Comment on Tomaskova et al. Mortality in Miners with Coal-Workers' Pneumoconiosis in the Czech Republic in the Period 1992-2013. Int. J. Environ. Res. Public Health, 2017, 14, 269

Proteomics and Metabolomics Analyses Reveal a Dynamic Landscape of Coal Workers' Pneumoconiosis: An Insight into Disease Progression

Coal worker's pneumoconiosis (CWP) is characterized by chronic inflammation and pulmonary fibrosis. The key factor contributing to the incurability of CWP is the unclear pathogenesis. This study explored the characteristic changes in proteomics and metabolomics of early and advanced CWP patients through proteomics and metabolomics techniques. Proteomics identified proteins that change with the progression of CWP, with significant enrichment in the TGF-β signaling pathway and autoimmune disease pathways. Metabolomics revealed the metabolic characteristics of CWP at different stages. These metabolites mainly include changes in amino acid metabolism, unsaturated fatty acid synthesis, and related metabolites. Integrated analysis found that ABC transporters are a shared pathway among the three groups, and ABCD2 is involved in the ABC transporter pathway. In the subsequent independent sample verification analysis, consistent with proteomics experiments, compared to the CM group, FMOD expression level was upregulated in the NIC group. TFR expression level was consistently downregulated in both the IC and NIC groups. Additionally, ABCD2 increased in the IC group but decreased in the NIC group. In summary, this study revealed the metabolic characteristics of CWP at different stages. These findings may provide valuable insights for the early prediction, diagnosis, and treatment of CWP.

Coal Miners and Lung Cancer: Can Mortality Studies Offer a Perspective on Rat Inhalation Studies of Poorly Soluble Low Toxicity Particles?

Inhalation studies involving laboratory rats exposed to poorly soluble particles (PSLTs), such as carbon black and titanium dioxide, among others, have led to the development of lung cancer in conditions characterized as lung overload. Lung overload has been described as a physiological state in which pulmonary clearance is impaired, particles are not effectively removed from the lungs and chronic inflammation develops, ultimately leading to tumor growth. Since lung tumors have not occurred under similar states of lung overload in other laboratory animal species, such as mice, hamsters and guinea pigs, the relevance of the rat as a model for human risk assessment has presented regulatory challenges. It has been suggested that coal workers' pneumoconiosis may reflect a human example of apparent "lung overload" of poorly soluble particles. In turn, studies of risk of lung cancer in coal miners may offer a valuable perspective for understanding the significance of rat inhalation studies of PSLTs on humans. This report addresses whether coal can be considered a PSLT based on its composition in contrast to carbon black and titanium dioxide. We also review cohort mortality studies and case-control studies of coal workers. We conclude that coal differs substantially from carbon black and titanium dioxide in its structure and composition. Carbon black, a manufactured product, is virtually pure carbon (upwards of 98%); TiO2 is also a manufactured product. Coal contains carcinogens such as crystalline silica, beryllium, cadmium and iron, among others; in addition, coal mining activities tend to occur in the presence of operating machinery in which diesel exhaust particles, a Type I Human carcinogen, may be present in the occupational environment. As a result of its composition and the environment in which coal mining occurs, it is scientifically inappropriate to consider coal a PSLT. Despite coal not being similar to carbon black or TiO2, through the use of a weight of evidence approach-considered the preferred method when evaluating disparate studies to assess risk- studies of coal-mine workers do not indicate a consistent increase in lung cancer risk. Slight elevations in SMR cannot lead to a reliable conclusion about an increased risk due to limitations in exposure assessment and control of inherent biases in case-control studies, most notably confounding and recall bias. In conclusion, the weight of the scientific literature suggests that coal mine dust is not a PSLT, and it does not increase lung cancer risk.