Occupational silica exposure and risk of various diseases: an analysis using death certificates from 27 states of the United States

Occupational exposures and sarcoidosis: a rapid review of the evidence

BACKGROUND

Sarcoidosis is a rare, multisystem, inflammatory condition associated with the formation of granulomas. Diagnosis can be challenging because of non-specific symptoms complicating epidemiological investigations of its aetiology. Despite research efforts, a review of the current state of the evidence is needed.

AIMS

To assess the evidence for an association between occupational exposures and the development of sarcoidosis. To determine if workers in any occupation are at a greater risk of developing sarcoidosis.

METHODS

This rapid review follows the methodology suggested by the World Health Organization. Two electronic databases were systematically searched until April 2022. The methodological quality of the studies was critically appraised, and a best-evidence approach was used to synthesize the results.

RESULTS

Titles and abstracts of 2916 articles were screened, with 67 full-text articles reviewed for eligibility. Among the 13 studies eligible for this review, none were of high quality (i.e. low risk of bias). Six studies exploring the association between sarcoidosis and a range of occupations and exposures, and one previous systematic review were of low quality reporting inconsistent findings. Six studies examined the risk of sarcoidosis associated with occupational silica exposure, two of which were of acceptable quality. Overall, the study methodologies and results were inadequate to support causal relationships.

CONCLUSIONS

There is limited evidence of acceptable methodological quality to assess the risk of sarcoidosis associated with occupational exposures. There is a growing body of research examining occupational exposure to silica and sarcoidosis. Additional high-quality confirmatory research is needed.

Environmental exposure to polycyclic aromatic hydrocarbons: An underestimated risk factor for systemic lupus erythematosus onset and progression

OBJECTIVE

To investigate the link between systemic lupus erythematosus (SLE) incidence and exposure to environmental polycyclic aromatic hydrocarbons (PAH).

METHODS

A case-control study (ChiCTR2000038187) involving 316 SLE patients and 851 healthy controls (HCs) was executed. Environmental exposure was assessed via a questionnaire, stratified by gender and age (females <35 and ≥35 years, males). Blood samples collected from 89 HCs, 85 inactive, and 95 active SLE patients were used to measure serum benzo[a]pyrene diol epoxide -albumin (BPDE-Alb) adducts and PAH concentrations, indicating long-term and short-term exposure respectively. Intergroup comparisons and statistical analyses were conducted using R version 4.3.1.

RESULTS

Diverse patterns were found in how environmental factors affect SLE onset across different demographics. Lifestyle exposure factors were found to be a stronger determinant of SLE onset than occupational exposure factors in women under 35. Indoor air pollution had a significant impact on SLE incidence, potentially comparable to outdoor air pollution. Lifestyle-related PAH exposure had a greater impact on SLE than occupational PAH exposure. PAH exposure levels progressively increase from HCs to inactive and active SLE patients. Active SLE patients show markedly higher BPDE-Alb levels than HCs.

CONCLUSIONS

Environmental PAH, particularly lifestyle-related, are significant, yet under-recognized, risk factors for SLE.

STATEMENT OF ENVIRONMENTAL IMPLICATION

We examined the relationship between exposure to environmental polycyclic aromatic hydrocarbons (PAH) and the incidence of systemic lupus erythematosus (SLE). PAH, prevalent in sources such as cigarette smoke, air pollution, and charred food, pose significant health hazards. This study is the first to investigate specific PAH exposure levels in SLE patients. We determined actual PAH exposure levels in both SLE patients and healthy individuals and indicated that long-term PAH exposure biomarker is more reliable for evaluating exposure in non-occupationally exposed groups like SLE, compared to short-term markers. These findings provide valuable insights for future research on similar non-occupationally exposed populations.

Latent tuberculosis infection and infection-associated risk factors for miner workers with silicosis in eastern China

OBJECTIVES

Silicosis people are at high risk of developing pulmonary tuberculosis. Whether silica exposure increases the likelihood of latent tuberculosis infection (LTBI) was not well understood, and potential factors involved in LTBI risk among silicosis people were not evaluated before. Thus, LTBI among silicosis people and potential risk factors for LTBI among silicosis people were evaluated in this study.

METHODS

A cross-sectional study was undertaken for 130 miner workers with silicosis. The QFT-GIT was performed for LTBI detection.

RESULTS

The LTBI was high to 31.6% (36/114) for silicosis participants, and 13.1% (13/99) had a history of tuberculosis. Drinking was associated with LTBI risk (OR = 6.92, 95%CI, 1.47-32.66, P = 0.015). Meanwhile, tunneling work was associated with an increased risk of LTBI compared with other mining occupations (OR = 3.91,95%CI,1.20-12.70, P = 0.024).

CONCLUSIONS

The LTBI rate of silicosis participants was high and more than 10% had a history of tuberculosis. Drinking alcohol and tunneling were independent risk factors for LTBI in silicosis participants.

Risk of Silico-Tuberculosis in Miners: A Systematic Review and Meta-Analysis

Context

Tuberculosis (TB) and Silicosis are public health problems with high morbidity and mortality. They also exist as comorbidities and are highly prevalent among mine workers.

Aims

This study aims to estimate the risk of TB in miners with silicosis than in miners not having silicosis.

Methods and Material

This systematic review was conducted by literature search using PubMed, and EMBASE for studies published from 1st Jan 2017 till 20th July 2022. From the data obtained using relevant keywords for the search, a total of 345 articles were selected for screening after applying our inclusion-exclusion criteria and removing duplicates. PRISMA guidelines were followed. items JBI critical appraisal checklist for cross-sectional studies was used for assessment of the risk of bias. The odds ratio was used to estimate the strength of the association.

Results

After extensive screening, four studies have met our selection criteria. The meta-analysis of those studies revealed that the prevalence of TB in miners with silicosis is 27.11% while the prevalence of TB in miners with non-silicosis is 16.75%. The estimated pooled odds ratio (fixed effect model) is 1.34 (95% CI 1.01 - 1.76).

Conclusions

The present study reveals that there is an increased risk of TB in miners with Silicosis. Newer initiatives must be taken to prevent TB in miners.

Exploring the Impact of Silicosis Incidence on Tuberculosis Mortality and Morbidity: A Multi-Country Study

INTRODUCTION

There are several risk factors attributed to tuberculosis (TB) mortality and morbidity. There are few studies and systematic reviews showing the association of silicosis and tuberculosis at a country level. Very limited studies have been conducted using multi-country data in studying the association of incidence of silicosis with TB mortality and morbidity. Hence, the aim of this research was to explore the association of incidence of silicosis and other important risk factors with TB mortality and morbidity using multi-country data.

METHODS

Data from 217 WHO region countries were utilized, sourcing TB-related statistics from the Institute of Health Metrics and Evaluation and additional risk factors from the Demographic and Health Survey, Global Burden of Disease, and World Bank for 2019. Regression analysis was conducted to examine the association between silicosis incidence and TB outcomes.

RESULTS

The study found an average silicosis incidence of 121.92 per 100,000 population. Additionally, 62.69% of the sample population are exposed to air pollution from solid fuel cooking. Sanitation access stands at an average of 59.67%. Regression outcomes indicate that while alcohol consumption's influence on TB is not statistically significant, a unit increase in silicosis incidence significantly elevates TB deaths (235.9, p = 0.005), YLL (9399.3, p = 0.011), and YLD (910.8, p = 0.002).

CONCLUSION

The burden of silicosis is found to be one of the important determinants of deaths, YLL, and YLD due to tuberculosis. Country-specific strategies to prevent and control silicosis is a need of the hour.

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.

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.

A Descriptive Study of a Turkish Pneumoconiosis Case-Series

BACKGROUND

The study aimed to examine the conditions and factors affecting pneumoconiosis cases to determine the dimensions of the pneumoconiosis problem.

METHODS

This retrospective study was conducted in a tertiary research hospital between January 1, 2014, and December 31, 2021. Five hundred ninety-seven patients with pneumo- coniosis were included in the study.

RESULTS

Large opacities were detected in 157 cases. When we compared cases with and without Pulmonary Massive Fibrosis (PMF), age and concomitant pulmonary disease were higher in PMF cases, which also showed lower FEV1, FVC, and FEV1/FVC. PMF was more frequent in subjects with long dust exposure duration (more than 20 years) and concomitant pulmonary diseases, particularly tuberculosis. Three occupations, sandblasters, dental technicians, and ceramic workers, showed the earliest onset of pneumoconiosis.

CONCLUSIONS

The study presents pneumoconiosis data in a mixed and large population and contributes to the imple- mentation of evidence-based policies and interventions for countries like Turkey striving to cope with the problem of pneumoconiosis.

Otorhinolaryngologic Evaluation of Brick Kiln Workers: ENT Findings of Brick Kiln Workers

Brick kiln workers were evaluated in the field using otorhinolaryngologic and head and neck surgery (ENT) assessments. One-hundred and twenty laborers were assessed. The subjects were divided into three categories according to the work area: before the brick kiln, in the brick kiln, and after the brick kiln. Two evaluations were made, a questionnaire and an ENT examination. If structural changes were observed during the examination, the complication was deemed structural. Seventeen laborers who completed the questionnaire did not participate in the examination. A total of 103 laborers participated in the study: 29 before the brick kiln, 63 in the brick kiln, and 11 after the brick kiln. While general otologic complications were observed in 26 (25.2%) laborers, structural otologic complications were observed in 2 (1.9%). While general nasal complications were observed in 70 (68.0%) laborers, structural nasal complications were observed in 27 (26.2%). Although the general otologic and structural nasal complication rates were higher in the brick kiln group, the general, structural otologic, and nasal complication rates did not reach statistical significance among groups (p > 0.05). Both the general and structural nasal complication rates were significantly higher in laborers who had worked for more than 10 years and did not wear a mask (p < 0.01). We detected prominent nasal pathologies in brick kiln workers in our ENT-based study. These pathologies were much more common in laborers who had worked for over 10 years and did not wear a mask.

Occupational Silica Exposure and Dose-Response for Related Disorders-Silicosis, Pulmonary TB, AIDs and Renal Diseases: Results of a 15-Year Israeli Surveillance

BACKGROUND

The exposure patterns of respirable crystalline silica based on environmental records, as well as the link to different diseases, are not well described.

AIMS AND OBJECTIVES

In this study, we evaluated the risk for various diseases in relation to occupational silica exposure, including Silicosis, pulmonary tuberculosis (TB), Autoimmune disorders (AIDs) and Renal diseases.

METHODS

We assessed the relationship between silica exposure and the rate of various diseases such as silicosis, pulmonary TB, AIDs and renal diseases in a cross-sectional study. We reviewed the medical records and exposure level of workers exposed to silica during the past two decades.

RESULTS

261 workers were included in the study, total duration of exposure 15.6 years (±SD 8.74); 42.15% of them were employed in the artificial marble industry and 29.5% in manufacturing and construction industries. The average yearly silica exposure levels were 0.23 mg/m³ (±0.34). The average cumulative silica concentration was 3.59 mg/m³/y (±4.80). We found 25 (9.58%) incident cases of silicosis, 10 cases of chronic obstructive pulmonary disease (COPD) and emphysema (3.83%), six cases of several AIDs (2.30%), five cases of pulmonary TB (1.92%), three cases of renal diseases (1.15%), two cases of sarcoidosis (0.77%) and no lung cancer cases. When compared to studies with the same endpoint we found excess risk of silicosis (RR = 2.67/0.13 = 20.5, 95% CI 9.85 to 42.86)), pulmonary TB (RR = 30.70, CI 3.43-274.49, p = 0.002) and AIDs (RR = 2.87, 95% CI = 1.27 to 6.48 p = 0.01).

CONCLUSIONS

Silica exposure was a significant risk factor for silicosis, pulmonary TB and AIDs. Our findings are important given persistent worldwide silica-related epidemics in low and high-income countries.

Mortality among mine and mill workers exposed to respirable crystalline silica

BACKGROUND

Millions of workers are potentially exposed to respirable crystalline silica (RCS) which has been associated with several diseases. We updated the mortality experience of a cohort of 2,650 mine and mill workers at four manufacturing facilities to assess cause-specific mortality risks associated with estimated cumulative RCS exposure.

METHODS

Study eligibility was defined as any employee who had ≥1 year of service by 2000, with work history experience available from 1945 through 2004. Vital status and cause of death were ascertained from 1945 through 2015. RCS exposure was estimated across plant-, department-, job-, and time-dependent categories using historic industrial hygiene sampling data and professional judgment. Associations between cumulative RCS (mg/m3-years) and cause-specific mortality were examined using Cox proportional hazard regression models.

RESULTS

In the exposure-response analysis defined on quartiles of cumulative RCS exposure, no increasing trend (ptrend = 0.37) in lung cancer mortality (n = 116 deaths) was observed (Hazard ratio (HR) = 1.00 (referent), 1.20, 1.85, 0.92). Mortality risk for non-malignant respiratory disease was increased across quartiles (HR = 1.00, 1.35, 1.89, 1.70; ptrend = 0.15), based on 83 deaths. Non-malignant renal disease mortality was increased across quartiles (HR = 1.00, 6.64, 3.79, 3.29; ptrend = 0.11), based on 26 deaths.

CONCLUSIONS

After nearly seven decades of follow-up, the exposure-response analyses showed no evidence of a positive trend for lung cancer, and limited evidence of a trend for non-malignant respiratory disease, and non-malignant renal disease mortality as a result of cumulative RCS exposure in this occupational cohort.

Gaseous Air Pollutants and Respirable Crystalline Silica Inside and Outside Homes at Brick Kilns in Bhaktapur, Kathmandu Valley, Nepal

Household and ambient air pollution remain public health problems in much of the world. Brick kiln employees in Nepal may be particularly at risk of high air pollution exposures and resulting health effects due to high levels of outdoor air pollution, substandard housing, and indoor biomass cooking. We conducted a cross-sectional study of indoor and outdoor air pollution concentrations at workers' homes at four fixed chimney Bull's trench brick kilns in Bhaktapur, Kathmandu Valley, Nepal. We measured air concentrations of carbon monoxide (CO), carbon dioxide (CO₂), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and respirable crystalline silica (SiO₂; cristobalite, quartz, tridymite) using established methods and conducted a survey about characteristics of homes or samples that may be associated with air pollution concentrations. Geometric mean concentrations of CO, CO₂, and SiO₂ (quartz) were 0.84 ppm, 1447.34 ppm, and 6.22 µg/m³, respectively, whereas concentrations of all other air pollutants measured below lower detection limits. Most characteristics of homes or samples were not associated with air pollution concentrations. We found a positive association between the variable how long lived in house and SiO₂ (quartz) concentrations, which may reflect sustained take-home exposure to SiO₂ (quartz) over time. Interventions should focus on administrative controls to reduce take-home exposure to SiO₂ (quartz) in this population.

Gene Expression Profiling of Mono- and Co-Culture Models of the Respiratory Tract Exposed to Crystalline Quartz under Submerged and Air-Liquid Interface Conditions

In vitro lung cell models like air-liquid interface (ALI) and 3D cell cultures have advanced greatly in recent years, being especially valuable for testing advanced materials (e.g., nanomaterials, fibrous substances) when considering inhalative exposure. Within this study, we established submerged and ALI cell culture models utilizing A549 cells as mono-cultures and co-cultures with differentiated THP-1 (dTHP-1), as well as mono-cultures of dTHP-1. After ALI and submerged exposures towards α-quartz particles (Min-U-Sil5), with depositions ranging from 15 to 60 µg/cm2, comparison was made with respect to their transcriptional cellular responses employing high-throughput RT-qPCR. A significant dose- and time-dependent induction of genes coding for inflammatory proteins, e.g., IL-1A, IL-1B, IL-6, IL-8, and CCL22, as well as genes associated with oxidative stress response such as SOD2, was observed, even more pronounced in co-cultures. Changes in the expression of similar genes were more pronounced under submerged conditions when compared to ALI exposure in the case of A549 mono-cultures. Hereby, the activation of the NF-κB signaling pathway and the NLRP3 inflammasome seem to play an important role. Regarding genotoxicity, neither DNA strand breaks in ALI cultivated cells nor a transcriptional response to DNA damage were observed. Altogether, the toxicological responses depended considerably on the cell culture model and exposure scenario, relevant to be considered to improve toxicological risk assessment.

Comparing α-Quartz-Induced Cytotoxicity and Interleukin-8 Release in Pulmonary Mono- and Co-Cultures Exposed under Submerged and Air-Liquid Interface Conditions

The occupational exposure to particles such as crystalline quartz and its impact on the respiratory tract have been studied extensively in recent years. For hazard assessment, the development of physiologically more relevant in-vitro models, i.e., air-liquid interface (ALI) cell cultures, has greatly progressed. Within this study, pulmonary culture models employing A549 and differentiated THP-1 cells as mono-and co-cultures were investigated. The different cultures were exposed to α-quartz particles (Min-U-Sil5) with doses ranging from 15 to 66 µg/cm² under submerged and ALI conditions and cytotoxicity as well as cytokine release were analyzed. No cytotoxicity was observed after ALI exposure. Contrarily, Min-U-Sil5 was cytotoxic at the highest dose in both submerged mono- and co-cultures. A concentration-dependent release of interleukin-8 was shown for both exposure types, which was overall stronger in co-cultures. Our findings showed considerable differences in the toxicological responses between ALI and submerged exposure and between mono- and co-cultures. A substantial influence of the presence or absence of serum in cell culture media was noted as well. Within this study, the submerged culture was revealed to be more sensitive. This shows the importance of considering different culture and exposure models and highlights the relevance of communication between different cell types for toxicological investigations.

Internal Exposure and Distribution of Airborne Fine Particles in the Human Body: Methodology, Current Understandings, and Research Needs

Exposure to airborne fine particles (PM_2.5, particulate matter with aerodynamic diameter <2.5 μm) severely threatens global human health. Understanding the distribution and processes of inhaled PM_2.5 in the human body is crucial to clarify the causal links between PM_2.5 pollution and diseases. In contrast to extensive research on the emission and formation of PM_2.5 in the ambient environment, reports about the occurrence and fate of PM_2.5 in humans are still limited, although many studies have focused on the exposure and adverse effects of PM_2.5 with animal models. It has been shown that PM_2.5, especially ultrafine particles (UFPs), have the potential to go across different biological barriers and translocate into different human organs (i.e., blood circulation, brain, heart, pleural cavity, and placenta). In this Perspective, we summarize the factors affecting the internal exposure of PM_2.5 and the relevant analytical methodology and review current knowledge about the exposure pathways and distribution of PM_2.5 in humans. We also discuss the research challenges and call for more studies on the identification and characterization of key toxic species of PM_2.5, quantification of internal exposure doses in the general population, and further clarification of translocation, metabolism, and clearance pathways of PM_2.5 in the human body. In this way, it is possible to develop toxicity-based air quality standards instead of the currently used mass-based standards.

The pro-inflammatory effects of combined exposure to diesel exhaust particles and mineral particles in human bronchial epithelial cells

Background

People are exposed to ambient particulate matter (PM) from multiple sources simultaneously in both environmental and occupational settings. However, combinatory effects of particles from different sources have received little attention in experimental studies. In the present study, the pro-inflammatory effects of combined exposure to diesel exhaust particles (DEP) and mineral particles, two common PM constituents, were explored in human lung epithelial cells.

Methods

Particle-induced secretion of pro-inflammatory cytokines (CXCL8 and IL-1β) and changes in expression of genes related to inflammation (CXCL8, IL-1α, IL-1β and COX-2), redox responses (HO-1) and xenobiotic metabolism (CYP1A1 and CYP1B1) were assessed in human bronchial epithelial cells (HBEC3-KT) after combined exposure to different samples of DEP and mineral particles. Combined exposure was also conducted using lipophilic organic extracts of DEP to assess the contribution of soluble organic chemicals. Moreover, the role of the aryl hydrocarbon receptor (AhR) pathway was assessed using an AhR-specific inhibitor (CH223191).

Results

Combined exposure to DEP and mineral particles induced increases in pro-inflammatory cytokines and expression of genes related to inflammation and redox responses in HBEC3-KT cells that were greater than either particle sample alone. Moreover, robust increases in the expression of CYP1A1 and CYP1B1 were observed. The effects were most pronounced after combined exposure to α-quartz and DEP from an older fossil diesel, but enhanced responses were also observed using DEP generated from a modern biodiesel blend and several stone particle samples of mixed mineral composition. Moreover, the effect of combined exposure on cytokine secretion could also be induced by lipophilic organic extracts of DEP. Pre-incubation with an AhR-specific inhibitor reduced the particle-induced cytokine responses, suggesting that the effects were at least partially dependent on AhR.

Conclusions

Exposure to DEP and mineral particles in combination induces enhanced pro-inflammatory responses in human bronchial epithelial cells compared with exposure to the individual particle samples. The effects are partly mediated through an AhR-dependent pathway and lipophilic organic chemicals in DEP appear to play a central role. These possible combinatory effects between different sources and components of PM warrant further attention and should also be considered when assessing measures to reduce PM-induced health effects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00455-0.

Serum apolipoprotein A-I depletion is causative to silica nanoparticles-induced cardiovascular damage

The rapid development of nanotechnology has greatly benefited modern science and engineering and also led to an increased environmental exposure to nanoparticles (NPs). While recent research has established a correlation between the exposure of NPs and cardiovascular diseases, the intrinsic mechanisms of such a connection remain unclear. Inhaled NPs can penetrate the air-blood barrier from the lung to systemic circulation, thereby intruding the cardiovascular system and generating cardiotoxic effects. In this study, on-site cardiovascular damage was observed in mice upon respiratory exposure of silica nanoparticles (SiNPs), and the corresponding mechanism was investigated by focusing on the interaction of SiNPs and their encountered biomacromolecules en route. SiNPs were found to collect a significant amount of apolipoprotein A-I (Apo A-I) from the blood, in particular when the SiNPs were preadsorbed with pulmonary surfactants. While the adsorbed Apo A-I ameliorated the cytotoxic and proinflammatory effects of SiNPs, the protein was eliminated from the blood upon clearance of the NPs. However, supplementation of Apo A-I mimic peptide mitigated the atherosclerotic lesion induced by SiNPs. In addition, we found a further declined plasma Apo A-I level in clinical silicosis patients than coronary heart disease patients, suggesting clearance of SiNPs sequestered Apo A-I to compromise the coronal protein's regular biological functions. Together, this study has provided evidence that the protein corona of SiNPs acquired in the blood depletes Apo A-I, a biomarker for prediction of cardiovascular diseases, which gives rise to unexpected toxic effects of the nanoparticles.

Silica Dust Exposure Increases Risk for Rheumatoid Arthritis: A Swedish National Registry Case-Control Study

OBJECTIVE

Rheumatoid arthritis (RA) is an inflammatory disease with unknown etiology. This study examines if silica dust exposure increases the risk for seropositive and seronegative RA.

METHODS

A nationwide registry case-control study was conducted that included all cases of RA in Sweden between 2005 and 2016. In total, 31,139 cases with two matched controls were included. A JEM was used to estimate exposure.

RESULTS

Silica dust exposure was associated with a statistically significant increase in odds ratio (OR) for seropositive (OR 1.22, 95% CI 1.05 to 1.40) and seronegative (OR 1.23, 95% CI 1.04 to 1.46) RA among men.

CONCLUSION

This study found an increased OR for RA in silica-exposed men. The OR was equal for seropositive and seronegative RA. These findings further support the hypothesis that silica dust may be a trigger for RA.

Transdisciplinary Online Health Assessment of an Artisanal and Small-Scale Gold Mining Community during the COVID-19 Pandemic in the Mandalay Region of Myanmar

Artisanal and small-scale gold mining (ASGM) has a known negative effect on the community's health; therefore, assessment to monitor community health is essential to detect any issues and enable early treatment. Because ASGM-related health issues are complex and cannot be addressed effectively with a traditional one-time health assessment alone, both long-term and regular health assessments using a transdisciplinary approach should be considered. In response to this need, we designed an online health assessment tool as a reference for a future long-term health assessment system. An online video interview was conducted with 54 respondents living in the ASGM area of Chaung Gyi Village, Thabeikkyin Township, Mandalay Region, Myanmar, via a social networking service application. The tool was used to evaluate community health during the coronavirus 2019 pandemic, including mercury intoxication symptoms, mining-related diseases, and other diseases. Results show that persons working in mining versus non-mining occupations had a greater prevalence of pulmonary diseases, such as pulmonary tuberculosis, silicosis, and bronchial asthma, in addition to malaria. Based on these findings, online health assessment using a transdisciplinary approach can be recommended as an effective tool for sustainable and long-term health assessment of ASGM-related disease and should be performed regularly following physical health surveys.

Tuberculosis Screening in Silica-Exposed Workers : Developing a Tool for Health Care Providers

Both the Occupational Safety and Health Administration and Washington State require safety and health protections for workers exposed to respirable crystalline silica, including tuberculosis (TB) screening as part of occupational medical surveillance. We describe the creation of a TB screening tool for silica-exposed workers receiving regulated medical surveillance examinations in Washington State. The tool provides relevant clinical recommendations to assist health care providers and public health practitioners who choose to use the tool when performing such examinations. A cross-disciplinary team at the Washington State Department of Labor and Industries created the TB screening tool to help health care providers identify silica-exposed workers who should receive a comprehensive evaluation for active TB disease and workers who should or must receive testing for latent TB infection. The Washington State Adult Tuberculosis Screening Tool for Workers Exposed to Respirable Crystalline Silica benefits occupational and respiratory clinicians and public health practitioners by aiding both the individual- and population-level delivery of occupational health and TB screening services to silica-exposed workers receiving required medical surveillance examinations.

Apigenin exerts chemopreventive effects on lung injury induced by SiO2 nanoparticles through the activation of Nrf2

Apigenin (APG) is a flavonoid widely distributed in fruits, vegetables, and herbs, with comprehensive pharmacological effects. In this paper, we report that APG can elicit a protective effect, which is comparable to those induced by gymnoside II/n-BuOH extracts of Bletilla striata, on SiO₂-induced lung injury in vitro and in vivo. In vitro experiments showed that APG (25 μM) could restore the SiO₂-decreased A549 cell viability and lower the apoptotic rate and the production of intracellular reactive oxygen species (ROS) in A549 cells treated with nm SiO₂. Western blot results showed that APG (25 μM) could increase the level of Nuclear factor E2-related factor 2 (Nrf2) and its downstream proteins. In vivo experiments showed that APG (20 mg/kg) could potently alleviate the SiO₂-elicited lung injury by enhancing the Nrf2 expression and thereby suppressing Bax/Bcl-2 pathway. The present study suggests that APG can significantly alleviate the SiO₂-induced lung injury both in vitro and in vivo through, at least partially, activating Nrf2 expression.

Occupational exposure to respirable crystalline silica in municipal household waste collection and road cleaning workers

Despite the increase in the number of cases among South Korean sanitation workers, lung cancer as a result of exposure to occupational carcinogen has not been sufficiently investigated. This study aimed to identify exposure levels of sanitation workers to respirable crystalline silica (RCS) for various tasks and factors that affect individual RCS exposure. Exposure to RCS was assessed for 90 sanitation workers from seven companies. The obtained geometric mean value of the RCS was 2.6 µg m^–3, which is a similar level to recommendations set by California’s Office of Environmental Health Hazard Assessment's Recommended Exposure Limit. Meanwhile, coal briquette ash (CBA) collectors exhibited the highest RCS concentration (24 µg m^–3), followed by road cleaning workers who used a blower, municipal household waste collectors, sweepers, and drivers (p < 0.05). Additionally, when the ANOVA was conducted, statistically significant differences were observed in RCS concentrations among various factors such as job task, season, employment type and city scale. Our study confirmed that sanitation workers who work outdoors could be exposed to RCS. Due to the possibility of exposure to high RCS concentrations, special attention should be paid to the collection of used CBA and road cleaning involving the use of a blower.

Epidemiology of tuberculosis among different occupational groups in Makkah region, Saudi Arabia

Each year in Saudi Arabia, the Hajj season represents one of the world's most significant annual mass gatherings, attracting high proportion of immigrants from different parts of the world in small crowded areas, posing a risk for Tuberculosis (TB) transmission. There is a high potential for TB contact and infection in the workplace as it is transmitted through the air. Most of the studies in Saudi Arabia assessed the TB infection among health care workers. However, the TB incidence rate among other variant occupational groups was not yet determined. This study was conducted to assess the incidence rate of tuberculosis, and determine the risk factors of TB infection among different occupational groups in the Makkah region, Saudi Arabia 2016. A cross-sectional study was carried out based on the secondary data of the patients registered in the Saudi national tuberculosis control and prevention program in 2016. Data were then organized and analyzed for age, gender, nationality, educational level, average monthly wage, average weekly working hours, and occupation of the patients. Occupations were reclassified according to the Saudi Standard Classification of Occupation (SSCO). A total of 1270 cases were included in this study, 300 (23.6%) of them were workers. The incidence rate of TB among workers in the Makkah region was 9 per 100,000 workers compared to 31 per 100,000 persons among the general population in 2016. The TB incidence rate was the highest among occupation of supporting basic engineering with 13 per 100,000 workers in 2016. The highest incidence rate of TB among occupations of supporting basic engineering could be attributed to close contact with the general population in closed spaces for long periods of time, and low socioeconomic status.

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.

Systematic Review and Meta-analysis on the Association of Occupational Exposure to Free Crystalline Silica and Rheumatoid Arthritis

• Occupational exposure to free crystalline silica and tobacco smoking are associated with an increased risk rheumatoid arthritis, with the evidence of an interaction in seropositive subjects.

• Further studies in the field are needed to support such association

We carried out a systematic search for all published epidemiological studies concerning the association between occupational exposure to free crystalline silica (FCS) and subsequent development of rheumatoid arthritis (RA). A meta-analysis was conducted on relevant studies. We searched PubMed and Embase, search engines, for original articles published (from 1960 to November 2019) in any language. In addition, we also searched reference lists of included studies manually for additional relevant articles. Finally, twelve studies were included in the meta-analysis (seven case-control cases and five cohort studies). The odds risks and 95% confidence interval (CI) were calculated using a random effect meta-analysis. A primary meta-analysis (using a random effect model)—regarding RA risk in subjects exposed to FCS—yelled to an overall OR of 1.94 (95% CI 1.46–2.58). We also conducted three further meta-analysis, taking into account the presence of autoantibodies (anti-RF or anti-ACPA) and smoking habits and found a significant association between FCS and RA in both seropositive and seronegative subjects (OR 1.74, 95% CI 1.35–2.25 and OR 1.23, 95% CI 1.06–1.4, respectively) and in seropositive subjects which were smokers (OR 3.30, 95% CI 2.40–4.54). The studies that have investigated the association between RA and occupatational exposure to FCS are still scarce and the heterogeneity between the studies remains high. Some critical limitations have been identified within studies, among which, the methods for assessing exposure stand out. Although with due caution, our results confirm the hypothesis of an association between occupational exposure to FCS and RA development. There was an interaction between FCS and tobacco smoking in RA seropositive workers.

Silicosis, progressive massive fibrosis and silico-tuberculosis among workers with occupational exposure to silica dusts in sandstone mines of Rajasthan state: An urgent need for initiating national silicosis control programme in India

Context:

Silicosis is a progressive, irreversible and incurable respiratory morbidity and often becomes a cause for pre-mature mortality among occupationally silica dust-exposed workers in India and similar countries. It has a dual problem of associated silico-tuberculosis as a co-morbidity. The present study was done to assess the respiratory morbidity caused by silicosis in sandstone mine of Rajasthan, India.

Methods:

The chest X-rays of 529 subjects having history of employment in stone mines with respiratory morbidity were subjected for this study and evaluated in accordance with ILO Classification 2000. The X-rays were classified into various categories of silicosis and progressive massive fibrosis (PMF) in relation to years of work in stone mines.

Results:

Out of 529 chest radiographs evaluated, 275 (52%) showed radiological evidence of silicosis. Of them, 40 (7.5%) subjects showed large opacities suggestive of progressive massive fibrosis. Both silicosis and progressive massive fibrosis were associated with increasing duration of work in stone mines. Sixty-one (12.4%) subjects with silicosis also had associated pulmonary tuberculosis, termed as silico-tuberculosis.

Conclusion:

The present study showed a high prevalence of silicosis, progressive massive fibrosis and silico-tuberculosis among stone mine workers. It appears that that unless silicosis is controlled, elimination of tuberculosis is far from reality in the country. Hence, states and central authorities must work together towards control of both silicosis as well as silico-tuberculosis. Similarly, there is an urgent need of initiation of national silicosis control programme, similar to existing national tuberculosis control programme, considering the huge burden of silicosis in India

Mini-review: Silico-tuberculosis

Silicosis continues to be a serious health issue in many countries and its elimination by 2030 (a target set by WHO and the International Labour Organization in 1995) is virtually impossible. The risk to develop pulmonary tuberculosis for silicosis patients is higher than for non-silicosis people, and there is also an increased risk of both pulmonary and extrapulmonary tuberculosis in individuals exposed to silica. HIV coinfection adds further to the risk, and in some countries, such as South Africa, miners living with HIV are a considerable number. The diagnosis of active tuberculosis superimposed on silicosis is often problematic, especially in initial phases, and chest X-ray and smear examination are particularly important for the diagnosis of pulmonary tuberculosis. Treatment is difficult; directly observed therapy is recommended, a duration of at least eight months is probably needed, drug reactions are frequent and the risk of relapse higher than in non-silicosis patients. TB prevention in silicosis patients is essential and include active surveillance of the workers, periodic chest X-rays, tuberculin skin test or interferon-gamma releasing assay testing, and, importantly, adoption of measures to reduce the exposure to silica dust. Chemoprophylaxis is possible with different regimens and needs to be expanded around the world, but efficacy is unfortunately limited. Silico-tuberculosis is still a challenging health problem in many countries and deserves attention worldwide.

n-BuOH extract of Bletilla striata exerts chemopreventive effects on lung against SiO2 nanoparticles through activation of Nrf2 pathway

BACKGROUND

SiO₂ nanoparticles (nm SiO₂) are ubiquitous in daily life and are acknowledged to be detrimental to human health. Bletilla striata is a traditional medicine used for generations in China and its polysaccharide has the anti-pulmonary fibrosis effect.

PURPOSE

To investigate the lung protective effect of the small molecules (n-BuOH extract) of B. striata and clarify the underlying mechanism.

STUDY DESIGN AND METHODS

C57BL/6 mice were subjected to intratracheal instillation with nm SiO₂ nanoparticle suspension (7 mg/kg) to construct the in vivo model of nm SiO₂-induced lung injury. The chemical profile of the n-BuOH extract of B. striata was investigated by HPLC analysis using authentic samples isolated from B. striata. Gymnoside II with the most potent chemoprotective capacity in the n-BuOH extract was used to clarify the potential bio-active molecular basis of the n-BuOH extract using in vitro experiments. The cytotoxicity, apoptosis, oxidative stress, and the Nrf2 signaling pathway were examined in SiO₂-induced A549 cells. ML385 was adopted to down-regulate the Nrf2 expression.

RESULTS

The n-BuOH extract of B. striata (40 mg/kg) could alleviate the SiO₂-induced lung injury by increasing Nrf2 expression and thereby suppressing Bax/Bcl-2 pathway in the nm SiO₂-induced mice model. The chemical profile study showed that militarine, gymnoside II, and 4-allyl-2, 6-dimethoxyphenol glucoside were the main constituents of n-BuOH extract. Studies on gymnoside II revealed that it could partially restore the SiO₂-induced decline in cell viability while did not affect the growth of normal A549 cells within the concentration range of 1-50 μM, suggesting a protective effect against nm SiO₂ in lung A549 cells. The hoechst 33258 staining, flow cytometry, and western blot experiments demonstrated that gymnoside II (25 μM) could partially reverse the SiO₂-induced cell apoptosis and ROS production by enhancing Nrf2, HO-1, and γ-GCSc expressions and Nrf2 silencing by ML385 abrogated the effects of gymnoside II (25 μM) on apoptosis and ROS production in A549 cells.

CONCLUSION

The present study suggests that in addition to the polysaccharide, small molecules (n-BuOH extract) of B. striata can also elicit a protective effect on lung injuries through the Nrf2-dependent mechanism and gymnoside II is one of the main bio-active constituents contributing to the n-BuOH extract-elicited lung protective effect against nm SiO₂.

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.

Mortality in Underground Miners in a Former Uranium Ore Mine–Results of a Cohort Study Among Former Employees of Wismut AG in Saxony and Thuringia

BACKGROUND

From 1946 to 1990, more than 400 000 people were employed by Wismut AG, a Soviet/Soviet-German corporation (German abbreviation: SAG/ SDAG), in the East German states of Saxony and Thuringia. In the early years in particular, employees were exposed to large amounts of radon and respirable crystalline silica.

METHODS

In a cohort of 35 204 former underground employees of Wismut AG, mortality was analyzed in comparison to the general male population of East Germany, and the pertaining standardized mortality ratios (SMRs) were calculated.

RESULTS

18 510 persons in the study cohort died in the follow-up period 1960-2013. Mortality from lung cancer was 2.36 higher in the study cohort than in the general population (95% confidence interval, [2.28; 2.45]); the associated SMRs rose markedly with increasing radon exposure. Mortality from silicosis and other types of pneumoconiosis was elevated by a factor of 22.62 [21.20; 24.11], and the associated SMRs rose exponentially with increasing exposure to respirable crystalline silica. Mortality from both of these causes was still markedly elevated more than 20 years after Wismut AG had ceased its activities. Mortality from a wide range of other diseases was elevated as well, with the following SMRs: stomach cancer, 1.28 [1.17; 1.40]; liver cancer, 1.34 [1.15; 1.55]; all tumors other than lung cancer, 1.06 [1.02; 1.09]; infections, 1.18 [1.01; 1.38]; cerebrovascular diseases, 1.33 [1.26; 1.41]; and influenza/pneumonia, 1.13 [1.01; 1.27]. Mortality from a small number of other causes was found to be markedly lowered in the study cohort (mental illness, renal diseases, and nervous system diseases). The role of occupational risk factors, lifestyle differences and other reasons for the latter results is unclear.

CONCLUSION

Underground miners employed by Wismut AG displayed marked excess mortality due to silicosis/other pneumoconiosis and lung cancer. The contribution of individual occupational risk factors for these and other causes of death with increased SMR are being further investigated in analyses within the study cohort.

Inhalants other than personal cigarette smoking and risk for developing rheumatoid arthritis

PURPOSE OF REVIEW

The current review summarizes the current evidence on inhalants other than personal cigarette smoking and risk for developing rheumatoid arthritis (RA).

RECENT FINDINGS

Personal cigarette smoking has been implicated as an environmental risk factor for seropositive RA, perhaps by inducing autoimmunity at pulmonary mucosa. Since many patients with RA are nonsmokers, other inhalants are being investigated as potential RA risk factors. Recent case-control and cohort studies have investigated passive cigarette smoking, air pollution, inhalant-related occupations, silica, pesticides, household environment, and allergic inhalants as inhalant exposures for RA risk. Inhalant-related occupations and silica inhalants have the most consistent evidence for associations with increased RA risk. However, most studies relied on retrospective designs and had limited ability to adjust for personal cigarette smoking or investigate associations among nonsmokers.

SUMMARY

Several inhalants other than personal cigarette smoking may be associated with increased risk for developing RA. These results support the hypothesis that inhalants, pulmonary mucosal inflammation, and RA pathogenesis may be linked. Future studies are needed to firmly establish the independence of these findings from personal cigarette smoking and to determine the specific inhalants and biologic mechanisms related to RA pathogenesis.

Utility of PET/CT in the diagnosis and staging of lung cancer after ecobronchoscopy in mining population

INTRODUCTION

Positron emission tomography (PET) with computerized axial tomography (CT) in a single device is known as PET/CT. It has been widely documented and validated, and it is currently a core part of the diagnosis and staging of lung cancer. However, its reliability has not been analysed in specific populations. The objective of this study is to determine the usefulness of PET/CT in patients exposed to mining activities in which an endobronchial ultrasound (EBUS) has been performed for the diagnosis and/or staging of lung cancer.

PATIENTS AND METHODS

With a prospective and real-time database, all the patients who had undergone an EBUS with suspicion of lung cancer and who had previously undergone a PET/CT were selected. The observation unit was the lymph node and, based on their history of exposure to mining activities, the sample was divided into two categories, group 1: not exposed; and group 2: exposed. In each group, and with the results from anatomical pathology as a dependent variable, logistic models were established to look for independent risk factors for malignancy.

RESULTS

In group 1, lymph nodes larger than 1 cm and PET/CT uptake with maximum standardized uptake value (SUVmax) over 2.5 were independent risk factors for malignancy. However, in group 2 (exposed patients), none of those factors were predictors for malignancy.

DISCUSSION

In the population of individuals with occupational exposure to mining, PET/CT is an imaging technique with diagnostic limitations for lung cancer.

Induction of DNA damage as a consequence of occupational exposure to crystalline silica: A review and meta-analysis

About 40 million workers are occupationally exposed to crystalline silica (CS) which was classified as a human carcinogen by the IARC. It is assumed that damage of the genetic material via inflammation and reactive oxygen species by CS lead to formation of malignant cells. We conducted a systematic literature search to find out if inhalation of CS containing dusts at workplaces causes damage of the genetic material. Thirteen studies were found eligible for this review, in most of them (n = 9) micronuclei (MN) which reflect structural/numerical chromosomal aberrations were monitored in lymphocytes and/or in exfoliated buccal cells. In 5 investigations DNA damage was measured in blood cells in single cell gel electrophoresis (comet) experiments. Frequently studied groups were potters, stone cutters, miners and construction workers. Results of meta-analyses show that exposure to CS causes formation of MN and DNA breaks, the overall ratio values were in exposed workers 2.06- and 1.96-fold higher than in controls, respectively. Two studies reported increased levels of oxidized guanine, and higher levels of DNA adducts with malondialdehyde indicating that exposure to CS leads to oxidative damage. The exposure of the workers to CS was quantified only in two studies, information concerning the size and chemical structures of the particles is lacking in most investigations. Therefore, it is not possible to use the results to derive occupational exposure limits of workers to CS which vary strongly in different countries. Nevertheless, the evaluation of the current state of knowledge shows that biomonitoring studies in which damage of the genetic material is measured in CS exposed workers can contribute to assess adverse health effects as consequence of DNA instability in specific occupations.

Sarcoidosis and silica dust exposure among men in Sweden: a case-control study

OBJECTIVE

To determine whether occupational exposure to silica dust is associated with an increased risk of developing sarcoidosis.

DESIGN

Case-control study of all individuals between 20 and 65 years of age diagnosed with sarcoidosis (D86) in Sweden between 2007 and 2016. Controls were matched to cases (2:1) based on age, sex and county at the time of diagnosis. A Job Exposure Matrix was used to estimate the occupational silica exposure of all cases and controls.

SETTING

Medical and occupational data from the National Outpatient Register were used to implement a case-control analysis, while the two controls used for each case were selected from the National Register of the Total Population. Information about occupation and time of employment were collected from the Swedish Occupational Register.

PARTICIPANTS

All men and women aged 20-65 years old who were diagnosed sarcoidosis (D86) from 2007 to 2016 were included and assigned two controls.

MAIN OUTCOMES

Silica dust exposure correlates with an increased risk of developing sarcoidosis in men.

RESULTS

The prevalence of silica exposure at work was statistically significantly higher among male cases than controls (OR 1.27, 95% CI 1.13 to 1.43). For men of an age of 35 years or younger the correlation seems to be stronger (OR 1.48, 95% CI 1.1 to 1.87) than in older men (OR 1.21, 95% CI 1.05 to 1.39). For men older than 35 with exposure to silica the prevalence of sarcoidosis increased with the exposure time, with an OR of 1.44 (95% CI 1.04 to 2.00) for exposure of more than 10 years.

CONCLUSIONS

Occupational exposure to silica dust seems to increase the risk of sarcoidosis among men between 20 and 65 years of age. The risk is higher among exposed men 35 years or younger and older men with longer exposure (>6 years).

Pulmonary Tuberculosis among Stone Miners of India vis-à-vis Silica Exposure

Background:

Tuberculosis is one of the biggest public health concerns in India with a prevalence of 195 cases per 100000. Silica is cytotoxic to macrophage which is primary defense mechanism to tubercular bacilli and, hence, exposure to silica dust increases risk for TB. Silica exposed persons are at 2.8 to 39 times greater risk of affected by pulmonary tuberculosis in comparison to healthy subjects.

Methodology:

A cross-sectional epidemiological study was conducted among 935 workers in sandstone mining. Full-size posteroanterior view (PA) chest X-ray in full inspiration was evaluated and evidence of tuberculosis was noted. Fourier transform infrared spectrophotometer was used for determining the free silica in 23 dust samples.

Results:

6.4% X-rays showed evidence of TB and silica dust concentration was 0.11 to 0.16 mg/m³. The TB cases significantly increased from 2% to 6% to 12.7% as the work exposure increased from <10 years to 11–20 years to >20 years respectively. 8.5% of the TB cases were seen among the workers having more than 10 years of work exposure. The odds ratio (95% CI) for work exposure more than 10 years to less than 10 years was 4.53 (1.92–10.65).

Conclusion:

Reduction of silica particles from work environment can significantly reduce the number of TB cases and hence wet drilling should be practiced and personal protective equipment should be regularly used.

Segregation of respirable dust for chemical and toxicological analyses

Respirable dust can pass beyond ciliated airways of the respiratory tract and influence adverse health effects. Health effects can be studied using samples generated from bulk dust segregation. Because previous segregation methods diverge from size-selection criteria of the international convention for respirable particles (ICRP), a method was developed to approximate the ICRP. The method was compared to an ideal sampler by measuring the sample collection bias. The comparison shows that the uncertainty due to the bias was 0.10 based on European Standard EN13205:2014 criteria, which indicates that the segregator effectively follows the ICRP. Respirable particle size distributions were confirmed by an aerodynamic particle sizer and by computer-controlled scanning electron microscopy. Consequently, a systematic way to generate respirable powders for health effects studies and chemical analyses was developed.

Silica dust and sarcoidosis in Swedish construction workers

Background

The aetiology of sarcoidosis is not well established. In previous studies, smoking has been negatively associated with sarcoidosis and there are some indications of an association between exposure to silica dust and sarcoidosis.

Aims

To study the risk of sarcoidosis in relation to silica dust exposure.

Methods

A longitudinal cohort of construction workers linked with a registry of Swedish inpatient diagnoses. Workers were designated as exposed or unexposed to silica based on job titles in a job–exposure matrix. The relative risk (RR) was analysed with Poisson regression adjusting for age and smoking.

Results

We identified 371 cases of sarcoidosis among 297 917 male workers. There was an increased risk of sarcoidosis in the medium- to high-exposure group [RR 1.83 (95% confidence interval {CI} 1.14–2.95)]. A stratified analysis according to smoking showed that ever-smoking workers had an increased risk of sarcoidosis if highly exposed to silica dust [RR 2.44 (95% CI 1.37–4.33)] compared to non-exposed ever-smokers. The risk of non-smokers highly exposed to silica was not significantly increased [RR 1.07 (95% CI 0.72–1.58)] compared to non-exposed non-smokers.

Conclusion

The study indicates an increased risk of developing sarcoidosis in ever-smoking men exposed to silica.

Pro-inflammatory effects of crystalline- and nano-sized non-crystalline silica particles in a 3D alveolar model

BACKGROUND

Silica nanoparticles (SiNPs) are among the most widely manufactured and used nanoparticles. Concerns about potential health effects of SiNPs have therefore risen. Using a 3D tri-culture model of the alveolar lung barrier we examined effects of exposure to SiNPs (Si10) and crystalline silica (quartz; Min-U-Sil) in the apical compartment consisting of human alveolar epithelial A549 cells and THP-1-derived macrophages, as well as in the basolateral compartment with Ea.hy926 endothelial cells. Inflammation-related responses were measured by ELISA and gene expression.

RESULTS

Exposure to both Si10 and Min-U-Sil induced gene expression and release of CXCL8, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α) and interleukin-1β (IL-1β) in a concentration-dependent manner. Cytokine/chemokine expression and protein levels were highest in the apical compartment. Si10 and Min-U-Sil also induced expression of adhesion molecules ICAM-1 and E-selectin in the apical compartment. In the basolateral endothelial compartment we observed marked, but postponed effects on expression of all these genes, but only at the highest particle concentrations. Geneexpressions of heme oxygenase-1 (HO-1) and the metalloproteases (MMP-1 and MMP-9) were less affected. The IL-1 receptor antagonist (IL-1RA), markedly reduced effects of Si10 and Min-U-Sil exposures on gene expression of cytokines and adhesion molecules, as well as cytokine-release in both compartments.

CONCLUSIONS

Si10 and Min-U-Sil induced gene expression and release of pro-inflammatory cytokines/adhesion molecules at both the epithelial/macrophage and endothelial side of a 3D tri-culture. Responses in the basolateral endothelial cells were only induced at high concentrations, and seemed to be mediated by IL-1α/β released from the apical epithelial cells and macrophages.

Silibinin Attenuates Silica Dioxide Nanoparticles-Induced Inflammation by Suppressing TXNIP/MAPKs/AP-1 Signaling

Silica dioxide nanoparticles (SiONPs) have been applied to several fields, such as drug delivery and gene therapy. However, SiONPs are a constituent of fine dust and can induce excessive inflammatory responses in the lungs via the airways. Silibinin, a major component of silymarin, has been known for its anti-oxidant and anti-inflammatory effects. In the present study, we explored the protective effects of silibinin against SiONPs-induced airway inflammation and explored its underlying mechanism of action, focusing on thioredoxin-interacting protein (TXNIP)/mitogen-activated protein kinases (MAPKs) in vitro and in vivo. In SiONPs-stimulated NCI-H292 airway epithelial cells, silibinin treatment effectively suppressed the elevation of the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β, which was accompanied by the reduction in the expression of TXNIP, MAPKs, and activator protein-1 (AP-1). In SiONPs-treated mice, silibinin administration inhibited the increase in inflammatory cell counts and proinflammatory mediators, and it alleviated airway inflammation by SiONPs exposure. In addition, silibinin administration effectively suppressed the elevation of TXNIP/MAPKs/AP-1 signaling by SiONPs exposure. Taken together, silibinin effectively inhibited SiONPs-induced inflammatory responses, and this effect was closely related to the inhibition of TXNIP/MAPK/AP-1 signaling. These results suggested that silibinin might be useful for reducing pulmonary inflammation induced by SiONPs.

The Occupational Burden of Nonmalignant Respiratory Diseases. An Official American Thoracic Society and European Respiratory Society Statement

Rationale: Workplace inhalational hazards remain common worldwide, even though they are ameliorable. Previous American Thoracic Society documents have assessed the contribution of workplace exposures to asthma and chronic obstructive pulmonary disease on a population level, but not to other chronic respiratory diseases. The goal of this document is to report an in-depth literature review and data synthesis of the occupational contribution to the burden of the major nonmalignant respiratory diseases, including airway diseases; interstitial fibrosis; hypersensitivity pneumonitis; other noninfectious granulomatous lung diseases, including sarcoidosis; and selected respiratory infections. Methods: Relevant literature was identified for each respiratory condition. The occupational population attributable fraction (PAF) was estimated for those conditions for which there were sufficient population-based studies to allow pooled estimates. For the other conditions, the occupational burden of disease was estimated on the basis of attribution in case series, incidence rate ratios, or attributable fraction within an exposed group. Results: Workplace exposures contribute substantially to the burden of multiple chronic respiratory diseases, including asthma (PAF, 16%); chronic obstructive pulmonary disease (PAF, 14%); chronic bronchitis (PAF, 13%); idiopathic pulmonary fibrosis (PAF, 26%); hypersensitivity pneumonitis (occupational burden, 19%); other granulomatous diseases, including sarcoidosis (occupational burden, 30%); pulmonary alveolar proteinosis (occupational burden, 29%); tuberculosis (occupational burden, 2.3% in silica-exposed workers and 1% in healthcare workers); and community-acquired pneumonia in working-age adults (PAF, 10%). Conclusions: Workplace exposures contribute to the burden of disease across a range of nonmalignant lung conditions in adults (in addition to the 100% burden for the classic occupational pneumoconioses). This burden has important clinical, research, and policy implications. There is a pressing need to improve clinical recognition and public health awareness of the contribution of occupational factors across a range of nonmalignant respiratory diseases.

Cytotoxic and genotoxic potential of respirable fraction of composite dust on human bronchial cells

OBJECTIVE

To determine the cytotoxic and genotoxic potential of the respirable fraction of composite dust (<4 μm) on human bronchial epithelial cells.

METHODS

Composite sticks of three commercial dental composites (Filtek Supreme XTE, Grandio, Transbond XT) were ground in an enclosed plexiglass chamber with a rough dental bur (grain-size 100 μm) and the generated airborne respirable dust was collected in a personal cyclone on a teflon filter (pore size 5 μm). Immediately after particle collection, the dust was quantified gravimetrically and the particles were suspended in cell culturing medium. Next, human bronchial epithelial cells (16HBE14o-) were exposed to the suspensions (3 μg/ml-400 μg/ml). After 24 h, cell viability (WST-1 assay) and membrane integrity (LDH assay) were evaluated. Furthermore, the genotoxic effect of a sub-cytotoxic concentration (50 μg/ml) of composite dust was evaluated by the comet assay after 3 h exposure and cell cycle disturbances were analyzed by flow cytometry. Cellular uptake of particles was evaluated by transmission electronic microscope (TEM).

RESULTS

For all three tested composite materials, a decrease in metabolic activity of 10-35% was observed when the cells were exposed to the highest concentrations (100 μg/ml-400 μg/ml). Toxicity was partially linked to membrane disruption especially after 72 h exposure. All tested composites provoked a mild genotoxic effect after short-term exposure compared to the control groups. TEM revealed that respirable particles of all tested composites were taken up by the cells.

SIGNIFICANCE

The respirable fraction of composite dust only showed cytotoxic effects at the highest concentrations, whereas mild genotoxicity was observed after exposure to a sub-cytotoxic concentration.

Evaluation of Occupational Exposure to Silica Dust in Mining Workers in Eastern Iran

Background and Objective:

Silica dust is present in almost all mining operations and can cause various health problems such as silicosis in workers. The present study aimed to determine the total and respirable dust levels and the crystalline silica content of the soil in the breathing zone of workers in Iranian mines.

Methods:

This cross-sectional study was carried out in 2016-2017 on six Iranian silica mines. Dust sampling was performed according to the National Institute of Occupational Safety and Health (NIOSH) method No. 0600. The samples were collected from the respiratory zone of workers at 114 stations in different units of the mines. The silica content was measured using the standard NIOSH method No. 7601. The crystalline silica content in bulk samples collected from the soil was determined by using the X-Ray Diffraction (XRD) spectroscopy method.

Results:

The highest concentration of crystalline silica dust was 2.81±0.49 mg/m3 and was observed in the air of crushing unit of mine no. 6, and the lowest was 0.08±0.208 mg/m3 and was measured in the management/administration unit of mine no.1. The mean silica content in the solid surface of the mines was 91%. The total and respirable dust levels in all units of the mines except management/administration were higher than the permissible limit. The free silica content of all collected samples was substantially higher than the permissible limits, and in some cases, it was as much as 100 times above the standard level, which reflects the extremely high risk of working in these mines.

Conclusion:

Exposure of workers with crystalline silica dust in all units was higher than the standard recommended limits. It is imperative to adopt immediate measures based on technical, managerial, and personal protection solutions to reduce the exposure of workers to silica.

Multiorgan accelerated silicosis misdiagnosed as sarcoidosis in two workers exposed to quartz conglomerate dust

Introduction

Clusters of silicosis cases have been reported in the fabrication of quartz conglomerate, a new high-silica-content artificial stone for kitchen and bathroom benchtops (countertops).

Aim

We describe two cases of accelerated-type silicosis with hepatic granulomas arising in workers exposed to artificial quartz conglomerates.

Methods

A confident diagnosis of multiorgan silicosis was based on high level of respirable silica in the workplace, typical radiological alterations in chest high-resolution CT, histological findings in the lung and liver, and detection of silica crystals in both tissues by phase-contrast polarising light microscopy and scanning electron microscopy and energy dispersive spectroscopy.

Results

The development of the disease <10 years after the first exposure is consistent with an accelerated-type of silicosis. Compared with other studies related to quartz conglomerate exposure, we determined that the levels of airborne crystalline silica during activity in the finishing area were between 0.260 and 0.744 mg/m3, that is, much higher than the threshold limit value according to American Conference of Governmental Industrial Hygienists (0.025 mg/m3). Moreover, liver granulomas were associated with accumulation of crystalline silica particles in the hepatic tissue.

Conclusions

Quartz conglomerate fabrication is a potentially dangerous occupation. General practitioners and physicians should have awareness of this newly described occupational hazard. Accurate occupational history is critical in avoiding misdiagnosis, as silicosis caused by inhalation of dust from artificial quartz conglomerates may exhibit atypical presentation. These features seem to be related to the extremely high level of silica exposure and, possibly, to an increased toxicity of the dust generated in this process.