Crystalline Silica Research Articles

Mining dust as a health threat to employees of extraction departments of coal mines

Mining dust as a health threat to employees of extraction departments of coal mines

Preclinical Mouse Model of Silicosis.

Silicosis is an untreatable occupational lung disease caused by chronic inhalation of crystalline silica. Cyclical release and reuptake of silica particles by macrophages and airway epithelial cells causes repeated tissue damage, characterized by widespread inflammation and progressive diffuse fibrosis. While inhalation is the main route of entry for silica particles in humans, most preclinical studies administer silica via the intratracheal route. In vivo mouse models of lung disease are valuable tools required to bridge the translational gap between in vitro cell culture and human disease. This chapter describes a mouse model of silicosis which mimics clinical features of human silicosis, as well as methods for intranasal instillation of silica and disease analysis. Lung tissue can be collected for histological assessment of silica particle distribution, inflammation, structural damage, and fibrosis in sections stained with hematoxylin and eosin or Masson's trichrome. This approach can be extended to other chronic fibrotic lung diseases where inhalation of small damaging particles such as pollutants causes irreversible disease.

Relationship between Occupational Exposure to Respirable Crystalline Silica and Serum Copper Level as an Indicator of Silicosis: A Systematic Review and Meta-analysis.

This systematic review and meta-analysis study evaluates a relationship between occupational exposure to respirable crystalline silica and serum copper (Cu) levels as an indicator for early detection of silicosis. A systematic search was conducted, and the quality of results was evaluated in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The following databases were searched, including Web of Sciences, Scopus, and PubMed from inception until November 2021. The following keywords were selected for searching in the mentioned databases including, "copper" OR "serum copper" AND "silicosis". The mean (standard deviation [SD]) of Cu was extracted for both silicosis and non-silicosis subjects. The differences in mean effect size were pooled using the random-effect model. Heterogeneity and publication bias were evaluated using the I2 value and Begg's test and Egger's test, respectively. A total of 159 studies were initially found, among which eight studies were included in the meta-analysis. Random-effect meta-analysis of these eight studies showed that silicosis patients had higher copper levels than the non-silicosis group with a pooled standardized mean difference (SMD) of 3.02 (95% confidence interval: 0.25, 5.78); I2 = 99.3%, P value < 0.001. The subgroup analysis showed that the corresponding figures in those with mean age >40 years and <40 years were 5.79 (2.06, 9.52) and -0.43 (-4.57, 3.70), respectively. Moreover, no publication bias was found in the analyses. The results of the present study demonstrated that silica exposure may be associated with increasing serum Cu levels.

Environmentally friendly mesoporous SiO2 with mixed fiber/particle morphology and large surface area for enhanced dye adsorption

Rice straw is made up of hemicelluloses (19–27%), celluloses (32–47%), lignin (5–24%), and ash (13–20%), which are all agricultural waste. Rice straw ash is considered a green/eco-friendly source of silicon dioxide (SiO2). This study focuses on the synthesis and characterization of different mesoporous SiO2 nanostructures derived from rice straw waste material through controlling the pH of the extraction process for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR), diffuse reflectance spectroscopy (DRS), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscope (HRTEM), zeta potential, and surface area analyzer were used to examine the produced materials. Amorphous silica nanostructures, S3 and S7, were produced at pH values of 3 and 7, respectively, according to XRD measurement, whereas higher pH causes the production of crystalline silica (S9). The pH of the extraction has a major effect on the morphology of the resultant nanosilica, as S3 has an irregular shape, S7 is made of distorted spherical particles, and S9 is composed of mixed fiber and spherical particle structures. For pollutant removal, greenly produced SiO2 nanostructures were used. The optimal mesoporous nanosilica (S9) demonstrated the highest surface roughness, the largest surface area (262.1 m2/g), the most negative zeta potential (− 20.2 mV), and the best dye adsorption capacity (71.4 mg/g).

Various admixtures to mitigate the long-term strength retrogression of Portland cement cured under high pressure and high temperature conditions

In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature (HPHT) curing conditions, various influencing factors, including cement sources, particle sizes of silica flour, and additions of silica fume, alumina, colloidal iron oxide and nano-graphene, were investigated. To simulate the environment of cementing geothermal wells and deep wells, cement slurries were directly cured at 50 MPa and 200 °C. Mineral compositions (as determined by X-ray diffraction Rietveld refinement), water permeability, compressive strength and Young's modulus were used to evaluate the qualities of the set cement. Short-term curing (2–30 d) test results indicated that the adoption of 6 μm ultrafine crystalline silica played the most important role in stabilizing the mechanical properties of oil well cement systems, while the addition of silica fume had a detrimental effect on strength stability. Long-term curing (2–180 d) test results indicated that nano-graphene could stabilize the Young’s modulus of oil well cement systems. However, none of the admixtures studied here can completely prevent the strength retrogression phenomenon due to their inability to stop the conversion of amorphous to crystalline phases.

Inflammatory biomarkers in workers exposed to silica dust: integrative review

Inflammatory biomarkers in workers exposed to silica dust: integrative review

Lung Function Loss in Relation to Silica Dust Exposure at a Gold Mine

Lung Function Loss in Relation to Silica Dust Exposure at a Gold Mine

The aggravate role of exosomal circRNA11:120406118|12040782 on macrophage pyroptosis through miR-30b-5p/NLRP3 axis in silica-induced lung fibrosis.

Silica dust inhalation could lead to silicosis, and there is no specific biomarker for its early diagnosis and no effective treatment due to the lack of research on its pathogenesis. The homeostasis of macrophages was considered to be crucial during the development of silicosis from persistent chronic inflammation to irreversible fibrosis. However, its regulatory mechanism and the communication between macrophages and others are still not clear. Exosomal circRNAs emerge as favorable candidates for cellular communication. Therefore, our study aimed to illustrate the regulatory mechanism of silicosis from the view of exosomal circRNAs. Our study identified a novel exosomal circRNA, circRNA11:120406118|12040782, in the peripheral serum of silicosis patients. Furthermore, the detailed role of circRNA11:120406118|12040782 was investigated both in silicosis mouse model and in silica-stimulated macrophages and fibroblasts. On the one hand, circRNA11:120406118|12040782 was shown to regulate silica-stimulated macrophage pyroptosis through circRNA11:120406118|12040782/miR-30b-5p/NLRP3 network. And this macrophage-derived cirRNA could promote the activation of fibroblasts. On the other hand, overexpressing miR-30b-5p, the crucial component of circRNA11:120406118|12040782/miR-30b-5p/NLRP3 regulatory network, could inhibit pyroptosis and attenuate silica-induced lung inflammation and fibrosis in mice. Our findings suggested that exosomal circRNA11:120406118|12040782 could aggravate NLRP3-mediated macrophages pyroptosis through sponging miR-30b-5p in silicosis development, which provide an experimental basis and shed light on the early diagnosis and treatment of silicosis.

Potential consequences of screening of occupational silica dust exposed workers for early detection of silicosis/silico-tuberculosis using a novel biomarker, club cell protein-16, with possible intervention by repurposing metformin

Earlier, a study conducted by the Indian Council of Medical Research – National Institute of Occupational Health (ICMR-NIOH), India, evidenced that CC16 may be used as a proxy marker and screening tool for early detection and progression of silica-induced lung damage. Once CC16 indicates early silicosis, it needs to be confirmed by chest radiography. Next, ICMR-NIOH and ICMR-National Institute of Virology (ICMR-NIV) jointly developed a semi-quantitative and point-of-care CC16 detection kit using lateral flow immune chromatography. The said test can be done from one drop of blood collected through a finger prick. All trained peripheral healthcare workers can screen the silica dust-exposed workers periodically, under the national silicosis control program. Once early silicosis is detected, their sputum may be examined periodically by CB-NAAT/True-NAT for early detection of silicotuberculosis. The serum CC-16 detection kit is the first of its kind for early detection of silicosis through periodic screening, which is approved by the Indian Council of Medical Research, Ministry of Health, Govt. of India. Unless silicosis is controlled, elimination of TB appears to be difficult in India as there is a huge burden of silicosis including sub-radiological silicosis in India and considering the fact that silicosis is a stronger risk factor for lung tuberculosis due to its progressive declining effect of lung immunity. Since occupational silica dust exposure facilitates progressive fibrosis of lung tissue, a clinical trial using metformin may be the need of the day as animal experiments have already shown metformin's anti-fibroblastic effect in silica-induced animals.

Occupational exposure to silica dust in Slovenia is grossly underestimated.

As a by-product or material used in various industries crystalline silica contaminates the air many occupational settings. If its fine particles are inhaled, they are deposited in the lungs and may cause the development of silicosis, chronic obstructive pulmonary disease, and lung cancer. The goal of this study was to estimate occupational exposure to respirable crystalline silica (RCS) in Slovenia and the associated health risks. To do that, we ran two cross-sectional studies, one to determine the number of workers at risk of occupational exposure to RCS in Slovene industries and the other to determine and classify changes in the lung radiographs of glass factory workers exposed to RCS, as a means to infer health risks for other RCS exposed workers in Slovenia. However, the first study shows that official public data on occupational exposure to silica in Slovenia are unreliable and incomplete and that company representatives strongly underestimate occupational exposure to silica. Measurements of total and silica dust are made by 8.3 % and 1.8 % of companies working with silica, respectively. The second study shows that about a third of the exposed workers had lung changes associated with silicosis. We have failed to achieve the goal of our study, as the obtained data are grossly underestimated and unreliable, but it has opened our eyes as to what needs to be improved. All companies need to systematically be informed about occupational health risks, field inspections need to be consistent, regular, and intensified, and health surveillance of all exposed workers implemented regularly.

Biomonitoring Exposure and Early Diagnosis in Silicosis: A Comprehensive Review of the Current Literature.

Silicosis is a particular form of lung fibrosis attributable to occupational exposure to crystalline silica. The occupational exposure to crystalline silica also increases the risk of chronic obstructive pulmonary disease (COPD), cancer and lung infections, especially pulmonary tuberculosis. Silicosis is currently diagnosed in previously exposed workers by standard chest X-ray, when lesions are visible and irreversible. Therefore, it would be necessary to find specific and non-invasive markers that could detect silicosis in earlier stages, before the occurrence of X-ray opacities. In this narrative review, we present several diagnostic, monitoring and predictive biomarkers with high potential in the management of silicosis, such as: pro- and anti-inflammatory cytokines (TNF (Tumour necrosis factor-α), IL-1 (Interleukin-1), IL-6, IL-10), CC16 (Clara cell 16, an indirect marker of epithelial cell destruction), KL-6 (Krebs von den Lungen 6, an indirect marker of alveolar epithelial damage), neopterin (indicator of cellular immunity) and MUC5B gene (Mucin 5B, a gel-forming mucin in mucus). Studies have shown that all the aforementioned markers have a high potential for early diagnosis or evaluation of progression in silicosis and represent promising alternatives to radiology. We consider that a multicentric study is needed to evaluate these biomarkers in correlation with occupational history, histopathological examination, imaging signs and pulmonary functions tests on large groups of subjects to better evaluate the accuracy of the presented biomarkers.

Yangqing Chenfei formula attenuates silica-induced pulmonary fibrosis by suppressing activation of fibroblast via regulating PI3K/AKT, JAK/STAT, and Wnt signaling pathway

BackgroundYangqing Chenfei formula (YCF) has been demonstrated its clinical efficiency on silicosis patients. However, the effect of YCF against silicotic fibrosis and its mechanism remain unclear. PurposeThis study is aimed to investigate active compounds and molecular mechanism of YCF in treating silicosis. MethodYCF was orally administrated to silicosis rats induced by crystalline silica. The effective fraction of YCF and the compounds was isolated and identified by using macroporous resin and HPLC-MS, respectively. The targets and potential molecular mechanism of YCF against silicotic fibrosis were investigated through pharmacological network and RNA-sequencing analysis and in vitro-experimental validation. ResultsYCF could remarkably improve the lung function and pathological changes of silicotic rats, reduce the aggregation of fibrocytes and deposition of ECM, such as collagen I, III, FN, and α-SMA, and suppress the TGF-β/Smad3 signaling. Furthermore, YCF6, the effective fraction derived from YCF, could significantly inhibit fibroblast activation induced by TGF-β. Then, 135 compounds were identified from YCF6 by using HPLC-MS, and Network pharmacology analysis predicted total 941 targets for these compounds. Moreover, 409 differentially expressed genes of fibroblast activation induced by TGF-β were identified. Then, integrated analysis of the 941 targets with 409 differentially expressed genes showed that YCF6 contains multiple compounds, such as tangeretin, L-Malic acid, 2-Monolinolein etc., which inhibits fibroblast activation probably by targeting different proteins, such as PIK3CA, AKT1, JAK2, STAT3, GSK3β, leading to regulate the signal network, such as PI3K/AKT signaling pathway, JAK/STAT signaling pathway, and Wnt signaling pathway. Finally, in vitro experiment indicated that tangeretin, the active compound contained in YCF6, could significantly inhibit TGF-β induced fibroblast activation. Moreover, YCF6 and tangeretin could markedly inhibit the activation of PI3K/AKT, JAK/STAT, and Wnt pathway. ConclusionYCF contained multiple compounds and targeted various proteins that regulated the fibroblast activation, which might be the molecular mechanisms of it in treating silicosis.

About the Transient Effects of Synthetic Amorphous Silica: An In Vitro Study on Macrophages.

Silica (either crystalline or amorphous) is widely used for different applications and its toxicological assessment depends on its characteristics and intended use. As sustained inflammation induced by crystalline silica is at the root of silicosis, investigating the inflammatory effects induced by amorphous silicas and their persistence is needed. For the development of new grades of synthetic amorphous silicas, it is also desirable to be able to understand better the factors underlying potential adverse effects. Therefore, we used an optimized in vitro macrophage system to investigate the effects of amorphous silicas, and their persistence. By using different amorphous silicas, we demonstrated that the main driver for the adverse effects is a low size of the overall particle/agglomerate; the second driver being a low size of the primary particle. We also demonstrated that the effects were transient. By using silicon dosage in cells, we showed that the transient effects are coupled with a decrease of intracellular silicon levels over time after exposure. To further investigate this phenomenon, a mild enzymatic cell lysis allowed us to show that amorphous silicas are degraded in macrophages over time, explaining the decrease in silicon content and thus the transiency of the effects of amorphous silicas on macrophages.

Urinary levels of amorphous urate crystals as a biological marker for occupational exposure to crystalline free silica

Introduction: Due to the obvious adverse effects of exposure to free crystalline silica and the high exposure level in silica-related occupations, the present study aimed at the investigation of renal symptoms in cement factory workers.&#x0D; Materials and methods: For this reason, 128 workers who were working cement factory with a determined occupational exposure to crystalline-free silica were selected as the case group, and 143 workers who were working in the Hamedan Province Rural Water and Wastewater company without being exposed to crystalline free silica were selected as controls. Various kidney- related parameters were evaluated and compared between the selected case and control groups.&#x0D; Results: The results of urine analysis between cases and control showed that there was a statistical difference between the cases and controls regarding Red Blood Cell (RBC), epithelial count, and bacteria (p&lt;0.05). Moreover, the percentage of amorphous urate crystals of the exposed workers (cases) and control were 80.7% and 38.3%, respectively (p&lt;0.001). The results of adjusted results showed that the odd presence of amorphous urate crystals among cases was 7.65 times of the control group (p&lt;0.001).&#x0D; Conclusion: Our findings clearly showed that the level of urinary levels of amorphous urate crystals in silica-exposed individuals is higher than that of non-exposed individuals. Therefore, the presence of urinary amorphous urate crystals in exposed workers may be used as a cheap, non-invasive, and efficient method and urine biological maker for detecting silica exposure in silica-related industries.

Evaluation of a self-cleaning portable dust collector for reducing worker exposures to silica at hydraulic-fracturing sites

ABSTRACT National Institute for Occupational Safety and Health (NIOSH) researchers continue to study worker exposure to respirable crystalline silica (RCS) and develop interventions to reduce these exposures. Occupational overexposures to RCS continue to cause illness and deaths in many industries and RCS has been identified as a serious exposure risk associated with hydraulic- fracturing operations during oil and gas extraction. In 2016 the Occupational Safety and Health Administration (OSHA) reduced the permissible exposure limit (PEL) to 0.05 milligrams of silica per cubic meter of air, averaged over an 8-hour day. This mandate requires hydraulic-fracturing operations to implement dust controls and safer work methods to protect workers from silica exposures above this PEL by June 23, 2021. At hydraulic-fracturing sites utilizing sand movers, pneumatic transfer of fracking sand is the primary source of aerosolized RCS. Currently, there are limited commercially available engineering controls for the collection of dust emitted from thief hatches on sand movers. The goal of this research is to develop a robust, cost-effective, weather resistant, portable, self-cleaning dust collection system that can be retrofitted onto sand mover thief hatches. A prototype was designed, built, and tested, and it was determined that the system could handle flows in the range of 600 to 1300 cfm with loading/cleaning cycle times of 40 and 5 minutes respectively and demonstrated operating efficiencies of 97–99%. Further development of this NIOSH prototype is being done in collaboration with an industry partner with the goal of developing a commercially viable, cost-effective solution to reduce RCS at hydraulic-fracturing sites around the world. Implications: This research has verified that airborne dust created by pneumatic transfer of fracking sand can be effectively collected using a passive cartridge filter system, and that the filters can be cleaned using blasts of air. Mounting these units to the thief hatches of sand movers will significantly reduce dust emissions from sand movers on hydraulic fracturing sites. Thus, this system offers the Oil and Gas Industry a method to reduce worker exposure to RCS on hydraulic fracturing sites that utilize sand movers. The success of this prototype has led researchers to devise a modified version for collecting dust at conveyor transfer points.

Estimation and Health Risk Assessment of Respirable Silica in the Ambient Particulate Matter of Dhaka City

A simple, rapid, and efficient spectrophotometric method was developed for the quantification of respirable crystalline silica (SiO2) in atmospheric particulate matter (PM). The PM samples were collected for 24 hours from two different locations at the University of Dhaka (Mukarram Hussain Khundker Building-MHK and Teacher Student Centre-TSC) using a low-volume air sampler from September to December 2021. The extraction of PM loaded filters followed by filtration resulted in a clear solution. Using UV-visible spectroscopy, the concentration of silica in the filtrate was evaluated by treating the filtrate with molybdate-3 reagent and an amino acid suspension. The average PM-bound silica concentrations at MHK and TSC were 7.72 and 33.86 μgm-3 respectively. Compared to MHK, the silica content in the ambient atmosphere of TSC was four times higher, owing to extensive metro-rail construction work at TSC. The contribution of silica to PM was 3.47% (Site 1) and 5.15% (Site 2). The Hazard Quotient (HQ) was used to characterize the non-cancer risk posed by respirable silica. TSC recorded a high value of 12.87 for the hazard quotient of respirable silica compared to 2.57 for MHK indicating that the exposed inhabitants may have adverse noncancer health impacts. Carcinogenic risk assessment of silica showed that 1 in 341 individuals at MHK and 1 in 78 individuals at TSC could get cancer in their lifetime. This is the first study that demonstrated the high level of PM-bound respirable silica severely degraded air quality as well as potential human health in Dhaka. Dhaka Univ. J. Sci. 70(2): 35-41, 2022 (July)

Occupational exposure to respirable crystalline silica and acute myocardial infarction among men and women in Sweden

ObjectivesOccupational exposure to respirable crystalline silica (RCS) is common. The study aimed to assess the risk for acute myocardial infarction (AMI) after long-term exposure to RCS and to explore differences...

A2aR inhibits fibrosis and the EMT process in silicosis by regulating Wnt/β-catenin pathway

Silicosis, a disease characterized by diffuse fibrosis of the lung tissue, is caused by long-term inhalation of free silica (SiO2) dust in the occupational environment and is currently the most serious occupational diseases of pneumoconiosis. Several studies have suggested that alveolar type Ⅱ epithelial cells (AEC Ⅱ) undergo epithelial-mesenchymal transition (EMT) as one of the crucial components of silicosis in lung fibroblasts. A2aR can play a critical regulatory role in fibrosis-related diseases by modulating the Wnt/β-catenin pathway, but its function in the EMT process of silicosis has not been explained. In this study, an EMT model of A549 cells was established. The results revealed that A2aR expression is reduced in the EMT model. Furthermore, activation of A2aR or suppression of the Wnt/β-catenin pathway reversed the EMT process, while the opposite result was obtained by inhibiting A2aR. In addition, activation of A2aR in a mouse silicosis model inhibited the Wnt/β-catenin pathway and ameliorated the extent of silica-induced lung fibrosis in mice. To sum up, we uncovered that A2aR inhibits fibrosis and the EMT process in silicosis by regulating the Wnt/β-catenin pathway. Our study can provide an experimental basis for elucidating the role of A2aR in the development of silicosis and offer new ideas for further exploration of interventions for silicosis.

Hyaluronic acid as a predictor of exacerbation of occupational chronic obstructive pulmonary disease

The frequency of exacerbations of chronic obstructive pulmonary disease (COPD) is one of the main factors determining the outcome. The search for biomarkers which reflect the risk of exacerbations is one of the urgent scientific and practical objectives. Aim. The study aimed to analyze the relationship between the serum concentration of hyaluronic acid (HA) and the frequency of exacerbations of occupational COPD caused by exposure to silica dust and to substantiate the use of HA as a predictor of exacerbations of COPD. Methods. 78 individuals with a diagnosis of occupational COPD were examined. Respiratory function was assessed based on forced vital capacity of the lungs (FVC, %), the forced expiratory volume in 1 second (FEV1, %) and the calculated ratio of these parameters (FEV1/FVC, %), i.e., modified Tiffno index. The serum concentration of hyaluronic acid (ng/ml) was determined in all individuals using solid-phase enzyme-linked immunosorbent assay (ELISA). The absolute blood level of eosinophils (cell/μl) was determined by a unified method of morphological study of hemocytes with white blood cell differential count. Results. Serum HA concentration in patients with occupational COPD with frequent exacerbations was 25% higher than in the patients with rare exacerbations (the difference was statistically significant; р = 0,004). The analysis of the obtained data showed that the most significant moderate correlation was found between the level of HA and the frequency of COPD exacerbations (direct relationship, r = 0.32; p &lt; 0.05), and FEV1 and the frequency of COPD exacerbations (feedback, r = -0.32;p &lt; 0.05). A weak relationship was found between the relative number of eosinophils and the frequency of COPD exacerbations (direct relationship, r = 0.2; p &lt; 0.05). Weak correlations were also found between the level of HA and FEV1 (feedback, r = -0.23; p &lt; 0.05), between the level of HA and the relative number of eosinophils (direct relationship, r = 0.18; p &lt; 0.05). Conclusion. Quantitative analysis of serum HA in patients with occupational COPD can be used in clinical practice as a biochemical marker for assessing the risk of exacerbations and progression of bronchopulmonary pathology.

Exosomal miR-125a-5p regulates T lymphocyte subsets to promote silica-induced pulmonary fibrosis by targeting TRAF6

Silicosis caused by long-term inhalation of crystalline silica during occupational activities seriously threatens the health of occupational populations. Imbalances in T helper 1(Th1), Th2, Th17, and regulatory T cells (Tregs) promote the development of pulmonary silicosis. Exosomes and their contents, especially microRNAs (miRNAs), represent a new type of intercellular signal transmission mediator related to various diseases including pulmonary fibrosis. However, whether exosomal miRNAs can affect the progression of silicosis by regulating T cell differentiation remains to be determined. To test this hypothesis, we established a miR-125a-5p antagomir mouse model and examined changes in miR-125a-5p levels and T cell subtypes. We found that miR-125a-5p levels were increased in lung tissues and serum exosomes in the silica group at 7 days and 28 days. Downregulation of miR-125a-5p attenuated α-smooth muscle actin (α-SMA), collagen I, fibronectin, p-p65, and p-inhibitor of nuclear factor kappa B (NF-κB) kinase (IKK) protein expression, while tumor necrosis factor receptor-associated factor 6 (TRAF6) and p-inhibitor of κBα (IKBα) expression were increased. MiR-125a-5p anta-miR treatment contributes to the maintenance of Th1/Th2 balance during the progression of pulmonary fibrosis. Our findings indicated that knockdown miR-125a-5p could regulate T lymphocyte subsets and significantly reduce pulmonary fibrosis by targeting TRAF6.