Silicosis: A Review

Silicosis and tuberculosis: A systematic review and meta-analysis

INTRODUCTION

Silicosis mostly happens in workers with high silica exposure and may accompany the development of various diseases like tuberculosis, cancer, or autoimmune diseases. The term silico-tuberculosis describes a condition in which an individual is affected by both silicosis and tuberculosis at the same time. This systematic review and meta-analysis study was conducted to evaluate the risk of tuberculosis in silicosis patients and individuals exposed to silica dust.

METHODS

We performed a systematic search for relevant studies up to 6 September 2022 using PubMed/ Medline, and Embase with the following keywords in titles or abstracts: "silicosis" OR "silicoses" OR "pneumoconiosis" OR "pneumoconioses" AND "tuberculosis". Cohort and case-control studies containing relevant and original information about tuberculosis infection in silicosis patients were included for further analysis. Pooled estimates and 95% confidence intervals (CI) for the relative risk of tuberculosis in individuals with silicosis compared to those without; these were evaluated using the random effects model due to the estimated heterogeneity of the true effect sizes.

RESULTS

Out of 5352 potentially relevant articles, 7 studies were eligible for systematic review, of which 4 cohort studies were included for meta-analysis. The total population of all studies was 5884, and 90.63% were male. The mean age of participants was 47.7 years. Our meta-analysis revealed a pooled risk ratio of 1.35 (95%CI 1.18-1.53, I 2: 94.30%) which means an increased risk of silicosis patients and silica-exposed individuals to tuberculosis infection.

CONCLUSION

Silicosis and silica dust exposure increase the risk of tuberculosis. Therefore, we suggest that individuals with long-time silica exposure, like mine workers, be routinely considered for both silicosis and tuberculosis screening programs.

Exploring the efficacy and constraints of platinum nanoparticles as adjuvant therapy in silicosis management

Silicosis represents a formidable occupational lung pathology precipitated by the pulmonary assimilation of respirable crystalline silica particulates. This condition engenders a cascade of cellular oxidative stress via the activation of bioavailable silica, culminating in the generation of reactive oxygen species (ROS). Such oxidative mechanisms lead to irrevocable pulmonary impairment. Contemporary scholarly examinations have underscored the substantial antioxidative efficacy of platinum nanoparticles (PtNPs), postulating their utility as an adjunct therapeutic modality in silicosis management. The physicochemical interaction between PtNPs and silica demonstrates a propensity for adsorption, thereby facilitating the amelioration and subsequent pulmonary clearance of silica aggregates. In addition to their detoxifying attributes, PtNPs exhibit pronounced anti-inflammatory and antioxidative activities, which can neutralize ROS and inhibit macrophage-mediated inflammatory processes. Such attributes are instrumental in attenuating inflammatory responses and forestalling subsequent lung tissue damage. This discourse delineates the interplay between ROS and PtNPs, the pathogenesis of silicosis and its progression to pulmonary fibrosis, and critically evaluates the potential adjunct role of PtNPs in the therapeutic landscape of silicosis, alongside a contemplation of the inherent limitations associated with PtNPs application in this context.

A novel, rapid, and effective technique for whole lung lavage in patients with pulmonary alveolar proteinosis and silicosis: retrospective study

BACKGROUND

Pulmonary alveolar proteinosis (PAP) presents a significant challenge due to its progressive and potentially fatal nature. Whole lung lavage (WLL) is a key treatment for primary PAP with respiratory failure. Despite its efficacy, the lack of standardised protocols has led to diverse practice techniques across different institutions. Our study introduces a novel approach, employing a cardiopulmonary bypass (CPB) system for infusing lavage fluid, a method not previously utilised. This paper will share our pioneering experience with this technique at a tertiary referral centre, focusing on its implementation and safety profile.

METHODS

This retrospective study included patients aged ≥ 18 who underwent WLL for PAP or silicosis. Pre-lavage preparations included chest X-rays and pulmonary function tests (PFT). Preprocedural empiric antibiotics were administered. During lavage, warm saline was infused using a CPB, with cycles of normal saline infusion and degassing until fluid clarity was reached. Positioning techniques facilitated saline drainage. The procedure concluded with intravenous furosemide administration.

RESULTS

Fifty-two WLLs were identified between 2010 and 2024; complete data was available for 33 procedures. Of these, 91% were due to PAP, and 9% to silicosis. Almost half of the patients did not require additional WLL, while 43% needed sequential contralateral WLL. Median operative and mechanical ventilation times were 65 [58.5, 67.5] and 118 [97, 195] minutes, respectively. The median length of hospital stay was two days [2, 3]. Although not statistically significant, O2 saturation and a 6-minute walk distance increase were observed after the WLL.

CONCLUSION

This study outlines our novel approach to WLL, which incorporates rapid saline infusion via a CPB system. Our findings indicate reduced procedure time while maintaining safety and efficacy for treating PAP and silicosis. Despite promising results, the retrospective design and small sample size limit generalizability. Further high-quality studies are warranted to validate and refine this technique.

PD-L1 upregulation in activated fibroblasts promotes silica particle-induced pulmonary fibrosis

Silicosis is a severe interstitial lung disease resulting from prolonged exposure to silica dust in working environment, characterized by inflammation and fibrosis. This condition is closely associated with immune dysregulation, although the precise regulatory mechanisms remain elusive. Immune checkpoints (ICs) comprise receptor-ligand pairs crucial for immune cell activation and coordination of immune responses. Among these, PD-1 and its ligand PD-L1 have garnered significant attention in tumor research and have recently been implicated in the regulation of fibrotic diseases. Nonetheless, their involvement in silicosis remains unexplored. In this study, we observed a global upregulation of PD-1 and PD-L1 expression concomitant with the progression of silicosis, exhibiting cell specificity. Targeting PD-1/PD-L1 signaling mitigated silicosis in mice by modulating T cell homeostasis, macrophage polarization, and activation of fibrotic effector cells. Notably, PD-L1 expression on activated fibroblasts emerged as a pivotal driver of silicosis progression. Mechanistically, elevated PD-L1 levels in fibroblast activation fostered a positive feedback loop by binding to p-Smad2/3 and p-STAT3 proteins, thereby facilitating their nuclear translocation and augmenting protein stability, ultimately promoting fibroblast transdifferentiation. Consistently, knockdown of PD-L1 in lung fibroblasts significantly ameliorated silicosis in mice. In summary, PD-1/PD-L1 signaling mediates critical profibrotic signals during the progression of silicosis.

Prevalence of pulmonary hypertension in chronic simple silicosis patients and its correlation with smoking history, occupation type, age and duration of silica exposure

Silicosis is a preventable occupational health hazard with the potential for permanent physical disability and increased socio-economic burden. Pulmonary hypertension (PH) secondary to chronic respiratory diseases signifies a poorer prognosis and transthoracic echocardiography (TTE) has proven its usefulness as a screening tool for PH diagnosis. The objectives were to determine PH prevalence in chronic simple silicosis patients through TTE screening and correlate PH prevalence with smoking status, occupation type, age, and duration of silica exposure (DSE). We enrolled 104 patients in the study based on occupational exposure to silica dust and radiologic confirmation of chronic simple silicosis. The study sample was divided into significant smokers (SS group) and insignificant smokers (InS group) based on ≥10 pack years smoking history, and into drillers and dressers based on occupation type. TTE examination was performed to measure resting mean pulmonary artery pressure (mPAP) and the patients were classified into: no PH (mPAP≤20 mm Hg), borderline PH (mPAP>20 and <25 mmHg), and PH (mPAP≥25). PH prevalence was 25% in study subjects (26/104); 29.6% (16/54) among SS group vs. 20% (10/50) among InS group (0.52); and 34.2% (14/41) among drillers vs. 19.1% (12/63) among dressers (p=0.024). Mean age and mean DSE among SS and InS groups were comparatively similar, while they had lower values among dressers against dressers with no statistical significance. Logistic regression analysis established a significant association of PH prevalence with higher age in the study sample, SS group, and drillers group, while a significant association of PH prevalence with longer DSE was only seen in the study sample. PH prevalence was significantly associated (p=0.007) with the SS-driller group when comparing TTE findings with combined smoking and occupation type-based groups. This study has shown PH prevalence in chronic simple silicosis patients at alarming levels, having associations with driller occupation, older age, and longer DSE with varying results among groups and complex interplay with smoking exposure, suggesting the need for large sample-based molecular and genetic studies. Including TTE in the initial work-up of silicosis patients will promote timely intervention and reduce morbidity and mortality with a high benefit-cost ratio.

The role of the PI3K/AKT/mTOR pathway in mediating PD-L1 upregulation during fibroblast transdifferentiation

Silicosis is a progressive interstitial lung disease characterized by diffuse pulmonary fibrosis. The transdifferentiation of lung fibroblasts into myofibroblasts is a key cellular event driving the progression of silicosis fibrosis. Recent studies have shown that PD-L1 expression is significantly upregulated in activated fibroblasts, and PD-L1 plays a crucial role in mediating fibroblast transdifferentiation. This study aims to elucidate the molecular mechanisms regulating PD-L1 expression in fibroblasts and analyze the functional significance of PD-L1 upregulation in fibroblast activity and silicosis fibrosis. In this research, an in vitro model of TGF-β1-induced NIH-3 T3 fibroblast transdifferentiation was established. Small molecule inhibitors, siRNA, and plasmids were used to interfere with the PI3K/AKT/mTOR signaling pathway and PD-L1 expression. It was found that TGF-β1 stimulation increased PD-L1 expression in fibroblasts, while blocking the PI3K/AKT/mTOR pathway inhibited this upregulation. Knockdown of PD-L1 significantly inhibited fibroblast transdifferentiation and impeded TGF-β1-induced activation of the PI3K/AKT/mTOR pathway, whereas PD-L1 overexpression had the opposite effect. Additionally, PD-L1 protein in fibroblasts undergoes ubiquitin-proteasome-mediated degradation, negatively regulating PD-L1 upregulation. In vivo, adeno-associated virus was used to specifically knockdown PD-L1 in mouse lung fibroblasts, resulting in significantly reduced lung tissue damage and fibrosis in silicosis mice. This effect was associated with the involvement of the PI3K/AKT/mTOR pathway. In summary, PD-L1 expression in fibroblasts is upregulated during transdifferentiation, a process regulated by the PI3K/AKT/mTOR pathway. Upregulated PD-L1 enhances PI3K/AKT/mTOR signaling through positive feedback, sustaining fibroblast activation. Ubiquitin-proteasome-mediated protein degradation may serve as a negative feedback mechanism maintaining PD-L1 homeostasis.

Novel pilot study on plasma metabolites and biomarkers in a rat model of silica-induced lung inflammation and fibrosis

Silica-induced lung damage may be associated with changes in distinct metabolites potentially serving as biomarkers. Due to the lack of metabolomic data from animal models, this pilot study aimed to evaluate changes in markers of inflammation and fibrosis, as well as plasma metabolites in rats at 14 and 28 days after silica instillation. Adult male Wistar rats were administered a single oropharyngeal intratracheal dose of silica suspension or sterile saline in controls. Selected markers of inflammation, oxidative stress, fibrosis, and cell counts in blood and bronchoalveolar lavage fluid have been evaluated. Finally, plasma metabolites were detected using a targeted metabolomics approach with an MxP® Quant 500 kit. Silica instillation induced noticeable inflammatory, oxidative, and fibrotic changes in lung tissue within the first 14 days. During the next two weeks, the shifts in some markers were further accentuated. After exposure to silica, the metabolomic analysis identified significant changes in metabolites associated with lipid metabolism, biogenic amines, amino acid derivatives, carboxylic acids, bile acids, putrescine, glycosylceramides, and acylcarnitines. This pilot study provides initial evidence that significant alterations in plasma metabolite profiles accompany silica-induced lung injury in rats. These findings suggest a possible systemic impact, particularly on lipid metabolism, and indicate the urgent need for a deeper understanding of the metabolic reprogramming associated with silica-induced lung injury to pave the way for the discovery of novel biomarkers.

Progression of Chest X-ray Findings of Silicosis Among Fluorspar Miners and Prognostic Factors: Retrospective Cohort Study in Mongolia

OBJECTIVE

This study aimed to delineate the natural progression of silicosis in fluorspar miners after the termination of dust exposure and identify its prognostic factors.

METHODS

This retrospective cohort study, conducted from 2000 to 2019, included 67 former miners. Radiological images were evaluated by comparing the initial and most recent radiographs using the International Classification of Radiographs of Pneumoconiosis. Cox multivariate proportional hazard models were used to estimate the hazard ratios using follow-up time to analyze the multivariable study of associated prognostic factors.

RESULTS

Among the participants, 50 (75%) exhibited progression over 2 to 16 years (median, 5.8 years). The Cox analysis highlighted older age as a likely precursor to the progression of significant opacities. Additionally, higher International Labour Organization category grades at onset were associated with disease progression.

CONCLUSIONS

Nearly three-quarters of the miners diagnosed with silicosis demonstrated radiological progression even after the termination of dust exposure. Advancement in age and the degree of initial radiological opacity were associated with progression.

Silico-tuberculosis: An updated review

Silico-Tuberculosis (silico-TB) is a severe combination of tuberculosis and silicosis, caused by occupational exposure to fine crystalline silica dust, which has become a global health concern. This comprehensive review compiles the updated knowledge regarding pathophysiology, clinical manifestations, important diagnostic techniques, treatment aspects, and challenges in understanding silico-TB. The review compiles the disease's history and epidemiology, highlighting a lack of data owing to poor monitoring and healthcare particularly in low- and middle-income countries like India. Further weak safety regulations, lack of preventative measures, and inadequate education increase the rates of silico-TB. The pathophysiology shows how silica particles impair the immune system and stimulate Th2 cells and M2 macrophages, which exacerbate TB, while inhibiting Th1 cells and M1 macrophages, which fight against the disease. Subsequently, it can be difficult to distinguish current TB from pre-existing silicosis. In cases where sputum and X-ray results are negative, chest CT scans may be helpful since radiographic screening identifies TB earlier than sputum assessment. Isoniazid, rifampicin, or both minimize the risk of active tuberculosis in people with silicosis. Consistent anti-tuberculosis drug therapy is recommended for 8-9 months to stop recurrence. The assessment recommends integrating silicosis and TB control initiatives to fight this combined health issue.

The role of Keap1-Nrf2 signaling pathway in the treatment of respiratory diseases and the research progress on targeted drugs

Lungs are exposed to external oxidants from the environment as in harmful particles and smog, causing oxidative stress in the lungs and consequently respiratory ailment. The NF-E2-related factor 2 (Nrf2) is the one with transcriptional regulatory function, while its related protein Kelch-like ECH-associated protein 1 (Keap1) inhibits Nrf2 activity. Together, they form the Keap1-Nrf2 pathway, which regulates the body's defense against oxidative stress. This pathway has been shown to maintain cellular homeostasis during oxidative stressing, inflammation, oncogenesis, and apoptosis by coordinating the expression of cytoprotective genes and making it a potential therapeutic target for respiratory diseases. This paper summarizes this point in detail in Chapter 2. In addition, this article summarizes the current drug development and clinical research progress related to the Keap1-Nrf2 signaling pathway, with a focus on the potential of Nrf2 agonists in treating respiratory diseases. Overall, the article reviews the regulatory mechanisms of the Keap1-Nrf2 signaling pathway in respiratory diseases and the progress of targeted drug research, aiming to provide new insights for treatment.

Impact of Respiratory Dust on Health: A Comparison Based on the Toxicity of PM2.5, Silica, and Nanosilica

Respiratory dust of different particle sizes in the environment causes diverse health effects when entering the human body and makes acute or chronic damage through multiple systems and organs. However, the precise toxic effects and potential mechanisms induced by dust of different particle sizes have not been systematically summarized. In this study, we described the sources and characteristics of three different particle sizes of dust: PM2.5 (<2.5 μm), silica (<5 μm), and nanosilica (<100 nm). Based on their respective characteristics, we further explored the main toxicity induced by silica, PM2.5, and nanosilica in vivo and in vitro. Furthermore, we evaluated the health implications of respiratory dust on the human body, and especially proposed potential synergistic effects, considering current studies. In summary, this review summarized the health hazards and toxic mechanisms associated with respiratory dust of different particle sizes. It could provide new insights for investigating the synergistic effects of co-exposure to respiratory dust of different particle sizes in mixed environments.

Occupational exposure to respirable crystalline silica and incident idiopathic interstitial pneumonias and pulmonary sarcoidosis: a national prospective follow-up study

BACKGROUND

Respirable crystalline silica is a well-known cause of silicosis but may also be associated with other types of interstitial lung disease. We examined the associations between occupational exposure to respirable crystalline silica and the risk of idiopathic interstitial pneumonias, pulmonary sarcoidosis and silicosis.

METHODS

The total Danish working population was followed 1977-2015. Annual individual exposure to respirable crystalline silica was estimated using a quantitative job exposure matrix. Cases were identified in the Danish National Patient Register. We conducted adjusted analyses of exposure-response relations between cumulative silica exposure and other exposure metrics and idiopathic interstitial pneumonias, pulmonary sarcoidosis and silicosis.

RESULTS

Mean cumulative exposure was 125 µg/m3-years among exposed workers. We observed increasing incidence rate ratios with increasing cumulative silica exposure for idiopathic interstitial pneumonias, pulmonary sarcoidosis and silicosis. For idiopathic interstitial pneumonias and pulmonary sarcoidosis, trends per 50 µg/m3-years were 1.03 (95% CI 1.02 to 1.03) and 1.06 (95% CI 1.04 to 1.07), respectively. For silicosis, we observed the well-known exposure-response relation with a trend per 50 µg/m3-years of 1.20 (95% CI 1.17 to 1.23).

CONCLUSION

This study suggests that silica inhalation may be related to pulmonary sarcoidosis and idiopathic interstitial pneumonias, though these findings may to some extent be explained by diagnostic misclassification. The observed exposure-response relations for silicosis at lower cumulative exposure levels than previously reported need to be corroborated in analyses that address the limitations of this study.

Impact of the diseased lung microenvironment on the in vivo fate of inhaled particles

Inhalation drug delivery is superior for local lung disease therapy. However, there are several unique absorption barriers for inhaled drugs to overcome, including limited drug deposition at the target site, mucociliary clearance, pulmonary macrophage phagocytosis, and systemic exposure. Moreover, the respiratory disease state can affect or even destroy the physiology of the lung, thus influencing the in vivo fate of inhaled particles compared with that in healthy lungs. Nevertheless, limited information is available on this effect. Thus, in this review, we present pathological changes of the lung microenvironment under varied respiratory diseases and their influence on the in vivo fate of inhaled particles; such insights could provide a basis for rational inhalation particle design based on specific disease states.

Silicosis mortality in Spain (1999-2020): A temporal and geographical approach

Background

Silicosis is an occupational respiratory disease linked to silica dust inhalation. The main driver was traditional coal mining, but in recent decades, new sources of exposure have emerged. Our aim in this study was to assess the temporal and spatial distribution of mortality due to this disease over a 22-year period in Spain.

Methods

Silicosis records, as an Underlying Cause of Death, were extracted from the National Institute of Statistics from 1999 to 2020 using the International Classification of Diseases 10th revision (code J62.8). Age- and sex-adjusted mortality rates per 1,000,000 inhabitants were calculated for the territory and by province. A geographic analysis was performed, and clusters of deaths were identified at the municipal level, and then the outcomes were compared in two periods of 11 years.

Results

There were 2618 deaths due to silicosis in Spain. The mean age of death increased significantly by 0.66% annually from 1999 to 2013. The age-adjusted mortality rate decreased by 7.30% per year, falling from 3.00 to 0.65 per 1,000,000 inhabitants. The temporal pattern showed a significant decrease of mortality rate in 31% of the provinces (16 out of 52), while it increased in Pontevedra. Regarding the spatial analysis, 11 clusters were found in both periods, but some variations were observed in terms of their distribution in the Spanish territory, as well as in the affected municipalities.

Conclusions

The decrease in mortality due to Silicosis could be related to less exposure to silica dust over the years and an improvement in the survival of those affected. It is thus essential to analyze the role of preventive measures for this occupational disease.

Assessing the inhaled dose of nanomaterials by nanoparticle tracking analysis (NTA) of exhaled breath condensate (EBC) and its relationship with lung inflammatory biomarkers

The widespread and increasing use of nanomaterials has resulted in a higher likelihood of exposure by inhalation for nanotechnology workers. However, tracking the internal dose of nanoparticles deposited at the airways level, is still challenging. To assess the suitability of particle number concentration determination as biomarker of internal dose, we carried out a cross sectional investigation involving 80 workers handling nanomaterials. External exposure was characterized by portable counters of particles DISCminiTM (Testo, DE), allowing to categorize 51 workers as exposed and 29 as non-exposed (NE) to nanoparticles. Each subject filled in a questionnaire reporting working practices and health status. Exhaled breath condensate was collected and analysed for the number of particles/ml as well as for inflammatory biomarkers. A clear-cut relationship between the number of airborne particles in the nano-size range determined by the particle counters and the particle concentration in exhaled breath condensate (EBC) was apparent. Moreover, inflammatory cytokines (IL-1β, IL-10, and TNF-α) measured in EBC, were significantly higher in the exposed subjects as compared to not exposed. Finally, significant correlations were found between external exposure, the number concentration of particles measured by the nanoparticle tracking analysis (NTA) and inflammatory cytokines. As a whole, the present study, suggests that NTA can be regarded as a reliable tool to assess the inhaled dose of particles and that this dose can effectively elicit inflammatory effects.

Systemic inflammation indices as hematological biomarkers of inflammatory response in non-silicotic workers exposed to respirable silica dust

This cross-sectional study was performed to assess whether systemic inflammatory indices, including systemic inflammation response index (SIRI), systemic immune‑inflammation index (SII), and aggregate index of systemic inflammation (AISI), can be considered as possible inflammatory markers in silica-exposed workers with no diagnosis of silicosis. We studied 371 non-silicotic workers exposed to respirable silica dust (RSD) and 1422 reference workers. The workers' exposure to RSD were assessed and the inflammatory indices were compared between subgroups of the exposed workers based on the severity and duration of exposure. Correlations between inflammatory indices and the pulmonary function parameters were investigated. Also, the receiver operating characteristic (ROC) curve and Youden index were used to determine the cut-off values of the SII, SIRI, and AISI. Significant dose-response relationships were observed between duration of exposure and all indices except monocytes and LMR. No significant interaction was observed between duration of exposure to RSD and smoking. Borderline significant correlations were observed between AISI and SIRI with forced expiratory volume (FEV1) and FEV1 to forced vital capacity (FVC) ratio. Higher AUCs were obtained for SII and AISI, respectively. The cut-off values for these biomarkers to be considered abnormal were > 348.48 for SII, > 183.78 for AISI, and > 0.768 for SIRI. Overall, the present study showed for the first time, that SII, AISI, and SIRI might be considered as available, easy-to-obtain, and non-expensive markers of inflammation in non-silicotic workers with a long duration of exposure to RSD who are at risk of developing silicosis in subsequent years.

Elevated Levels of the Cancer Marker Neuron-Specific Enolase in a Patient With Coexisting Silicosis and Sarcoidosis

In a periodical medical checkup, a 39-year-old Mongolian underground miner was diagnosed with silicosis based on chest radiography, computed tomography (CT), and work history. Chest radiography showed diffuse bilateral rounded nodules in both lung fields, with upper lobe dominance and large opacities in the right upper zone. Chest CT presented conglomerated massive changes in the right upper lobe and the coalescence of small nodules in the left upper lung. In the blood test, serum levels of the lung cancer marker neuron-specific enolase (NSE) were elevated (24.58 ng/mL). Carcinoembryonic antigen (CEA) and cytokeratin 19 fragment (CYFRA 21-1) levels were within the reference range. Subsequent to the suspicion of a tumour in the right upper lobe, a right upper lobectomy was performed. The histopathological examination of the lung specimen revealed the coalescence of numerous silica nodules, accompanied by indications of associated sarcoidosis. The histological features suggested the presence of two concurrent pathological processes: silicosis and sarcoidosis. This case demonstrated the combination of three clinical conditions diagnosed in one patient, including complicated silicosis associated with sarcoidosis and elevated serum NSE levels. This case report may serve as a foundation for future investigations exploring the potential of NSE as a marker for silicosis.

Implementation and Cost Analysis of a Novel Silicosis Case-Finding Program For Mine Workers in Rural Rwanda

Little is known about the burden of silicosis in Africa, despite extensive mining and construction operations in the region putting numerous people at risk. The implementation experience and costs of case-finding for occupational lung disease in resource-limited settings are also currently unknown. We describe the first-ever silicosis case-finding project in rural Rwanda using chest X-ray, symptom questionnaires, and spirometry. This was coupled with routine noncommunicable disease case-finding for diabetes and hypertension. We performed an ingredient-based analysis of the costs of all case-finding activities. In 2022, over 25 days, 1,032 mine workers were included in the program, of which 1,014 (98.3%) completed silicosis case-finding activities. The total cost of the program was estimated to be US$38,656, representing a cost of US$37.49 per person. We conclude that conducting large-scale occupational lung disease case-finding is clinically and economically feasible in resource-limited settings and can be effectively integrated with routine noncommunicable disease case-finding.

Toward targeted treatments for silicosis

PURPOSE OF REVIEW

There has been a rapid increase in silicosis cases, particularly related to artificial stone. The key to management is avoidance of silica exposure. Despite this, many develop progressive disease and there are no routinely recommended treatments. This review provides a summary of the literature pertaining to pharmacological therapies for silicosis and examines the plausibility of success of such treatments given the disease pathogenesis.

RECENT FINDINGS

In-vitro and in-vivo models demonstrate potential efficacy for drugs, which target inflammasomes, cytokines, effector cells, fibrosis, autophagy, and oxidation.

SUMMARY

There is some evidence for potential therapeutic targets in silicosis but limited translation into human studies. Treatment of silicosis likely requires a multimodal approach, and there is considerable cross-talk between pathways; agents that modulate both inflammation, fibrosis, autophagy, and ROS production are likely to be most efficacious.

Prolonged cough and dyspnea following a single episode of intense silica exposure

Long term exposure to silica at worksites can cause silicosis. This typically has two radiographic forms, simple silicosis and complicated or conglomerate silicosis. Patients with acute silicosis have rapid progression of disease with fulminant respiratory failure over months rather than years. The patient described in this case report had a one-time 4 to 5-h exposure to silica and sand dust at work when his mask malfunctioned. He developed cough and shortness of breath. During his initial clinic visit he had significant cough. His chest examination was clear without crackles or wheezes. His pulmonary function tests were within normal limits. His chest x-ray was clear. Both symptoms, especially the cough, persisted over the next 6+ months even after treatment with oral corticosteroids and inhaled corticosteroids and long-acting beta agonists. Consequently, this patient developed severe cough following a one-time exposure to silica particulates. Laboratory studies have demonstrated that silica exposure can cause reactive oxygen species which potentially could have activated transient receptor potential vanilloid 1 channels in the afferent sensory nerves in his bronchial epithelium. This could cause sustained cough for more than 6 months. His symptoms improved but did not resolve with corticosteroid treatment. Therefore, this case demonstrates that acute silica exposure can cause sustained airway symptoms in healthy workers.

Exploring the Impact of Occupational Silica Exposure Progressing to Systemic Sclerosis: A Report on the Development of Silica-Induced Systemic Sclerosis Cases

Erasmus syndrome is an uncommon disease brought on by exposure to silica and later manifests as systemic sclerosis (SSc) with or without silicosis. The body of literature on Erasmus syndrome is scarce. Here, we report two cases of male patients presenting with SSc after silica exposure. One of the patients had worked in the steel industry, and another had worked in the sculpture manufacturing for a decade before the presentation. It is imperative to raise awareness of this uncommon illness because avoiding further exposure remains the mainstay of management. Our case reports reemphasize the importance of occupational history in all patients of SSc.

Potential Effect of Combined Exposure of Crystalline Silica Dust and Cigarette Smoking on the Incidence of Silicosis among Chinese Male Stone Processing Workers: A Cross-Sectional Study

Background: Silicosis is a progressive and irreversible disease primarily caused by exposure to crystalline silica dust and, to a lesser extent, cigarette smoking. However, further research is needed to validate the potential combined effect of these risk factors on the increased incidence of the disease. Methods: A total of 1688 male workers employed at a Chinese stone processing plant between 1 January 1999 and 31 December 2019, were included in the study. Cumulative exposure to industrial crystalline silica dust and packyears of smoking were collected through health surveillance, and odds ratios (ORs) with 95% confidence intervals (CIs) for silicotic changes due to industrial silica exposure and cigarette smoking were estimated using logistic regression models. Results: Among all participants, a significant exposure-response relationship was observed between long-term exposure to industrial silica dust and radiographic findings resembling silicosis (OR 1.74, 95% CI 1.25 to 2.41). However, among middle-aged workers, a weak and statistically insignificant relationship was found between prolonged cigarette smoking and X-ray evidence of lung silicosis (OR 1.59, 95% CI 1.00 to 2.53). Furthermore, significant combined effects, exceeding the additive models, were identified in each age group and employment sector (relative risk due to interaction 0.51, 95% CI 0.08 to 3.42). Conclusions: It is critically important to implement effective dust removal measures and tobacco control strategies in order to enhance respiratory health among employees across all age groups in the stone processing industry.

Dynamics of the inhibitory immune checkpoint TIM-3 in mouse pulmonary phagocytes after silica exposure

Long-term inhalation of silica particles in the workplace causes silicosis, which is incurable and seriously endangers the health of workers. It is believed that silicosis is caused by an imbalance of the pulmonary immune microenvironment, in which pulmonary phagocytes play a crucial role. As an emerging immunomodulatory factor, it is unclear whether T cell immunoglobulin and mucin domain-containing protein 3 (TIM3) participate in silicosis by modulating pulmonary phagocytes function. The purpose of this study was to investigate the dynamic changes of the TIM-3 in pulmonary macrophages, dendritic cells (DCs), and monocytes during the development of silicosis in mice. The plasma levels of soluble TIM-3 in silicosis patients were also examined. Flow cytometry was used to identify alveolar macrophages (AMs), interstitial macrophages (IMs), CD11b+ DC, CD103+ DC, Ly6C+, and Ly6C- monocytes in mouse lung tissues, and further analyses were conducted on the expression of TIM-3. Results showed that soluble TIM-3 was significantly elevated in plasma of silicosis patients, and the level of which was higher in stage II and III patients than that in stage I. In silicosis mice, the protein and mRNA levels of TIM-3 and Galectin9 were significantly upregulated in lung tissues. Specific to pulmonary phagocytes, silica exposure affected TIM-3 expression in a cell-specific and dynamic manner. In macrophages, TIM-3 expression upregulated in AM after 28 days and 56 days of silica instillation, while the expression of TIM-3 in IM decreased at all observation time points. In DCs, silica exposure only caused a decrease of TIM-3 expression in CD11b+ DCs. In monocytes, TIM-3 dynamics in Ly6C+ and Ly6C- monocytes were generally consistent during silicosis development, which significant decrease after 7 and 28 days of silica exposure. In conclusion, TIM-3 may mediate the development of silicosis by regulating pulmonary phagocytes.

Exploratory study on noninvasive biomarker of silicosis in exhaled breath by solid-phase microextraction-gas chromatography-mass spectrometry analysis

BACKGROUND

As a chronic occupational disease, silicosis could cause irreversible and incurable impair to the lung. The current diagnosis of silicosis relies on imaging of X-ray or CT, but these methods cannot detect lung lesions in the early stage of silicosis.

OBJECTIVE

To establish a regular screening and early diagnosis methods for silicosis, which could be helpful for the prevention and treatment of silicosis.

METHODS

A total of 161 subjects were enrolled in the study, including 69 patients with silicosis (SILs) and 92 healthy controls. The exhaled breath samples of the subjects were collected with breath sampler and Tedlar bag. The analysis of volatile organic compounds (VOCs) in exhaled breath was performed by solid-phase microextraction (SPME) combined with gas chromatography mass spectrometry (GC-MS).

RESULTS

After excluding the pollutants from sampling bags and instruments, 86 VOCs have been identified in the exhaled breath. The orthogonal partial least squares-discriminant analysis (OPLS-DA) was employed for the screening of potential biomarkers of silicosis. Those components that related to smoking were also excluded from the biomarkers. Finally, nine possible biomarkers for silicosis were screened out, including 2,3-butanedione, ethyl acetate, chlorobenzene, o-cymene, 4-ethylhex-2-ynal, 3,5-dimethyl-3-heptanol, hydroquinone, phthalic anhydride and 5-(2-methylpropyl)nonane. Based on these biomarkers screened, a predicted model for silicosis was generated with the accuracy of 89.61%.

CONCLUSION

The nine biomarkers in exhaled breath were preliminarily screened out for the early diagnosis of silicosis, which can be helpful to the establishment of a noninvasive screening method for silicosis. Follow-up studies should be conducted to further verify these markers.

A systematic review of the effectiveness of dust control measures adopted to reduce workplace exposure

The recent increase in silicosis cases in several countries casts doubt on dust control practices and their effectiveness in preventing respirable crystalline silica (RCS) exposure. Apart from silicosis, RCS may lead to other illnesses, health-related quality of life losses for workers and their families, and economic losses for companies. Thus, this systematic literature review examined the effectiveness of interventions employed to prevent exposure to RCS and increase the use of dust control measures. The review used keywords related to dust control interventions to search seven databases. Search results were screened and extracted for synthesis. The narrative synthesis showed the extent of research investment in China. In several designs and combinations, the interventions utilized water, surfactant, foam, and air currents to reduce dust exposure. These interventions offer varying degrees of dust control effectiveness against RCS and respirable dust. Although evidence indicates that interventions significantly decrease dust concentration levels, the control measures in place may not effectively prevent workplace overexposure to RCS. The review found that education and training interventions are employed to improve dust controls and respiratory protective equipment (RPE) use. Also, marketing strategies promote the use of RPE. These interventions can increase the frequency of use of RPE and the adoption of best practice dust control measures. Interventions increase knowledge, awareness, and attitudes about RPE usage and generate positive perceptions while reducing misconceptions. However, the benefits obtained from an intervention may diminish after its implementation, indicating that the interventions may not continually motivate workers to adopt control measures or use RPE.

Histology, prevalence, and environmental sources for pulmonary silicates depositions in domestic and wild animals

The source and significance of pulmonary silicate crystals in animals and people are poorly understood. To estimate the prevalence and characterize the pulmonary crystalline material in animals from St. Kitts, tissue samples from dogs, horses, cattle, sheep, goats, pigs, chickens, mongooses, and monkeys were examined by light microscopy, scanning electron microscopy with energy-dispersive x-ray analysis (SEM/EDXA), and x-ray diffraction. Crystalline material was seen in 201 of 259 (77.6%) lung samples as perivascular and interstitial accumulations of heterogeneous crystalline particulate material, free or within macrophages (silicate-laden macrophages [SLMs]), mostly lacking evidence of chronic inflammation or fibrosis. The crystalline material was birefringent, basophilic on acid-fast, and composed of silicas on SEM/EDXA. Mongooses (100%) and monkeys (98%) had the highest prevalence of SLM, followed by cattle and chickens. Lesions were graded on a 3-point scale based on the histologic location and extent of silicates and SLM and were significantly more severe in mongooses (median = 3) than in monkeys (median = 2), dogs (median = 2), and chickens (median = 1). On EDXA, the crystalline material from lungs, air, and topsoil was composed of silicon, oxygen, aluminum, and iron, with a particulate matter size between 2.5 and 10 µm. We hypothesize Saharan dust, volcanic ash, topsoil, and rock quarry dust are potential sources of siliceous dust inhalation and SLM accumulations lacking chronic inflammation (silicosis); dust generation may be potentiated by road vehicle or wind suspension. Future investigations are warranted on the role of silicate inhalation and respiratory comorbidities in people, with monkeys, mongooses, or chickens serving as possible sentinels for exposure.

Occupational Interstitial Lung Diseases

Occupational exposures are directly causal or partially contributory to the development of interstitial lung diseases. A detailed occupational history, relevant high-resolution computed tomography findings, and where relevant additional histopathology, are required to make a diagnosis. Treatment options are limited, and further exposure avoidance is likely to reduce disease progression.

Evaluation of Lung Functions, Blood Pressure, and Hearing Deterioration in Tile Setters

INTRODUCTION

Tile setters in construction industries are exposed to a potent risk of silicosis as they are constantly exposed to crystalline silica dust during concrete finishing, cutting and fixing of the ceramic tiles. The noise produced by instruments used in tile settings may lead to noise-induced hearing loss. Noise above the permissible limit of 85 dB may lead to autonomic changes and alteration in blood pressure. These facts gave us an impetus to evaluate the pulmonary functions, blood pressure and hearing deterioration in tile setters and correlate these parameters for their present functional status with duration of exposure to tile cutting profession.

METHODS

The pulmonary functions were evaluated with spirometer, autonomic status by recording the blood pressure and hearing loss by calculating the Hearing Deterioration Index (HDI) for hearing loss.

RESULTS

There was significant decline in forced vital capacity (FVC), forced expiratory volume 1 sec (FEV1) and forced expiratory volume 1% (FEV1%) in tile setters. The decline in FVC, FEV1 and FEV1% was significantly higher in subjects with exposure of more than five years. There was increased systolic and diastolic blood pressure in those having more than five years of exposure in the tile setting profession as compared to less than five years. There was a positive correlation between years of service in the tile setting profession as well as sound exposure level with HDI and blood pressure in our subjects.

CONCLUSION

Prolonged exposure to the tile setting profession may lead to compromised lung function, hypertension and hearing deterioration in tile setters.

Cytotoxic effects of crystalline silica in form of micro and nanoparticles on the human lung cell line A549

Airborne crystalline silica (SiO₂) particles are one of the most common pollutants in stone industries. Limited studies have investigated the health effects of crystalline SiO₂ nanoparticles. Hence, the objective of this study was to study the cytotoxicity of SiO₂ in nano and micron sizes. A mineral quartz sample in the range of 0.2-0.8 mm sizes was purchased. These particles were ground at about 5 and 0.1 microns. Human cell line A549 was exposed to micro and nanometer particles at concentrations of 10, 50, 100, and 250 μg/ml for 24 and 72 h. Subsequently, the cytotoxicity of exposed cells was investigated by measuring cell survival, ROS generation, mitochondrial permeability, and intracellular glutathione content. The results showed that crystalline SiO₂ nano and microparticles decreased cell survival, increased ROS generation, damaged the mitochondrial membrane, and lowered the antioxidant content of these cells in a concentration- and time-dependent manner. The toxicity of crystalline SiO₂ microparticles at concentrations ≤50 μg/mL was greater than for nanoparticles, which was the opposite at concentrations ≥100 μg/mL. Exposure time and concentration were crucial factors for the cytotoxicity of exposed A549 cells to crystalline SiO₂ particles, which can affect the severity of the effect of particle size. Due to the limitation of exposure concentration and test durations in this study, further studies on the parameters of nanoparticle toxicity and underlying mechanisms could advance our knowledge.

The Role of Pulmonary Surfactant Phospholipids in Fibrotic Lung Diseases

Diffuse parenchymal lung diseases (DPLD) or Interstitial lung diseases (ILD) are a heterogeneous group of lung conditions with common characteristics that can progress to fibrosis. Within this group of pneumonias, idiopathic pulmonary fibrosis (IPF) is considered the most common. This disease has no known cause, is devastating and has no cure. Chronic lesion of alveolar type II (ATII) cells represents a key mechanism for the development of IPF. ATII cells are specialized in the biosynthesis and secretion of pulmonary surfactant (PS), a lipid-protein complex that reduces surface tension and minimizes breathing effort. Some differences in PS composition have been reported between patients with idiopathic pulmonary disease and healthy individuals, especially regarding some specific proteins in the PS; however, few reports have been conducted on the lipid components. This review focuses on the mechanisms by which phospholipids (PLs) could be involved in the development of the fibroproliferative response.

Effects of early dexamethasone treatment on several markers of inflammation and fibrosis in an animal model of lung silicosis in rats – A pilot study

Lung silicosis is primarily caused by inhalation of particles of silicon oxide (silica). Despite a huge progress in understanding the interactions among the pathomechanisms of lung silicosis in the last years, there is a lack of effective therapy. With respect to a wide therapeutic action of corticosteroids, the purpose of this pilot study was to evaluate early effects of dexamethasone on several markers of inflammation and lung fibrosis in a rat model of silicosis. The silicosis model was induced by a single transoral intratracheal instillation of silica (50 mg/ml/animal), while the controls received an equivalent volume of sterile saline. The treatment with intraperitoneal dexamethasone initiated the next day after the silica instillation and was given 2-times a week at a dose of 1 mg/kg, while the controls received an equivalent volume of saline. The animals were euthanized 14 or 28 days after the treatment onset. Total and differential counts of leukocytes in the blood and bronchoalveolar lavage (BAL) fluid were determined. The presence of collagen in the bronchioles and lung vessels was detected by Sirius red staining and a smooth muscle mass was detected by smooth muscle actin. In comparison to saline, the instillation of silica increased the total count of circulating leukocytes after 14 and 28 days of the experiment (both p<0.05), which was associated with higher counts of lymphocytes (p<0.05 after 14 days, p>0.05 after 28 days) and slight but non-significant increases in neutrophils and eosinophils (both p>0.05). Although the total cell count in the BAL fluid did not change significantly, the percentages and absolute counts of neutrophils, eosinophils, and lymphocytes (p<0.05, p<0.01 or p<0.001) elevated after 14 and 28 days of the experiment. Silica induced an accumulation of collagen in the bronchioles (p<0.001 after both 14 and 28 days) and pulmonary vessels (p<0.01 after both 14 and 28 days) and elevated a formation of smooth muscle mass (p<0.05 after 14 days, p<0.01 or p<0.001 after 28 days). Treatment with dexamethasone decreased circulating leukocytes (p<0.01) and lymphocytes (p<0.001) and increased neutrophils (p<0.05), which was associated with a slightly decreased total cell count in BAL (p>0.05), decline in lymphocytes (p<0.01), and slight decreases in neutrophils and eosinophils after 28 days of the treatment. Moreover, dexamethasone reduced the accumulation of collagen (p<0.01 after 14 days and p<0.001 after 28 days) and the formation of smooth muscle mass (p<0.01 for bronchioles and p>0.05 for vessels after 24 days, p<0.001 for both bronchioles and vessels after 28 days). In conclusion, early dexamethasone treatment mitigated silica-induced granulocytic-lymphocytic inflammation and decreased a formation of collagen and smooth muscle mass in the bronchiolar and vascular walls, demonstrating a therapeutic potential of dexamethasone in the lung silicosis.

The emerging role of epigenetic regulation in the progression of silicosis

Silicosis is one of the most severe occupational diseases worldwide and is characterized by silicon nodules and diffuse pulmonary fibrosis. However, specific treatments for silicosis are still lacking at present. Therefore, elucidating the pathogenesis of silicosis plays a significant guiding role for its treatment and prevention. The occurrence and development of silicosis are accompanied by many regulatory mechanisms, including epigenetic regulation. The main epigenetic regulatory mechanisms of silicosis include DNA methylation, non-coding RNA (ncRNA), and histone modifications. In recent years, the expression and regulation of genes related to silicosis have been explored at epigenetic level to reveal its pathogenesis further, and the identification of aberrant epigenetic markers provides new biomarkers for prediction and diagnosis of silicosis. Here, we summarize the studies on the role of epigenetic changes in the pathogenesis of silicosis to give some clues for finding specific therapeutic targets for silicosis.

Differential immunological effects of silica nanoparticles on peripheral blood mononuclear cells of silicosis patients and controls

Silicosis is a fibrotic disease caused by the inhalation of respirable silica particles, which are typically engulfed by alveolar macrophages and subsequently induce the release of inflammatory cytokines. Various animal experimental and human studies have focused on modeling silicosis, to assess the interactions of macrophages and other cell types with silica particles. There is still, however, limited knowledge on the differential response upon silica-exposure between silicosis patients and controls. We focused on studying the responsiveness of peripheral blood mononuclear cells (PBMCs) to silica nanoparticles (SiNPs) - Ludox and NM-200 - of silicosis patients and controls. The proliferative capacity of T- CD3⁺ and B- CD19⁺ cells, were evaluated via Carboxyfluorescein succinimidyl ester (CFSE) assay. The activation status of lymphocyte subsets and response to silica were also evaluated by comparing the extent of micro-granuloma or aggregate formation with the cytokine secretion profiles between both groups of individuals. The proliferative capacity of CD19⁺ cells was elevated in silicotic patients as opposed to controls. Subsets of regulatory T cells (CD4⁺ CD25⁺ and CD8⁺ CD25⁺) and immunoglobulins IgM and IgG were also significantly increased in patients. The number and the size of aggregates formed were higher with SiNPs stimulation in patients compared to controls. Multivariable analysis also elucidated the role of key cytokines like interleukin-1β (IL-1β), IL-6 and interferon-gamma (IFN-γ), which were upregulated in SiNP-stimulated PBMCs of patients compared to controls. Our ex vivo model thus has potential to provide insights into the immunological effects of silica particles in lymphocytes of silicosis patients and controls.

A toxicological profile of silica nanoparticles

Humans are regularly exposed to silica nanoparticles in environmental and occupational contexts, and these exposures have been implicated in the onset of adverse health effects. Existing reviews on silica nanoparticle toxicity are few and not comprehensive. There are natural and synthetic sources by which crystalline and amorphous silica nanoparticles are produced. These processes influence physiochemical properties, which are factors that can dictate toxicological effects. Toxicological assessment includes exposure scenario (e.g. environmental, occupational), route of exposure, toxicokinetics, and toxicodynamics. Broader considerations include pathology, risk assessment, regulation, and treatment after injury. This review aims to consolidate the most relevant and up-to-date research in these areas to provide an exhaustive toxicological profile of silica nanoparticles.

Protective effects of intranasal curcumin on silica-induced lung damage

OBJECTIVE

Being anti-inflammatory and an antioxidant in nature, curcumin has been studied for its anti-asthmatic effects, but its impact on silicosis has not been investigated before. It is a form of occupational lung illness caused by inhaling crystalline silica. It is particularly common among those who work in construction-related sectors. Therefore, present study has been undertaken to investigate impact of intranasal curcumin on silica induced lung damage in mice model of silicosis.

MATERIALS AND METHODS

Mice model of silicosis was developed by intranasal silica instillation (2.5 mg/mice) for different durations mainly 7, 14 and 21 days, where the longest duration of silica exposure (21 days) mimics chronic occupational exposure of silica dust leading to silicosis. Curcumin (5 mg/kg,i.n) and /or dexamethasone, a known corticosteroid (10 mg/kg,i.p) was administered an hour prior to silica administration.

RESULTS

Present study revealed silica induced lung damage in the mice model of silicosis characterized by airway inflammation, collagen deposition and enhanced expression of fibrosis markers (MMP-9, α-SMA, Hydroxyproline), which were significantly reduced in curcumin treatment groups. Inhibitory effects of curcumin were compared with standard drug, dexamethasone, a corticosteroid and was found better in protecting structural alterations in the lung. Damaged and abnormal mitochondria (enlarged and irregular shapes) were observed in silicosis group which were reduced in curcumin and dexamethasone treatment groups as revealed in transmission electron microscopic studies.

CONCLUSIONS

Present study shows protective effects of intranasal curcumin on silica-induced airway inflammation and structural changes thereby lung damage. Hence, it can be considered as an alternative and complementary medication for silicosis.

Three's Company: Coexistence of Silicosis, Scleroderma, and Sjogren Syndrome in a Single Patient

We describe a patient who presented with silicosis, scleroderma, and Sjogren syndrome all at the same time. The diagnoses in this case are all associated with continuous exposure to crystalline silica at the patient's workplace. The following report discusses this unique presentation.

Asian dust storms result in a higher risk of the silicosis hospital admissions

PURPOSE

Previous studies found that silicosis was majorly associated with occupation-related risks. However, little evidence was available to clarify the relation between Asian dust storm (ADS) and silicosis hospital admissions. This present paper aims to investigate the association between ADS events and hospital admissions for silicosis.

METHODS

We applied a Poisson time-series regression on the 2000-2012 National Health Insurance Research Database in Taiwan, linking air quality data and ambient temperature data to estimate the impact of ADS on silicosis hospital admissions in the age-specific groups.

RESULTS

A total of 2154 hospital admissions were recorded for silicosis in Taiwan, for a daily average number of 0.45. The number rises from 0.43 on a day without ADS to 0.70 on the outbreak day and continues increasing to 0.83 one day after outbreak. Among patients under 45, the effect of ADS appears on the event day as well as several post-event days (lag2-6) at the significant level of p < 0.1. There is also a significant lag effect on post-event day 2 (p < 0.05) for those aged above 74.

CONCLUSION

Asian dust storms do result in a rise of silicosis hospital admissions, particularly for those above 74, those under 45, and for females.

Dietary Postbiotics Reduce Cytotoxicity and Inflammation Induced by Crystalline Silica in an In Vitro RAW 264.7 Macrophage Model

Crystalline silica (cSiO₂) particles are naturally existing environmental toxicants. Exposure to cSiO₂ could cause local or systemic inflammation and aggregate inflammation-associated diseases. Dietary postbiotics are reported to possess anti-inflammatory activities; however, their effects on cSiO₂-triggered inflammation are unknown. Here, we investigate the impact of postbiotics from Lacticaseibacillus rhamnosus (LGG), Limosilactobacillus reuteri (L.reu), and Bifidobacterium animalis subsp. lactis Bb12 (BB12) on cSiO₂-induced cytotoxicity and IL-1 cytokines in vitro using macrophages. The postbiotics used in this study were cell-free fractions of a probiotic growth medium collected at different time points. The in vitro model used was the wild-type murine macrophage RAW 264.7 cell line stably transfected with the inflammasome adapter protein, ASC. Our results indicate that all the postbiotics could reduce cSiO₂-induced cytotoxicity in the wild-type and ASC macrophages and the effects were OD-dependent. Following priming with a lipopolysaccharide, cSiO₂ treatment resulted in robust inflammasome activation in ASC, as reflected by the IL-1β release. These responses were minimal or absent in the wild-type RAW cells. All the postbiotics decreased the release of IL-1β from ASC; however, only LGG and BB12 reduced the IL-1β secretion from wild-type cells. Only the L.reu postbiotics reduced the IL-1α release from ASC. We conclude that the postbiotics from LGG, BB12, and L.reu can protect macrophages against cSiO₂-induced cytotoxicity and suppress IL-1β activation.

Engineering solutions to breath tests based on an e-nose system for silicosis screening and early detection in miners

OBJECTIVES

This study aims to develop an engineering solution to breath tests using an electronic nose (e-nose), and evaluate its diagnosis accuracy for silicosis. Influencing factors of this technique were explored.

METHODS

398 non-silicosis miners and 221 silicosis miners were enrolled in this cross-sectional study. Exhaled breath was analyzed by an array of 16 organic nanofiber sensors along with a customized sample processing system. Principal Component Analysis was used to visualize the breath data, and classifiers were trained by two improved cost-sensitive ensemble algorithms (RF and XGBoost) and two classical algorithms (KNN and SVM). All subjects were included to train the screening model, and an early detection model was run with silicosis cases in stage I. Both 5-fold cross-validation and external validation were adopted. Difference in classifiers caused by algorithms and subjects was quantified using a two-factor analysis of variance. The association between personal smoking habits and classification was investigated by the chi-square test.

RESULTS

Classifiers of ensemble learning performed well in both screening and early detection model, with an accuracy range of 0.817 to 0.987. Classical classifiers showed relatively worse performance. Besides, the ensemble algorithm type and silicosis cases inclusion had no significant effect on classification (p>0.05). There was no connection between personal smoking habits and classification accuracy.

CONCLUSION

Breath tests based on an e-nose consisted of 16x sensor array performed well in silicosis screening and early detection. Raw data input showed a more significant effect on classification compared with the algorithm. Personal smoking habits had little impact on models, supporting the applicability of models in large-scale silicosis screening. The e-nose technique and the breath analysis methods reported are expected to provide a quick and accurate screening for silicosis, and extensible for other diseases.

The Utility of Length of Mining Service and Latency in Predicting Silicosis among Claimants to a Compensation Trust

In the wake of a large burden of silicosis and tuberculosis among ex-miners from the South African gold mining industry, several programmes have been engaged in examining and compensating those at risk of these diseases. Availability of a database from one such programme, the Q(h)ubeka Trust, provided an opportunity to examine the accuracy of length of service in predicting compensable silicosis, and the concordance between self-reported employment and that officially recorded. Compensable silicosis was determined by expert panels, with ILO profusion ≥1/0 as the threshold for compensability. Age, officially recorded and self-reported years of service, and years since first and last service of 3146 claimants for compensable silicosis were analysed. Self-reported and recorded service were moderately correlated (R = 0.66, 95% confidence interval 0.64−0.68), with a Bland−Altman plot showing no systematic bias. There was reasonably high agreement with 75% of the differences being less than two years. Logistic regression and receiver operating characteristic curve analysis were used to test prediction of compensable silicosis. There was little predictive difference between length of service on its own and a model adjusting for length of service, age, and years since last exposure. Predictive accuracy was moderate, with significant potential misclassification. Twenty percent of claimants with compensable silicosis had a length of service <10 years; in almost all these claims, the interval between last exposure and the claim was 10 years or more. In conclusion, self-reported service length in the absence of an official service record could be accepted in claims with compatible clinical findings. Length of service offers, at best, moderate predictive capability for silicosis. Relatively short service compensable silicosis, when combined with at least 10 years since last exposure, was not uncommon.

Environmental pollution, a hidden culprit for health issues

The environmental and health impacts from the massive discharge of chemicals and subsequent pollution have been gaining increasing public concern. The unintended exposure to different pollutants, such as heavy metals, air pollutants and organic chemicals, may cause diverse deleterious effects on human bodies, resulting in the incidence and progression of different diseases. The article reviewed the outbreak of environmental pollution-related public health emergencies, the epidemiological evidence on certain pollution-correlated health effects, and the pathological studies on specific pollutant exposure. By recalling the notable historical life-threatening disasters incurred by local chemical pollution, the damning evidence was presented to criminate certain pollutants as the main culprit for the given health issues. The epidemiological data on the prevalence of some common diseases revealed a variety of environmental pollutants to blame, such as endocrine-disrupting chemicals (EDCs), fine particulate matters (PMs) and heavy metals. The retrospection of toxicological studies provided illustrative clues for evaluating ambient pollutant-induced health risks. Overall, environmental pollution, as the hidden culprit, should answer for the increasing public health burden, and more efforts are highly encouraged to strive to explore the cause-and-effect relationships through extensive epidemiological and pathological studies.

Environmental and health risks posed to children by artisanal gold mining: A systematic review

There are an estimated 5 million children working in artisanal and small-scale gold mines worldwide; however, the hazards are poorly characterized and often underreported. We systematically reviewed the literature on reports of hazards among children as a consequence of such activities through PubMed database using pre-defined search terms. We identified 113 articles published between 1984 and 2021 from 31 countries. Toxicological hazards were reported in 91 articles, including mercury, lead, and arsenic. Infectious hazards, noted in 18 articles, included malaria, cholera, and hepatitis. Six articles reported occupational hazards, including malnutrition, heat stroke, and reactive airway disease. Three articles reported traumatic hazards, including cave-ins, burns, animal attacks, falls, and weapon-inflected wounds. Those findings likely indicate a profound underreporting of the prevalence and consequences of such hazards among children. More work is needed both to characterize the burdens of those hazards and to address the underlying drivers of child labor in those settings.

Activation of canonical inflammasome complex by acute silica exposure in experimental rat model

Silicosis is a chronic irreversible pulmonary disease caused by the inhalation of silica crystals in occupational settings in most cases. Persistent inflammation in the alveolar space is considered to be the major reason for tissue damage and lung fibrogenesis. The mechanisms by which silica exposure activates immune cells are not well understood. Here, we employed an in vivo silicosis disease model by intratracheal instillation of a large dose of silica suspension in rats and explored the involvement of inflammasome activation. Marked leukocyte infiltration and edema were observed 3 days following silica exposure in treated animals compared to controls. Using this model, we compared the expression of inflammasome sensors (AIM2 and NLRP3) and effector protein (caspase-1) by western blot and immunohistochemical staining using the lung homogenates and lung tissue sections. Our results demonstrated that following acute silica exposure, AIM2, NLRP3 and caspase-1 expressions were increased in macrophages or/and lung epithelial cells compared to control animals. We also analyzed interleukin 1β expression using lung homogenates, and significant increase in interleukin 1β was observed in 3-day silica-exposed rats. The activation of inflammasome sensors AIM2 and NLRP3 suggested to us that blocking these activators may attenuate silica-associated tissue damage and inflammation.

What is a Therapeutic Potential of N-Acetylcysteine in Lung Silicosis?

Lung silicosis is a serious pulmonary disease caused by an exposure of lung to inhaled silicon dioxide (SiO2) or silica. Although pathomechanisms of the disease have not been fully elucidated, oxidative stress has been recognized as a fundamental factor triggering a fibrotizing inflammation leading to irreversible changes in lung tissue. Based on this knowledge, therapeutic potential of various antioxidants has been intensively discussed. Among them, N-acetylcysteine with its multiple anti-inflammatory and antioxidant actions and a long-term experience with its clinical use in various diseases appears as a very promising choice. The purpose of this article is to review the therapeutic effects of N-acetylcysteine particularly in relation to a lung injury and to point out a potential of N-acetylcysteine in the treatment of lung silicosis.

Caveolin-1 negatively regulates inflammation and fibrosis in silicosis

Inhalation of crystalline silica causes silicosis, the most common and serious occupational disease, which is characterized by progressive lung inflammation and fibrosis. Recent studies revealed the anti-inflammatory and anti-fibrosis role of Caveolin-1 (Cav-1) in lung, but this role in silicosis has not been investigated. Thus, this study evaluated Cav-1 regulatory effects in silicosis. It was found that Cav-1 levels were significantly reduced in the lung from silicosis patients and silicotic mice. The silicosis models were established in C57BL/6 (wild-type) and Cav-1 deficiency (Cav-1^-/- ) mice, and Cav-1^-/- mice displayed wider alveolar septa, increased collagen deposition and more silicotic nodules. The mice peritoneal-derived macrophages were used to explore the role of Cav-1 in silica-induced inflammation, which plays a central role in mechanism of silicosis. Cav-1 inhibited silica-induced infiltration of inflammatory cells and secretion of inflammatory factors in vitro and in vivo, partly by downregulating NF-κB pathway. Additionally, silica uptake and expression of 4-hydroxynonenal in silicotic mice were observed, and it was found that Cav-1 absence triggered excessive silica deposition, causing a stronger oxidative stress response. These findings demonstrate the protective effects of Cav-1 in silica-induced lung injury, suggesting its potential therapeutic value in silicosis.

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.

Interpreting Immunoregulation in Lung Fibrosis: A New Branch of the Immune Model

Immunostimulation is recognized as an important contribution in lung fibrosis in some animal models and patient subsets. With this review, we illustrate an additional scenario covering the possible implication of immunoregulation during fibrogenesis. Available animal and human data indicate that pulmonary fibrosis also includes diverse and discrete immunoregulating populations comprising regulatory lymphocytes (T and B regs) and myeloid cells (immunosuppressive macrophages and myeloid-derived suppressive cells; MDSC). They are initially recruited to limit the establishment of deleterious inflammation but participate in the development of lung fibrosis by producing immunoregulatory mediators (mainly TGF-β1 and IL-10) that directly or indirectly stimulate fibroblasts and matrix protein deposition. The existence of this silent immunoregulatory environment sustains an alternative mechanism of fibrosis that explains why in some conditions neither pro-inflammatory cytokine deficiency nor steroid and immunosuppressive therapies limit lung fibrosis. Therefore, the persistent presence of immunoregulation is an important parameter to consider for refining therapeutical strategies in lung fibrotic disorders under non-immunostimulatory conditions.

Early Detection Methods for Silicosis in Australia and Internationally: A Review of the Literature

Pneumoconiosis, or occupational lung disease, is one of the world’s most prevalent work-related diseases. Silicosis, a type of pneumoconiosis, is caused by inhaling respirable crystalline silica (RCS) dust. Although silicosis can be fatal, it is completely preventable. Hundreds of thousands of workers globally are at risk of being exposed to RCS at the workplace from various activities in many industries. Currently, in Australia and internationally, there are a range of methods used for the respiratory surveillance of workers exposed to RCS. These methods include health and exposure questionnaires, spirometry, chest X-rays, and HRCT. However, these methods predominantly do not detect the disease until it has significantly progressed. For this reason, there is a growing body of research investigating early detection methods for silicosis, particularly biomarkers. This literature review summarises the research to date on early detection methods for silicosis and makes recommendations for future work in this area. Findings from this review conclude that there is a critical need for an early detection method for silicosis, however, further laboratory- and field-based research is required.

Occupational exposure to crystalline silica and peripheral biomarkers: An update

Peripheral biomarkers are important tools for detecting occupational exposures to prevent the onset and/or progression of diseases. Studies that reveal early peripheral biomarkers are highly important to preserve the health of workers and can potentially contribute to diagnosing and/or prognosing occupational pathologies. Exposure to crystalline silica is a problem in several workplaces because it increases the risk of chronic obstructive pulmonary disease (COPD), tuberculosis, cancer, and pulmonary fibrosis, clinically defined as silicosis. Silicosis is diagnosed by chest radiography and/or lung tomography in advanced stages when there is a severe loss of lung function. Peripheral biomarkers can help in diagnosing early changes prior to silicosis and represent a highly important technical-scientific advance that is minimally invasive. This review aimed to investigate the biomarkers studied for evaluating occupational exposure to crystalline silica and to understand the recent advances in this area. Potential oxidative, inflammatory, and immunological biomarkers were reviewed, as well as routine biomarkers such as biochemical parameters. It was found that biomarkers of effect such as serum CC16 and l-selectin levels could represent promising alternatives. Additionally, studies have shown that neopterin levels in urine and serum can be used to monitor worker exposure. However, further studies are needed that include a greater number of participants, different times of exposure to crystalline silica, and a combination of silicosis patients and healthy volunteers. Evaluating the concentration of crystalline silica in occupational environments, its impact on biomarkers of effect, and alterations in lung function could contribute to revealing early health alterations in workers in a more robust manner.