Understanding the chemical properties of macerals and minerals in coal and its potential application for occupational lung disease prevention

The impact of coal mine dust characteristics on pathways to respiratory harm: investigating the pneumoconiotic potency of coals

Exposure to dust from the mining environment has historically resulted in epidemic levels of mortality and morbidity from pneumoconiotic diseases such as silicosis, coal workers' pneumoconiosis (CWP), and asbestosis. Studies have shown that CWP remains a critical issue at collieries across the globe, with some countries facing resurgent patterns of the disease and additional pathologies from long-term exposure. Compliance measures to reduce dust exposure rely primarily on the assumption that all "fine" particles are equally toxic irrespective of source or chemical composition. For several ore types, but more specifically coal, such an assumption is not practical due to the complex and highly variable nature of the material. Additionally, several studies have identified possible mechanisms of pathogenesis from the minerals and deleterious metals in coal. The purpose of this review was to provide a reassessment of the perspectives and strategies used to evaluate the pneumoconiotic potency of coal mine dust. Emphasis is on the physicochemical characteristics of coal mine dust such as mineralogy/mineral chemistry, particle shape, size, specific surface area, and free surface area-all of which have been highlighted as contributing factors to the expression of pro-inflammatory responses in the lung. The review also highlights the potential opportunity for more holistic risk characterisation strategies for coal mine dust, which consider the mineralogical and physicochemical aspects of the dust as variables relevant to the current proposed mechanisms for CWP pathogenesis.

The Potential Diagnostic Biomarkers for the IgG Subclass in Coal Workers' Pneumoconiosis

Evidence suggests that exposure to coal dust increases immunoglobulin concentration. However, there is a paucity of data reporting immunoglobulin G (IgG) subclass in coal workers' pneumoconiosis (CWP). Therefore, this study intended to evaluate potential diagnostic biomarkers for the disease. CWP patients, dust-exposed workers without pneumoconiosis (DEW), and matched healthy controls (HCs) presented to the General Hospital of Datong Coal Mining Group and Occupational Disease Prevention and Treatment Hospital of Datong Coal Mining Group between May 2019 and September 2019 were recruited. The serum immunoglobulin concentration was determined by the multiplex immunoassay technique. Totally, 104 CWP patients, 109 DEWs, and 74 HCs were enrolled. Serum levels of IgG1, IgG2, IgM, and IgA were elevated in CWPs compared with those in DEWs and HCs (P < 0.05). The order of diagnostic accuracy between CWPs and DEWs depicted by the receiver operating characteristic (ROC) curve was IgG2, IgM, IgG1, IgG3, and IgA. Significantly higher IgG1/IgG3 and IgG2/IgG3 ratios were observed in the CWP group than in DEW and HC groups. Based on the IgG2/IgG3 ratio, the area under the ROC curve between CWP and DEW was 0.785 (95% CI 0.723-0.838), with a sensitivity of 73.1% and a specificity of 73.4%. Our findings suggest that IgG1, IgG2, IgM, and IgA are higher in the CWPs than DEWs and HCs. The IgG2/IgG3 ratio provides a viable alternative for the diagnosis of CWP.

Effects of chemical composition on the lung cell response to coal particles: Implications for coal workers' pneumoconiosis

Background and objective

Coal mine dust has a complex and heterogeneous chemical composition. It has been suggested that coal particle chemistry plays a critical role in determining the pathogenesis of coal workers' pneumoconiosis (CWP). In this study, we aimed to establish the association between the detrimental cellular response and the chemical composition of coal particles.

Methods

We sourced 19 real‐world coal samples. Samples were crushed prior to use to minimize the impact of particle size on the response and to ensure the particles were respirable. Key chemical components and inorganic compounds were quantified in the coal samples. The cytotoxic, inflammatory and pro‐fibrotic responses in epithelial cells, macrophages and fibroblasts were assessed following 24 h of exposure to coal particles. Principal component analysis (PCA) and stepwise regression were used to determine which chemical components of the coal particles were associated with the cell response.

Results

The cytotoxic, inflammatory and pro‐fibrotic response varied considerably between coal samples. There was a high level of collinearity in the cell responses and between the chemical compounds within the coal samples. PCA identified three factors that explained 75% of the variance in the cell response. Stepwise multiple regression analysis identified K₂O (p <0.001) and Fe₂O₃ (p = 0.011) as significant predictors of cytotoxicity and cytokine production, respectively.

Conclusion

Our data clearly demonstrate that the detrimental cellular effects of exposure to coal mine dusts are highly dependent on particle chemistry. This has implications for understanding the pathogenesis of CWP.

To determine whether chemistry is a key determinant of the lung cell response to coal particles, we examined the correlation between the chemical constituents of 19 coal samples and cellular response. We identified K₂O and Fe₂O₃ as the constituents of the coal associated with the greatest detrimental cell response.

Associations of SMAD4 rs10502913 and NLRP3 rs1539019 Polymorphisms with Risk of Coal Workers’ Pneumoconiosis Susceptibility in Chinese Han Population

Purpose

CWP is an untreatable but preventable fibrotic lung disease caused by the chronic inhalation of coal dust. Genetic factors such as polymorphisms play an important role in the development of CWP. The present study investigated the association between the polymorphisms of SMAD4 and NLRP3 and CWP risk in a Chinese Han population.

Patients and Methods

SMAD4 rs10502913 and NLRP3rs1539019 polymorphisms were examined in 292 CWP subjects and 315 coal dust-exposed controls. The genotypes were analyzed using direct sequencing. The allele and genotype proportion between the cases and controls were compared using the chi-square test.

Results

The AG and GG genotypes of SMAD4 rs10502913 were not associated with altered CWP risk compared with AA genotype (adjusted OR = 1.535 and 1.426, 95% CI = 0.785–3.000 and 0.732–2.781, p = 0.210 and 0.297, respectively). Also, the NLRP3 rs1539019 heterozygous and homozygous variants CA and CC genotypes were not associated with the risk of CWP compared with the AA genotype (adjusted OR = 0.985 and 1.127, 95% CI = 0.652–1.489 and 0.713–1.782, p = 0.944 and 0.608, respectively). In addition, there was no interaction between SMAD4 rs10502913 and NLRP3 rs1539019 genotypes and smoking status on CWP risk in the stratified analyses.

Conclusion

In this present study, SMAD4 rs10502913 and NLRP3 rs1539019 genotypes were not associated with altered CWP risk in the Chinese Han population. Large sample sizes and multicenter studies are needed to elucidate these results in the future.

Coal Dust Exposures Change the Spiral Artery Remodeling and Natural Killer Cells Counts in the Uterus of Pregnant Rats

BACKGROUND: Indonesia has numerous coal resources, but the effects of environmental pollution by coal dust to human health, especially the reproductive system, are still less investigated. Chronic coal exposures during pregnancy might cause systemic and uterine inflammation that induces disturbances of spiral artery remodeling. AIM: This research was conducted to analyze the effect of coal dust exposures to uterine spiral artery remodeling and natural killer (NK) cell counts. METHODS: There were 42 female adult Rattus norvegicus rats which had been simultaneously mated after synchronization of estrous cycle used as animal subjects. The rats then divided into seven groups, those were K0 (without exposure); K1-1, K1-2, K1-3; and K2-1, K2-2, K2-3 which were exposed to 6.25 mg/m3, 12.5 mg/m3, and 25 mg/m3 dose for 1 h (K1) and 2 h (K2) per day, respectively. The rats were exposed by a dust exposure machine (NKBS-1-2010- 0.5) every morning starting from the day-1 to day-19 post-mating and were sacrificed on day-19 afternoon. All uterus lobes of each pregnant rat were taken and histologically processed by HE staining. Five histological slides were randomly taken as samples representing each pregnant rat and were examined for ten visual fields per slide for the measurements of diameter and wall thickness of spiral arteries. NK cells were observed immunobiological. Data analyses used Kruskal–Wallis. RESULTS: Result showed that there were significant differences of diameters and wall thickness of spiral arteries and uterine NK cells in all exposed groups compared to control (P < 0.05). Diameter and wall thickness of spiral arteries were thicker in coal dust exposure than normal pregnant rats. NK cell number was more in coal dust exposure than normal pregnant. CONCLUSION: Coal dust exposures caused the thickening of wall and narrowing of lumen of spiral arteries and NK cell counts that might influence pregnancy.

Geochemistry and oxidative potential of the respirable fraction of powdered mined Chinese coals

This study evaluates geochemical and oxidative potential (OP) properties of the respirable (finer than 4 μm) fractions of 22 powdered coal samples from channel profiles (CP₄) in Chinese mined coals. The CP₄ fractions extracted from milled samples of 22 different coals were mineralogically and geochemically analysed and the relationships with the OP evaluated. The evaluation between CP₄/CP demonstrated that CP₄ increased concentrations of anatase, Cs, W, Zn and Zr, whereas sulphates, Fe, S, Mo, Mn, Hf and Ge decreased their CP₄ concentrations. OP results from ascorbic acid (AA), glutathione (GSH) and dithiothreitol (DTT) tests evidenced a clear link between specific inorganic components of CP₄ with OP^AA and the organic fraction of OP^GSH and OP^DTT. Correlation analyses were performed for OP indicators and the geochemical patterns of CP₄. These were compared with respirable dust samples from prior studies. They indicate that Fe (r = 0.83), pyrite (r = 0.66) and sulphate minerals (r = 0.42) (tracing acidic species from pyrite oxidation), followed by S (r = 0.50) and ash yield (r = 0.46), and, to a much lesser extent, Ti, anatase, U, Mo, V and Pb, are clearly linked with OP^AA. Moreover, OP^GSH correlation was identified by organic matter, as moisture (r = 0.73), Na (r = 0.56) and B (r = 0.51), and to a lesser extent by the coarse particle size, Ca and carbonate minerals. In addition, Mg (r = 0.70), B (r = 0.47), Na (r = 0.59), Mn, Ba, quartz, particle size and Sr regulate OP^DTT correlations. These became more noticeable when the analysis was done for samples of the same type of coal rank, in this case, bituminous.

Association of single nucleotide polymorphisms in the CYBA gene with coal workers' pneumoconiosis in the Han Chinese population

Coal workers' pneumoconiosis (CWP) is caused by long-term exposure to inhaled coal dust; it is likely influenced by the interaction between environmental factors and multiple susceptibility genes, such as the CYBA (cytochrome b-245α polypeptide) gene that has recently been identified to be involved in the genetic susceptibility for several pulmonary diseases. The aim of this case-control study was to explore the association between CYBA gene polymorphisms and the development of CWP in coal miners belonging to the Han ethnic group in China. Single nucleotide polymorphisms (SNPs) rs7195830, rs13306296, rs4673, rs9932581, and rs16966671 of the CYBA gene were analyzed in CWP patients (n = 652) and dust-exposed control subjects (n = 648) using the matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) on the Sequenom MassARRAY® platform (Sequenom, San Diego, CA, USA). Results from the present study showed a strong allele association between CWP patients and the CYBA SNP rs7195830 polymorphism (p < .001, OR = 1.550). Using the additive and the dominant model, the CYBA SNP rs7195830 polymorphism also showed significant associations with CWP patients (p < .001, OR = 1.621; p = .003, OR = 1.711, respectively). No statistically significant difference was demonstrated in either the allele or genotype frequencies of the other four examined SNPs (rs13306296, rs4673, rs9932581, and rs16966671) between the CWP group and dust-exposed control group (all p > .05). The present study is the first to have demonstrated an association between CYBA (rs7195830) polymorphism and the risk of developing CWP in subjects belong to the Han ethnic group in China and provides further clues for research into the pathogenesis of CWP.

Interactions of Oxygen and Water Molecules with Pyrite Surface: A New Insight

Pyrite is the most common sulfide in nature, and it is well-known for its roles in acid mine drainage, flotation separation of useful metal (Cu, Pb, Zn, and Mo) sulfide minerals, optoelectronic and photovoltaic application, pneumoconiosis, and even in the origin of life. However, the detailed oxidation behaviors of pyrite are still unclear and not well-understood. New oxidation pathways by O₂ on the pyrite (100) surface have been found in this work for the first time using density functional theory simulation; that is, besides Fe sites, S sites are also possible oxidation sites in the initial oxidation state of pyrite, where easier and stronger oxidation may occur. This is the first time to confirm the other researchers' conjecture on the direct oxidation of S sites, which explains the isotopic composition experiments that a minor amount of O₂ is permanently incorporated into SO₄^2- during pyrite oxidation (O in SO₄^2- is mainly derived from water). We constructed various H₂O-O₂ coadsorption models on the pyrite surface by considering the adsorption sequence of H₂O and O₂. It is found that the H₂O molecule undergoes step-wise dissociation in the presence of the O₂ molecule. Hydroxyl radical •OH is the reactive oxygen species during H₂O dissociation. Cyclic voltammetric measurements confirm the presence of •OH. In addition, H₂O₂ may also be formed on the surface in terms of H₂O-then-O₂ sequence adsorption.

High systemic IL-6 is associated with worse prognosis in patients with non-small cell lung cancer

Characteristic cytokine patterns have been described in different cancer patients and they are related to their diagnosis, prognosis, prediction of treatment responses and survival. A panel of cytokines was evaluated in the plasma of non-small cell lung cancer (NSCLC) patients and healthy controls to investigate their profile and relationship with clinical characteristics and overall survival. The case-controlled cross-sectional study design recruited 77 patients with confirmed diagnosis of NSCLC (cases) and 91 healthy subjects (controls) aimed to examine peripheral pro-inflammatory and anti-inflammatory cytokines (IL-2, IL-4, IL-6, IL-10, IL-17A, TNF and IFN-γ) by Cytometry Beads Arrays (CBA Flex) in. The cytokine IL-6 showed a statistically significant difference among groups with increased expression in the case group (p < 0.001). The correlation between the cytokines expression with patient’s clinical characteristics variables revealed the cytokine IL-6 was found to be associated with gender, showing higher levels in male (p = 0.036), whereas IL-17A levels were associated with TNM stage, being higher in III–IV stages (p = 0.044). We observed worse overall survival for individuals with high levels of IL-6 when compared to those with low levels of this cytokine in 6, 12 and 24 months. Further studies of IL-6 levels in independent cohort could clarify the real role of IL-6 as an independent marker of prognostic of NSCLC.

Destabilization dynamics of clay and acid-free polymers of ferric and magnesium salts in AMD without pH adjustment

The physicochemical treatment was employed to treat acid mine drainage (AMD) in the removal of turbid materials using clay only (exp A) and a combination of clay, FeCl3 and Mg(OH)2 (exp B) to form a polymer. A 5 g sample of clay (bentonite) was added to 1.2 L of AMD and treated in a jar test at 250 rpm for 2 min and reduced to 100 rpm for 10 min. A 200 mL sub-sample from the 1.2 L mother liquor was poured into five 500 mL glass beakers, and 20 mL dosages of a polymer of 0.1 M Fe(3+) in (FeCl3) and 0.1 M Mg(2+) in (Mg(OH)2) was added to the beakers. The samples were allowed to settle for 1 h, after which the supernatant was analyzed for pH, total suspended solids (TSS), dissolved oxygen (DO) and oxidation-reduction potential (ORP) (exp A). A similar set of experiments was conducted where 200 mL of the AMD sample was poured into 500 mL glass beakers and (20-60 mL) dosages of a combination of 5 g clay, 0.1 M Fe(3+) (FeCl3) and Mg(2+) (Mg(OH)2) polymer was added and similar mixing, settling time and measurements were conducted (exp B). The polymers used in exp A exhibited TSS removal efficiency (E%) which was slightly lower compared with the polymer used in exp B, above 90%. Clay has a high TSS removal efficiency in the treatment of the AMD, indicating that adsorption was a predominant process in exps A and B. The scanning electron microscope (SEM) micrographs of the AMD sludge of both exps A and B, with a rigid and compacted structure consisting of dense flocs surrounded by the smaller flocs bound together, corroborate the fact that adsorption is a predominant process.

GITR promoter polymorphism contributes to risk of coal workers' pneumoconiosis: a case-control study from China

BACKGROUND

Glucocorticoid-induced tumor necrosis factor (TNF) receptor-related protein (GITR) mainly affects the functions of effector T cells and regulatory T cells thus it may influence various diseases. Coal workers' pneumoconiosis (CWP) is a serious occupational disease worldwide. In the present study, we examined the association between the functional polymorphisms in GITR and risk of CWP in a Chinese population.

METHODS

An association study analyzing three polymorphisms (rs3753348, rs2298213, and rs11466668) in GITR were performed in a case-control study including 693 patients with CWP and 690 controls. Genotyping was carried out by Taqman method.

RESULTS

The GITR rs3753348 GG/GC genotypes significantly enhanced the risk of CWP (adjusted OR=1.32, 95%CI=1.02-1.71), compared with the CC genotype, particularly among subgroups of long exposure years (adjusted OR=1.47, 95%CI=1.06-2.04) and non-smokers (adjusted OR=1.45, 95%CI=1.01-2.09). Moreover, the polymorphism was significantly associated with risk for CWP cases with stage II.

CONCLUSIONS

This is the first report revealing an association between the GITR rs3753348 polymorphism and CWP, and our results suggest that the GITR rs3753348 polymorphism may be involved in the development and susceptibility of CWP.

MUC5B promoter polymorphisms and risk of coal workers' pneumoconiosis in a Chinese population

Coal workers' pneumoconiosis (CWP) is characterized by fibrosing nodular lesions that eventually develop into progressive pulmonary fibrosis. Genetic variations have been recognized to be involved in the multi-factorial susceptibility to CWP, and MUC5B is a candidate lung fibrosis susceptibility gene. In the present study, we investigated possible genetic associations between three single nucleotide polymorphisms in MUC5B promoter region and CWP in a case-control study including 686 CWP patients and 680 controls. Genotyping was carried out by TaqMan method. Only rs2672794 allele and genotype frequencies distributions were significantly different between CWP patients and controls (P = 0.017 and 0.046 for allele and genotype, respectively). The MUC5B rs2672794 CC genotype was associated with a significantly increased risk of CWP, compared with the TT genotype. Moreover, individuals with TC/CC genotype had an obviously increased risk of CWP than those with TT genotype, particularly among subgroups of dust exposure <27 years and smokers. This is the first report showing an association between the MUC5B rs2672794 polymorphism and CWP, and our results suggest that MUC5B rs2672794 CC genotype could increase the risk of CWP. Further studies are warranted to confirm our findings.

Association of transforming growth factor-β1 gene variants with risk of coal workers' pneumoconiosis

Objective

The aim of this case-control study was to explore whether five tagging single nucleotide polymorphisms (tSNPs) within the transforming growthfactor-β1 (TGF-β1) gene were involved in manifestation of inflammatory and fibrotic processes associated with coal workers' pneumoconiosis (CWP).

Methods

The study included 508 CWP patients and 526 controls who were underground coal miners from Xuzhou Mining Business Group. Five tSNPs were selected from the HapMap and detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

Results

The single SNP analysis showed that the genotype frequencies of SNP2 (rs1800470, +869T/C, extron 1) and SNP5 (rs11466345, intron 5) in CWP cases were significantly different from those in controls. Multivariate logistic regression analysis revealed that SNP2 (rs1800470) CC genotype was associated with decreased risk of CWP (OR = 0.50, 95% CI = 0.32-0.78), which was evident among subgroups of those never smoke (OR = 0.40, 95%CI = 0.24-0.66), cases with stage II (OR = 0.41, 95%CI = 0.22-0.76) and exposure period (< 28 y: OR = 0.54, 95%CI = 0.31-0.95; ≥28 y: OR = 0.52, 95%CI = 0.32-0.96). However, the SNP5 (rs11466345) GG genotype was associated with an increased risk of CWP (OR = 2.5, 95%CI = 1.36-4.57), and further stratification analysis showed that the risk of CWP was increased in both smoking and nonsmoking groups, shorter and longer exposure groups, while the risk of CWP was only increased in patients with stage I and II.

Conclusion

This study suggests that TGF-β1 polymorphisms may contribute to susceptibility of CWP.

Laboratory studies of the impact of calcite on in vitro and in vivo effects of coal dust: a potential preventive agent for coal workers' pneumoconiosis?

BACKGROUND

Bioavailable iron (BAI) in coal, which may play a key role in causing coal workers' pneumoconiosis (CWP), is present at relatively high levels in Appalachian coals. Calcite decreases BAI and is more plentiful in Western coals than in Appalachian coals, possibly explaining the lower CWP prevalence among Western miners.

METHODS

We measured effects of calcite on BAI in non-cellular and cellular systems involving Pennsylvania (PA) coal dust. We also tested in vivo effects of calcite on transferrin receptor and markers of epithelial mesenchymal transition (EMT) and inflammation in mice exposed to PA coal.

RESULTS

Calcite rapidly eliminated BAI in an aqueous suspension of PA coal. Ferritin induction in human lung epithelial cells exposed to PA coal was effectively eliminated by calcite. Mouse lung tissue markers indicated increased EMT after exposure to PA coal dust, but not after exposure to PA coal plus calcite. Markers of inflammation increased following exposure to PA coal alone, but not following exposure to PA coal plus calcite.

CONCLUSION

Additional research may lead to the use of supplemental calcite in coal mining as a safe and effective way to prevent CWP among Appalachian coal miners.

Associations of IL-4, IL-4R, and IL-13 gene polymorphisms in coal workers' pneumoconiosis in China: a case-control study

BACKGROUND

The IL-4, IL-4 receptor (IL4R), and IL-13 genes are crucial immune factors and may influence the course of various diseases. In the present study, we investigated the association between the potential functional polymorphisms in IL-4, IL-4R, and IL-13 and coal workers' pneumoconiosis (CWP) risk in a Chinese population.

METHODS

Six polymorphisms (C-590T in IL-4, Ile50Val, Ser478Pro, and Gln551Arg in IL-4R, C-1055T and Arg130Gln in IL-13) were genotyped and analyzed in a case-control study of 556 CWP and 541 control subjects.

RESULTS

Our results revealed that the IL-4 CT/CC genotypes were associated with a significantly decreased risk of CWP (odds ratio (OR) = 0.74, 95% confidence interval (CI) = 0.58-0.95), compared with the TT genotype, particularly among subgroups of age <65 years (OR = 0.68, 95%CI = 0.46-0.99) and dust exposure years ≥26 years (OR = 0.69, 95%CI = 0.50-0.94). Moreover, the polymorphism was significantly associated with risk of CWP patients with stage I. In addition, a combined effect was observed in a dose-dependent manner with increasing numbers of risk variant alleles (P(trend) = 0.023), and individuals with 11-12 risk alleles had a 47% higher risk of CWP than those with 0-8 risk alleles (OR = 1.47, 95% CI = 1.05-2.05).

CONCLUSIONS

Our results suggest that the IL-4 C-590T polymorphism is involved in the etiology of CWP and susceptibility to this disease. Larger studies are warranted to validate our findings.

Leaching of potential hazardous elements of coal cleaning rejects

The geochemical characteristics of coal cleaning rejects (CCR) in Santa Catarina State, Brazil, were investigated. Around 3.5 million ton/year of coal waste are dumped in Santa Catarina State. Coal beneficiation by froth flotation results in large amounts of CCR composed of coaly and mineral matter, the latter characterised by the occurrence of sulphide minerals and a broad array of leachable elements. The total and leachable contents of more than 60 elements were analysed. Atmospheric exposure promotes sulphide oxidation that releases substantial sulphate loads as well as Ca2+, K+, Mg2+, Cl- and Al3+. The metals with the most severe discharges were Zn, Cu, Mn, Co, Ni and Cd. Most trace pollutants in the CCR displayed a marked pH-dependent solubility, being immobile in near-neutral samples. The results highlight the complex interactions among mineral matter solubility, pH and the leaching of potentially hazardous elements.