Artificial stone-associated silicosis: a rapidly emerging occupational lung disease

Risk Factors of Silicosis Progression: A Retrospective Cohort Study in China

Background

Silicosis poses a threat to workers’ health due to the irreversible lung lesions.

Design

A retrospective cohort study.

Methods

A total of 259 patients [80 worked with artificial stone (AS), 179 with non-artificial stone (non-AS)] with confirmed silicosis were included in this study. Forty-one of AS and 91 of non-AS had approximately 2 years’ follow-up records [lung function tests and high-resolution computer tomography (HRCT)]. Compared with the first records, increased, densified, or newly emerging lesions in lung HRCT images were judged as progression of the disease. Cox proportional hazards models were used to determine the risk factors. Kaplan–Meier survival curve and log-rank test were used to compare prognostic factors for cumulative risk of progression.

Results

In 132 patients with median follow-up of 24.0 months (IQR, 13.8, 24.9), 66 patients showed progression, in them, 36 (87.8%) were from AS group and 30 (32.9%) from non-AS group. Working experience of AS processing (hazard ratio, 5.671; 95% CI, 3.048–10.550) and complicated silicosis in CT images (hazard ratio, 2.373; 95% CI, 1.379–4.082) were the main risk factors associated with progression. Forced vital capacity decreased after 1-year (241.5 vs. 55.2 mL) and 2-year (328.1 vs. 68.8 mL) follow-up in the two groups (AS vs. non-AS). History of anti-tuberculosis medication, chest oppression and pain, ground-glass opacity, pleural abnormalities, and restrictive pulmonary dysfunction were more frequently found on HRCT images in the AS group than non-AS group. Lung functions (DL_CO, %) were lower in the current/former smokers than the non-smokers (P < 0.05) in AS patients.

Conclusion

Prevention and protection rules are needed to be enforced in the occupation involving AS processing; smoking may be associated with declined lung function in AS patients.

Current global perspectives on silicosis-Convergence of old and newly emergent hazards

Silicosis not a disease of the past. It is an irreversible, fibrotic lung disease specifically caused by exposure to respirable crystalline silica (RCS) dust. Over 20,000 incident cases of silicosis were identified in 2017 and millions of workers continue to be exposed to RCS. Identified case numbers are however a substantial underestimation due to deficiencies in reporting systems and occupational respiratory health surveillance programmes in many countries. Insecure workers, immigrants and workers in small businesses are at particular risk of more intense RCS exposure. Much of the focus of research and prevention activities has been on the mining sector. Hazardous RCS exposure however occurs in a wide range of occupational setting which receive less attention, in particular the construction industry. Recent outbreaks of silicosis associated with the fabrication of domestic kitchen benchtops from high‐silica content artificial stone have been particularly notable because of the young age of affected workers, short duration of RCS exposure and often rapid disease progression. Developments in nanotechnology and hydraulic fracking provide further examples of how rapid changes in technology and industrial processes require governments to maintain constant vigilance to identify and control potential sources of RCS exposure. Despite countries around the world dealing with similar issues related to RCS exposure, there is an absence of sustained global public health response including lack of consensus of an occupational exposure limit that would provide protection to workers. Although there are complex challenges, global elimination of silicosis must remain the goal.

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Characterisation of dust emissions from machined engineered stones to understand the hazard for accelerated silicosis

Engineered stones are novel construction materials associated with a recent upsurge in silicosis cases among workers in the stonemason industry. In order to understand the hazard for the short latency of lung disease among stonemasons, we simulated real-time dust exposure scenario by dry-machining engineered stones in controlled conditions, capturing and analysing the respirable dust generated for physical and chemical characteristics. Natural granite and marble were included for comparison. Cutting engineered stones generated high concentrations of very fine particles (< 1 µm) with > 80% respirable crystalline silica content, in the form of quartz and cristobalite. Engineered stones also contained 8–20% resin and 1–8% by weight metal elements. In comparison, natural stones had far lower respirable crystalline silica (4- 30%) and much higher metal content, 29–37%. Natural stone dust emissions also had a smaller surface area than engineered stone, as well as lower surface charge. This study highlighted the physical and chemical variability within engineered stone types as well as between engineered and natural stones. This information will ultimately help understand the unique hazard posed by engineered stone fabrication work and help guide the development of specific engineering control measures targeting lower exposure to respirable crystalline silica.

Excess iron promotes emergence of foamy macrophages that overexpress ferritin in the lungs of silicosis patients

Background and objective

Inhalation of high concentrations of respirable crystalline silica (RCS) can lead to silicosis. RCS contains varying levels of iron, which can cause oxidative stress and stimulate ferritin production. This study evaluated iron‐related and inflammatory markers in control and silicosis patients.

Methods

A cohort of stone benchtop industry workers (n = 18) were radiologically classified by disease severity into simple or complicated silicosis. Peripheral blood and bronchoalveolar lavage (BAL) were collected to measure iron, ferritin, C‐reactive protein, serum amyloid A and serum silicon levels. Ferritin subunit expression in BAL and transbronchial biopsies was analysed by reverse transcription quantitative PCR. Lipid accumulation in BAL macrophages was assessed by Oil Red O staining.

Results

Serum iron levels were significantly elevated in patients with silicosis, with a strong positive association with serum ferritin levels. In contrast, markers of systemic inflammation were not increased in silicosis patients. Serum silicon levels were significantly elevated in complicated disease. BAL macrophages from silicosis patients were morphologically consistent with lipid‐laden foamy macrophages. Ferritin light chain (FTL) mRNA expression in BAL macrophages was also significantly elevated in simple silicosis patients and correlated with systemic ferritin.

Conclusion

Our findings suggest that elevated iron levels during the early phases of silicosis increase FTL expression in BAL macrophages, which drives elevated BAL and serum ferritin levels. Excess iron and ferritin were also associated with the emergence of a foamy BAL macrophage phenotype. Ferritin may represent an early disease marker for silicosis, where increased levels are independent of inflammation and may contribute to fibrotic lung remodelling.

Silicosis is an aggressive and incurable lung disease. In this study, serum iron levels were increased in silicosis patients, and these levels were strongly associated with serum ferritin levels. Lipid‐laden bronchoalveolar lavage macrophages were identified as a major source of ferritin, whereas markers of inflammation were not increased.

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Alveolar crystal burden in stone workers with artificial stone silicosis

Background and objective

An epidemic of silicosis has emerged due to a failure to control risks associated with exposure to high‐silica content respirable dust generated while working with artificial stone products. Methods for quantification of alveolar crystal burden are needed to advance our understanding of the pathobiology of silica‐related lung injury as well as assisting in the diagnosis, clinical management and prognostication of affected workers. The objective of this study was to develop and validate novel methods to quantify alveolar crystal burden in bronchoalveolar lavage (BAL) fluid from patients with artificial stone silicosis.

Methods

New methods to quantify and analyse alveolar crystal in BAL from patients with artificial stone silicosis were developed. Crystals were isolated and counted by microscopy and alveolar crystal burden was calculated using a standard curve generated by titration of respirable α‐Quartz. The utility of the assay was then assessed in 23 patients with artificial stone silicosis.

Results

Alveolar crystal burden was greater in patients with silicosis (0.44 picograms [pg]/cell [0.08–3.49]) compared to patients with other respiratory diagnoses (0.057 pg/cell [0.01–0.34]; p < 0.001). Alveolar crystal burden was positively correlated with years of silica exposure (ρ = 0.49, p = 0.02) and with decline in diffusing capacity of the lungs for carbon monoxide (ρ = −0.50, p = 0.02).

Conclusion

Alveolar crystal burden quantification differentiates patients with silicosis from patients with other respiratory disorders. Furthermore, crystal burden is correlated with the rate of decline in lung function in patients with artificial stone silicosis.

Exposure to silicates and systemic autoimmune-related outcomes in rodents: a systematic review

BACKGROUND

Autoimmunity can result from the interplay between genetic background and effects of environmental and/or occupational exposure to hazardous materials. Several compounds, including silica dust, have been linked with systemic autoimmunity and systemic autoimmune diseases, based on epidemiological evidence. For asbestos, a strong link with systemic autoimmune diseases does not yet exist, however, several studies have documented features of autoimmunity following asbestos exposure. Even so, human studies are limited in their ability to identify and examine isolated exposures, making it difficult to demonstrate causation or to assess pathogenic mechanisms. Therefore, this systematic review examines the existing animal evidence regarding autoimmunity and exposure to silicates (silica and asbestos).

METHODS

PubMed and EMBASE were systematically searched for peer-reviewed studies examining systemic autoimmune disease-related outcomes after silicate exposure in rodents. Literature databases were searched up to September 2021 for studies written in English and where the full text was available. Search strings were established based on a PECO (Population, Exposure, Comparator, Outcome) format. After title, abstract, and full-text screening, thirty-four studies were identified for further analysis. Quality assessment through ToxR tool and qualitative analysis of the results was performed.

RESULTS

Although there was significant heterogeneity in the included studies in terms of exposure protocol and genetic background of the rodent models used, it was noted that both genetic background and exposure to silicates [(crystalline) silica and asbestos] are highly relevant to the development of (sub-) clinical systemic autoimmune disease.

CONCLUSION

Parallels were observed between the findings from the animal (this review) and human (epidemiological) studies, arguing that experimental animal models are valuable tools for examining exacerbation or development of autoimmune disease after silicate exposure. However, genetic background and synergism between exposures should be considered in future studies.

Silica Exposure Estimates in Artificial Stone Benchtop Fabrication and Adverse Respiratory Outcomes

Silicosis is being increasingly reported among young stonemasons in the artificial stone (AS) benchtop fabrication and installation industry. Respiratory health screening, which included a job and exposure history, a chest X-ray (CXR), a respiratory health questionnaire, and gas transfer testing, were offered to stonemasons in Victoria, Australia. Workers typically reported a variety of tasks, including cleaning and labouring, which made exposure assessment complex. We estimated the relative respirable crystalline silica exposure intensity of each job from the proportion of time using AS and the proportion of time doing dry work (work without water suppression). The relative average intensity of exposure for up to five jobs was calculated. Cumulative exposure was calculated as the sum of the duration multiplied by intensity for each job. Installers and factory machinists (other than computer numeric control operators) were the most likely to report dry work with AS, and so had a greater average intensity of exposure. Exposure intensity and cumulative exposure were associated with increased odds of an ILO (International Labour Organisation) CXR profusion major category of ≥1 and with dyspnoea. Exposure duration was also associated with ILO profusion category. In multivariate analyses of health outcomes, only job type was associated with the ILO profusion category. For both most recent and longest-duration job types, when compared to the lowest exposure group, factory machinists were more likely to have an ILO category ≥1. This suggests that intensity of exposure estimated from the proportion of time dry cutting and proportion of time working on AS can predict the risk of adverse respiratory outcomes for workers in this industry.

An outbreak of work-related asthma and silicosis at a US countertop manufacturing and fabrication facility

BACKGROUND

Outbreaks of severe silicosis have affected workers who fabricate artificial stone countertops. Work-related asthma (WRA) has not been a prominent feature of those prior outbreaks.

METHODS

This report describes an outbreak of WRA and silicosis at a facility that manufactures and fabricates chemical-resistant countertops comprised of sand, epoxy resin, and phthalic anhydride (PA), a known respiratory sensitizer. The multi-disciplinary investigation included clinical examinations of workers, an industrial hygiene survey with qualitative and quantitative exposure assessments, and a cross-sectional questionnaire.

RESULTS

Engineering controls and personal protective equipment were inadequate. Some workers were exposed to PA or silica above permissible exposure limits established by the Occupational Safety and Health Administration (OSHA). Clinical and epidemiologic investigations identified 16 workers with confirmed or suspected WRA. Two years later, after OSHA began to enforce its new silica standards, 12 workers received medical surveillance for silicosis. Of these 12 workers, four (33.3%) were diagnosed with silicosis based on abnormal chest computed tomography examinations.

CONCLUSIONS

Artificial stone countertop workers can develop asthma or silicosis. Risk of asthma may be highest in workers exposed to asthmagens such as PA and epoxy resins while manufacturing the artificial stone material.

OUP accepted manuscript

Artificial stone (AS) is a composite material that has seen widespread use in construction, particularly for kitchen benchtops. However, fabrication processes with AS have been associated with serious lung disease. Safety data sheets (SDSs) aim to provide important information pertaining to composition and health risks. In the case of a complex mixture, SDSs may be problematic in terms of specific information on overall health risks. To assess this issue, we compared empirically determined mineral, metallic, and organic resin content of 25 individual AS products across six suppliers, with the corresponding SDS information. X-ray diffraction was used to quantitate the mineralogical components of AS samples, and X-ray fluorescence was used to estimate the metallic components. Organic material (resin content) was estimated using weight loss during calcination. Although the resin content for all AS samples was within the SDS-reported ranges, there was considerable variability in the crystalline silica content when comparing with supplier’s SDS. Potentially toxicologically relevant metallic and mineral constituents were not reported. Some supplier SDSs were found to provide more information than others. Only one of the six suppliers provided crystalline mineral content other than silica, and only two suppliers provided any information about metals. There remains a limited understanding of lung pathogenesis from AS, and this study highlights the need for more comprehensive and standardized SDS information for risk assessment and management.

Occupational exposure to crystalline silica in artificial stone processing

Respirable Crystalline Silica (RCS) is a hazardous substance with known effects that can be well correlated with exposure levels that still persist in many traditional sectors, such as construction or stone processing. In the past decade, exposure scenarios for RCS have been found in the sector of artificial stone processing. The aim of this study is to evaluate the levels of RCS in facilities specialized in the production of artificial stone countertops and other accessories for the furnishing of kitchens, bathrooms, and offices after the introduction of some preventive technical measures such as wet processing or local exhaust ventilation systems. The study involved 51 subjects in four facilities. Personal silica exposure assessment was carried out using GS3 cyclones positioned in the breathing zone during the work shift. Quantitative determination of silica was carried out by X-ray diffraction analysis. Respirable dust levels were in the range 0.046-1.154 mg/m³ with RCS levels within the range <0.003-0.098 mg/m³. The highest exposure was found in dry finishing operations. Although there was a remarkable reduction in RCS exposure levels compared to what was observed in the past before the introduction of preventive measures, the data still showed hazardous exposure levels for some of the monitored activities.

Exploration study on serum metabolic profiles of Chinese male patients with artificial stone silicosis, silicosis, and coal worker's pneumoconiosis

Long-term exposure to inhaled silica dust induces pneumoconiosis, which remains a heavy burden in developing countries. Modern industry provides new resources of occupational SiO₂ leading to artificial stone silicosis especially in developed countries. This study aimed to characterize the serum metabolic profile of pneumoconiosis and artificial stone silicosis patients. Our case-control study recruited 46 pairs of pneumoconiosis patients and dust-exposed workers. Nontargeted metabolomics and lipidomics by ultra-high-performance liquid chromatography-tandem mass spectrometry platform were conducted to characterize serum metabolic profile in propensity score-matched (PSM) pilot study. 54 differential metabolites were screened, 24 of which showed good screening efficiency through receiver operating characteristics (ROC) in pilot study and validation study (both AUC > 0.75). 4 of the 24 metabolites can predict pneumoconiosis stages, which are 1,2-dioctanoylthiophosphatidylcholine, phosphatidylcholine(O-18:1/20:1), indole-3-acetamide and l-homoarginine. Kynurenine, N-tetradecanoylsphingosine 1-phosphate, 5-methoxytryptophol and phosphatidylethanolamine(22:6/18:1) displayed the potential as specific biomarkers for artificial stone silicosis. Taken together, our results confirmed that tryptophan metabolism is closely related to pneumoconiosis and may be related to disease progression. Hopefully, our results could supplement the biomarkers of pneumoconiosis and provide evidence for the discovery of artificial stone silicosis-specific biomarkers.

Compositional and structural analysis of engineered stones and inorganic particles in silicotic nodules of exposed workers

BACKGROUND

Engineered stone silicosis is an emerging disease in many countries worldwide produced by the inhalation of respirable dust of engineered stone. This silicosis has a high incidence among young workers, with a short latency period and greater aggressiveness than silicosis caused by natural materials. Although the silica content is very high and this is the key factor, it has been postulated that other constituents in engineered stones can influence the aggressiveness of the disease. Different samples of engineered stone countertops (fabricated by workers during the years prior to their diagnoses), as well as seven lung samples from exposed patients, were analyzed by multiple techniques.

RESULTS

The different countertops were composed of SiO2 in percentages between 87.9 and 99.6%, with variable relationships of quartz and cristobalite depending on the sample. The most abundant metals were Al, Na, Fe, Ca and Ti. The most frequent volatile organic compounds were styrene, toluene and m-xylene, and among the polycyclic aromatic hydrocarbons, phenanthrene and naphthalene were detected in all samples. Patients were all males, between 26 and 46 years-old (average age: 36) at the moment of the diagnosis. They were exposed to the engineered stone an average time of 14 years. At diagnosis, only one patient had progressive massive fibrosis. After a follow-up period of 8 ± 3 years, four patients presented progressive massive fibrosis. Samples obtained from lung biopsies most frequently showed well or ill-defined nodules, composed of histiocytic cells and fibroblasts without central hyalinization. All tissue samples showed high proportion of Si and Al at the center of the nodules, becoming sparser at the periphery. Al to Si content ratios turned out to be higher than 1 in two of the studied cases. Correlation between Si and Al was very high (r = 0.93).

CONCLUSION

Some of the volatile organic compounds, polycyclic aromatic hydrocarbons and metals detected in the studied countertop samples have been described as causative of lung inflammation and respiratory disease. Among inorganic constituents, aluminum has been a relevant component within the silicotic nodule, reaching atomic concentrations even higher than silicon in some cases. Such concentrations, both for silicon and aluminum showed a decreasing tendency from the center of the nodule towards its frontier.

Artificial Stone Silicosis: Accumulation of errors in the resurgence of an occupational disease: A qualitative study

BACKGROUND

Exposure to artificial stone machining, under the conditions in which marble workers work with this new product, can cause silicosis.

OBJECTIVE

To examine the experiences of marble workers affected, both in workshop and during home installation of countertops, before diagnosis of silicosis.

METHODS

Qualitative study in which 10 open-ended semistructured interviews were conducted with marble workers diagnosed with silicosis after machining artificial stone countertops in Cádiz, Spain. Interviews were recorded, transcribed, and coded using a directed content analysis. Codes were organized into themes.

RESULTS

Interviews up to 120 minutes and transcript analysis revealed three themes: 1) Heavy exposure for piecework: construction boom in an environment of labor deregulation and high demand for the novel product; 2) Poor working conditions: dry machining of artificial stone without proper protection in the workshop and greater exposure during home installation of countertops; 3) Concatenated legal transgressions: deficiencies in prevention and health surveillance without safety conditions for the correct handling of artificial stone.

CONCLUSIONS

The fight against an emerging occupational disease-artificial stone silicosis-should focus on detecting affected workers and avoiding new cases, forcing joint efforts to achieve rigorous compliance with health surveillance and protecting marble workers to achieve healthy and safe workplaces.

Pulmonary function parameters among marble industry workers in Lahore, Pakistan

Background: Occupational contact with dust particles is a well-known phenomenon, particularly in developing countries of the world. Crystalline silica present in marble dust is the main etiology of a rising prevalence of obstructive lung diseases in marble stone workers, who are in direct contact with marble dust in the surrounding environment during their regular work.  The purpose of this study was to compare the pulmonary function parameters of workers in marble workshops and age matched healthy individuals in the Lahore District of Pakistan. Methods: The study included 164 male individuals, 82 individuals working in marble workshops and 82 healthy individuals from the same community. Data were collected through in-person interviews using a structured questionnaire after obtaining written consent. A Spiro Lab spirometry for pulmonary function tests was used to identify any change in the lung function parameters. FVC% (forced vital capacity), FEV 1 (forced expiratory volume in first second) and FEV1 / FVC ratio were evaluated. Results: Mean age in the exposed group (marble workers) and non-exposed group (healthy individuals) were 29.92 ± 6.19 and 30.58 ± 6.37 years, respectively. The mean years of work experience of the exposed group was 11.92 ± 5.67 years. A statistically insignificant difference was observed between marble exposed workers & healthy individuals from the demographic variables. Lung function parameters in marble workers exhibited a highly significant (P < 0.001) decrease in FVC%, FEV 1 & FEV 1 / FVC ratio when compared to healthy individuals. Seventy-one percent of marble workers had abnormal pulmonary parameters whereas 34% of workers had restrictive pulmonary impairment. Marble workers who had worked for more than 15 years had a highly significant risk of developing abnormal pulmonary function (P < 0.001). Conclusion: Continuous exposure to marble dust deteriorates the lung function of marble workers.

Characterizing and Comparing Emissions of Dust, Respirable Crystalline Silica, and Volatile Organic Compounds from Natural and Artificial Stones

The frequency of cases of accelerated silicosis associated with exposure to dust from processing artificial stones is rapidly increasing globally. Artificial stones are increasingly popular materials, commonly used to fabricate kitchen and bathroom worktops. Artificial stones can contain very high levels of crystalline silica, hence cutting and polishing them without adequate exposure controls represents a significant health risk. The aim of this research was to determine any differences in the emission profiles of dust generated from artificial and natural stones when cutting and polishing. For artificial stones containing resins, the nature of the volatile organic compounds (VOCs) emitted during processing was also investigated. A selection of stones (two natural, two artificial containing resin, and one artificial sintered) were cut and polished inside a large dust tunnel to characterize the emissions produced. The inhalable, thoracic, and respirable mass concentrations of emissions were measured gravimetrically and the amount of crystalline silica in different size fractions was determined by X-ray diffraction. Emissions were viewed using scanning electron microscopy and the particle size distribution was measured using a wide range aerosol spectrometer. VOCs emitted when cutting resin-artificial stones were also sampled. The mass of dust emitted when cutting stones was higher than that emitted when polishing. For each process, the mass of dust generated was similar whether the stone was artificial or natural. The percentage of crystalline silica in bulk stone is likely to be a reasonable, or conservative, estimate of that in stone dust generated by cutting or polishing. Larger particles were produced when cutting compared with when polishing. For each process, normalized particle size distributions were similar whether the stone was artificial or natural. VOCs were released when cutting resin-artificial stones. The higher the level of silica in the bulk material, the higher the level of silica in any dust emissions produced when processing the stone. When working with new stones containing higher levels of silica, existing control measures may need to be adapted and improved in order to achieve adequate control.

Metal Ion Release from Engineered Stone Dust in Artificial Lysosomal Fluid-Variation with Time and Stone Type

Inhalational exposure to dust from engineered stone (ES), also known as artificial or composite stone, is associated with a specific disease profile, namely accelerated silicosis, and scleroderma. The pathogenic mechanisms are poorly understood, particularly the role of resin and metal ions. Metal ions are present in pigments and constituent minerals and may be considered potential contributors to toxicity. The aim of this preliminary study was to understand the solubility of ES-containing metals in artificial lysosomal fluid (ALF) simulating the acidic intracellular environment of the lung macrophage lysosome. Differences with respect to ES types and temporal release were explored. Ten ES products of variable colour and company origin were comminuted and assessed for four different metals, solubilized into ALF solutions at 1,2,4 and 8 weeks at 37 °C. There was significant variability in metal release, particularly with regard to iron and manganese, which could be correlated with the reflected brightness of the stone. A majority of the available Mn, Fe, Al and Ti was solubilized. Time trends for metal release varied with ES type but also with metal ion. The data suggest a high metal ion bioavailability once engulfed by lung macrophages. There is a need to investigate a wider range of ES dust and relate metal content to markers of ES toxicity.

Artificial stone-associated silicosis with concurrent Cryptococcus infection

Acute silicoproteinosis is a disease that develops in weeks, and lasting for years, after massive exposure to silica dust in relatively closed spaces. It was rare, but the cases have recently increased worldwide due to the development of artificial stone industry. Compared with traditional silicosis, artificial stone-associated silicosis is more rapidly progressive and lethal. Hence, a correct diagnosis and optimal treatment are crucial. Here, we present the clinical course of a 33-year-old artificial stonemason who suffered from acute silicoproteinosis with concurrent Cryptococcus infection resulting in profound respiratory failure. This patient was treated by bronchoscope-assisted therapeutic segmental lung lavage and antifungal agent, under mechanical ventilator and ECMO support and recovered well. A brief review of acute silicoproteinosis and artificial stone-associated silicosis is also presented and highlights the new form of industry exposure to silica.

Association between Crystalline Silica Dust Exposure and Silicosis Development in Artificial Stone Workers

Occupational exposure to respirable crystalline silica (SiO₂) is one of the most common and serious risks because of the health consequences for the workers involved. Silicosis is a progressive, irreversible, and incurable fibrotic lung disease caused by the inhalation of respirable crystalline silica dust. A cross-sectional epidemiological study was carried out to assess the occupational risk factors that may contribute to the onset of silicosis in workers carrying out work activities with the inhalation of silica compact dust. The study population consisted of 311 artificial stone workers from the province of Almeria (southeast of Spain). Among them, 64 were previously diagnosed with silicosis and the rest of the participants (n = 247 workers) were not diagnosed with such a disease. The workers showing a greater risk of developing silicosis were those who installed kitchen worktops at consumers’ homes, as they did not use face-masks or were not provided with personal protective equipment (PPE) by their business. The results of this study provide support for the evidence indicating that silicosis is a major emerging health concern for workers in the artificial stone sector. Exposure to crystalline silica dust thus can influence the development of silicosis in those cases where individual and collective protection measures are not used or adequately applied.

Extracellular signal-regulated kinase signaling pathway and silicosis

Silicosis is a scarring lung disease caused by inhaling fine particles of crystalline silica in the workplace of many industries. Due to the lack of effective treatment and management, the continued high incidence of silicosis remains a major public health concern worldwide, especially in the developing countries. Till now, related molecular mechanisms underlying silicosis are still not completely understood. Multiple pathways have been reported to be participated in the pathological process of silicosis, and more complex signaling pathways are receiving attention. The activated extracellular signal-regulated kinase (ERK) signaling pathway has been recognized to control some functions in the cell. Recent studies have identified that the ERK signaling pathway contributes to the formation and development of silicosis through regulating the processes of oxidative stress, inflammatory response, proliferation and activation of fibroblasts, epithelial-mesenchymal transformation, autophagy, and apoptosis of cells. In this review article, we summarize the latest findings on the role of ERK signaling pathway in silica-induced experimental models of silicosis, as well as clinical perspectives.

Artificial stone silicosis

PURPOSE OF REVIEW

This review details recent findings related to the health effects of occupational exposure to artificial stone dust and the rapid increase in cases of artificial stone associated silicosis around the world.

RECENT FINDINGS

High crystalline silica content artificial stone is now commonly used for the production of kitchen benchtops. Reports of artificial stone silicosis from many countries have noted that workers were typically employed at small workplaces and were often diagnosed in their 30s or 40s. Poor exposure control measures were common, including the practice of 'dry processing'. Dust generated from artificial stone has been noted to have properties that influence toxicity, including high silica content, generation of nanosized particles and presence of metals and resins. Artificial stone silicosis differs from silicosis associated with other occupational settings including shorter latency and rapid disease progression. High-resolution computed tomography (CT) chest imaging of artificial stone silicosis has often noted the presence of ground glass opacities, which may not be detected in chest x-ray screening. Increased prevalence of autoimmune disease, such as scleroderma, has also been reported in this industry.

SUMMARY

Further evaluation of the safety of work with artificial stone is required, including the effectiveness of dust control measures. Current reports of artificial stone silicosis indicate the potential for widespread undiagnosed respiratory disease in this industry. Provision of more sensitive health screening methods for all at-risk workers and the development of new treatment options particularly for this form of silicosis is urgently required.

The role of macrophage-derived TGF-β1 on SiO2-induced pulmonary fibrosis: A review

Silicosis is an occupational fibrotic lung disease caused by inhaling large amounts of crystalline silica dust. Transforming growth factor-β1 (TGF-β1), which is secreted from macrophages, has an important role in the development of this disease. Macrophages can recognize and capture silicon dust, undergo M2 polarization, synthesize TGF-β1 precursors, and secrete them out of the cell where they are activated. Activated TGF-β1 induces cells from different sources, transforming them into myofibroblasts through autocrine and paracrine mechanisms, ultimately causing silicosis. These processes involve complex molecular events, which are not yet fully understood. This systematic summary may further elucidate the location and development of pulmonary fibrosis in the formation of silicosis. In this review, we discussed the proposed cellular and molecular mechanisms of production, secretion, activation of TGF-β1, as well as the mechanisms through which TGF-β1 induces cells from three different sources into myofibroblasts during the pathogenesis of silicosis. This study furthers the medical understanding of the pathogenesis and theoretical basis for diagnosing silicosis, thereby promoting silicosis prevention and treatment.

Silicosis: An Update and Guide for Clinicians

This overview provides an update on silicosis epidemiology with review of exposures and emerging trends in acute and accelerated silicosis in the twenty-first century. The silicosis epidemics in mining, denim sandblasting, and engineering stone industries are highlighted. Clinical presentations of silicosis and silica-related conditions such as autoimmune, kidney, and mycobacterial disease, as well as lung cancer, are discussed. Important aspects of the new OSHA 2017 Silica Standard are presented. This review also includes practical guidance for clinicians to address questions that may arise when evaluating silica-exposed patients and to the public health responses needed following a diagnosis of silica-related disease.

Serum angiotensin converting enzyme elevation in association with artificial stone silicosis

BACKGROUND

Silicosis is a rapidly emerging major health concern for workers in the artificial stone benchtop industry. The association between serum angiotensin converting enzyme (sACE) levels and artificial stone silicosis is unknown.

METHODS

We investigated 179 male workers (median age 40 years, interquartile range (IQR) 33-48 years) from the stone benchtop industry in Victoria, Australia. All had worked in an environment where dry processing of artificial stone had occurred and were registered with the Victorian Silica-associated Disease Registry between June 2019 and August 2020. Workers had undergone protocolised assessments including respiratory function testing, high resolution CT chest and blood tests panel, including sACE.

FINDINGS

Sixty workers with artificial stone silicosis were identified and they had a higher median sACE level (64.1 U/L, IQR 51.5, 87.5), compared to 119 without silicosis (35.0 U/L, IQR 25.0, 47.0). Compared to those with a normal assessment, regression modelling noted significantly higher average differences in sACE levels for workers with lymphadenopathy alone (12.1 U/L, 95% confidence interval (CI): 1.3, 22.9), simple silicosis (28.7 U/L, 95% CI: 21.3, 36.0) and complicated silicosis (36.0 U/L, 95% CI 25.2, 46.9). There was a small negative association with gas transfer, but no associations with exposure duration or spirometry.

CONCLUSION

sACE levels were noted to be higher in artificial stone workers with silicosis compared to those without disease and was highest in those with complicated silicosis. Longitudinal follow up is required to evaluate sACE as a prognostic biomarker for workers with this rapidly emerging occupational lung disease.

Respiratory surveillance for coal mine dust and artificial stone exposed workers in Australia and New Zealand: A position statement from the Thoracic Society of Australia and New Zealand

Coal mine lung dust disease (CMDLD) and artificial stone (AS) silicosis are preventable diseases which have occurred in serious outbreaks in Australia recently. This has prompted a TSANZ review of Australia's approach to respiratory periodic health surveillance. While regulating respirable dust exposure remains the foundation of primary and secondary prevention, identification of workers with early disease assists with control of further exposure, and with the aims of preserving lung function and decreasing respiratory morbidity in those affected. Prompt detection of an abnormality also allows for ongoing respiratory specialist clinical management. This review outlines a medical framework for improvements in respiratory surveillance to detect CMDLD and AS silicosis in Australia. This includes appropriate referral, improved data collection and interpretation, enhanced surveillance, the establishment of a nationwide Occupational Lung Disease Registry and an independent advisory group. These measures are designed to improve health outcomes for workers in the coal mining, AS and other dust-exposed and mining industries.

Silica-related diseases in the modern world

Silicosis is an ancient and potentially fatal pneumoconiosis caused by exposure to respirable crystalline silica. Silicosis is historically a disease of miners; however, failure to recognize and control the risk associated with silica exposure in contemporary work practices such as sandblasting denim jeans and manufacturing of artificial stone benchtops has led to re-emergence of silicosis around the world. This review outlines the mineralogy, epidemiology, clinical and radiological features of the various forms of silicosis and other silica-associated diseases. Perspective is provided on the most recent studies shedding light on pathogenesis, including the central role of innate immune effector cells and subsequent inflammatory cascades in propagating pulmonary fibrosis and the extrapulmonary manifestations, which uniquely characterize this pneumoconiosis. Clinical conundrums in differential diagnosis, particularly between silicosis and sarcoidosis, are highlighted, as is the importance of obtaining a careful occupational history in the patient presenting with pulmonary infiltrates and/or fibrosis. While silicosis is a completely preventable disease, unfortunately workers around the world continue to be affected and experience progressive or even fatal disease. Although no treatments have been proven, opportunities to intervene to prevent progressive disease, founded in a thorough cellular and molecular understanding of the immunopathology of silicosis, are highlighted.

Identification of early-stage silicosis through health screening of stone benchtop industry workers in Victoria, Australia

OBJECTIVES

The popularity of high silica content artificial stone has been associated with emergence of severe, progressive silicosis as a major health issue affecting workers in the stone benchtop industry. This population-based health assessment programme has been implemented with the aim of identifcation of silica-associated disease at a preclinical stage.

METHODS

All current and former workers from the stone benchtop industry in the State of Victoria are offered free health assessments. Primary evaluations include a standardised questionnaire, physical examination, spirometry and gas transfer assessment and International Labour Organisation-categorised chest X-ray. Secondary evaluations include high-resolution CT chest, blood tests and a respiratory physician evaluation.

RESULTS

At the end of the first 12 months, 86/239 (36%) workers who had completed secondary evaluation were diagnosed with silicosis (65 simple silicosis and 21 complicated silicosis). 22 had worked in the industry for less than 10 years at the time of diagnosis. Of those with simple silicosis, 80% of workers reported breathlessness only with strenuous exercise (modified Medical Research Council score of 0), and lung function was well preserved (prebronchodilator forced vital capacity mean 99.8% predicted (SD 13.6), diffusion capacity of the lung for carbon monoxide mean 96.2% predicted (SD 18.0)). Antinuclear antibodies were detected in 37% with silicosis and 24% without silicosis.

CONCLUSION

Early results from this comprehensive health assessment programme have indicated a high proportion of referred artificial stone benchtop workers have silicosis, including many with early-stage disease. The common finding of antinuclear antibodies suggest significant potential for autoimmune disease in this occupational group.

Transplantation for work-related lung disease in the USA

OBJECTIVES

Work-related lung diseases (WRLDs) are entirely preventable. To assess the impact of WRLDs on the US transplant system, we identified adult lung transplant recipients with a WRLD diagnosis specified at the time of transplant to describe demographic, payer and clinical characteristics of these patients and to assess post-transplant survival.

METHODS

Using US registry data from 1991 to 2018, we identified lung transplant recipients with WRLDs including coal workers' pneumoconiosis, silicosis, asbestosis, metal pneumoconiosis and berylliosis.

RESULTS

The frequency of WRLD-associated transplants has increased over time. Among 230 lung transplants for WRLD, a majority were performed since 2009; 79 were for coal workers' pneumoconiosis and 78 were for silicosis. Patients with coal workers' pneumoconiosis were predominantly from West Virginia (n=31), Kentucky (n=23) or Virginia (n=10). States with the highest number of patients with silicosis transplant were Pennsylvania (n=12) and West Virginia (n=8). Patients with metal pneumoconiosis and asbestosis had the lowest and highest mean age at transplant (48.8 and 62.1 years). Median post-transplant survival was 8.2 years for patients with asbestosis, 6.6 years for coal workers' pneumoconiosis and 7.8 years for silicosis. Risk of death among patients with silicosis, coal workers' pneumoconiosis and asbestosis did not differ when compared with patients with idiopathic pulmonary fibrosis.

CONCLUSIONS

Lung transplants for WRLDs are increasingly common, indicating a need for primary prevention and surveillance in high-risk occupations. Collection of patient occupational history by the registry could enhance case identification and inform prevention strategies.

Occupational lung diseases in the 21st century: the changing landscape and future challenges

PURPOSE OF REVIEW

Occupational exposures remain an underrecognized and preventable cause of lung disease in high-income countries. The present review highlights the emergence of cleaning-related respiratory disease and the re-emergence of silicosis as examples of trends in occupational lung diseases in the 21st century.

RECENT FINDINGS

Employment trends, such as the shift from large-scale manufacturing to a service economy, the growth of the healthcare sector, and changing consumer products have changed the spectrum of work-related lung diseases. Following decades of progress in reducing traditional hazards such as silica in U.S. workplaces, cases of advanced silicosis have recently re-emerged with the production of engineered stone countertops. With growth in the healthcare and service sectors in the United States, cleaning products have become an important cause of work-related asthma and have recently been associated with an increased risk of chronic obstructive pulmonary disease (COPD) in women. However, these occupational lung diseases largely go unrecognized by practicing clinicians.

SUMMARY

The present article highlights how changes in the economy and work structure can lead to new patterns of inhalational workplace hazards and respiratory disease, including cleaning-related respiratory disease and silicosis. Pulmonary clinicians need to be able to recognize and diagnose these occupational lung diseases, which requires a high index of suspicion and a careful occupational history.

Characterization of Silica Exposure during Manufacturing of Artificial Stone Countertops

Artificial stone is increasing in popularity in construction applications, including commercial and residential countertops. Eco-friendliness, durability, and resistance to staining, make artificial stone attractive to consumers. Health concerns have arisen during manufacturing of artificial stone due to increased incidence of silicosis after relatively short exposure. Three artificial stone samples (A, B, and C) and one natural granite sample were subjected to cutting and grinding in a controlled environment. Gravimetric analysis, X-Ray diffraction, and scanning electron microscopy with energy dispersive spectroscopy were employed to determine crystalline silica concentrations and particle morphology of bulk and respirable particles. Silica content of bulk dust from artificial samples A and B was 91%, sample C was <10%, while granite was 31%. Silica percent in the respirable fraction for samples A and B was 53% and 54%, respectively, while sample C was <5% and granite was 8%. Number concentrations for samples A and B were mainly in the nano-fraction, indicating potential for translocation of silica particles to other organs outside of the lungs. Respirable dust concentrations inside the chamber were well above Occupational Safety and Health Administration standards for all materials, indicating that confined-space exposures require ventilation to lower risks of acute silicosis regardless of the nature of the stone.

ACR Appropriateness Criteria® Occupational Lung Diseases

Ordering the appropriate diagnostic imaging for occupational lung disease requires a firm understanding of the relationship between occupational exposure and expected lower respiratory track manifestation. Where particular inorganic dust exposures typically lead to nodular and interstitial lung disease, other occupational exposures may lead to isolated small airway obstruction. Certain workplace exposures, like asbestos, increase the risk of malignancy, but also produce pulmonary findings that mimic malignancy. This publication aims to delineate the common and special considerations associated with occupational lung disease to assist the ordering physician in selecting the most appropriate imaging study, while still stressing the importance of a multidisciplinary approach. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Artificial stone-associated silicosis in China: A prospective comparison with natural stone-associated silicosis

BACKGROUND AND OBJECTIVE

We recently noted a dramatic increase in the number of patients with accelerated silicosis associated with exposure to artificial stone dust. Therefore, the natural history of artificial stone-associated silicosis was compared with that of natural stone-associated silicosis.

METHODS

A total of 18 patients with artificial stone-associated silicosis and 63 with natural stone-associated silicosis were diagnosed sequentially in 2018 and followed up for a period of 6-12 months. Data were collected from clinical charts.

RESULTS

The median duration of exposure prior to onset of symptoms of silicosis was shorter for patients who had been exposed to artificial stone dust (6.4 vs 29.3 years, P < 0.01). Four of the 18 patients experienced rapid deterioration in lung function over the follow-up period, with declines in pre-bronchodilator FVC of 587 (210-960) mL/year and FEV1 of 625 (360-860) mL/year. GGO, PMF, emphysema and pulmonary artery widening were more frequently observed on computed tomography scans of patients with artificial stone-associated silicosis than of those with natural stone-associated silicosis. Approximately 38.9% of the patients with artificial stone-associated silicosis were lung transplant candidates and 27.8% died, both rates being significantly higher than in patients with natural stone-associated silicosis (3.2% and 0%, both P < 0.01).

CONCLUSION

Compared to natural stone-associated silicosis, artificial stone-associated silicosis was characterized by short latency, rapid radiological progression, accelerated decline in lung function and high mortality.

Silicosis in finishing workers in quartz conglomerates processing

INTRODUCTION

Outbreaks of silicosis have bene recently reported in artificial stone workers.

AIM

To describe the features of silicosis in quartz conglomerate workers in North-Eastern Italy.

METHODS

Active search of pneumoconiosis was performed in 11 companies of North-Eastern Italy involved in the fabrication of quartz conglomerate countertops. Occupational history, lung function tests, chest X-ray and high resolution computed tomography (HRCT) were performed. In selected cases, trans-bronchial biopsies were taken for histological evaluation and identification of silica crystals in the tissue. Cumulative exposure to crystalline silica was estimated.

RESULTS

We recruited 45 workers and 24 cases of silicosis were diagnosed. Mean age at diagnosis was 43 years and duration of exposure to quartz conglomerate dust was 3.5 to 20 years. The average silica cumulative exposure was 4.3 mg/m3/y. Abnormal findings were detected in 42% of chest X-rays, in 33% of spirometry and 50% of carbon monoxide lung diffusion (DLco). HRCTs were abnormal in all cases showing well-defined rounded opacities, irregular/linear intralobular opacities and bilateral enlarged mediastinal lymph-nodes. Histological findings consistent with silicosis were observed in 24 cases. Numerous silica particles (diameter 0.1-5 µm) were identified in lung tissue.

CONCLUSIONS

We reported an unexpected high incidence of silicosis in Italian workers exposed to quartz conglomerate dust. The results suggest that chest HRCT is indicated for screening of workers with high exposure to silica and DLco should be added to spirometry in health surveillance. More rigorous application of safety regulations and more effective preventive interventions at work are necessary.

Respiratory surveillance in mineral dust-exposed workers

Recently, there has been a worldwide resurgence in pneumoconiosis, or pulmonary fibrosis due to occupational mineral dust exposure. In Queensland, Australia, there has been a re-emergence of coal workers' pneumoconiosis and silicosis. Some coal mining communities have experienced a resurgence of progressive massive fibrosis in the USA and a worldwide epidemic is occurring of accelerated silicosis due to exposure to artificial stone.

These diseases are all preventable and should not be occurring in the 21st century. Best practice prevention includes reduction of exposure to mineral dusts or, ideally, prevention of exposure altogether. However, where dust exposure has occurred, respiratory surveillance can provide a strategy for early disease detection. It is important to identify early signs of occupational lung disease at a stage where intervention may be beneficial, though it must be acknowledged that progression may occur even after cessation of exposure to dusts. Respiratory surveillance should be distinguished from population screening and case finding, which are different methods used for disease investigation and control. Designing an ideal respiratory surveillance programme is challenging, as there is no single test that accurately identifies early disease. Several different respiratory disorders may occur related to the same exposure(s). Physicians organising and interpreting tests used in respiratory surveillance must be aware of the broad range of potential work-related respiratory conditions, complexities in diagnosis, and appropriate interpretation of the exposure history, as well as current management options. A working knowledge of the compensation and medicolegal avenues available to workers in individual jurisdictions is also useful.

Organising and interpreting respiratory surveillance for mineral dust-exposed workers requires specialist knowledge and understanding of the potential range of diseases, as well as a detailed occupational historyhttp://bit.ly/37KXSE4

P2Y12 Receptor Antagonist Clopidogrel Attenuates Lung Inflammation Triggered by Silica Particles

Silicosis is an occupational lung disease caused by inhalation of silica particles. It is characterized by intense lung inflammation, with progressive and irreversible fibrosis, leading to impaired lung function. Purinergic signaling modulates silica-induced lung inflammation and fibrosis through P2X7 receptor. In the present study, we investigate the role of P2Y12, the G-protein-coupled subfamily prototype of P2 receptor class in silicosis. To that end, BALB/c mice received an intratracheal injection of PBS or silica particles (20 mg), without or with P2Y12 receptor blockade by clopidogrel (20 mg/kg body weight by gavage every 48 h) - groups CTRL, SIL, and SIL + Clopi, respectively. After 14 days, lung mechanics were determined by the end-inflation occlusion method. Lung histology was analyzed, and lung parenchyma production of nitric oxide and cytokines (IL-1β, IL-6, TNF-α, and TGF-β) were determined. Silica injection reduced animal survival and increased all lung mechanical parameters in relation to CTRL, followed by diffuse lung parenchyma inflammation, increased neutrophil infiltration, collagen deposition and increased pro-inflammatory and pro-fibrogenic cytokine secretion, as well as increased nitrite production. Clopidogrel treatment prevented silica-induced changes in lung function, and significantly reduced lung inflammation, fibrosis, as well as cytokine and nitrite production. These data suggest that inhibition of P2Y12 signaling improves silica-induced lung inflammation, preventing lung functional changes and mortality. Our results corroborate previous observations of silica-induced lung changes and expand the understanding of purinergic signaling in this process.

Trends in global, regional and national incidence of pneumoconiosis caused by different aetiologies: an analysis from the Global Burden of Disease Study 2017

OBJECTIVES

Pneumoconiosis remains a major global occupational health hazard and illness. Accurate data on the incidence of pneumoconiosis are critical for health resource planning and development of health policy.

METHODS

We collected data for the period between 1990 and 2017 on the annual incident cases and the age-standardised incidence rates (ASIR) of pneumoconiosis aetiology from the Global Burden of Disease Study 2017. We calculated the average annual percentage changes of ASIR by sex, region and aetiology in order to determine the trends of pneumoconiosis.

RESULTS

Globally, the number of pneumoconiosis cases increased by a measure of 66.0%, from 36 186 in 1990 to 60 055 in 2017. The overall ASIR decreased by an average of 0.6% per year in the same period. The number of pneumoconiosis cases increased across the five sociodemographic index regions, and there was a decrease in the ASIR from 1990 to 2017. The ASIR of silicosis, coal workers' pneumoconiosis and other pneumoconiosis decreased. In contrast, measures of the ASIR of asbestosis displayed an increasing trend. Patterns of the incidence of pneumoconiosis caused by different aetiologies were found to have been heterogeneous for analyses across regions and among countries.

CONCLUSION

Incidence patterns of pneumoconiosis which were caused by different aetiologies varied considerably across regions and countries of the world. The patterns of incidence and temporal trends should facilitate the establishment of more effective and increasingly targeted methods for prevention of pneumoconiosis and reduce associated disease burden.

Global and regional burden of chronic respiratory disease in 2016 arising from non-infectious airborne occupational exposures: a systematic analysis for the Global Burden of Disease Study 2016

OBJECTIVES

This paper presents detailed analysis of the global and regional burden of chronic respiratory disease arising from occupational airborne exposures, as estimated in the Global Burden of Disease 2016 study.

METHODS

The burden of chronic obstructive pulmonary disease (COPD) due to occupational exposure to particulate matter, gases and fumes, and secondhand smoke, and the burden of asthma resulting from occupational exposure to asthmagens, was estimated using the population attributable fraction (PAF), calculated using exposure prevalence and relative risks from the literature. PAFs were applied to the number of deaths and disability-adjusted life years (DALYs) for COPD and asthma. Pneumoconioses were estimated directly from cause of death data. Age-standardised rates were based only on persons aged 15 years and above.

RESULTS

The estimated PAFs (based on DALYs) were 17% (95% uncertainty interval (UI) 14%-20%) for COPD and 10% (95% UI 9%-11%) for asthma. There were estimated to be 519 000 (95% UI 441,000-609,000) deaths from chronic respiratory disease in 2016 due to occupational airborne risk factors (COPD: 460,100 [95% UI 382,000-551,000]; asthma: 37,600 [95% UI 28,400-47,900]; pneumoconioses: 21,500 [95% UI 17,900-25,400]. The equivalent overall burden estimate was 13.6 million (95% UI 11.9-15.5 million); DALYs (COPD: 10.7 [95% UI 9.0-12.5] million; asthma: 2.3 [95% UI 1.9-2.9] million; pneumoconioses: 0.58 [95% UI 0.46-0.67] million). Rates were highest in males; older persons and mainly in Oceania, Asia and sub-Saharan Africa; and decreased from 1990 to 2016.

CONCLUSIONS

Workplace exposures resulting in COPD, asthma and pneumoconiosis continue to be important contributors to the burden of disease in all regions of the world. This should be reducible through improved prevention and control of relevant exposures.

The Protective Role of Tanshinone IIA in Silicosis Rat Model via TGF-β1/Smad Signaling Suppression, NOX4 Inhibition and Nrf2/ARE Signaling Activation

Purpose

Silicosis is an occupational disease caused by inhalation of silica and there are no effective drugs to treat this disease. Tanshinone IIA (Tan IIA), a traditional natural component, has been reported to possess anti-inflammatory, antioxidant, and anti-fibrotic properties. The current study’s purpose was to examine Tan IIA’s protective effects against silica-induced pulmonary fibrosis and to explore the underlying mechanisms.

Methods

48 male SD rats were randomly divided into four groups (n=12): i) Control group; ii) Silicosis group; iii) Tan IIA group; iv) Silicosis +Tan IIA group. Two days after modeling, the rats of Tan IIA group and Silicosis +Tan IIA group were given intraperitoneal administration 25 mg/kg/d Tan IIA for 40 days. Then, the four groups of rats were sacrificed and the lung inflammatory responses were measured by ELISA, lung damage and fibrosis were analyzed by hematoxylin and eosin (H&E) staining and Masson staining, the expression levels of collagen I, fibronectin and α-smooth muscle actin (α-SMA) were measured by immunohistochemistry. The markers of oxidative stress were measured by commercial kits, and the activity of the TGF-β1/Smad and NOX4, Nrf2/ARE signaling pathways were measured by RT-PCR and Western blotting.

Results

The silica-induced pulmonary inflammtory responses, structural damage and fibrosis were significantly attenuated by Tan IIA treatment. In addition, treatment with Tan IIA decreased collagen I, fibronectin and α-SMA expression, and inhibited TGF-β1/Smad signaling in the lung tissue. The upregulated levels of oxidative stress markers in silicosis rats were also markedly restored following Tan IIA treatment. Furthermore, treatment with Tan IIA reduced NOX4 expression and enhanced activation of the Nrf2/ARE pathway in the lung tissue of silicosis rats.

Conclusion

These findings suggest that Tan IIA may protect lung from silica damage via the suppression of TGF-β1/Smad signaling, inhibition of NOX4 expression and activation of the Nrf2/ARE pathway.

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Artificial stone-associated silicosis: clinical-pathological-radiological correlates of disease

Occupational lung disease secondary to inhalation of silica particles is variable and potentially life-threatening. As the artificial stone industry has grown over the last two decades, the development of silicosis has been seen to accelerate and behave differently to chronic silicosis. In this case report, we present two patients who underwent lung transplantation for silicosis at the Alfred Hospital, both with predominantly artificial stone masonry exposure. We have identified the presence of both fibrotic/nodular silicosis and conspicuous alveolar proteinosis within the same lung parenchyma of both patients. We then demonstrate the radiological and histopathological correlates of disease; the first time this has been shown clearly in the literature.

Severe Silicosis in Engineered Stone Fabrication Workers - California, Colorado, Texas, and Washington, 2017-2019

Silicosis is an incurable occupational lung disease caused by inhaling particles of respirable crystalline silica. These particles trigger inflammation and fibrosis in the lungs, leading to progressive, irreversible, and potentially disabling disease. Silica exposure is also associated with increased risk for lung infection (notably, tuberculosis), lung cancer, emphysema, autoimmune diseases, and kidney disease (1). Because quartz, a type of crystalline silica, is commonly found in stone, workers who cut, polish, or grind stone materials can be exposed to silica dust. Recently, silicosis outbreaks have been reported in several countries among workers who cut and finish stone slabs for countertops, a process known as stone fabrication (2-5). Most worked with engineered stone, a manufactured, quartz-based composite material that can contain >90% crystalline silica (6). This report describes 18 cases of silicosis, including the first two fatalities reported in the United States, among workers in the stone fabrication industry in California, Colorado, Texas, and Washington. Several patients had severe progressive disease, and some had associated autoimmune diseases and latent tuberculosis infection. Cases were identified through independent investigations in each state and confirmed based on computed tomography (CT) scan of the chest or lung biopsy findings. Silica dust exposure reduction and effective regulatory enforcement, along with enhanced workplace medical and public health surveillance, are urgently needed to address the emerging public health threat of silicosis in the stone fabrication industry.