Silica exposure and silicosis are strongly associated with pulmonary tuberculosis (TB), with ex-miners from the South African gold mines carrying a large burden of both diseases. We present a case of lymph node silicosis and recurrent TB complicated by cavitation with aspergilloma requiring right upper lobectomy, in a 38-year-old ex-goldminer with only 19 months of silica exposure. While silicosis was detected histologically in the lymph nodes, radiological findings and histopathological lung parenchyma lesions were consistent with inactive TB. A worker’s compensation claim for silicotuberculosis was unsuccessful. The findings highlight the need to take into account the contribution of subradiological silicosis and/or a low silica exposure threshold to increased TB risk, and the persistence of such TB risk following exit from exposure. The case also demonstrates the need to differentiate between the radiological and pathological features of silicosis and TB, and the possible mechanistic role of lymph node silicosis in increasing TB risk. These considerations have relevance to the surveillance of silica-exposed workers in high TB settings and the potential to reduce TB risk through silica dust control.

Background:Lymph node silicosis (LNS) may be found when investigating lung and mediastinal diseases. Co-occurrence of LNS and pulmonary silicosis (PS) has been described but no studies have investigated the diagnostic accuracy of LNS for PS, the aim of this study. Methods:This cross-sectional study included South African miners with exclusive gold-mining employment who had autopsy examinations from 1975 to 2018. Routinely recorded pathologist-diagnosed LNS and PS and occupational histories were retrieved from the PATHAUT database. Pulmonary silicosis was the reference standard. Sensitivity, specificity, positive and negative predictive values (PPV and NPV) and summary diagnostic accuracy were calculated overall and by PS severity and employment duration. Results:Of the 69 802 miners, the prevalences of LNS and PS were 39.2% (n=27 373) and 17.7% (n=12 345), respectively. There were 24.1% false-positive LNS tests. Sensitivity was 85.2% (95% CI 84.6-85.6), but specificity was lower (70.7%, 95% CI 70.3-71.0). The PPV and NPV were 38.4% (95% CI 37.9-39.0) and 95.7% (95% CI 95.5-95.9), respectively. Sensitivity increased and specificity decreased with increasing employment duration. Conclusions:Our findings are consistent with LNS occurring at concentrations of respirable crystalline silica too low to cause PS and possibly being a portent of PS. LNS had deficits as a diagnostic test for PS. The low PPV raises uncertainty about the presence of PS in patients with LNS. LNS may perform better in populations with higher prevalence of silicosis, for example in patients with clinically suspected PS.

CONTEXT.—The pathology of coal workers' pneumoconiosis (CWP) and its most severe form-progressive massive fibrosis (PMF)-in US coal miners has changed in recent years. Severe disease is occurring in younger miners and has been linked to an increase in silica dust exposure.OBJECTIVE.—To update the description of the pathologic features of CWP in contemporary miners compared to historical miners.DESIGN.—This study is a retrospective expert classification of lung tissue from 85 historical and contemporary coal miners with PMF. Significant pathologic features were scored by using a standardized instrument with consensus achieved for major findings, including newly defined categories of PMF as coal-type, mixed-type, and silica-type.RESULTS.—Pathologic features associated with silica dust exposure, including silica-type PMF, mineral dust alveolar proteinosis (MDAP), and immature (early stage) silicotic nodules were increased in contemporary miners. Detailed descriptions of the pathology of contemporary CWP with illustrative figures are provided.CONCLUSIONS.—Silica-related pathologies are more common in contemporary miners. Severe forms of CWP can be detected by subtyping PMF lesions (if present) or by identification of mature and immature silicotic nodules, coal mine dust-related alveolar proteinosis, and severe inflammation in coal miners' lungs. Silica-type PMF cases showed significantly higher levels of MDAP than either mixed- or coal-type PMF (P < .001). High profusion of birefringent silica/silicate particles was observed more frequently in cases with immature (early stage) silicotic nodules (P = .04). Severe inflammation was also significantly increased in contemporary miners (P = .03). Our findings underscore the urgent need to revise current exposure limits and monitoring of respirable crystalline silica in US coal mines.

Abstract Introduction The Pathology Division (National Institute for Occupational Health) performs autopsies on mineworkers for statutory occupational lung diseases (OLD) compensation. From 1975, the PATHAUT database contains findings from over 110 000 autopsies. The data have been used extensively for OLD research, surveillance and findings have informed preventative disease initiatives. We explored factors that influenced the production of research outputs (1975-2019). Methods Research outputs were identified from the Division’s records. Production was explored by year of publication, population, disease and commodity mined in relation to contextual factors. Results There were 218 peer-reviewed journal articles and 73 scientific reports. The publication rate increased from 2.9 per year before 1994 (the year of democratic elections) to 6.5 per year post-1994. Studies shifted from descriptive to analytical (epidemiological). Research focused largely on OLDs in gold mineworkers. From the 1990s, studies on platinum miners increased as the industry grew. Other commodities studied include coal and manganese. Most studies were on silicosis, tuberculosis, and emphysema. Fewer studies were on asbestos-related diseases. Emerging health concerns e.g., ischaemic heart disease and HIV were investigated. Increasingly, studies focused on black mineworkers, a hitherto neglected sub-population. 34% of the scientific reports were funded by the Mine Health and Safety Council (South Africa). More recently, international collaborative partnerships became important influences. Discussion Over the 45-year period reviewed, several contextual factors, including changes in disease patterns, methodological approaches, politics, legislation, funding, and collaborative partnerships influenced research outputs. Conclusion Contextual factors have influenced research using the PATHAUT data. Studies have provided useful information for OLD control and prevention.

Silicotuberculosis, the combination of silicosis and pulmonary tuberculosis (TB), remains a substantial clinical and public health problem in high TB burden countries with silica-exposed workforces. The objectives of this narrative review are to propose a definition of silicotuberculosis which includes post-tuberculous lung disease, to emphasise the importance of understanding how the two diseases modify each other, and to identify as yet unanswered questions relevant to clinical practice and disease control and mitigation. The unique aetiological relationship between silica exposure and TB is now firmly established, as is the accelerated impairment and mortality imposed by TB on individuals with silicosis. However, the rich clinical, pathology and laboratory literature on combined disease from the pre-TB treatment era appears to have been largely forgotten. The close clinical and pathological appearance of the two diseases continues to pose a challenge to imaging, diagnosis and pathological description, while inconsistent evidence regarding TB treatment and TB preventive treatment prevails. Many other topics raise questions to be answered, inter alia: the range of phenotypes of combined disease; the rates and determinants of disease progression; the role of computed tomography in identifying and characterising combined disease; appropriate screening practice; acceptable policies of management of workers that combine risk reduction with social security; and the workplace respirable silica concentration that protects against the excess TB attributable to inhaled silica.

BACKGROUND:Pneumoconiosis among coal miners in the USA has been resurgent over the past two decades, despite modern dust controls and regulatory standards. Previously published studies have suggested that respirable crystalline silica (RCS) is a contributor to this disease resurgence. However, evidence has been primarily indirect, in the form of radiographic features. METHODS:We obtained lung tissue specimens and data from the National Coal Workers' Autopsy Study. We evaluated specimens for the presence of progressive massive fibrosis (PMF) and used histopathological classifications to type these specimens into coal-type, mixed-type and silica-type PMF. Rates of each were compared by birth cohort. Logistic regression was used to assess demographic and mining characteristics associated with silica-type PMF. RESULTS:Of 322 cases found to have PMF, study pathologists characterised 138 (43%) as coal-type, 129 (40%) as mixed-type and 55 (17%) as silica-type PMF. Among earlier birth cohorts, coal-type and mixed-type PMF were more common than silica-type PMF, but their rates declined in later birth cohorts. In contrast, the rate of silica-type PMF did not decline in cases from more recent birth cohorts. More recent year of birth was significantly associated with silica-type PMF. CONCLUSIONS:Our findings demonstrate a shift in PMF types among US coal miners, from a predominance of coal- and mixed-type PMF to a more commonly encountered silica-type PMF. These results are further evidence of the prominent role of RCS in the pathogenesis of pneumoconiosis among contemporary US coal miners.

OBJECTIVE:To characterize differences in mining jobs and tenure between contemporary (born 1930+, working primarily with modern mining technologies) and historic coal miners with progressive massive fibrosis (PMF).METHODS:We classified jobs as designated occupations (DOs) and non-DOs based on regulatory sampling requirements. Demographic, occupational characteristics, and histopathological PMF type were compared between groups.RESULTS:Contemporary miners ( n = 33) had significantly shorter mean total (30.4 years vs 37.1 years, P = 0.0006) and underground (28.8 years vs 35.8 years, P = 0.001) mining tenure compared with historic miners ( n = 289). Silica-type PMF was significantly more common among miners in non-DOs (30.1% vs 15.8%, P = 0.03) and contemporary miners (58.1% vs 15.2%, P < 0.0001).CONCLUSIONS:Primary jobs changed over time with the introduction of modern mining technologies and likely changed exposures for workers. Elevated crystalline silica exposures are likely in non-DOs and require attention.

Rationale: The reasons for resurgent coal workers' pneumoconiosis and its most severe forms, rapidly progressive pneumoconiosis and progressive massive fibrosis (PMF), in the United States are not yet fully understood. Objectives: To compare the pathologic and mineralogic features of contemporary coal miners with severe pneumoconiosis with those of their historical counterparts. Methods: Lung pathology specimens from 85 coal miners with PMF were included for evaluation and analysis. We compared the proportion of cases with pathologic and mineralogic findings in miners born between 1910 and 1930 (historical) with those in miners born in or after 1930 (contemporary). Results: We found a significantly higher proportion of silica-type PMF (57% vs. 18%; P < 0.001) among contemporary miners compared with their historical counterparts. Mineral dust alveolar proteinosis was also more common in contemporary miners compared with their historical counterparts (70% vs. 37%; P < 0.01). In situ mineralogic analysis showed that the percentage (26.1% vs. 17.8%; P < 0.01) and concentration (47.3 × 108 vs. 25.8 × 108 particles/cm3; P = 0.036) of silica particles were significantly greater in specimens from contemporary miners compared with their historical counterparts. The concentration of silica particles was significantly greater when silica-type PMF, mineral dust alveolar proteinosis, silicotic nodules, or immature silicotic nodules were present (P < 0.05). Conclusions: Exposure to respirable crystalline silica appears causal in the unexpected surge of severe disease in contemporary miners. Our findings underscore the importance of controlling workplace silica exposure to prevent the disabling and untreatable adverse health effects afflicting U.S. coal miners.

To examine associations between mine commodity such as coal, platinum, or diamonds and emphysema among South African miners at autopsy. We examined the association between mine commodity and emphysema using the Pathology Automation (PATHAUT) database, 1975–2014. Exposure was characterized as longest tenure in each commodity. We constructed separate multivariable logistic regression models for black and white miners. Smoking was assessed in a sub-analysis of white miners. Among black miners, coal mining was significantly associated with increased odds of emphysema [OR = 2.39 (95% CI 1.86, 3.07)] when compared to gold mining. Asbestos was also associated with significantly increased odds of emphysema among black miners [OR = 1.47 (95% CI 1.01, 2.12)]. No associations between commodity and emphysema were observed among white miners. Cumulative years of exposure and age at death were significant predictors for emphysema for both black and white miners. Smoking was a significant predictor of emphysema in the sub-analysis of white miners with smoking information, but no effect of commodity was observed. We observed a significant association between coal mining and emphysema among black miners. Adverse health effects of coal mining are evidenced by more than twofold increase in emphysema among black coal miners compared to gold miners. This suggests that South African Coal miners are exposed to high dust concentrations or more damaging components compared to other commodities, resulting in elevated risk of emphysema.