of selection of participants into the studies. The largest bodies of evidence for silica related to the industrial sectors of Construction (ISIC 41-43), Manufacturing (ISIC 20, 23-25, 27, 31-32) and Mining (ISIC 05, 07, 08). For Construction, the pooled prevalence estimate was 0.89 (95% CI 0.84 to 0.93, 17 studies, I2 91%, moderate quality of evidence) and the level estimate was rated as of very low quality of evidence. For Manufacturing, the pooled prevalence estimate was 0.85 (95% CI 0.78 to 0.91, 24 studies, I2 100%, moderate quality of evidence) and the pooled level estimate was rated as of very low quality of evidence. The pooled prevalence estimate for Mining was 0.75 (95% CI 0.68 to 0.82, 20 studies, I2 100%, moderate quality of evidence) and the pooled level estimate was 0.04 mg/m3 (95% CI 0.03 to 0.05, 17 studies, I2 100%, low quality of evidence). Smaller bodies of evidence were identified for Crop and animal production (ISIC 01; very low quality of evidence for both prevalence and level); Professional, scientific and technical activities (ISIC 71, 74; very low quality of evidence for both prevalence and level); and Electricity, gas, steam and air conditioning supply (ISIC 35; very low quality of evidence for both prevalence and level). For asbestos, the pooled prevalence estimate for Construction (ISIC 41, 43, 45,) was 0.77 (95% CI 0.65 to 0.87, six studies, I2 99%, low quality of evidence) and the level estimate was rated as of very low quality of evidence. For Manufacturing (ISIC 13, 23-24, 29-30), the pooled prevalence and level estimates were rated as being of very low quality of evidence. Smaller bodies of evidence were identified for Other mining and quarrying (ISIC 08; very low quality of evidence for both prevalence and level); Electricity, gas, steam and air conditioning supply (ISIC 35; very low quality of evidence for both prevalence and level); and Water supply, sewerage, waste management and remediation (ISIC 37; very low quality of evidence for levels). For coal dust, the pooled prevalence estimate for Mining of coal and lignite (ISIC 05), was 1.00 (95% CI 1.00 to 1.00, six studies, I2 16%, moderate quality of evidence) and the pooled level estimate was 0.77 mg/m3 (95% CI 0.68 to 0.86, three studies, I2 100%, low quality of evidence). A small body of evidence was identified for Electricity, gas, steam and air conditioning supply (ISIC 35); with very low quality of evidence for prevalence, and the pooled level estimate being 0.60 mg/m3 (95% CI -6.95 to 8.14, one study, low quality of evidence).

CONCLUSIONS

Overall, we judged the bodies of evidence for occupational exposure to silica to vary by industrial sector between very low and moderate quality of evidence for prevalence, and very low and low for level. For occupational exposure to asbestos, the bodies of evidence varied by industrial sector between very low and low quality of evidence for prevalence and were of very low quality of evidence for level. For occupational exposure to coal dust, the bodies of evidence were of very low or moderate quality of evidence for prevalence, and low for level. None of the included studies were population-based studies (i.e., covered the entire workers' population in the industrial sector), which we judged to present serious concern for indirectness, except for occupational exposure to coal dust within the industrial sector of mining of coal and lignite. Selected estimates of the prevalences and levels of occupational exposure to silica by industrial sector are considered suitable as input data for the WHO/ILO Joint Estimates, and selected estimates of the prevalences and levels of occupational exposure to asbestos and coal dust may perhaps also be suitable for estimation purposes. Protocol identifier: https://doi.org/10.1016/j.envint.2018.06.005. PROSPERO registration number: CRD42018084131.

Mining Migrant Worker Recruitment Policy and the Production of a Silicosis Epidemic in Late 20th-Century Southern Africa

Objectives

Between the 1980s and 2000s, an epidemic of silicosis was identified in migrant black gold miners, many from neighbouring countries, who had worked in the South African gold mines. This study uses the newly available employment database of a large gold mining company to demonstrate how a sustained rise in employment duration in a new cohort of black migrant workers resulted from changes in recruitment policy, and it examines the implications for current surveillance and redress.

Methods

Contract data of 300,774 workers from the employment database of a multi-mine gold mining company were analysed for 1973-2018. Piecewise linear regression was applied to determine trends in cumulative employment, including South African versus cross-border miners. The proportions with cumulative employment of at least 10, 15, or 20 years, typical thresholds for chronic silicosis, were also calculated.

Results

Five calendar phases were identified between 1973 and 2018. During the second phase, 1985-2013, mean cumulative duration of employment rose fivefold, from 4 to 20 years. Cumulative employment continued to rise, although more slowly, before peaking in 2014 at 23.5 years and falling thereafter to 20.1 years in 2018. Over most of the 1973-2018 period, miners from neighbouring countries had greater cumulative employment than South African miners. Overall, the proportion of miners exiting with at least 15 years of cumulative employment rose from 5% in 1988 to 75% in 2018. This report identifies a number of fundamental changes in labour recruitment policy in the gold mining industry in the 1970s which provide an explanation for the subsequent rise in cumulative exposure and associated silicosis risk.

Conclusions

These new data support the hypothesis of a silicosis epidemic driven by increasing cumulative silica dust exposure in a new cohort of circular migrant workers from the 1970s. They inform current programmes to improve surveillance of this neglected population for silicosis and related disease and to provide medical examinations and compensation to a large number of former gold mines. The analysis highlights the lack of information on cumulative employment and silicosis risk among migrant miners in previous decades. The findings have global relevance to the plight of such migrant workers in hazardous occupations.

Occupational Silica Exposure and Dose-Response for Related Disorders-Silicosis, Pulmonary TB, AIDs and Renal Diseases: Results of a 15-Year Israeli Surveillance

BACKGROUND

The exposure patterns of respirable crystalline silica based on environmental records, as well as the link to different diseases, are not well described.

AIMS AND OBJECTIVES

In this study, we evaluated the risk for various diseases in relation to occupational silica exposure, including Silicosis, pulmonary tuberculosis (TB), Autoimmune disorders (AIDs) and Renal diseases.

METHODS

We assessed the relationship between silica exposure and the rate of various diseases such as silicosis, pulmonary TB, AIDs and renal diseases in a cross-sectional study. We reviewed the medical records and exposure level of workers exposed to silica during the past two decades.

RESULTS

261 workers were included in the study, total duration of exposure 15.6 years (±SD 8.74); 42.15% of them were employed in the artificial marble industry and 29.5% in manufacturing and construction industries. The average yearly silica exposure levels were 0.23 mg/m³ (±0.34). The average cumulative silica concentration was 3.59 mg/m³/y (±4.80). We found 25 (9.58%) incident cases of silicosis, 10 cases of chronic obstructive pulmonary disease (COPD) and emphysema (3.83%), six cases of several AIDs (2.30%), five cases of pulmonary TB (1.92%), three cases of renal diseases (1.15%), two cases of sarcoidosis (0.77%) and no lung cancer cases. When compared to studies with the same endpoint we found excess risk of silicosis (RR = 2.67/0.13 = 20.5, 95% CI 9.85 to 42.86)), pulmonary TB (RR = 30.70, CI 3.43-274.49, p = 0.002) and AIDs (RR = 2.87, 95% CI = 1.27 to 6.48 p = 0.01).

CONCLUSIONS

Silica exposure was a significant risk factor for silicosis, pulmonary TB and AIDs. Our findings are important given persistent worldwide silica-related epidemics in low and high-income countries.

Diagnostic approach and management of bilateral pneumothorax due to silicosis in Indonesian male: A rare case

BACKGROUND

Bilateral pneumothorax due to silicosis was a rare case, so diagnosis and management are essential to the report.

CASE PRESENTATION

A 29-year-old Indonesian male complained of shortness of breath, cough, and body weight loss. Medical history interpreted pulmonary tuberculosis and successful treatment in 6 months. Physical examination and chest radiograph showed bilateral pneumothorax. The patient was diagnosed with bilateral pneumothorax due to silicosis and treated usage chest tube insertion and video-assisted thoracoscopic surgery (VATS). The patient has improved his condition after a few days of receiving post-surgery treatment.

DISCUSSION

Exposure to silica can determine through a spectrophotometer. The therapy of silicosis is still challenging because of the disease's progressivity and complications.

CONCLUSION

Silicosis is not only a chronic and progressive disease but also leads to many complications, including bilateral pneumothorax.

Current global perspectives on silicosis-Convergence of old and newly emergent hazards

Silicosis not a disease of the past. It is an irreversible, fibrotic lung disease specifically caused by exposure to respirable crystalline silica (RCS) dust. Over 20,000 incident cases of silicosis were identified in 2017 and millions of workers continue to be exposed to RCS. Identified case numbers are however a substantial underestimation due to deficiencies in reporting systems and occupational respiratory health surveillance programmes in many countries. Insecure workers, immigrants and workers in small businesses are at particular risk of more intense RCS exposure. Much of the focus of research and prevention activities has been on the mining sector. Hazardous RCS exposure however occurs in a wide range of occupational setting which receive less attention, in particular the construction industry. Recent outbreaks of silicosis associated with the fabrication of domestic kitchen benchtops from high‐silica content artificial stone have been particularly notable because of the young age of affected workers, short duration of RCS exposure and often rapid disease progression. Developments in nanotechnology and hydraulic fracking provide further examples of how rapid changes in technology and industrial processes require governments to maintain constant vigilance to identify and control potential sources of RCS exposure. Despite countries around the world dealing with similar issues related to RCS exposure, there is an absence of sustained global public health response including lack of consensus of an occupational exposure limit that would provide protection to workers. Although there are complex challenges, global elimination of silicosis must remain the goal.

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Access of migrant gold miners to compensation for occupational lung disease: Quantifying a legacy of injustice

Background

A legacy of the South African gold mining industry, now in decline, is a large burden of silicosis and tuberculosis among former migrant miners from rural South Africa and surrounding countries, particularly Lesotho and Mozambique. This neglected population faces significant barriers in filing claims for compensation for occupational lung disease. The objective of the study was to gain insight into the extent of such barriers, particularly for former miners and cross-border migrants.

Methods

The database of a large gold mining company and the statutory compensation authority were analyzed for the period 1973–2018 by country of origin, age, and employment status at the time of claim filing. Proportions and odds ratios (ORs) for each of the compensable diseases were calculated by the above variables. Processing delays of claims were also calculated.

Results

Annual company employment declined from 240,718 in 1989 to 43,024 in 2018 and the proportion of cross-border migrants within the workforce from 51.0 to 28.1%. The compensation database contained 68,612 claims. The majority of compensable claims in all diagnostic categories were from active miners. The odds of cross-border miners relative to South African miners filing a claim depended on employment status. For example, the OR for Lesotho miners filing while in active employment was 1.86 (95% CI 1.81, 1.91), falling to 0.94 (95% CI 0.91, 0.98) among former miners. The equivalent findings for Mozambiquan miners were 0.95 (95% CI 0.91, 1.00), falling to 0.44 (95% CI 0.41, 0.47). Median processing delays over the whole period were from 1.1 years from filing to adjudication, and 3.8 years from filing to payment.

Conclusions

The findings provide a quantitative view of differential access to occupational lung disease compensation, including long processing delays, among groups of migrant miners from the South African gold mines. There is a deficit of compensable claims for silicosis and silico-tuberculosis among former miners irrespective of country of origin. While cross-border miner groups appear to file more claims while active, this is reversed once they leave employment. Current large-scale efforts to provide medical examinations and compensation justice to this migrant miner population need political and public support and scrutiny of progress.

Urgent Need for a Comprehensive Public Health Response to Artisanal Small-Scale Mining

Informal sector mining is a growing enterprise in countries around the world providing livelihood to >40 million self-employed miners. The use of mercury in gold processing has been the sole focus of most research and public health interventions in artisanal mining. Few programs work to improve health among communities mining other commodities including sand, aggregates, quartz, lead, gemstones, coal and other materials. Although mercury is a major environmental challenge in countries with extensive gold mining, artisanal miners are also exposed to silica dust, metals and other safety hazards. The available evidence regarding hazardous exposures among self-employed miners suggests that the public health implications are much broader. There is a growing body of evidence linking exposures to silica dust to tuberculosis and other lung diseases among artisanal miners. Studies have also documented exposures to lead and other metals including arsenic, cadmium, cobalt and chromium in informal mining communities. Silica-dust exposures are higher in artisanal mining than levels reported in large industrial mining. There is ample evidence that artisanal miners are experiencing health impacts not just from mercury but also from exposures to noise, silica dust and metals. Practical, low-cost solutions have been pilot tested and shown to reduce respirable silica dust and metal exposures among miners and ore processors. Governments, development agencies and global health funders should invest in comprehensive public health programs to respond to these needs.

Occupational exposure to crystalline silica and peripheral biomarkers: An update

Peripheral biomarkers are important tools for detecting occupational exposures to prevent the onset and/or progression of diseases. Studies that reveal early peripheral biomarkers are highly important to preserve the health of workers and can potentially contribute to diagnosing and/or prognosing occupational pathologies. Exposure to crystalline silica is a problem in several workplaces because it increases the risk of chronic obstructive pulmonary disease (COPD), tuberculosis, cancer, and pulmonary fibrosis, clinically defined as silicosis. Silicosis is diagnosed by chest radiography and/or lung tomography in advanced stages when there is a severe loss of lung function. Peripheral biomarkers can help in diagnosing early changes prior to silicosis and represent a highly important technical-scientific advance that is minimally invasive. This review aimed to investigate the biomarkers studied for evaluating occupational exposure to crystalline silica and to understand the recent advances in this area. Potential oxidative, inflammatory, and immunological biomarkers were reviewed, as well as routine biomarkers such as biochemical parameters. It was found that biomarkers of effect such as serum CC16 and l-selectin levels could represent promising alternatives. Additionally, studies have shown that neopterin levels in urine and serum can be used to monitor worker exposure. However, further studies are needed that include a greater number of participants, different times of exposure to crystalline silica, and a combination of silicosis patients and healthy volunteers. Evaluating the concentration of crystalline silica in occupational environments, its impact on biomarkers of effect, and alterations in lung function could contribute to revealing early health alterations in workers in a more robust manner.

Respirable dust and crystalline silica exposure among different mining sectors in India

Silicosis is one of the major occupational lung diseases among miners worldwide. The objective of this study was to characterize respirable dust and crystalline silica from limestone, iron, and bauxite mines in India. In total, 86 personal dust samples were collected from limestone (n = 30), iron (n = 30), and bauxite (n = 26) mines using dust sampler. The concentration of crystalline silica was analyzed using FTIR spectroscopy. Geometric mean respirable dust concentrations observed were 0.92, 1.08, and 1.07 mg/m³ for limestone, iron, and bauxite mines respectively, similarly for crystalline silica concentration observations were 0.015, 0.012 and 0.008 mg/m³ respectively. Among the three studied ores, mean crystalline silica concentration was statistically significant (p < 0.05) using an analysis of variance test. Although the detected levels of exposure are within the Indian exposure limits, attention should be paid to lower crystalline silica levels to minimize the risk of silicosis.

COVID-19: a new burden of respiratory disease among South African miners?

PURPOSE OF REVIEW

Mineworkers in South Africa experience a triple burden of disease due to their distinct work experience. Silicosis increases their risk of tuberculosis (TB), exacerbated by the HIV epidemic. Work-related factors are likely to increase transmission, severity, and post infection sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Understanding these relationships is important to control the impact of the epidemic.

RECENT FINDINGS

SARS-CoV-2 infection rates among mineworkers exceed the population rates in the provinces in which those mines are located. Migrant work, living in crowded hostels, working in narrow poorly ventilated shafts mainly underground constitute important factors that increase transmission risk. Mineworkers continue to experience high levels of silica exposure. The prevalences of silicosis, HIV and pulmonary TB, remain high. Interstitial lung disease, pulmonary TB, and HIV have all been associated with poorer outcomes of SARS-CoV-2 infections. Mineworkers with post infection respiratory sequelae are likely to lose their jobs or lose income, due to the physically demanding nature of underground minework.

SUMMARY

Further research into the unique work-related risk factors in mining that influence the COVID-19 epidemic is crucial for optimizing current interventions. Reducing SARS-CoV-2 infection transmission, health monitoring of infected and vulnerable workers, and following up of postinfection outcomes is essential to protect the respiratory health of miners.

Predictors of silicosis and variation in prevalence across mines among employed gold miners in South Africa

Background

The stated intention to eliminate silicosis from the South African goldmining industry as well as current programmes to find and compensate ex-miners with silicosis require an understanding of variation in silicosis prevalence across the industry. We aimed to identify the predictors of radiological silicosis in a large sample of working miners across gold mines in South Africa.

Methods

Routine surveillance chest radiographs were collected from 15 goldmine “clusters” in a baseline survey undertaken in preparation for a separate tuberculosis isoniazid prophylaxis trial. All images were read for silicosis by a health professional experienced in using the International Labour Organisation (ILO) classification. Profusion thresholds of > 1/0 and > 1/1 were used. Demographic and occupational information was obtained by questionnaire. Predictors of silicosis were examined in a multivariable logistic regression model, including age, gender, racial ascription, country of origin, years since starting mine employment, mine shaft, skill category, underground work status and tuberculosis.

Results

The crude silicosis prevalence at ILO > 1/1 was 3.8% [95% confidence interval (CI) 3.5–4.1%]. The range across mine shafts was 0.8–6.9%. After adjustment for covariates, the interquartile range across shafts was reduced from 2.4 to 1.2%. Black miners [adjusted odds ratio (aOR) 2.8; 95% CI 1.1–7.2] and miners in full-time underground work (aOR 2.1; 95% CI 1.3–3.4) had substantially elevated odds of silicosis, while workers from Mozambique had lower odds (aOR 0.54; 95% CI 0.38–0.77). Silicosis odds rose sharply with both age and years since starting in the industry (p for linear trend < 0.005), with 95.5% of affected miners having > 15 years since first exposure and 2.2% < 10 years.

Conclusions

In surveillance of silicosis in working gold miners time since first exposure remains a powerful predictor. Age appears to be an independent predictor, while the detection of radiological silicosis in short-service miners requires attention. Public risk reporting by mines should include factors bearing on silicosis prevalence, specifically dust concentrations, with independent verification. Studies of silicosis and tuberculosis in ex-miners are needed, supported by an accessible electronic database of the relevant medical and dust exposure records of all gold miners.

Can the South African Milestones for Reducing Exposure to Respirable Crystalline Silica and Silicosis be Achieved and Reliably Monitored?

Silicosis and other respirable crystalline silica-associated diseases, most notably tuberculosis, have long been substantial causes of morbidity and mortality in South Africa. For the mining and non-mining industries, silicosis elimination programmes have been developed with milestones regarding reduction of levels of exposure to respirable crystalline silica (RCS) and targets regarding the date of eradication. The present paper explores the feasibility of achieving these targets by investigating the evidence that levels of exposure and silicosis incidence rates have declined by an appraisal of the methods for data collection and reporting. In the mining industry the silicosis elimination programme is supported by the development and advocacy of leading practices to reduce the exposure. RCS exposure data are routinely collected according to a Code of Practice (CoP) and the results are reported to the Mine Health and Safety Inspectorate. As the CoP and the actual workplace practices have been demonstrated to have some flaws, there is some concern about the accuracy of the actual exposure data and the data interpretation. The annually reported levels of exposure suggest a decline, however, the actual levels of RCS as well as the number of exposed workers, were not reported over the last few years. With regard to the silicosis incidence rates, a steady decline of new cases is reported. However, there is a risk of under-diagnosis and- reporting especially in former miners. In the non-mining industries, a systematic baseline of RCS exposure levels and silicosis incidence is lacking. The reporting by industries on assigning of the workforce to exposure categories seems to be fragmented and incomplete. Consequently, any evidence of progress toward achieving the silicosis elimination target cannot be documented. Both the silicosis elimination target and the exposure milestone are aspirational but are unlikely to be achieved. Nevertheless, the formal mining industry may get close. Exposure control interventions, especially in the non-mining industries, should be developed and implemented and pragmatic methods need to be put in place to identify sources of new silicosis cases for targeted intervention.

Occupational Respirable Mine Dust and Diesel Particulate Matter Hazard Assessment in an Underground Gold Mine in Ghana

BACKGROUND

Underground miners can experience occupational health diseases due to exposure to particulate matter hazards.

OBJECTIVES

The aim of the present study was to examine occupational exposures of underground miners to dust and diesel particulate matter and to identify exposure groups with high potential to develop associated health effects due to the presence of dust and diesel particulate matter (DPM) hazards in an underground gold mine in Ghana.

METHODS

Purposive sampling was employed using gravimetric air samplers over an 8-hour time weighted average period. The National Institute for Occupational Safety and Health (NIOSH) analytical Chapter Q and 5040 were used in determining crystalline silica dust and diesel particulate matter fractions, respectively. Structured questionnaires were administered to gather data on workers' level of awareness to dust and DPM exposures.

RESULTS

It was found that 41% of the sampled groups were exposed to higher crystalline silica levels above the (NIOSH) permissible exposure limit (PEL) level of 0.05 mg/m³. For DPM, 49% of these groups had exposures above the Mine Safety and Health Administration (MSHA) PEL level of 160 μg/m³. Among the 94 mine workers who responded to this study, 62% were found to be aware of the presence and hazardous nature of silica dust, 28% had minimal knowledge and the remaining were found to be unaware.

CONCLUSIONS

There are varying levels of dust and DPM due to the presence of silica-bearing rocks, the production of diesel fumes and inefficiencies of available mitigation measures. Research carried out over the past decades has found confirmed cases of silicosis and lung cancer due to high dust exposure levels. Rock drillers, blast men and shotcrete operators were found to be exposed to higher levels of dust and diesel particulate matter and are at greater risk of silicosis.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

This study was approved by the Ethics Committee of the Kwame Nkrumah University of Science and Technology, Ghana and carried out under full consent of the mining company under study.

COMPETING INTERESTS

The authors declare no competing financial interests.

Silicosis in rhinestone-manufacturing workers in South China

BACKGROUND

Silicosis is caused by long-term exposure to silica dust. Crystal rhinestone workers can be exposed to high levels of silica dust and are at risk of silicosis.

AIMS

To explore silicosis cases, silica dust exposure and control measures in a rhinestone factory in South China.

METHODS

We extracted and analysed data on new silicosis cases reported to China's occupational disease and occupational health information monitoring system between 2006 and 2012 from a rhinestone factory in South China. We measured the quartz content of bulk dust, static total and respirable dust samples.

RESULTS

Ninety-eight silicosis cases were reported between 2006 and 2012. The mean duration of silica dust exposure was 9.2 years (range 3-16). Drilling and polishing workers accounted for 96 (98%) of cases. We collected 1479 static samples including 690 total dust and 789 respirable dust samples. Mean dust levels for drilling were 1.01 mg/m3 (range 0.20-3.80) for total dust and 0.51 mg/m3 (range 0.04-1.70) for respirable dust. Mean dust levels for polishing were 0.59 mg/m3 (range 0.20-2.10) for total dust and 0.28 mg/m3 (range 0.08-0.71) for respirable dust. Over a third [289/789 (37%)] of total dust samples and 129/690 (19%) respirable dust samples exceeded the national permissible exposure limit.

CONCLUSION

Exposure to silica dust, ineffective dust control measures and inefficient health surveillance may have contributed to the incidence of silicosis in the factory we studied. Identification of silica dust exposure and effective dust control measures would reduce the risk of silicosis in rhinestone workers.

Usefulness of occupation and industry information in mortality data in South Africa from 2006 to 2015

BACKGROUND

There is no population based occupational health surveillance system in South Africa, thus mortality data may be a cost effective means of monitoring trends and possible associations with occupation. The aim of this study was to use deaths due to pneumoconiosis (a known occupational disease) to determine if the South African mortality data are a valid data source for occupational health surveillance in South Africa.

METHODS

Proportions of complete occupation and industry information for the years 2006-2015 were calculated for working age and retired adults. Deaths due to pneumoconiosis were identified in the data set and mortality odds ratios calculated for specific occupations and industry in reference to those who reported being unemployed using logistic regression.

RESULTS

Only 16.1% of death notifications provided a usual occupation despite 43.1% of the population being employed in the year. The MORs for occupation provided significant increased odds of pneumoconiosis for miners (9.04), those involved in manufacturing (4.77), engineers and machinery mechanics (6.85). Along with these jobs the Mining (9.8), Manufacture (2.2) and Maintenance and repair industries (6.0) have significantly increased odds of pneumoconiosis deaths. The data can be said to provide a useful source of occupational disease information for surveillance where active surveillance systems do not exist.

CONCLUSION

The findings indicate valid associations were found between occupational disease and expected jobs and industry. The most useful data are from 2013 onwards due to more detailed coding of occupation and industry.

Those Who Don't Return: Improving Efforts to Address Tuberculosis Among Former Miners in Southern Africa

Despite increasing awareness regarding the role of oscillating migration in the mining industry as a major driving force in the spread of tuberculosis (TB) throughout southern Africa, very little work has focused on the historical and contextual factors which may contribute to former migrant miners' present-day risk of TB. Most research regarding migration-related and occupational influences on TB has been done on current miners still employed by the mining industry. Through both a historical and contemporary lens, this paper explores and elucidates the need to address the TB epidemic among former migrant mine workers and provides considerations to improve current interventions among this critical population.

Subradiological silicosis

The purpose of this commentary is to bring the neglected phenomenon of subradiological silicosis and its implications to the attention of readers. We define subradiological silicosis as silicosis detectable on pathological examination of lung tissue but not visible radiologically. For extent of the phenomenon, we draw on a study using a large South African autopsy database of deceased miners and chest radiographs taken in life. At an International Labour Organization threshold of >1/0 only 43% of all pathologically detected cases were detected on chest radiograph, and only 62% of those classified on pathology as "moderate or marked" silicosis. Subradiological silicosis has a number of implications for research and practice: for dose-response studies of silicosis; for studies of the relationship between silica and conditions such as tuberculosis, lung cancer, and autoimmune disease, including the mechanistic role of fibrogenesis; for prognostication in silica exposed workers; and for workers' compensation criteria.

Precarious transition: a mortality study of South African ex-miners

Background

Despite their burden of a triple epidemic of silicosis, tuberculosis and HIV infection, little is known about the mortality experience of miners from the South African mining industry once they leave employment. Such information is important because of the size and dispersion of this population across a number of countries and the progressive nature of these diseases.

Methods

This study included 306,297 South African miners who left the industry during 2001–2013. The study aimed to calculate crude and standardised mortality rates, identify secular trends in mortality and model demographic and occupational risk factors for mortality.

Results

Crude mortality rates peaked in the first year after exit (32.8/1000 person-years), decreasing with each year from exit. Overall mortality was 20% higher than in the general population. Adjusted annual mortality halved over the 12 year period. Mortality predictors were being a black miner [adjusted hazard ratio (aHR) 3.30; 95% confidence interval (CI) 3.15–3.46]; underground work (aHR 1.33; 95% CI 1.28–1.39); and gold aHR 1.15 (95% CI 1.12–1.19) or multiple commodity employment (aHR 1.15; 95% CI 1.11–1.19).

Conclusions

This is the first long-term mortality assessment in the large ex-miner population from the South African mining industry. Mortality patterns follow that of the national HIV-tuberculosis epidemic and antiretroviral treatment availability. However, ex-miners have further elevated mortality and a very high mortality risk in the year after leaving the workforce. Coordinated action between the mining industry, governments and non-governmental organisations is needed to reduce the impact of this precarious transition.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-5749-2) contains supplementary material, which is available to authorized users.

Modificação do perfil da silicose na mineração subterrânea de ouro em Minas Gerais

Resumo Introdução: Minas Gerais é o estado brasileiro com maior registro de casos de silicose, sendo grande parte proveniente de casuísticas acumuladas das minerações de ouro. Objetivos: descrever e analisar temporalmente a ocorrência de silicose na mineração de ouro identificando fatores ocupacionais relacionados. Métodos: estudo transversal com 1.020 ex-mineiros da região de Nova Lima/MG, avaliados entre 1995 e 2011. Resultados: o diagnóstico de silicose foi confirmado em 19,7% dos avaliados. Nenhum caso da doença foi identificado em indivíduos que trabalharam apenas na superfície. A prevalência no grupo que trabalhou até 5 anos no subterrâneo foi de 3,8% e no grupo com mais de 20 anos de trabalho nesse local foi de 44,2%. Os admitidos para trabalho subterrâneo até 1950 apresentaram prevalência de 57,9%. Entre os admitidos após 1990, não houve registro de casos. Conclusão: verificou-se uma queda expressiva na ocorrência de silicose no período analisado. Uma vez que a doença é sabidamente dose-dependente, é esperado que a diminuição dos níveis de exposição, obtido pelas melhorias dos ambientes ocupacionais, tenha refletido nestes resultados. É fundamental que tais medidas continuem a ser adotadas na mineração e em outros ramos de atividade visando reduzir a ocorrência da doença.

Tackling injustices of occupational lung disease acquired in South African mines: recent developments and ongoing challenges

BACKGROUND

South Africa's mineral resources have produced, and continue to produce, enormous economic wealth; yet decades of colonialism, apartheid, capital flight, and challenges in the neoliberal post-apartheid era have resulted in high rates of occupational lung disease and low rates of compensation for ex-miners and their families. Given growing advocacy and activism of current and former mine workers, initiatives were launched by the South African government in 2012 to begin to address the legacy of injustice. This study aimed to assess developments over the last 5 years in providing compensation, quantify shortfalls and explore underlying challenges.

METHODS

Using the database with compensable disease claims from over 200,000 miners, the medical assessment database of 400,000 health records and the employment database with 1.6 million miners, we calculated rates of claims, unpaid claims and shortfall in claim filing for each of the southern African countries with at least 25,000 miners who worked in South African mines, by disease type and gender. We also conducted interviews in Johannesburg, Eastern Cape, Lesotho and a local service unit near a mine site, supplemented by document review and auto-reflection, adopting the lens of a critical rights-based approach.

RESULTS

By the end of 2017, 111,166 miners had received compensation (of which 55,864 were for permanent lung impairment, and another 52,473 for tuberculosis), however 107,714 compensable claims remained unpaid. Many (28.4%) compensable claims are from Mozambique, Lesotho, Swaziland, Botswana and elsewhere in southern Africa, a large proportion of which have been longstanding. A myriad of diverse systemic barriers persist, especially for workers and their families outside South Africa. Calculating predicted burden of occupational lung disease compared to compensable claims paid suggests a major shortfall in filing claims in addition to the large burden of still unpaid claims.

CONCLUSION

Despite progress made, our analysis reveals ongoing complex barriers and illustrates that the considerable underfunding of the systems required for sustained prevention and social protection (including compensation) needs urgent attention. With class action suits in the process of settlement, the globalized mining sector is now beginning to be held accountable. A critical rights-based approach underlines the importance of ongoing concerted action by all.

Four decades of pulmonary tuberculosis in deceased South African miners: trends and determinants

OBJECTIVE

We investigated trends and determinants of pulmonary tuberculosis (PTB) in deceased South African miners.

METHODS

Statutory autopsies are performed on miners for occupational lung disease compensation, irrespective of cause of death. Data were extracted from the PATHAUT (Pathology Automation System) autopsy database. PTB trends were analysed and explanatory variables (year of autopsy, age at death, gold employment duration, silicosis and HIV) were evaluated using binary logistic regression modelling. Analyses were stratified by population group because of racial differences in socioeconomic status, employment patterns and access to facilities for autopsies. The analyses were segmented to represent the pre-HIV (1975-1989), rapid HIV spread (1990-2004) and antiretroviral therapy (2005-2014) periods.

RESULTS

The proportions of men with PTB at autopsy increased from 4.62% in 1975 to 27.18% in 2014 in black miners, and from 2.07% to 5.19% in white miners, with peaks in 2007 (43.12% and 9.51%, respectively). The magnitude and significance of adjusted ORs of determinants differed by population group and calendar period. PTB was largely associated with silicosis, increasing gold employment duration and year of autopsy (a surrogate for unmeasured confounders, such as unknown HIV status and tuberculosis transmission).

CONCLUSIONS

Changes in PTB time trends and determinants reflect the complex social and political environment in which mining occurs. Silica dust reduction remains a key intervention for tuberculosis reduction, together with tuberculosis and HIV treatment and management. The autopsy data provide reliable information to monitor progress towards the achievement of industry and national targets to reduce tuberculosis.

Small contribution of gold mines to the ongoing tuberculosis epidemic in South Africa: a modeling-based study

BACKGROUND

Gold mines represent a potential hotspot for Mycobacterium tuberculosis (Mtb) transmission and may be exacerbating the tuberculosis (TB) epidemic in South Africa. However, the presence of multiple factors complicates estimation of the mining contribution to the TB burden in South Africa.

METHODS

We developed two models of TB in South Africa, a static risk model and an individual-based model that accounts for longer-term trends. Both models account for four populations - mine workers, peri-mining residents, labor-sending residents, and other residents of South Africa - including the size and prevalence of latent TB infection, active TB, and HIV of each population and mixing between populations. We calibrated to mine- and country-level data and used the static model to estimate force of infection (FOI) and new infections attributable to local residents in each community compared to other residents. Using the individual-based model, we simulated a counterfactual scenario to estimate the fraction of overall TB incidence in South Africa attributable to recent transmission in mines.

RESULTS

We estimated that the majority of FOI in each community is attributable to local residents: 93.9% (95% confidence interval 92.4-95.1%), 91.5% (91.4-91.5%), and 94.7% (94.7-94.7%) in gold mining, peri-mining, and labor-sending communities, respectively. Assuming a higher rate of Mtb transmission in mines, 4.1% (2.6-5.8%), 5.0% (4.5-5.5%), and 9.0% (8.8-9.1%) of new infections in South Africa are attributable to gold mine workers, peri-mining residents, and labor-sending residents, respectively. Therefore, mine workers with TB disease, who constitute ~ 2.5% of the prevalent TB cases in South Africa, contribute 1.62 (1.04-2.30) times as many new infections as TB cases in South Africa on average. By modeling TB on a longer time scale, we estimate 63.0% (58.5-67.7%) of incident TB disease in gold mining communities to be attributable to recent transmission, of which 92.5% (92.1-92.9%) is attributable to local transmission.

CONCLUSIONS

Gold mine workers are estimated to contribute a disproportionately large number of Mtb infections in South Africa on a per-capita basis. However, mine workers contribute only a small fraction of overall Mtb infections in South Africa. Our results suggest that curtailing transmission in mines may have limited impact at the country level, despite potentially significant impact at the mining level.

Exceedance of environmental exposure limits to crystalline silica in communities surrounding gold mine tailings storage facilities in South Africa

BACKGROUND

Unlike occupational silica exposures, the association between non-occupational silica exposures and adverse health effects is not well researched, despite its occurrence in communities close to dust-generating sources such as tailings storage facilities (TSFs). Recent studies have shown that communities surrounding TSFs in South Africa often complain about the onset of dust-related health effects. Even though international interim non-occupational crystalline silica limits have been established, South Africa is yet to enforce its own limits for residential areas close to TSF sites.

OBJECTIVE

The objective of the study was to assess the need to enforce non-occupational crystalline silica limits for South Africa.

METHODS

The methods involved (1) Quantifying the silica polymorph content in bulk dust collected from TSFs in South Africa; (2) Assessing the possibility of the dust to reach surrounding communities through ambient and personal filter sampling and; (3) Conducting risk characterisation for both cancer and non-cancer endpoints.

RESULTS

All bulk dust samples consisted mostly of crystalline silica (73.14-87.09%). Large percentages of nanoparticles were identified in all bulk samples (66.8-70.7%) indicating the possibility of the dust to lodge deep within the lungs. The crystalline silica levels obtained from ambient PM₁₀ sampling and personal PM₄ sampling all exceeded the international crystalline silica interim limits and reached maximum levels of 90 and 50.9μg·m^-3, respectively. For three TSFs, sampling sites close to the TSFs showed higher PM₄ silica levels compared to sites further from TSFs. Risk characterisation revealed the possibility of cancer and non-cancer health effects when chronically exposed to silica levels recorded during the study.

CONCLUSION

The results indicate unacceptable crystalline silica exposures in surrounding communities and the need for enforcement of an ambient silica limit for South Africa.

Nudging for Prevention in Occupational Health and Safety in South Africa Using Fiscal Policies

Currently, in some countries occupational health and safety policy and practice have a bias toward secondary prevention and workers' compensation rather than primary prevention. Particularly, in emerging economies, research has not adequately contributed to effective interventions and improvements in workers' health. This article, using South Africa as a case study, describes a methodology for identifying candidate fiscal policy interventions and describes the policy interventions selected for occupational health and safety. It is argued that fiscal policies are well placed to deal with complex intersectoral health problems and to focus efforts on primary prevention. A major challenge is the lack of empirical evidence to support the effectiveness of fiscal policies in improving workers' health. A second challenge is the underprioritization of occupational health and safety partly due to the relatively small burden of disease attributed to occupational exposures. Both challenges can and should be overcome by (i) conducting policy-relevant research to fill the empirical gaps and (ii) reconceptualizing, both for policy and research purposes, the role of work as a determinant of population health. Fiscal policies to prevent exposure to hazards at work have face validity and are thus appealing, not as a replacement for other efforts to improve health, but as part of a comprehensive effort toward prevention.

Silica exposure and disease in semi-precious stone craftsmen, Minas Gerais, Brazil

BACKGROUND

Brazil is an exporter of precious stones and craftsmen often work in poor conditions. We assessed silica-related diseases among crystal craftsmen and the complexity of its control.

METHODS

Case-series including 118 subjects evaluated from 2006 to 2015, based on medical interviews, chest X-rays, spirometry, and respirable silica samples.

RESULTS

Median age and length of exposure were 32 and 13 years, respectively. Silicosis, with 1/0 as a threshold, was diagnosed radiologically in 57 individuals (48.3%). Respirable silica concentrations were 0.9-29.3 times greater than the Brazilian occupational exposure limit. A Receiver Operating Characteristic (ROC) curve with the same diagnosis threshold showed best discrimination at a cut point of 12.5 years of exposure, corresponding to 4.85 mg-y/m³ of cumulative silica exposure. There was a significant decline in FEV₁ across radiological and cumulative silica exposure categories. Eleven individuals (9.3%) had mycobacterial diseases at baseline or follow-up.

CONCLUSION

Crystal craftsmen continue to suffer from silicosis, lung function impairment, comorbidity, and death due to silicosis. To date collective protection in some work sheds has not diminished silica levels. Long-term follow-up is needed to evaluate further improvements in preventive measures. Am. J. Ind. Med. 60:239-247, 2017. © 2017 Wiley Periodicals, Inc.

Hazards identified and the need for health risk assessment in the South African mining industry

Although mining plays a prominent role in the economy of South Africa, it is associated with many chemical hazards. Exposure to dust from mining can lead to many pathological effects depending on mineralogical composition, size, shape and levels and duration of exposure. Mining and processing of minerals also result in occupational exposure to toxic substances such as platinum, chromium, vanadium, manganese, mercury, cyanide and diesel particulate. South Africa has set occupational exposure limits (OELs) for some hazards, but mine workers are still at a risk. Since the hazard posed by a mineral depends on its physiochemical properties, it is recommended that South Africa should not simply adopt OELs from other countries but rather set her own standards based on local toxicity studies. The limits should take into account the issue of mixtures to which workers could be exposed as well as the health status of the workers. The mining industry is also a source of contamination of the environment, due inter alia to the large areas of tailings dams and dumps left behind. Therefore, there is need to develop guidelines for safe land-uses of contaminated lands after mine closure.

The risk of pulmonary tuberculosis in underground copper miners in Zambia exposed to respirable silica: a cross-sectional study

Background

Pulmonary tuberculosis (PTB) among underground miners exposed to silica remains a global problem. Although well described in gold and coal mining, risk in other mining entities are not as well documented. This study aims to determine dust-related dose response risk for PTB among underground miners exposed to silica dust in Zambia's copper mines.

Methods

A cross sectional study of in-service miners (n = 357) was conducted at Occupational Health and Safety Institute (OHSI), Zambia. A systematic review of medical data over a 5-year period from assessments conducted by doctors at OHSI and statutory silica exposure data (n = 16678) from the Mine Safety Department (MSD) were analysed. Lifetime cumulative exposure metrics were calculated. Multivariate logistic regression analysis was used to determine the association between PTB and lifetime exposure to silica, while adjusting for various confounders.

Results

The median respirable silica dust level was 0.3 mg/m³ (range 0.1–1.3). The overall prevalence of PTB was 9.5 % (n = 34). High cumulative respirable silica dust category showed a statistically significant association with PTB (OR = 6.4 (95 % CI 1. 8–23)) and a significant trend of increasing disease prevalence with increasing cumulative respirable silica dust categories was observed (p_trend < 0.01). Smoking showed a statistically significant association with PTB with OR = 4.3 (95 % CI 1.9–9.9).

Conclusions

Our results demonstrate the association of increased risk for certified active TB with cumulative respirable dust in a dose related manner among this sample of copper miners. There is need to intensify dust control measures and incorporate anti-smoking interventions into TB prevention and control programmes in the mines.

Controlled fire use in early humans might have triggered the evolutionary emergence of tuberculosis

Tuberculosis (TB) is caused by the Mycobacterium tuberculosis complex (MTBC), a wildly successful group of organisms and the leading cause of death resulting from a single bacterial pathogen worldwide. It is generally accepted that MTBC established itself in human populations in Africa and that animal-infecting strains diverged from human strains. However, the precise causal factors of TB emergence remain unknown. Here, we propose that the advent of controlled fire use in early humans created the ideal conditions for the emergence of TB as a transmissible disease. This hypothesis is supported by mathematical modeling together with a synthesis of evidence from epidemiology, evolutionary genetics, and paleoanthropology.

Trends in silicosis prevalence and the healthy worker effect among gold miners in South Africa: a prevalence study with follow up of employment status

Background

Given the intimate association between silicosis and tuberculosis, understanding the epidemiology of the South African gold mining industry silicosis epidemic is essential to current initiatives to control both silicosis and tuberculosis in this population, one of the most heavily affected globally. The study’s objectives were to compare the prevalence of silicosis among working black gold miners in South Africa during 2004–2009 to that of previous studies, including autopsy series, and to analyse the influence of silicosis and/or tuberculosis on exiting employment.

Methods

Routine chest radiographs from a cohort of gold miners were read for silicosis by an experienced reader (I), and a subset re-read by a B-trained reader (II). Two methods of presenting the readings were used. Additionally, with baseline status of silicosis and previous or active tuberculosis as predictors, survival analysis examined the probability of exiting the workforce for any reason during 2006–2011.

Results

Reader I read 11 557 chest radiographs and reader II re-read 841. Overall, silicosis prevalence (ILO ≥1/0: 5.7 and 6.2 % depending on reader method) was similar to the age adjusted prevalence found in a large study in 1984 (5.0 %). When comparison was restricted to a single mine shaft previously studied in 2000, a decline in prevalence (ILO ≥1/1) was suggested for one of the reading methods (duration adjusted 20.5 % vs. 13.0 % in the current study). These findings are discordant with a long-term rising autopsy prevalence of silicosis over this period. Overall, relative to miners with neither disease, the adjusted hazard ratio for exiting employment during the follow-up period was 1.54 for baseline silicosis [95 % confidence interval (CI) 1.17, 2.04], 1.71 for tuberculosis (95 % CI 1.51, 1.94) and 1.53 for combined disease (95 % CI 1.20, 1.96).

Conclusions

This study found, a) there was no significant decline in overall silicosis prevalence among working black miners in the South African gold mining industry between 1984 and 2004–2009, and b) a possible decline at one mine shaft more recently. In the absence of evidence of declining respirable silica concentrations between the 1980s and 2000s, the trends found are plausibly due to a healthy worker survivor effect, which may be accelerating.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2566-8) contains supplementary material, which is available to authorized users.

Silica Exposures in Artisanal Small-Scale Gold Mining in Tanzania and Implications for Tuberculosis Prevention

Gold miners exposed to crystalline silica are at risk of silicosis, lung cancer, and experience higher incidence rates of pulmonary tuberculosis (TB). Although the hazards associated with mercury exposure in artisanal small-scale gold mining (ASGM) have been well documented, no published data was available on crystalline silica exposures in this population. Air sampling was conducted in the breathing zone of workers in five villages in Tanzania with battery-operated sampling pumps and bulk samples were collected to measure the type and concentration of crystalline silica in the ore. Samples were analyzed at an accredited laboratory with X-ray diffraction. Airborne crystalline silica exposures exceeded recommended limits for all tasks monitored with an average exposure of 16.85 mg/m(3) for underground drilling that was 337 fold greater than the recommended exposure limit (REL) published by the U.S. National Institute for Occupational Safety and Health (NIOSH) and 0.19 mg/m(3) for aboveground operations or 4-fold greater than the REL. The exposures measured raise concern for possible acute and chronic silicosis and are known to significantly contribute to TB incidence rates in mining communities. The use of wet methods could greatly reduce exposures and the risk of TB and silicosis in ASGM. Ongoing efforts to address mercury and other hazards in ASGM should incorporate crystalline silica dust controls.

Aspiring to zero tuberculosis deaths among southern Africa's miners: is there a way forward?

Tuberculosis notification rates among South African miners range from 4,000 to 7,000 per 100,000 people. These rates far exceed national tuberculosis notification rates for the general population. Tuberculosis mortality also surpasses deaths caused by mining accidents. These extraordinarily high rates of disease are unambiguously linked to a series of contributing factors, including exposure to silica dust, HIV infection, and poor working and living conditions. We argue that the only way to stop the transmission of this airborne disease is to treat the mine and its living quarters as one should any other congregate setting with individuals who have high rates of infection with drug-susceptible and drug-resistant strains of tuberculosis. This means implementing interventions that have been demonstrated to stop the spread of tuberculosis over the last 60 years: immediate treatment of active tuberculosis, concurrent treatment of latent tuberculosis disease to reduce the burden of active cases, and appropriate management of patients infected with HIV. Because tuberculosis is also a social disease, biomedical interventions must be coupled with improved living and working conditions. Achieving zero deaths from tuberculosis in the mines is possible if a clear commitment is made to a strategy that recognizes and ameliorates the biological and social antecedents to this epidemic.

Respirable dust and respirable silica exposure in Ontario gold mines

A comprehensive survey of respirable dust and respirable silica in Ontario gold mines was conducted by the Ontario Ministry of Labor during 1978-1979. The aim was to assess the feasibility of introducing gravimetric sampling to replace the assessment method which used konimeters, a device which gave results in terms of number of particles per cubic centimeter (ppcc) of air. The study involved both laboratory and field assessments. The field assessment involved measurement of airborne respirable dust and respirable silica at all eight operating gold mines of the time. This article describes the details of the field assessment. A total of 288 long-term (7-8 hr) personal respirable dust air samples were collected from seven occupational categories in eight gold mines. The respirable silica (α-quartz) was determined by x-ray diffraction method. The results show that during 1978-1979, the industry wide mean respirable dust was about 1 mg/m(3), and the mean respirable silica was 0.08 mg/m(3.)The mean% silica in respirable dust was 7.5%. The data set would be useful in future epidemiological and health studies, as well as in assessment of workers' compensation claims for occupational diseases such as silicosis, chronic obstructive pulmonary disease (COPD), and autoimmune diseases such as renal disease and rheumatoid arthritis.

Occupational respiratory diseases in the South African mining industry

Background

Crystalline silica and asbestos are common minerals that occur throughout South Africa, exposure to either causes respiratory disease. Most studies on silicosis in South Africa have been cross-sectional and long-term trends have not been reported. Although much research has been conducted on the health effects of silica dust and asbestos fibre in the gold-mining and asbestos-mining sectors, little is known about their health effects in other mining sectors.

Objective

The aims of this thesis were to describe silicosis trends in gold miners over three decades, and to explore the potential for diamond mine workers to develop asbestos-related diseases and platinum mine workers to develop silicosis.

Methods

Mine workers for the three sub-studies were identified from a mine worker autopsy database at the National Institute for Occupational Health.

Results

From 1975 to 2007, the proportions of white and black gold mine workers with silicosis increased from 18 to 22% and from 3 to 32% respectively. Cases of diamond and platinum mine workers with asbestos-related diseases and silicosis, respectively, were also identified.

Conclusion

The trends in silicosis in gold miners at autopsy clearly demonstrate the failure of the gold mines to adequately control dust and prevent occupational respiratory disease. The two case series of diamond and platinum mine workers contribute to the evidence for the risk of asbestos-related diseases in diamond mine workers and silicosis in platinum mine workers, respectively. The absence of reliable environmental dust measurements and incomplete work history records impedes occupational health research in South Africa because it is difficult to identify and/or validate sources of dust exposure that may be associated with occupational respiratory disease.

Effects of 28 days silicon dioxide aerosol exposure on respiratory parameters, blood biochemical variables and lung histopathology in rats

Inhalation toxicity of silicon dioxide aerosol (150, 300 mg/m(3)) daily over a period of 28 days was carried out in rats. The changes in respiratory variables during the period of exposure were monitored using a computer programme that recognizes the modifications of the breathing pattern. Exposure to the aerosol caused a time dependent decrease in tidal volume, with an increase in respiratory frequency compared to the control. Biochemical variables and histopathological observation were noted at 28th day following the start of exposure. Biochemical markers of silica induced lung injury like plasma alkaline phosphatase, lactate dehydrogenase and angiotensine converting enzyme activities increased in a concentration dependent manner compared to control. Increase in the plasma enzymatic activities indicates endothelial lung damage, increased lung membrane permeability. Histopathological observation of the lungs confirmed concentration dependent granulomatous inflammation, fibrosis and proteinacious degeneration. Aggregates of mononuclear cells with entrapped silica particles circumscribed by fibroblast were observed in 300 mg/m(3) silica aerosol exposed group at higher magnification. Decrease in tidal volume and increase in respiratory frequency might be due to the thickening of the alveolar wall leading to a decreased alveolar volume and lowered elasticity of the lung tissue. The trends in histological and biochemical data are in conformity with the respiratory data in the present study. This study reports for the first time, the changes in respiratory variables during silica aerosol exposure over a period of 28 days.

Therapeutic associated with occupational exposure to silica

Occupational exposure to silica dust has been increasing the possible risk of varieties of pathologies. The aim of this study was to evaluate the protective activity of ethanolic extract of Glycyrrhiza glabra roots at doses of 500 and 1000 mg/kg, p.o., given for 7 days against the toxicity of SiO(2) nanoparticles (50mg/kg intraperitoneal for 6 weeks) in rats. Exposure to silica altered various respiratory and biochemical variables, including ALT, AST, albumin, urea, uric acid, creatinine, catalase, LPO and GSH. Treatments with G. glabra extract significantly improved antioxidant status towards control. Stone workers in the Gwalior region exposed to silica dust had higher prevalence of cough, wheezing and shortness of breath. Increased serum ACE level was noted in the silica exposed group. It is of immense need to monitor this problem for betterment of worker's health.

Occupational lung disease in the South African mining industry: research and policy implementation

South African miners face an epidemic of occupational lung diseases. Despite a plethora of research on the mining industry, and the gold mining industry in particular, research impact (including disease surveillance) on policy implementation and occupational health systems performance lags. We describe the gold mining environment, and research on silicosis, tuberculosis, HIV and AIDS, and compensation for occupational disease including initiatives to influence policy and thus reduce dust levels and disease. As these have been largely unsuccessful, we identify possible impediments, some common to other low- and middle-income countries, to the translation of research findings and policy initiatives into effective interventions.

Incidence of silicosis in flourmill workers

BACKGROUND

Silicosis is an ancient occupational illness reported in silica mill workers, agate stone workers, slate pen workers and mining industry. However its association in flour mill workers has not been established.

AIMS

To study the incidence of silicosis and respiratory morbidity in flour mill workers.

SETTINGS AND DESIGN

A prospective study of 56 flour mill workers working with open silica grinding stones was undertaken.

MATERIALS AND METHODS

56 flour mill workers who volunteered following information regarding the study purpose were recruited from the community. Detailed clinical and occupational history, lung functions, chest x-ray, and high resolution computed tomography (HRCT) were done. Diagnosis was made on the basis of radiological findings.

STATISTICAL ANALYSIS

Data analysis was done with the help of the statistical package for social sciences software. The Chi-square test was used for determining the relationship between qualitative data and descriptive statistics was used where required.

RESULTS

93% had respiratory symptoms that included cough (66.1%), dyspnea (75%), chest pain (17.1%), and rhinorrhea (46.4%). Radiological abnormalities were noted in chest X-ray (60.7%) and HRCT (81.48%). A significant correlation was seen between duration of exposure and HRCT abnormalities. Lung functions revealed obstruction in 28.5% subjects, restriction in 19%, mixed ventilatory defects in 21.4%, while 18.9% had a reduced diffusion capacity.

CONCLUSION

Incidence of silicosis in our study on flour mill workers working with silica containing grinding stones was 30.4%. They had high respiratory morbidity (93%) cough and dyspnea being predominant symptoms. Duration of exposure correlates with radiological findings and increased incidence of silicosis.

Oscillating migration and the epidemics of silicosis, tuberculosis, and HIV infection in South African gold miners

BACKGROUND

Hundreds of thousands of men from rural areas of South Africa and neighboring countries have come to seek work in the gold mines. They are not immigrants in the usual sense as they work for periods in the mines, go home, and then return. This is termed oscillating or circular migration. Today we have serious interrelated epidemics of silicosis, tuberculosis, and HIV infection in the gold mining industry.

METHODS

This article discusses the role of oscillating migration in fuelling these epidemics, by examining the historical, political, social, and economic contexts of these diseases.

RESULTS

The impact of silicosis, tuberculosis, and HIV infection extends beyond individual miners to their families and communities.

CONCLUSION

Failure to control dust and tuberculosis has resulted in serious consequences decades later. The economic and political migrant labor system provided the foundations for the epidemics seen in southern Africa today.

Three decades of silicosis: disease trends at autopsy in South African gold miners

BACKGROUND

Eliminating silicosis is a priority of the International Labour Organization and the World Health Organization. Prevalence is particularly high in developing countries.

OBJECTIVES

We describe trends in silicosis among South African gold miners who had had an autopsy between 1975 and 2007 and quantify the contributions of age at autopsy and employment duration to these trends.

METHODS

South African miners and ex-miners are eligible for autopsy examination for occupational lung disease, regardless of the clinical cause of death, and the families of deceased mine workers may receive compensation from the government of South Africa. Miners who died from external causes and who had been employed in the gold mines for > 1 year were stratified by population group because of differences in exposure, patterns of employment, and autopsy referral patterns. We extracted data from PATHAUT (Pathology Automation System) and used Stata 10 to estimate trends in relative proportions of silicosis that were standardized for age and employment duration.

RESULTS

The crude proportion of silicosis for white miners was six times that of black miners in 1975. By 2007, it was 1.5 times higher for black miners. The proportion of miners with silicosis increased from 0.03 to 0.32 for black miners and from 0.18 to 0.22 for white miners. The increase can be explained by increasing age and employment duration for white miners. For black miners, it can be only partly explained by these two factors.

CONCLUSION

As miners continue to age and work for longer periods, the burden of silicosis will continue to rise. South Africa is committed to global efforts to eliminate silicosis by 2030. The autopsy database allows for disease surveillance, which is necessary to monitor the success of this initiative.

Incidence of tuberculosis and HIV and progression of silicosis and lung function impairment among former Basotho gold miners

BACKGROUND

Pulmonary tuberculosis and HIV incidence, mortality, and the progression of silicosis and lung function impairment are described over a 1-year period in migrant ex-gold miners from Lesotho.

METHODS

Seven hundred seventy-nine Basotho miners were followed for 1 year starting 18 months after lay-off from a South African gold mine in 1998. At baseline and follow-up, they underwent a respiratory symptom interview, physical examination, HIV test, chest radiograph, and spirometry.

RESULTS

Five hundred thirteen of 779 (65.9%) participants attended both baseline and follow-up visits. HIV incidence was 5.4/100 person-years (95% CI: 3.4-8.2). Prevalence of silicosis (ILO score > or =1/1) was 26.6% at baseline and 27.0% at follow-up. Active tuberculosis diagnosed at baseline was a strong predictor of radiological progression of silicosis. Lung function as measured by FEV(1) declined an average of 91 ml between visits (95% CI: 67-116 ml). Calculated minimum incidence of tuberculosis was 3,085/100,000/years (95% CI: 1,797-4,940) at follow-up. Of those seen at baseline, 18 died before their scheduled follow-up visit (mean age: 51 years).

CONCLUSIONS

High rates of mortality and of HIV infection and pulmonary tuberculosis were found in this cohort after leaving the South African goldmines. Continuing lung function loss was also apparent. A partnership between the South African mining industry and governments in labor-sending areas of Southern Africa is needed to provide continuity of care and access to HIV and tuberculosis treatment and prevention services. Active silicosis surveillance and an improved statutory compensation system are also needed. These findings can serve as a baseline against which the impact of such interventions can be assessed.

Cross-sectional silica exposure measurements at two Zambian copper mines of Nkana and Mufulira

We measured the quartz content of 20 bulk settled dust and 200 respirable dust samples in a cross-sectional dust exposure assessment that is part of an epidemiological study to ascertain the risk of nonmalignant respiratory diseases among Zambian copper miners. Dust samples were collected from the copper mines of Mopani Copper Mine plc (Mufulira and Nkana Mines). Analytical measurements employed NIOSH Method 0600 for gravimetric analysis of respirable dust and NIOSH Method 7500 for quartz analysis in bulk and respirable dust samples. The measured quartz content of respirable dust showed that 59% and 26% of Mufulira and Nkana Mine samples, respectively, were above the calculated U.S. Occupational Safety and Health Administration permissible exposure limit. The mean intensities of respirable dust exposure at Mufulira and Nkana were 0.992 mg/m³ (range 0–7.674) and 0.868 mg/m³ (range 0–6.944), respectively while the mean intensities of respirable quartz at Mufulira and Nkana were 0.143 mg/m³ (range 0–1.302) and 0.060 mg/m³ (range 0–0.317), respectively. These results indicate weak dust monitoring at these mines which may increase the risk of nonmalignant disease in many miners. Since Zambian mining regulations do not have crystalline silica exposure limits, these results accord with the recommendation that Zambian mining houses and the government establish crystalline silica analysis laboratory capacity and adopt dust mass concentration occupational exposure limits for more protective dust monitoring of workers.

The burden of silicosis, pulmonary tuberculosis and COPD among former Basotho goldminers

BACKGROUND

The burden of silicosis, pulmonary tuberculosis and COPD is described in 624 South African gold miners 18 months after cessation of work.

METHODS

This was a prevalence study. Questionnaires were administered, and spirometry, chest radiography, tuberculosis investigations, and urine HIV antibody assays were performed.

RESULTS

Attendance was 80.1% (624/779), mean age 49.4 years, and mean employment duration 25.6 years. Most subjects had had medium (26.5%) or high (65.4%) dust-exposure jobs. Current smoking rate was 35%, with ever smoking 61%. HIV antibodies were detected in the urine in 22.3%. Prevalences were: silicosis 24.6%, past tuberculosis 26%, current tuberculosis 6.2%, airflow obstruction 13.4%, and chronic productive cough 17.7%. Almost 50% of these miners had at least one of these respiratory conditions.

CONCLUSIONS

A heavy burden of silicosis, tuberculosis and COPD was present in this group of former goldminers. Intensification of work place dust control measures and TB and HIV prevention activities are needed on South African gold mines. In labor sending communities investment is needed in silicosis and tuberculosis surveillance as well as HIV treatment and care.

State-of-the-science review of the occupational health hazards of crystalline silica in abrasive blasting operations and related requirements for respiratory protection

Excessive exposures to airborne crystalline silica have been known for over 100 years to pose a serious health hazard. Work practices and regulatory standards advanced as the knowledge of the hazards of crystalline silica evolved. This article presents a comprehensive historical examination of the literature on exposure, health effects, and personal protective equipment related to silica and abrasive blasting operations over the last century. In the early 1900s, increased death rates and prevalence of pulmonary disease were observed in industries that involved dusty operations. Studies of these occupational cohorts served as the basis for the first occupational exposure limits in the 1930s. Early exposure studies in foundries revealed that abrasive blasting operations were particularly hazardous and provided the basis for many of the engineering control and respiratory protection requirements that are still in place today. Studies involving abrasive blasters over the years revealed that engineering controls were often not completely effective at reducing airborne silica concentrations to a safe level; consequently, respiratory protection has always been an important component of protecting workers. During the last 15-20 yr, quantitative exposure-response modeling, experimental animal studies, and in vitro methods were used to better understand the relationship between exposure to silica and disease in the workplace. In light of Occupational Safety and Health Administration efforts to reexamine the protectiveness of the current permissible exposure limit (PEL) for crystalline silica and its focus on protecting workers who are known to still be exposed to silica in the workplace (including abrasive blasters), this state-of-the-science review of one of the most hazardous operations involving crystalline silica should provide useful background to employers, researchers, and regulators interested in the historical evolution of the recognized occupational health hazards of crystalline silica and abrasive blasting operations and the related requirements for respiratory protection.

South African platinum mine employees reduce smoking in 5 years

BACKGROUND

South Africa adopted comprehensive tobacco control policies in the 1990s. Smoking has since declined in the general population, but there is little information on the effect of the campaign in labour-intensive industries, especially the mining industry where workers are exposed to dust, which may interact with tobacco smoke to cause respiratory disease.

OBJECTIVES

To determine the prevalence of, and trends in, smoking in employees of a South African platinum mining company, from 1998 to 2002, and to describe some demographic factors associated with their smoking habits.

METHODS

This study used smoking data collected during annual fitness-to-work medical examinations. Employees were categorised into never, ever, continuous, new and ex-smokers. Data were analysed by race and age group. Age-standardised smoking prevalence rates were compared with rates in the South African general population.

RESULTS

There were 80,713 records of 25,274 mine employees for the 5-year period. The decrease in smoking prevalence over this period was significant in both black and white men, but was greater in the former (from 42.9% to 29.8%, and from 47.2% to 44.7%, respectively). In 2002, the prevalence of smoking in black mine employees was 12.1% lower than that in black men in the general population. The prevalence of smoking decreased in black mine employees in all age groups (p<0.001); no such trend was seen for white mine employees. The proportion of light smokers increased significantly from 59.9% to 64.7%, with a corresponding significant decrease in the proportion of moderate and heavy smokers from 28.0% to 25.4%, and from 12.1% to 9.8%, respectively.

CONCLUSION

This study showed a significant decrease in smoking prevalence over a relatively short period, despite the fact that there was no smoking cessation programme in the company. The decline can be largely attributed to the South African government's antismoking initiative and supports the drive to continue to increase excise taxes on cigarette products. Nevertheless, the relatively high prevalence of smoking in some groups of mine employees highlights the need for workplaces to support the government's initiatives to curb smoking by establishing smoking cessation and prevention programmes.

High prevalence of accelerated silicosis among gold miners in Jiangxi, China

BACKGROUND

Accelerated silicosis has become uncommon in developed countries, whereas serious health threat still exists in small-scale mining in developing countries. This study was to investigate the prevalence and risk factors of accelerated silicosis among Chinese gold miners.

METHODS

A cross-sectional medical examination was conducted among 574 Chinese gold miners. All participants were male rock-drillers. The concentrations of total dust and quartz content were obtained from the government documentations. Descriptive data analyses were performed.

RESULTS

The prevalence of accelerated silicosis was 29.1% (95% CI: 24.8-33.4%, 167 cases) after an average of 5.6 years of dust exposure, and a history of tuberculosis seemed to increase the risk. The concentration of respirable silica dust was estimated to be 89.5 mg/m(3) (ranged: 70.2-108.8) in the underground goldmine, far exceeding the permissible exposure limits.

CONCLUSIONS

This study illustrates a serious health threat to small-scale goldmine in China and indicates an urgent need for environmental control and disease prevention.