Mapping and prediction of coal workers' pneumoconiosis with bioavailable iron content in the bituminous coals

In vitro toxicity assessment of bioavailable iron in coal varieties of Central India

INTRODUCTION

Information on bioavailable Iron (BAI) content in respirable coal dust (RCD) is crucial to address occupational health and safety, especially in preventing coal workers' pneumoconiosis (CWP).

MATERIALS AND METHODS

In the present study, we determined BAI concentrations in seventy-seven coal samples collected from ten coal mining regions of Central India. The cytotoxic potential of BAI-RCD was established invitro by using alveolar epithelial (A549) and macrophage (U937) cell lines. The oxidative/antioxidant status, inflammations, and genotoxicity attributed to BAI-RCD exposure were evaluated and correlated with CWP pathophysiology.

RESULTS

The mean BAI concentrations in the coal samples (n = 77) range from (275 to 9065 mg kg-1) and showed wide variability. Both cell lines were exposed to low (275 mg kg-1), moderate (4650 mg kg-1), and high (9065 mg kg-1) BAI-RCD samples showed significant (p < 0.001) cytotoxicity in a dose-dependent manner (low < moderate < high) compared to the control. After BAI-RCD treatment, both cell lines showed a decrease in antioxidant stress measures (SOD, CAT, and GSH) and a significant (p < 0.001) increase in oxidative stress parameters (NADPH, MPO, LPO, and PC). Furthermore, these cell line models demonstrated a statistically significant (p < 0.001) dose-dependent increase in cytokines (TGF-β1, IL-1β, TNF-α, MCP-1, and IL-6 cytokines) and oxidative DNA damage marker (8-OH-dG).

CONCLUSION

Results indicated that the central India coals (even at low BAI content) may be accountable for inflammatory responses and cytotoxicity. Hence, BAI can be important characteristic to establish safety standards for coal dust exposure before active mining.

Predicting coal workers' pneumoconiosis trends: Leveraging historical data with the GARCH model in a Chinese Miner Cohort

Coal workers' pneumoconiosis (CWP) is one of the most common and severe occupational diseases worldwide. The main risk factor of CWP is exposure to respirable mine dust. Prediction theory was widely applied in the prediction of the epidemic. Here, it was used to identify the characteristics of CWP today and the incidence trends of CWP in the future. Eight thousand nine hundred twenty-eight coal workers from a state-owned coal mine were included during the observation period from 1963 to 2014. In observations, the dust concentration gradually decreased over time, and the incidence of tunnels and mine, transportation, and assistance workers showed an overall downward trend. We choose a better prediction model by comparing the prediction effect of the Auto Regression Integrate Moving Average model and Generalized Autoregressive Conditional Heteroskedasticity model. Compared with the Auto Regression Integrate Moving Average model, the Generalized Autoregressive Conditional Heteroskedasticity model has a better prediction effect. Furthermore, the status quo and future trend of coal miners' CWP are still at a high level.

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.

Incidence and influencing factors of occupational pneumoconiosis: a systematic review and meta-analysis

OBJECTIVES

To determine the incidence of pneumoconiosis worldwide and its influencing factors.

DESIGN

Systematic review and meta-analysis.

SETTING

Cohort studies on occupational pneumoconiosis.

PARTICIPANTS

PubMed, Embase, the Cochrane Library and Web of Science were searched until November 2021. Studies were selected for meta-analysis if they involved at least one variable investigated as an influencing factor for the incidence of pneumoconiosis and reported either the parameters and 95% CIs of the risk fit to the data, or sufficient information to allow for the calculation of those values.

PRIMARY OUTCOME MEASURES

The pooled incidence of pneumoconiosis and risk ratio (RR) and 95% CIs of influencing factors.

RESULTS

Our meta-analysis included 19 studies with a total of 335 424 participants, of whom 29 972 developed pneumoconiosis. The pooled incidence of pneumoconiosis was 0.093 (95% CI 0.085 to 0.135). We identified the following influencing factors: (1) male (RR 3.74; 95% CI 1.31 to 10.64; p=0.01), (2) smoking (RR 1.80; 95% CI 1.34 to 2.43; p=0.0001), (3) tunnelling category (RR 4.75; 95% CI 1.96 to 11.53; p<0.0001), (4) helping category (RR 0.07; 95% CI 0.13 to 0.16; p<0.0001), (5) age (the highest incidence occurs between the ages of 50 and 60), (6) duration of dust exposure (RR 4.59, 95% CI 2.41 to 8.74, p<0.01) and (7) cumulative total dust exposure (CTD) (RR 34.14, 95% CI 17.50 to 66.63, p<0.01). A dose-response analysis revealed a significant positive linear dose-response association between the risk of pneumoconiosis and duration of exposure and CTD (P-non-linearity=0.10, P-non-linearity=0.16; respectively). The Pearson correlation analysis revealed that silicosis incidence was highly correlated with cumulative silica exposure (r=0.794, p<0.001).

CONCLUSION

The incidence of pneumoconiosis in occupational workers was 0.093 and seven factors were found to be associated with the incidence, providing some insight into the prevention of pneumoconiosis.

PROSPERO REGISTRATION NUMBER

CRD42022323233.

Characterization Analysis of Airborne Particulates from Australian Underground Coal Mines Using the Mineral Liberation Analyser

Exposure monitoring and health surveillance of coal mine workers has been improved in Australia since coal workers’ pneumoconiosis was reidentified in 2015 in Queensland. Regional variations in the prevalence of mine dust lung disease have been observed, prompting a more detailed look into the size, shape, and mineralogical classes of the dust that workers are being exposed to. This study collected respirable samples of ambient air from three operating coal mines in Queensland and New South Wales for characterization analysis using the Mineral Liberation Analyser (MLA), a type of scanning electron microscope (SEM) that uses a combination of the backscattered electron (BSE) image and characteristic X-rays for mineral identification. This research identified 25 different minerals present in the coal samples with varying particle size distributions for the overall samples and the individual mineralogies. While Mine 8 was very consistent in mineralogy with a high carbon content, Mine 6 and 7 were found to differ more significantly by location within the mine.

Chemical signature and fractionation of trace elements in fine particles from anthropogenic and natural sources

The health effects of trace metal elements in atmospheric fine particulate matter (PM_2.5) are widely recognized, however, the emission factor profiles and chemical fractionation of metal elements in different sources were poorly understand. In this study, sixteen metal elements, including Cd, Pb, V, Zn, Ba, Sb, As, Fe, Sr, Cr, Rb, Co, Mn, Cu, Ni and Sn from biomass burning, bituminite and anthracite combustion, as well as dust, were quantified. The results show different emission sources were associated with distinct emission profiles, holding important implications for source apportionment of ambient particulate metals. Specifically, Fe was the dominant metal species (28-1922 mg/kg) for all samples, and was followed by different metals for different samples. For dust, Mn (39.9 mg/kg_dust) had the second-highest emission factor, while for biomass burning, it was Cr and Ba (7.5 and 7.4 mg/kg_biomass, respectively). For bituminous coal combustion, the emission factor of Zn and Ba was 6.2 and 6.0 mg/kg_bituminous, respectively, while for anthracite combustion the corresponding emission factor was 5.6 and 4.3 mg/kg_anthracite, respectively. Moreover, chemical fractionation (i.e., the exchangeable, reducible fraction, oxidizable, and residual fraction) and the bioavailability index (BI) values of the metal elements from different sources were further investigated to reveal the link between different emission sources and the potential health risk. The findings from this study hold important implications for source apportionment and source-specific particulate metal-associated health effects.

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.

Impact of reactive iron in coal mine dust on oxidant generation and epithelial lung cell viability

Coal workers' pneumoconiosis (CWP) is a preventable occupational lung disease caused by the chronic inhalation of coal mine dust. The inhalation of coal mine dusts can result in the development of a range of lung diseases termed coal mine dust lung diseases, which is not limited to CWP and includes silicosis, bronchitis, emphysema and cancer. For decades, the presence of elemental Fe, C and Si has been proposed to be the causal factors underlying CWP. The recent resurgence of CWP globally with examination of cases in the United States suggesting a potential but inconclusive role of Fe(II)-sulfide minerals. To obtain a better understanding of Australian coals, the existence and potential adverse impacts of iron minerals were examined using 24 representative Australian coal samples. The results of this work revealed that reduced iron minerals were widely distributed within samples obtained from Australian coal mines with pyrite and siderite being particularly abundant. Compared with carbon and crystalline silica, the presence of these specific iron minerals were negatively correlated to the viability of both alveolar macrophages (NR8383) and human lung epithelial cells (A549) (R² = 0.689) under scenarios reflecting biologically-relevant inflammatory response conditions. Further analysis using Welch's unpaired t-test indicated that the presence of reduced iron minerals statistically enhanced acellular oxidant production (90% CI [0.74 to 2.55]) and inflammatory response (90% CI [0.15 to 36.96]). Compared with Fe(II)-hydroxide, Fe(II)- and Fe(III)-(phyllo)silicate and Fe(II)-sulfate mineralogies, pyrite and siderite bearing dusts are likely to have greater adverse impacts on epithelial lung cells under inflammatory response conditions in view of both their iron content and reactivity.

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.

Respirable Coal Mine Dust: A Review of Respiratory Deposition, Regulations, and Characterization

In the late 1990s, despite years of efforts to understand and reduce coal worker’s pneumoconiosis (CWP) prevalence from more than 30% in 1970 to less than 4.2%, the level of occurrence among the US coal miners increased unexpectedly. The recent resurgence of lung diseases has raised concerns in the scientific and regulatory communities. In 2014, the United States Mine Safety and Health Administration (MSHA) issued a new dust rule changing the respirable coal mine dust (RCMD) exposure limits, measurement technology, and sampling protocol. The analysis for probable causes for the substantial increase in the CWP incidence rate is rather complicated. This paper aims to conduct a review of RCMD respiratory deposition, health effects, monitoring, regulations, and particle characteristics. The primary sources of RCMD along with the health risks from potential exposure are highlighted, and the current RCMD exposure regulations of the major coal producer countries are compared. A summary of RCMD characterization studies from 1972 to the present is provided. A review of the literature revealed that numerous factors, including geological and mining parameters, advancements in mining practices, particle characteristics, and monitoring approaches are considered to contribute to the recent resurgence of RCMD lung diseases. However, the root causes of the problem are still unknown. The effectiveness of the new dust rules in the United States will probably take years to be correctly assessed. Therefore, future research is needed to understand the relationship between RCMD particle characteristics and lung deposition, and the efficacy of current monitoring practices to measure the true dose of RCMD exposure.

No association between pyrite content and lung cell responses to coal particles

There has been an increase in the identification of cases of coal workers’ pneumoconiosis (CWP) in recent years around the world. While there are a range of possible explanations for this, studies have implicated the pyrite content of coal as a key determinant of CWP risk. However, experimental studies to support this link are limited. The aim of this study was to assess the association between the pyrite content, and subsequent release of bioavailable iron, in coal particles and the response of lung cells involved in the pathogenesis of CWP (epithelial cells, macrophages and fibroblasts). Using real-world Australian coal samples, we found no evidence of an association between the pyrite content of the coal and the magnitude of the detrimental cell response. We did find evidence of an increase in IL-8 production by epithelial cells with increasing bioavailable iron (p = 0.01), however, this was not linked to the pyrite content of the coal (p = 0.75) and we did not see any evidence of a positive association in the other cell types. Given the lack of association between the pyrite content of real-world coal particles and lung cell cytotoxicity (epithelial cells and macrophages), inflammatory cytokine production (epithelial cells, macrophages and fibroblasts), and cell proliferation (fibroblasts) our data do not support the use of coal pyrite content as a predictor of CWP risk.

Enrichment Mechanisms of Gallium and Indium in No. 9 Coals in Anjialing Mine, Ningwu Coalfield, North China, with a Preliminary Discussion on Their Potential Health Risks

To provide a comprehensive insight into the enrichment mechanism of gallium and indium in No. 9 coals, eighteen samples were collected from Anjialing mine, Ningwu Coalfield, Shanxi Province for coal petrological, mineralogical and geochemical analyses. The results suggested that Ga and In enrichment mainly hosted in the top horizons, with average concentration coefficients of 8.99 and 2.73 respectively, compared with the rest of horizons (2.46 for Ga and 1.69 for In). Source apportionment indicated that Ga and In were mainly derived from bauxite of Benxi Formation in Yinshan Oldland, while In could originate from felsic magmatic rocks in Yinshan Oldland as well. In addition, weak oxidation condition, medium to intensive weathering, transgression and input of terrestrial higher plants had positive effects on Ga and In enrichment. With the rapid expansion of emerging electronics manufacturing, Ga and In, of which potential risks on human health were neglected previously, were recently considered as hazardous elements. Therefore, this paper also discussed the potential pathways that these elements threatened human health. We suggested that potential risks on environment and human health caused by Ga and In enrichment in coals and coal-related products should be taken into account besides their economic value.

Mineralogy, geochemistry and toxicity of size-segregated respirable deposited dust in underground coal mines

We focus on a comparison of the geochemistry and mineralogy patterns found in coal, deposited dust (DD), respirable deposited dust (RDD) and inhalable suspended dust (PM10) from a number of underground mines located in China, with an emphasis on potential occupational health relevance. After obtaining the RDD from DD, a toxicological analysis (oxidative potential, OP) was carried out and compared with their geochemical patterns. The results demonstrate: i) a dependence of RDD/DD on the moisture content for high rank coals that does not exist for low rank coals; ii) RDD enrichment in a number of minerals and/or elements related to the parent coal, the wear on mining machinery, lime gunited walls and acid mine drainage; and iii) the geochemical patterns of RDD obtained from DD can be compared with PM10 with relatively good agreement, demonstrating that the characterization of DD and RDD can be used as a proxy to help evaluate the geochemical patterns of suspended PM10. With regards to the toxicological properties of RDD, the Fe content and other by-products of pyrite oxidation, as well as that of anatase, along with Si, Mn and Ba, and particle size (among others), were highly correlated with Ascorbic Acid and/or Glutathione OP.

Cross-section analysis of coal workers' pneumoconiosis and higher brachial-ankle pulse wave velocity within Kailuan study

BACKGROUND

Brachial-ankle pulse wave velocity (baPWV) is an independent predictor of cardiovascular events and mortality. However, there is no related data on the association of baPWVwith coal workers' pneumoconiosis (CWP). We explored the baPWV in subjects withCWP and the associated risk factors.

METHODS

Thiscase-control study included 1,007 male CWP cases without a history of stroke and coronary heart disease and 1,007 matched controls from the Kailuan cohort study. All of the participants underwent assessment for baPWV and traditional cardiovascular risk factors. The cumulative silica dust exposure (work history linked to a job-exposure matrix) was estimated for the CWP cases.

RESULTS

Compared with the controls, the CWP cases had higher baPWV (1762.0 ± 355 cm/s vs. 1718.6 ± 354 cm/s, P = 0.006) and a higher risk of increased baPWV (defined as more than the median baPWV of the population distribution; odds ratio 1.43, 95% confidence interval 1.11-1.83) after adjusting for traditional cardiovascular risk factors. Age ≥60 years, body mass index, heart rate, and hypertension were all significantly associated with increased baPWV in the CWP cases. Compared to non-CWP subjects without hypertension, the odds ratios for increased baPWV gradually increased (P for trend, 0.001) across the CWP subjects without hypertension (odds ratio 1.20, 95%confidence interval 0.90-1.61), subjects with hypertension alone (odds ratio 2.54, 95% confidence interval 1.95-3.30), and CWP subjects with hypertension (odds ratio 3.34, 95% confidence interval 2.56-4.37). We detected a significant positive exposure-response relationship between silica dust-exposure quartiles and increased baPWV in CWP cases (P for trend < 0.001).

CONCLUSIONS

For patients with CWP, increased baPWV was associated with traditional cardiovascular risk factors and long-term silica dust exposure.

A systematic review of occupational exposure to coal dust and the risk of interstitial lung diseases

Objective: Exposure to coal dust can cause interstitial lung disease (ILD), but whether this is due to pure coal or to the contents of quartz in coal is less clear. Here, we systematically reviewed the relation between 'pure coal' and ILD. Methods: In a systematic review based on PRISMA criteria 2945 articles were identified. Strict eligibility criteria, which evaluated the 'pure coal effect', led to the inclusion of only nine studies. Results: Among these nine studies six studies indicated an independent effect of the non-quartz part of coal on the development and progression of ILD, two did not demonstrate an effect and one was inconclusive. Conclusions: Although an independent effect of non-quartz coal dust on the development of ILD is supported, due to methodological limitations the evidence is limited and further evidence is needed.

Inflammatory stress response in A549 cells as a result of exposure to coal: evidence for the role of pyrite in coal workers' pneumoconiosis pathogenesis

On the basis of a recent epidemiological study it is hypothesized that pyrite content in coal is an important factor in coal workers' pneumoconiosis (CWP) pathogenesis. While the role of pyrite in pathogenesis remains to be resolved, the ability of the mineral to generate reactive oxygen species (ROS) through various mechanisms is likely a contributing factor. The aim of this study was to elucidate the importance of the pyrite content of coal in generating an inflammatory stress response (ISR), which is defined as the upregulation of ROS normalized by cell viability. The ISR of A549 human lung epithelial cells in the presence of natural coal samples with variable pyrite contents was measured. Normalized to surface area, five particle loadings for each coal reference standard were analyzed systematically for a total of 24 h. The ISR generated by coals containing 0.00, 0.01, and 0.49 wt.% pyritic sulfur is comparable to,though less than, the ISR generated by inert glass beads (299% of the control). The coals containing 0.52 and 1.15 wt.% pyritic sulfur generated the greatest ISR (798% and 1426% of the control, respectively).

CONCLUSIONS

While ISR does not increase proportionally to pyrite content in coal, the two coals with the highest pyritic sulfur and available iron contents generate the greatest ISR. Therefore, the present study indicates that coals with elevated pyrite contents are likely to induce a significant health burden by stimulating inflammation within the lungs, and may contribute to the development 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.

Pyrite-driven reactive oxygen species formation in simulated lung fluid: implications for coal workers' pneumoconiosis

The origin of coal worker's pneumoconiosis (CWP) has been long debated. A recent epidemiological study shows a correlation between what is essentially the concentration of pyrite within coal and the prevalence of CWP in miners. Hydrogen peroxide and hydroxyl radical, both reactive oxygen species (ROS), form as byproducts of pyrite oxidative dissolution in air-saturated water. Motivated by the possible importance of ROS in the pathogenesis of CWP, we conducted an experimental study to evaluate if ROS form as byproducts in the oxidative dissolution of pyrite in simulated lung fluid (SLF) under biologically applicable conditions and to determine the persistence of pyrite in SLF. While the rate of pyrite oxidative dissolution in SLF is suppressed by 51% when compared to that in air-saturated water, the initial amount of hydrogen peroxide formed as a byproduct in SLF is nearly doubled. Hydroxyl radical is also formed in the experiments with SLF, but at lower concentrations than in the experiments with water. The formation of these ROS indicates that the reaction mechanism for pyrite oxidative dissolution in SLF is no different from that in water. The elevated hydrogen peroxide concentration in SLF suggests that the decomposition, via the Fenton mechanism to hydroxyl radical or with Fe(III) to form water and molecular oxygen, is initially inhibited by the presence of SLF components. On the basis of the oxidative dissolution rate of pyrite measured in this paper, it is calculated that a respirable two micron pyrite particle will take over 3 years to dissolve completely.

Health disparities of coal miners and coal mining communities: the role of occupational health nurses

This article investigates how the health disparities of Appalachian coal miners and coal mining communities could be decreased through a partnership with occupational health nurses. On-site health clinics managed by occupational health nurses working in the coal mining industry are proposed as a means to improve health care outcomes. Health effects, economic considerations, environmental impacts, and U.S. coal mining legislation and regulation are examined. An epidemiological approach is presented to the unique health effects experienced by Appalachian coal miners and coal mining communities within the context of existent socioeconomic disparities. The long-standing health crisis in Appalachian coal mining communities requires a multidisciplinary approach led by occupational health nurses.

Adenine oxidation by pyrite-generated hydroxyl radicals

Cellular exposure to particulate matter with concomitant formation of reactive oxygen species (ROS) and oxidization of biomolecules may lead to negative health outcomes. Evaluating the particle-induced formation of ROS and the oxidation products from reaction of ROS with biomolecules is useful for gaining a mechanistic understanding of particle-induced oxidative stress. Aqueous suspensions of pyrite particles have been shown to form hydroxyl radicals and degrade nucleic acids. Reactions between pyrite-induced hydroxyl radicals and nucleic acid bases, however, remain to be determined. Here, we compared the oxidation of adenine by Fenton-generated (i.e., ferrous iron and hydrogen peroxide) hydroxyl radicals to adenine oxidation by hydroxyl radicals generated in pyrite aqueous suspensions. Results show that adenine oxidizes in the presence of pyrite (without the addition of hydrogen peroxide) and that the rate of oxidation is dependent on the pyrite loading. Adenine oxidation was prevented by addition of either catalase or ethanol to the pyrite/adenine suspensions, which implies that hydrogen peroxide and hydroxyl radicals are causing the adenine oxidation. The adenine oxidation products, 8-oxoadenine and 2-hydroxyadenine, were the same whether hydroxyl radicals were generated by Fenton or pyrite-initiated reactions. Although nucleic acid bases are unlikely to be directly exposed to pyrite particles, the formation of ROS in the vicinity of cells may lead to oxidative stress.

What component of coal causes coal workers' pneumoconiosis?

OBJECTIVE

To evaluate the component of coal responsible for coal workers' pneumoconiosis (CWP).

METHODS

A literature search of PubMED was conducted to address studies that have evaluated the risk of CWP based on the components of coal.

RESULTS

The risk of CWP (CWP) depends on the concentration and duration of exposure to coal dust. Epidemiology studies have shown inverse links between CWP and quartz content. Coal from the USA and Germany has demonstrated links between iron content and CWP; these same studies indicate virtually no role for quartz. In vitro studies indicate strong mechanistic links between iron content in coal and reactive oxygen species, which play a major role in the inflammatory response associated with CWP.

CONCLUSIONS

The active agent within coal appears to be iron, not quartz. By identifying components of coal before mining activities, the risk of developing CWP may be reduced.

Prevalence characteristics and prediction of coal workers' pneumoconiosis in the Tiefa Colliery in China

To explore characteristics of the development of coal workers' pneumoconiosis (CWP) at present and trend in the future, we investigated 16,154 coal miners exposed to dust for at least 1 yr in the Tiefa Colliery in China. Occupational categories were divided into tunneling, mining, combining and helping. Four cohorts (before 1958, 1958-, 1968-, and after 1978) were created according to years of first exposure. Life-Table Method was used to calculate cumulative incidence rates of CWP adjusted by duration of dust exposure and predict the number of the new CWP patients. Results indicated that cumulative incidence rates of CWP in four cohorts were 26.65%, 18.94%, 1.15%, and 0.06%, respectively (Chi(2)=493.57, p<0.0001). The 55-yr cumulative rate of CWP of tunneling miners (25.90%) or that of combining miners (14.53%) was statistically higher than that of mining miners (7.26%) or that of helping miners (0.89%). The number of new CWP patients predicted in future was approximately 77. New CWP patients predicted would mainly occur among coal miners with first dust exposure in 1958-1967 and those working at tunneling. Most of them could be diagnosed in the age group from 45 to 75 and in the period of the next 20 yr from 2008 to 2028.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

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

Recent increases in oil price further strengthen the argument that coal and coal products will play an increasingly important role in fulfilling the energy needs of our society. Coal is an aggregate of heterogeneous substances composed of organic (macerals) and inorganic (minerals) materials. The objective of this review was to assess whether some chemical parameters in coal play a role in producing environmental health problems. Basic properties of coal--such as chemical forms of the organic materials, structure, compositions of minerals--vary from one coal mine region to another as well as from coals of different ranks. Most importantly, changes in chemical properties of coals due to exposure to air and humidity after mining--a dynamic process--significantly affect toxicity attributed to coal and environmental fate. Although coal is an extremely complex and heterogeneous material, the fundamental properties of coal responsible for environmental and adverse health problems are probably related to the same inducing components of coal. For instance, oxidation of pyrite (FeS2) in the coal forms iron sulfate and sulfuric acid, which produces occupational lung diseases (e.g., pneumoconiosis) and other environmental problems (e.g., acid mine drainage and acid rain). Calcite (CaCO3) contained in certain coals alters the end products of pyrite oxidation, which may make these coals less toxic to human inhalation and less hazardous to environmental pollution. Finally, knowledge gained on understanding of the chemical properties of coals is illustrated to apply for prediction of toxicity due to coal possibly before large-scale mining and prevention of occupational lung disease during mining.

Role of pyrite in formation of hydroxyl radicals in coal: possible implications for human health

BACKGROUND

The harmful effects from inhalation of coal dust are well-documented. The prevalence of lung disease varies by mining region and may, in part, be related to regional differences in the bioavailable iron content of the coal. Pyrite (FeS2), a common inorganic component in coal, has been shown to spontaneously form reactive oxygen species (ROS) (i.e., hydrogen peroxide and hydroxyl radicals) and degrade nucleic acids. This raises the question regarding the potential for similar reactivity from coal that contains pyrite. Experiments were performed to specifically evaluate the role of pyrite in coal dust reactivity. Coal samples containing various amounts of FeS2 were compared for differences in their generation of ROS and degradation of RNA.

RESULTS

Coals that contain iron also show the presence of FeS2, generate ROS and degrade RNA. Coal samples that do not contain pyrite do not produce ROS nor degrade RNA. The concentration of generated ROS and degradation rate of RNA both increase with greater FeS2 content in the coals.

CONCLUSION

The prevalence of coal workers' pneumoconiosis can be correlated to the amount of FeS2 in the coals. Considering the harmful effects of generation of ROS by inhaled particles, the results presented here show a possible mechanism whereby coal samples may contribute to CWP. This suggests that the toxicity of coal may be explained, in part, by the presence of FeS2.