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

Global scenario of silica-associated diseases: A review on emerging pathophysiology of silicosis and potential therapeutic regimes

Silicosis is an occupational fibrotic lung disease caused by exposure to respirable crystalline silica dust particles produced during industrial activities. Other crystalline silica-induced pulmonary disorders include a predisposition to mycobacterial infections, obstructive airway diseases, idiopathic pulmonary fibrosis, and lung cancer. This review paper discusses the burden of silicosis and associated co-morbidities in developed as well as developing countries globally using the published data of various government agencies, related organizations, and epidemiological findings. Moreover, it sheds light on diverse mechanisms of silicosis, outlining molecular events and peculiar alterations in lung parenchyma leading to this occupational lung disease. Evaluation of pathophysiological mechanisms could aid in the identification of novel target molecules and treatments; to date, there is no curative treatment for silicosis. In recent periods, a lot of attention has been focused on the development and fabrication of suitable nanocarriers for improved and sustained drug delivery in the pulmonary system. Nanoparticle-based therapeutic modality has been evaluated in in-vitro and ex-vivo silicosis models for prolongation of drug activity and improved therapeutic outcomes. The preclinical findings open the doors to clinical trials for operational and regenerative nanoformulations, which eventually create a positive change in medical practice. The following review summarizes various therapeutic approaches available and in the pipe line for silicosis and also stresses the preventive practices for effectively combating this occupational hazard.

Critical evaluation of analytical methods for detection of respirable crystalline silica in dust-a review

Respirable crystalline silica (RCS) exposure is closely associated with the development of silicosis, underscoring the critical need for the accurate identification of RCS in workplace dust. Occupational health standards currently define the RCS exposure limit for an 8-hour shift and its measurement methods. However, there remains a gap in analyzing low-concentration samples and the detection of acute, high-intensity RCS exposure during specific short-term tasks or shifts. Addressing this gap is essential for facilitating rapid on-site decision-making and effectively mitigating hazards. This review evaluates current analytical methods for RCS detection and explores potential improvements to address these challenges. Established detection techniques, including the pyrophosphoric acid method, colorimetry, infrared spectrometry (IR), and X-ray diffraction (XRD), have been widely used; however, they exhibit certain limitations, such as low efficiency, limited sensitivity, and a prolonged analysis period. In recent years, both innovative technologies and refinements of traditional methods have emerged to address these shortcomings. The application of more potent laser sources, as seen in quantum cascade laser-based infrared spectroscopy (QCL-IR), has paved the way for the creation of sensitive filter-based laboratory protocols and portable sensors capable of near-real-time measurements of crystalline silica aerosol. Raman spectroscopy provides high sensitivity for detecting low-concentration RCS exposures. Beyond these advancements, additional techniques such as laser-induced breakdown spectroscopy (LIBS), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and photoacoustic spectroscopy (PAS) offer fresh perspectives on RCS measurements. The focus of RCS detection in workplace dust is shifting towards on-site, rapid assessment methods. This involves the use of portable, high-sensitivity equipment to provide real-time evaluation of workers' RCS exposure, which is crucial for promptly identifying hazardous levels, thereby improving worker safety and health. These advancements have the potential to impact occupational health practices by enabling immediate decision-making and effective risk mitigation.

Respirable dust and respirable crystalline silica exposures among workers at stone countertop fabrication shops in Georgia from 2017 through 2023

OBJECTIVES

This longitudinal study examines the severity of worker exposure to respirable crystalline silica (RCS) and respirable dust and demonstrates the need for increased education and implementation of both appropriate engineering controls and respiratory protection (RP) programs for stone fabricator shops, given the growing global number of accelerated silicosis cases associated with the fabrication of engineered stone (ES) countertops.

METHODS

Personal air sampling results and detailed job description notes obtained from 17 industrial hygiene air sampling visits conducted at 11 stone fabrication facilities between 2017 and 2023 in Georgia were used to align similar exposure groups (SEGs) for tasks for workers performing stone fabrication. Bayesian decision analysis was used to determine appropriate RP selection recommendations for the 4 proposed SEGs: SEG1-Support, SEG2-Automated Tool Operator, SEG 3-Small Tool Operator, and SEG 4-Fabrication/Lamination.

RESULTS

The analysis concluded that all employees in stone fabrication shops that process ES should wear a respirator with a minimum assigned protection factor (APF) of 10, regardless of the engineering controls in place. For SEG 4, it is recommended that workers use respirators with an APF between 50 and 1,000. Among the 75 full-shift personal air samples for RCS dust, 41 samples (53%) exceeded the permissible exposure limit of 50 µg/m³.

CONCLUSIONS

This is the first study to present the 4 SEG categories with sampling data to support the importance of including all employees (even support workers) in RP programs, exposure monitoring, and medical surveillance.

RECOMMENDATION AND IMPLICATIONS

Employers, occupational health professionals, and inspectors may use these SEG categories and corresponding RP recommendations to determine if employees have received appropriate RP for workers at stone countertop fabrication shops.

Correlation between occupational hazard exposure and abnormal bone mineral density in steelworkers

OBJECTIVES

To investigate the relationships between abnormal bone mineral density (BMD) and exposure to single or combined occupational hazards in steelworkers by analyzing the correlations between various occupational hazards (night-shift work, high temperature, dust and noise) and abnormal BMD with both a single-risk score model (SRSM) and a hybrid-risk score model (HRSM).

METHODS

Participants were selected from a cross-sectional study called "Cohort Study on the Health Effects of the Occupational Population in the Beijing-Tianjin-Hebei Region". A total of 6816 participants were recruited for this study. Night-shift work and high temperature, dust and noise exposure were considered occupational hazards and were analyzed separately and in combination (coexposure). The health risk factor score and partial regression coefficient were used to establish an SRSM and an HRSM.

RESULTS

The rate of abnormal BMD in steelworkers was 27.6% (28.0% in males and 23.3% in females). Logistic regression revealed that, compared with that of individuals with 0 cumulative days of night-shift work, the risk of abnormal BMD for individuals with various amounts of night-shift work was as follows: ~927.20 days (OR = 1.40, 95% CI: 1.15 ~ 1.72), ~ 1772.02 days (OR = 1.45, 95% CI: 1.19 ~ 1.77), and ≥ 2573.50 days (OR = 1.55, 95% CI: 1.27 ~ 1.89). Compared with that of the cumulative exposure to high temperatures in the 0 °C·y group, the risk of abnormal BMD in the other groups was as follows: 667.49~°C·y (OR = 1.34, 95% CI: 1.06 ~ 1.71) and ≥ 790.30 °C·y (OR = 1.32, 95% CI: 1.03 ~ 1.69). Compared with that of the cumulative amount of dust exposure in the 0 mg/m3·y group, the risk of abnormal BMD for the other groups was as follows: 30.42 ~ mg/m³·y (OR = 1.23, 95% CI: 1.02 ~ 1.49) and ≥ 40.17 mg/m³·y (OR = 1.37, 95% CI: 1.14 ~ 1.65). Compared with that of the cumulative amount of noise exposure in the 0 dB(A)·y group, the risk of abnormal BMD for the other groups was as follows: ≥1707.47 dB(A)·y (OR = 1.17, 95% CI: 1.00 ~ 1.40). When an SRSM was used, compared with that in the control group (score < 0.42), the risk of abnormal BMD in the other groups was as follows: ~0.42 (OR = 1.24, 95% CI: 1.03 ~ 1.19), ~ 0.72 (OR = 1.51, 95% CI: 1.24 ~ 1.83), and ≥ 0.97 (OR = 2.11, 95% CI: 1.71 ~ 2.60). When an HRSM was used, compared with that of the reference group (score < 0.360), the risk of abnormal BMD for the other groups was as follows: ~0.360 (OR = 1.26, 95% CI: 1.05 ~ 1.52), ~ 0.576 (OR = 1.43, 95% CI: 1.18 ~ 1.74), and ≥ 0.779 (OR = 2.08, 95% CI: 1.70 ~ 2.55).

CONCLUSIONS

(1) Night-shift work and high temperature and dust exposure may contribute to abnormal BMD in steelworkers. (2) The higher the corresponding risk score of occupational hazard coexposure is, the greater the risk of abnormal BMD in steelworkers. When workers are exposed to multiple occupational hazards at the same time, coexposure models could reveal the relationships between occupational hazard exposure and abnormal BMD in steelworkers more accurately.

A review of silicosis and other silica-related diseases in the engineered stone countertop processing industry

BACKGROUND

Engineered stone (ES), a material that has become widespread for its use in kitchen and bathroom countertops since the 1980s, is composed of over 90% crystalline silica by weight, significantly exceeding the silica content of natural stones such as granite (40-50%) and marble (< 10%). Workers fabricating ES are exposed to dangerously high levels of respirable crystalline silica (RCS) and other toxic chemicals, which increases the risk of developing silicosis and other lung and systemic diseases. The purpose of this review is to explore the epidemiology, occupational risks, regulatory gaps, diagnostic evaluation, and clinical challenges associated with ES dust exposure.

MAIN BODY

ES silicosis was first described in the early 2010s among ES countertop workers in Spain, Italy, and Israel. Since then, hundreds of cases have emerged worldwide, namely in China, Australia, the United States, the United Kingdom, and Belgium. Silicosis from ES dust is accelerated and diagnosed after 7-19 years of exposure, often affecting young individuals (median age 33-55 years) from marginalized or immigrant communities. Morbidity and mortality are poor, with high rates of lung transplantation and death. Industrial hygiene air sample monitoring data shows that despite engineering controls such as wet saws and exhaust ventilation, exposure to respirable crystalline silica when cutting ES frequently exceeds safe exposure levels. Diagnostic evaluation and treatment are clinically challenging due to delayed medical screening, misdiagnosis, and lack of treatment options.

CONCLUSIONS

This review underscores the urgent need for enhanced occupational safety regulations, active screening, and healthcare support to address the rising burden of ES silicosis among vulnerable worker populations globally.

Investigation of occupational exposure to respirable crystalline silica (RCS) among engineered stone fabricators in Chicago-A pilot study

Engineered stone countertops, popularly known as quartz or artificial stone countertops, have gained significant attraction due to their durability and aesthetic appeal. However, due to their high crystalline silica content, the fabrication of these countertops poses severe health risks to workers, as evidenced by numerous global cases of silicosis. The study aimed to assess occupational exposure to respirable crystalline silica (RCS) among fabricators in Chicago and characterize the elemental composition and physical properties of engineered stone dust. Eight professional fabricators from two local stone workshops were recruited for the study. The exposure levels to RCS were assessed using the NIOSH 7500 method. Bulk dust samples were collected on-site, and the elemental composition of the dust was analyzed using X-ray fluorescence (XRF) and reported in stoichiometric oxide units. A set of real-time air monitors was used to measure particle size distribution, particulate matter (PM) concentrations, and ambient conditions in the workplace. A questionnaire was administered, and worker activities were recorded during the visits. Workers were found to be overexposed to respirable quartz in their workplaces, with time-weighted averaged (TWA) concentrations ranging from 11 to 203 µg/m3, with a median concentration of 90 µg/m³. Seven samples (78%) exceeded the 50 µg/m3 TWA-8 hr occupational exposure limit for RCS. Engineered stone dust samples contain much higher silica content compared to natural stone dust (30%), with silica percentages ranging from 56% to 95%. Over 90% of the particles (90.3-98.7%) emitted from activities involving small hand tools were of size less than 2.5 µm. The use of respiratory protection was not observed during the visits. The study offers firsthand insights into the engineered stone fabrication industry. The findings reveal a combination of risk factors: elevated RCS concentrations, very high silica content in engineered stone, and a high prevalence of fine particles. These factors collectively pose significant health risks to workers that are unequaled in comparison to most other industries. The findings underscore the urgent need for regulatory measures to better protect workers' health in the engineered stone fabrication sector.

Release of Crystalline Silica Nanoparticles during Engineered Stone Fabrication

Inhalation exposure to respirable crystalline silica (RCS) during the fabrication of engineered stone-based kitchen countertops has been on the rise in recent years and has become a significant occupational health problem in the United States and globally. Little is known about the presence of nanocrystalline silica (NCS), i.e., particles below 100 nm. We present a methodology to quantify the crystalline silica content in the sub-100 nm size fraction of the aerosol released during engineered stone fabrication using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Aerosol was generated in a test chamber designed per EN 1093-3 and sampled using cascade impactors. XRD and FTIR analysis showed the presence of both α-quartz (15-60%) and cristobalite (10-50%) polymorphs in all size fractions. With increasing particle size, the cristobalite content increased. Seventy percent of the total aerosol mass in the sub-100 nm fraction was found to be crystalline silica, qualitatively confirmed by electron diffraction and electron energy loss spectroscopy. The presence of other minerals was detected in all size fractions; no polymeric resin binder was detected in the sub-100 nm fraction. Although the sub-100 nm fraction was about 1% of the aerosol mass, it accounted for 4-24% of the aerosol surface area based on the total lung deposition. If the surface area is a more relevant exposure metric, the assessment of the efficacy of current engineering control systems using mass as an exposure metric may not provide adequate protection.

Assessment of Sub-micrometer-Sized Particles with Practical Activities in an Underground Coal Mine

This assessment was designed to explore and characterize the airborne particles, especially for the sub-micrometer sizes, in an underground coal mine. Airborne particles present in the breathing zone were evaluated by using both (1) direct reading real-time instruments (RTIs) to measure real-time particle number concentrations in the workplaces and (2) gravimetric samplers to collect airborne particles to obtain mass concentrations and conduct further characterizations. Airborne coal mine particles were collected via three samplers: inhalable particle sampler (37 mm cassette with polyvinyl chloride (PVC) filter), respirable dust cyclone (10 mm nylon cyclone with 37 mm Zefon cassette and PVC filter), and a Tsai diffusion sampler (TDS). The TDS, a newly designed sampler, is for collecting particles in the nanometer and respirable size range with a polycarbonate filter and grid. The morphology and compositions of collected particles on the filters were characterized using electron microscopy (EM). RTIs reading showed that the belt entry had a greatly nine-times higher total particle number concentration in average (~ 34,700 particles/cm3) than those measured at both the underground entry and office building (~ 4630 particles/cm3). The belt entry exhibited not only the highest total particle number concentration, but it also had different particle size fractions, particularly in the submicron and smaller sizes. A high level of submicron and nanoparticles was found in the belt conveyor drift area (with concentrations ranging from 0.54 to 1.55 mg/m3 among three samplers). The data support that small particles less than 300 nm are present in the underground coal mine associated with dust generated from practical mining activities. The chemical composition of the air particles has been detected in the presence of Ca, Cu, Si, Al, Fe, and Co which were all found to be harmful to miners when inhaled.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42461-024-01140-w.

The aryl hydrocarbon receptor pathway is a marker of lung cell activation but does not play a central pathologic role in engineered stone-associated silicosis

Engineered stone-associated silicosis is characterised by a rapid progression of fibrosis linked to a shorter duration of exposure. To date, there is lack of information about molecular pathways that regulates disease development and the aggressiveness of this form of silicosis. Therefore, we compared transcriptome responses to different engineered stone samples and standard silica. We then identified and further tested a stone dust specific pathway (aryl hydrocarbon receptor [AhR]) in relation to mitigation of adverse lung cell responses. Cells (epithelial cells, A549; macrophages, THP-1) were exposed to two different benchtop stone samples, standard silica and vehicle control, followed by RNA sequencing analysis. Bioinformatics analyses were conducted, and the expression of dysregulated AhR pathway genes resulting from engineered stone exposure was then correlated with cytokine responses. Finally, we inhibited AhR pathway in cells pretreated with AhR antagonist and observed how this impacted cell cytotoxicity and inflammation. Through transcriptome analysis, we identified the AhR pathway genes (CYP1A1, CYP1B1 and TIPARP) that showed differential expression that was unique to engineered stones and common between both cell types. The expression of these genes was positively correlated with interleukin-8 production in A549 and THP-1 cells. However, we only observed a mild effect of AhR pathway inhibition on engineered stone dust induced cytokine responses. Given the dual roles of AhR pathway in physiological and pathological processes, our data showed that expression of AhR target genes could be markers for assessing toxicity of engineered stones; however, AhR pathway might not play a significant pathologic role in engineered stone-associated silicosis.

Silicosis initially presenting with empyema

The current global outbreak of artificial stone silicosis is a recrudescence of a major occupational disease in the context of a novel exposure source. Respirable crystalline silica exposure, even without frank pneumoconiosis, is associated with an increased risk of respiratory infection. Empyema is a well-recognized complication of bacterial pneumonia; pneumonia among working-age adults, in turn, has been epidemiologically linked to occupational exposure to fumes and dust, including silica. A connection between empyema and silica dust inhalation has not been reported, however, whether through antecedent pneumonia or another mechanism. We describe a case of silicosis initially presenting with empyema in a 31-year-old Computerized Numerical Control stone-cutting machine operator who had heavy exposure to artificial stone and other rock dust.

From Engineered Stone Slab to Silicosis: A Synthesis of Exposure Science and Medical Evidence

Engineered stone (ES) is a popular building product, due to its architectural versatility and generally lower cost. However, the fabrication of organic resin-based ES kitchen benchtops from slabs has been associated with alarming rates of silicosis among workers. In 2024, fifteen years after the first reported ES-related cases in the world, Australia became the first country to ban the use and importation of ES. A range of interacting factors are relevant for ES-associated silicosis, including ES material composition, characteristics of dust exposure and lung cell-particle response. In turn, these are influenced by consumer demand, work practices, particle size and chemistry, dust control measures, industry regulation and worker-related characteristics. This literature review provides an evidence synthesis using a narrative approach, with the themes of product, exposure and host. Exposure pathways and pathogenesis are explored. Apart from crystalline silica content, consideration is given to non-siliceous ES components such as resins and metals that may modify chemical interactions and disease risk. Preventive effort can be aligned with each theme and associated evidence.

Understanding the pathogenesis of engineered stone-associated silicosis: The effect of particle chemistry on the lung cell response

BACKGROUND AND OBJECTIVE

The resurgence of severe and progressive silicosis among engineered stone benchtop industry workers is a global health crisis. We investigated the link between the physico-chemical characteristics of engineered stone dust and lung cell responses to understand components that pose the greatest risk.

METHODS

Respirable dust from 50 resin-based engineered stones, 3 natural stones and 2 non-resin-based materials was generated and analysed for mineralogy, morphology, metals, resin, particle size and charge. Human alveolar epithelial cells and macrophages were exposed in vitro to dust and assessed for cytotoxicity and inflammation. Principal component analysis and stepwise linear regression were used to explore the relationship between engineered stone components and the cellular response.

RESULTS

Cutting engineered stone generated fine particles of <600 nm. Crystalline silica was the main component with metal elements such as Ti, Cu, Co and Fe also present. There was some evidence to suggest differences in cytotoxicity (p = 0.061) and IL-6 (p = 0.084) between dust samples. However, IL-8 (CXCL8) and TNF-α levels in macrophages were clearly variable (p < 0.05). Quartz explained 11% of the variance (p = 0.019) in macrophage inflammation while Co and Al accounted for 32% of the variance (p < 0.001) in macrophage toxicity, suggesting that crystalline silica only partly explains the cell response. Two of the reduced-silica, non-engineered stone products induced considerable inflammation in macrophages.

CONCLUSION

These data suggest that silica is not the only component of concern in these products, highlighting the caution required as alternative materials are produced in an effort to reduce disease risk.

2-Deoxy-D-glucose ameliorates inflammation and fibrosis in a silicosis mouse model by inhibiting hypoxia-inducible factor-1α in alveolar macrophages

Inhaling silica causes the occupational illness silicosis, which mostly results in the gradual fibrosis of lung tissue. Previous research has demonstrated that hypoxia-inducible factor-1α (HIF-1α) and glycolysis-related genes are up-regulated in silicosis. The role of 2-deoxy-D-glucose (2-DG) as an inhibitor of glycolysis in silicosis mouse models and its molecular mechanisms remain unclear. Therefore, we used 2-DG to observe its effect on pulmonary inflammation and fibrosis in a silicosis mouse model. Furthermore, in vitro cell experiments were conducted to explore the specific mechanisms of HIF-1α. Our study found that 2-DG down-regulated HIF-1α levels in alveolar macrophages induced by silica exposure and reduced the interleukin-1β (IL-1β) level in pulmonary inflammation. Additionally, 2-DG reduced silica-induced pulmonary fibrosis. From these findings, we hypothesize that 2-DG reduced glucose transporter 1 (GLUT1) expression by inhibiting glycolysis, which inhibits the expression of HIF-1α and ultimately reduces transcription of the inflammatory cytokine, IL-1β, thus alleviating lung damage. Therefore, we elucidated the important regulatory role of HIF-1α in an experimental silicosis model and the potential defense mechanisms of 2-DG. These results provide a possible effective strategy for 2-DG in the treatment of silicosis.

Characterization of the Emissions and Crystalline Silica Content of Airborne Dust Generated from Grinding Natural and Engineered Stones

In this study, we systematically characterized the airborne dust generated from grinding engineered and natural stone products using a laboratory testing system designed and operated to collect representative respirable dust samples. Four stone samples tested included two engineered stones consisting of crystalline silica in a polyester resin matrix (formulations differed with Stones A having up to 90wt% crystalline silica and Stone B up to 50wt% crystalline silica), an engineered stone consisting of recycled glass in a cement matrix (Stone C), and a granite. Aerosol samples were collected by respirable dust samplers, total dust samplers, and a Micro-Orifice Uniform Deposit Impactor. Aerosol samples were analyzed by gravimetric analysis and x-ray diffraction to determine dust generation rates, crystalline silica generation rates, and crystalline silica content. Additionally, bulk dust settled on the floor of the testing system was analyzed for crystalline silica content. Real-time particle size distributions were measured using an Aerodynamic Particle Sizer. All stone types generated similar trimodal lognormal number-weighted particle size distributions during grinding with the most prominent mode at an aerodynamic diameter of about 2.0-2.3 μm, suggesting dust formation from grinding different stones is similar. Bulk dust from Stone C contained no crystalline silica. Bulk dust from Stone A, Stone B, and granite contained 60, 23, and 30wt% crystalline silica, respectively. In Stones A and B, the cristobalite form of crystalline silica was more plentiful than the quartz form. Only the quartz form was detected in granite. The bulk dust, respirable dust, and total dust for each stone had comparable amounts of crystalline silica, suggesting that crystalline silica content in the bulk dust could be representative of that in respirable dust generated during grinding. Granite generated more dust per unit volume of material removed than the engineered stones, which all had similar normalized dust generation rates. Stone A had the highest normalized generation rates of crystalline silica, followed by granite, Stone B, and Stone C (no crystalline silica), which likely leads to the same trend of respirable crystalline silica (RCS) exposure when working with these different stones. Manufacturing and adoption of engineered stone products with formulations such as Stone B or Stone C could potentially lower or eliminate RCS exposure risks. Combining all the effects of dust generation rate, size-dependent silica content, and respirable fraction, the highest normalized generation rate of RCS consistently occurs at 3.2-5.6 µm for all the stones containing crystalline silica. Therefore, removing particles in this size range near the generation sources should be prioritized when developing engineering control measures.

Engineered Stone Fabrication Work Releases Volatile Organic Compounds Classified as Lung Irritants

Engineered stones are often characterized for their crystalline silica content. Their organic composition, particularly that of the emissions generated during fabrication work using hand-held power tools, is relatively unexplored. We forensically screened the emissions from dry-cutting 12 engineered stone products in a test chamber for their organic composition by pyrolysis-gas chromatography-mass spectrometry (GC-MS) plus selected traditional capture and analysis techniques. Phthalic anhydride, which has a Respiratory Sensitization (RSEN) Notation by the American Conference of Governmental Industrial Hygienists (ACGIH), was the most common and abundant compound, at 26-85% of the total organic composition of engineered stone emissions. Benzaldehyde and styrene were also present in all twelve samples. During active cutting, the predominant volatile organic compound (VOC) emitted was styrene, with phthalic anhydride, benzene, ethylbenzene, and toluene also detected. These results have important health implications as styrene and phthalic anhydride are irritants to the respiratory tract. This study suggests a risk of concurrent exposure to high levels of respirable crystalline silica and organic lung irritants during engineered stone fabrication work.

Pirfenidone ameliorates pulmonary inflammation and fibrosis in a rat silicosis model by inhibiting macrophage polarization and JAK2/STAT3 signaling pathways

Macrophages play an important role in causing silicosis eventually becoming an irreversible fibrotic disease, and there are no specific drugs for silicosis in the clinic so far. Pirfenidone has consistently been shown to have anti-inflammatory and anti-fibrotic effects, but the specific mechanism by which it ameliorates fibrosis in silicosis is unclear. A rat silicosis model was established in this study, and lung tissues and serum were collected by batch execution at 14, 28, and 56 days. Also, the effects of Pirfenidone on macrophage polarization and pulmonary fibrosis were evaluated in silicosis with early intervention and late treatment by histological examination, Enzyme-linked immunosorbent assay, Hydroxyproline assay, Western blot and Quantitative reverse transcription polymerase chain reaction. The results showed that Pirfenidone significantly reduced pulmonary fibrosis in rats with silicosis, and both early intervention and late treatment effectively inhibited the expression of α-SMA, Col-I, Vimentin, Hydroxyproline, IL-1β, IL-18, and the M2 macrophage marker CD206 and Arg-1, while only early intervention effectively inhibited E-cad, TGF-β1, TNF-α, and the M1 macrophage marker iNOS, CD86. Furthermore, Pirfenidone dramatically reduced the mRNA expression of the JAK2/STAT3. These findings imply that Pirfenidone may reduce pulmonary fibrosis in silicosis rats by inhibiting macrophage polarization via the JAK2/STAT3 signaling pathway.

Characterization of Si and SiO2 in Dust Emitted during Granite Polishing as a Function of Cutting Conditions

Particles emitted during manufacturing processes such as polishing can represent a serious danger for the environment and for occupational safety. The formation mechanisms responsible for these dust emissions include chip formation, friction at the tool/workpiece and chip/tool interfaces, shearing and cutting. These mechanisms thus depend on workpiece and tool properties, as well as the polishing conditions. In the case of granite polishing, particle emissions during polishing can contain chemical compounds such as silica, which represent harmful health risks for the worker. It is therefore important to characterize the particles emitted and to search for possible interactions between the particles (size and composition) and the machining conditions in order to find ways of reducing emissions at the source. In this study, an investigation was undertaken to characterize the particles emitted during granite polishing as a function of polishing conditions, type of granite, and abrasive grit sizes used. Scanning electron microscopy (SEM) was employed for particle morphology characterization and particle grain size and chemical composition were evaluated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX) techniques, respectively. Results show that the influence of polishing speed and feed rate on particle emission depends mainly on the granite type used, providing useful information for controlling the polishing procedure, and thereby dust emission.

Rapid Assessment of Oxidative Damage Potential: A Comparative Study of Engineered Stone Dusts Using a Deoxyguanosine Assay

The popularity of engineered stone (ES) has been associated with a global increase in occupational lung disease in workers exposed to respirable dust during the fabrication of benchtops and other ES products. In this study, the reactivity and subsequent oxidative reduction potential of freshly generated ES dusts were evaluated by (i) comparing different engineered and natural stones, (ii) comparing settled and respirable stone dust fractions and (iii) assessing the effect of ageing on the reactivity of freshly generated stone dust. An established cell-free deoxyguanosine hydroxylation assay was used to assess the potential for oxidative DNA damage. ES dust exhibited a higher relative reactivity than two of the three natural stones tested. Respirable dust fractions were found to be significantly more reactive than their corresponding settled fraction (ANOVA, p < 0.05) across all stone types and samples. However, settled dust still displayed high relative reactivity. The lower reactivity of the settled dust was not due to decay in reactivity of the respirable dust when it settled but rather a result of the admixture of larger nonrespirable particles. No significant change in respirable dust reactivity was observed for three ES samples over a 21-day time period, whereas a significant decrease in reactivity was observed in the natural stone studied. This study has practical implications for dust control and housekeeping in industry, risk assessment and hazard management.