Association of silica dust exposure with mortality among never smokers: A 44-year cohort study

Long-term exposure to low-level crystalline silica and risk assessment of silicosis: a cohort study

BACKGROUND

High-level exposure to crystalline silica dust is the key factor in silicosis. Long-term exposure to low-level silica dust, for example, lower than that in occupational exposure limits, still needs to be studied for their risk of silicosis.

METHODS

A total of 30 697 workers were included from a cohort in China. Low-level silica dust exposure was defined as those having a lifetime mean silica dust concentration equal to or under permissible exposure limits, including 0.05 mg/m3, 0.10 mg/m3 and 0.35 mg/m3. Cumulative respirable silica dust exposure (CDE) for individual workers was assessed by linking a job-exposure matrix to personal work history.

RESULTS

Among those with average exposure level equal to or lower than 0.05 mg/m3, compared with the lowest quartile CDE (Q1), the HRs of silicosis were 1.32 (95% CI 0.82 to 2.10) for Q2, 1.87 (95% CI 1.22 to 2.88) for Q3 and 2.00 (95% CI 1.30 to 3.09) for Q4. Among those exposed to 0.10 mg/m3 or less exposure level, compared with Q1, the HRs were 2.52 (95% CI 1.88 to 3.38) for Q2, 4.08 (95% CI 3.09 to 5.39) for Q3 and 4.02 (95% CI 3.04 to 5.32) for Q4. Among those exposed to 0.35 mg/m3 or less exposure level, compared with Q1, the HRs were 2.80 (95% CI 2.38 to 3.28) for Q2, 5.76 (95% CI 4.93 to 6.73) for Q3 and 7.14 (95% CI 6.07 to 8.40) for Q4, respectively. Stratified analysis showed that the results and trends did not change with facilities and smoking status.

CONCLUSION

Long-term exposure to low-level silica dust is still associated with a higher risk of silicosis. Control measurements and personal protective equipment should be emphasised to protect the health of workers.

Unveiling the threat of crystalline silica on the cardiovascular system. A comprehensive review of the current knowledge

Introduction

This paper aims to expose the link between occupational exposure to respirable crystalline silica (SiO2) and cardiovascular diseases (CVDs).

Methods

A comprehensive review of the literature was conducted, focusing on epidemiological studies that assessed the association between silicosis or SiO2 exposure and CVDs. Specific cardiovascular diseases, such as acute myocardial infarction, arrhythmias, pulmonary hypertension and pericarditis, were also pointed. Biomarkers commonly used in both silicosis and cardiovascular diseases were reviewed to underline the common pathological pathways.

Results

Published epidemiological data revealed a higher risk of ischemic heart disease, stroke, and hypertension in silica-exposed workers, even at low exposure levels. SiO2 exposure was linked to an increased risk of myocardial infarction, with potential mechanisms involving inflammation and platelet activation. Elevated risk of arrhythmias, particularly atrial fibrillation, correlated with occupational silica exposure. Consistent with the pathological mechanisms supporting the SiO2 exposure-CVDs relationship, biomarkers related to NLP3 inflammasome activation, reflecting oxidative stress, and revealing fibrosis have been presented.

Conclusion

Actual data support the relationship between occupational SiO2 exposure and various CVDs promoting cardiovascular monitoring in silica-exposed workers. Further studies are needed to identify specific/distinctive biomarkers to improve early detection of CVDs in silica exposed workers.

Update on Silicosis

Although silicosis has been an established disease with a recognized cause for more than 100 years, many workers continue to be exposed to silica and new outbreaks of disease continue to occur. This article describes some of the well-established and new exposures, including denim sandblasting, artificial stone cutting, and some forms of "coal worker's pneumoconiosis." The authors review the imaging and pathology of acute silicosis (silicoproteinosis), simple silicosis, and progressive massive fibrosis and summarize known and putative associations of silica exposure, including tuberculosis, lung cancer, connective tissue disease (especially systemic sclerosis), and vasculitis.

Occupational exposure to silica and risk of gastrointestinal cancers: a systematic review and meta-analysis of cohort studies

BACKGROUND

Although silica is a proven lung carcinogen, there is no convincing evidence linking crystalline silica to gastrointestinal malignancies.

METHODS

We detailedly searched studies on the link between gastrointestinal malignancies and occupational silica exposure. Studies published between 1987 and 2023 were found by searching PubMed, Scopus, Cochrane Library, and Web of Science databases. Further studies were included from reference searching. We conducted a meta-analysis of the incidence and mortality of gastrointestinal malignancies and occupational silica exposure. We computed pooled-risk estimates using random effects models. Egger's regression asymmetry test and a funnel plot were used to identify publication bias. Moreover, sensitivity analysis and subgroup analysis were out.

RESULTS

We identified 40 research with individuals from 13 different countries. The results indicate that occupational silica exposure raises the risk of gastric and esophageal cancer incidence, with pooled standardized incidence ratio of 1.35 (95% CI 1.21-1.51, p < 0.001), 1.31 (95% CI 1.04-1.65, p = 0.023), respectively, but there was a lack of statistically significant relationship between standardized mortality ratio. In addition, we found that silica exposure did not increase the risk of colorectal and pancreatic cancers. Occupational silica exposure was found to increase the risk of liver cancer, with pooled SIR and SMR of 1.19 (95% CI 1.04-1.35, p = 0.009), 1.24 (95% CI 1.03-1.49, p = 0.026), respectively.

CONCLUSIONS

We discovered a link between occupational silica exposure and gastrointestinal malignancies, with cancers of the liver, stomach, and esophagus being the most prevalent. Colorectal and pancreatic cancer were not linked to occupational silica exposure.

Occupational exposure to respirable crystalline silica and lung cancer: a systematic review of cut-off points

BACKGROUND

Respirable crystalline silica (RCS) is associated with the development of lung cancer. However, there is uncertainty around the exposure threshold at which exposure to RCS may pose a clear risk for the development of lung cancer. The objective of this study was to review the cut-off points at which the risk of mortality or incidence of lung cancer due to occupational exposure to RCS becomes evident through a systematic review.

METHODS

We conducted a search in PubMed, including cohort and case-control studies which assessed various categories of RCS exposure. A search was also conducted on the webpages of institutional organizations. A qualitative data synthesis was performed.

RESULTS

Twenty studies were included. Studies that assessed lung cancer mortality and incidence displayed wide variability both in RCS exposure categories and related risks. Although most studies found no significant association for RCS exposure categories, it appears to be a low risk of lung cancer for mean concentrations of less than 0.07mg/m3. Regulatory agencies set annual RCS exposure limits ranging from 0.025mg/m3 through 0.1mg/m3.

CONCLUSIONS

There is a wide degree of heterogeneity in RCS exposure categories, with most studies observing no significant risk of lung cancer for the lowest exposure categories. Cut-off points differ between agencies but are nonetheless very similar and do not exceed 0.1mg/m3.

Neutralization of interleukin-11 attenuates silica particles-induced pulmonary inflammation and fibrosis in vivo

Environmental exposure to crystalline silica particles can lead to silicosis, which is one of the most serious pulmonary interstitial fibrosis around the world. Unfortunately, the exact mechanism on silicosis is unclear, and the effective treatments are lacking to date. In this study, we aim to explore the molecular mechanism by which interleukin-11 (IL-11) affects silica particles-induced lung inflammation and fibrosis. We observed that IL-11 expressions in mouse lungs were significantly increased after silica exposure, and maintained at high levels across both inflammation and fibrosis phase. Immunofluorescent dual staining further revealed that the overexpression of IL-11 mainly located in mouse lung epithelial cells and fibroblasts. Using neutralizing anti-IL-11 antibody could effectively alleviate the overexpression of pro-inflammatory cytokines (i.e., interleukin-6 and tumor necrosis factor-α) and fibrotic proteins (i.e., collagen type I and matrix metalloproteinase-2) induced by silica particles. Most importantly, the expressions of IL-11 receptor subunit α (IL-11Rα), Glycoprotein 130 (GP130), and phosphorylated extracellular signal-regulated kinase (p-ERK) were significantly increased in response to silica, whereas blocking of IL-11 markedly reduced their levels. All findings suggested that the overexpression of IL-11 was involved in the pathological of silicosis, while neutralizing IL-11 antibody could effectively alleviate the silica-induced lung inflammation and fibrosis by inhibiting the IL-11Rα/GP130/ERK signaling pathway. IL-11 might be a promising therapeutic target for lung inflammation and fibrosis caused by silica particles exposure.

Risk factors for the development of lung cancer among never smokers: A systematic review

This review aimed to summarize the up-to-date evidence on non-genetic factors for the development of never smoking lung cancer (NSLC) and to explore reasons behind the conflicting results. Relevant literature was searched in three electronic databases (PubMed, Embase and Web of Science) from 1 January 2000-31 July 2022. Cohort studies that investigated non-genetic risk factors for primary lung cancer in never smokers were included. The effect of non-genetic factors about NSLC were summarized with pooled relative risk (RR) and 95 % confidence intervals (CIs) through meta-analysis or narrative description when unexplained statistical heterogeneity was observed. The Newcastle-Ottawa Scale was used to appraise the methodological quality of included studies. Sixty cohort studies were included, covering population from Asia, Europe and America. Most included studies (42, 70.0 %) were of high methodological quality. Over 50 years old (RR = 5.26), environmental tobacco smoke (Pooled RR = 1.30), Chronic obstructive pulmonary disease (COPD) (RR = 2.67), family history of lung cancer (Pooled RR = 1.83) and higher level of neutrophil-lymphocyte ratio (RR = 1.73) increased the risk of NSLC. Dairy foods consumption (RR = 0.79), isoflavone intake (Pooled RR = 0.65), and riboflavin intake (RR = 0.62) decreased the risk among female population. Inconsistency or unclear definition for never smokers and risk factors could be observed in included studies. Most life behavior factors associated with NSLC can be modified through lifestyle changes. Future cohort studies are suggested to adopt a clearer definition on never smokers and exposure, conducting subgroup analysis when evidence indicating there is heterogeneity between genders, and explore dose-response relationship between the identified factors and NSLC.