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.

Knowledge, Attitude, Behavior Practices and Compliance of Workers Exposed to Respirable Dust in a Zambian Copper Mine

Work in the copper mining industry is often associated with exposure to respirable dust and respirable crystalline silica. This exposure has the potential to cause silicosis, an incurable occupational respiratory lung disease. This study aimed at establishing the relationship between knowledge, attitudes, work behavioral practices and compliance with safety standards and workers' exposure to respirable dust. A cross-sectional descriptive survey was conducted on 528 mine workers. The Statistical Package for Social Sciences (SPSS) was used for the descriptives. Structural equation modeling (SEM) with latent variables and partial least squares (LVPLS) analysis were employed to determine the relationship among these variables. The results indicated that of the four hypotheses, two were supported, and two were rejected, showing that there is a significant relationship between exposure to respirable dust and work behavioral practices, as well as compliance with safety standards. Knowledge and attitudes toward respirable dust exposure did not significantly influence exposure. According to the results from the survey, positive work behavioral practices as well as compliance with safety standards were significantly associated with exposure to respirable dust. It is recommended that mines should focus on the miners' work behavioral practices and compliance with safety standards.

Occupational Dust Exposure and Respiratory Protection of Migrant Interior Construction Workers in Two Chinese Cities

Migrant interior construction workers are increasing in China. Construction workers are at an increased risk of work-related illness (WRI) due to prolonged exposure to and inhalation of dust. Dust concentrations in the air can be reduced significantly with effective respiratory protection measures. We assessed the dust exposure and factors associated with respiratory protection of migrant interior construction workers. The total dust concentration in the workplace ranged from 0.07 to 335.27 mg/m³, with a total dust exceedance rate of 50.00%. The respiratory dust loading ranged from 0.03 to 220.27 mg/m³, with a respiratory dust exceedance rate of 71.42 %. The highest total dust concentration occurred when masons were polishing cement walls. We performed a questionnaire survey of 296 persons in two cities in China, in which 87.84% had no respiratory protection or only one protection measure. Gender, workplace, respiratory disease, and protective attitude all had an effect on the level of respiratory protection. The dust exposure in most jobs exceeds hygiene standards. The respiratory protection of migrant interior construction workers in China is inadequate.

Occupational exposure to respirable crystalline silica and chronic non-malignant renal disease: systematic review and meta-analysis

Background

While occupational exposure to respirable silica is known to lead to lung disease, most notably silicosis, its association with chronic kidney disease is unclear.

Objectives

This review explores the association between occupational exposure to respirable silica and chronic non-malignant renal disease such as glomerulonephritis. The evidence has been collected and compiled. Possible sources of bias are thoroughly discussed.

Methods

Cohort studies with silica exposure and case–control studies of renal disease were searched in PubMed until January 2015. Two authors independently abstracted data; any disagreement was resolved by consulting a third reviewer. A meta-analysis was performed to evaluate the association to silica exposure.

Results

A total of 23 cohort and four case–control studies were included in the analysis. The meta-analysis of cohort studies yielded elevated overall SMRs for renal disease. Some studies, however, included dose–response analyses, most of which did not show a positive trend. The approaches and results of the case–control studies were very heterogeneous.

Conclusions

While the studies of cohorts exposed to silica found elevated SMRs for renal disease, no clear evidence of a dose–response relationship emerged. The elevated risk may be attributed to diagnostic and methodological issues. In order to permit a reliable estimation of a possible causal link, exposed cohorts should be monitored for renal disease, as the information from mortality studies is hardly reliable in this field.

Electronic supplementary material

The online version of this article (doi:10.1007/s00420-017-1219-x) contains supplementary material, which is available to authorized users.

Task distribution, work environment, and perceived health discomforts among Indian ceramic workers

BACKGROUND

The study examined the work environment of Indian ceramics workers and assessed associations between work hazards, work category, and self-reported symptoms.

METHODS

The multi-method ergonomic review technique (MMERT) checkpoints was used for work analysis and prevalence of self-reported symptoms among 329 male workers.

RESULTS

Ambient temperature and relative humidity in ceramic industries were 39.9°C and 17.4% respectively. Musculoskeletal discomfort was observed as a primary complaint; especially lower extremity pain (45%). Load handlers and machine operators had the highest levels of work hazards, including high skill requirement, strenuous work posture, poor commitment by the organization. Poor job autonomy, task clarity, hot workplace, inappropriate workplace design, inadequate auxiliary support, and mental overload were significantly associated with self-reported symptoms (P < 0.001).

CONCLUSION

Work categories are associated with work hazards and may lead to various health symptoms among ceramic workers. Control of workplace hazards may lower rates of symptoms and thus may lead to improved health, productivity, and well-being. Am. J. Ind. Med. 59:1145-1155, 2016. © 2016 Wiley Periodicals, Inc.

Occupational exposure to silica dust and risk of lung cancer: an updated meta-analysis of epidemiological studies

BACKGROUND

Crystalline silica is considered as one of the most common and serious occupational hazards to workers' health. Although its association with lung cancer has been studied for many decades, the conclusion remains somewhat controversial. Our objectives are to review and summarize the epidemiological evidence on the relationship between occupational silica exposure and risk of lung cancer and to provide an update on this major occupational health concern.

METHODS

Eligible studies up to 29 April 2016 were identified. Pooled effect estimates were calculated according to the reported outcome and the study design. Cohort, case control and proportional mortality studies were examined separately. Studies reporting results according to silicotic status were grouped together and analyzed. Due to the significant amount of heterogeneity expected, random effects models were implemented. Subgroup and meta-regression analyses (both univariate and multivariate) were performed in an attempt to explain heterogeneity. Studies which had adequate exposure characterization were selected to find out whether there was an exposure-response relationship between silica and lung cancer.

RESULTS

The risk of lung cancer was found to be elevated in both silicotics and non-silicotics. The pooled standardized mortality ratio (SMR) was 2.32 with a 95 % confidence interval (95 % CI) of 1.91-2.81 and 1.78 (95 % CI 1.07-2.96) respectively. The pooled standardized incidence ratio (SIR) was 2.49 (95 % CI 1.87-3.33) and 1.18 (95 % CI 0.86-1.62) respectively. Subgroup analysis showed that workers in the mining industry had the highest risk of lung cancer with a pooled SMR of 1.48 (95 % CI 1.18-1.86) and the weakest association was seen in potteries with a pooled SMR of 1.14 (95 % CI 1.05-1.23). A positive exposure-response relation was found between cumulative silica exposure and risk of lung cancer.

CONCLUSION

The results of our meta-analysis supported the carcinogenic role of silica on the lungs, which was more pronounced at higher levels of exposure, in the presence of silicosis and in the mining industry. Further research is needed to evaluate whether non-silicotics are truly at risk, whether a predisposing factor would explain this potential risk, and to determine the mechanism of carcinogenicity of silica in humans.

Formative research to reduce mine worker respirable silica dust exposure: a feasibility study to integrate technology into behavioral interventions

Background

The use of formative research as a critical component of intervention planning is highly supported in the literature. However, studies that report such processes in practice are minimal. This paper reports on the formative data collection and analysis that informed the development of a multilevel intervention that utilizes mine assessment technology to bridge health communication between workers and management to reduce mine worker overexposure to respirable silica dust.

Methods

Formative research to assess the feasibility and utility of this intervention design included stakeholder meetings and feedback, mine visits and observations, interviews with mine workers, and a focus group with mine management. Data collection took place at several US industrial mineral mine sites and a southeastern regional safety meeting. Interviews inquired about workers’ perceived susceptibility and severity to respirable silica exposure, barriers to preventing overexposure, behaviors that reduce exposure, and perceptions about respirable dust-monitoring technology. A focus group discussed mine stakeholders’ uses of various dust assessment technology.

Results

The data was qualitatively analyzed and coded using a thematic and theoretical analysis. Researchers found recurring themes for both target audiences that informed the need and subsequent development of a mixed-method multilevel intervention to improve communication quantity and quality around dust-control practices.

Conclusions

Results indicate that formative research is critical to: identify and develop an intervention that meets target audience needs; accurately represent the health problem; and develop positive relationships with research partners and stakeholders.

Instituting a filtration/pressurization system to reduce dust concentrations in a control room at a mineral processing plant

The National Institute for Occupational Safety and Health has observed that many control rooms and operator compartments in the U.S. mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room that had no cleaning system for intake air, a filtration and pressurization system originally designed for enclosed cabs was modified and installed. This system was composed of two filtering units: one to filter outside air and one to filter and recirculate the air inside the control room. Eighty-seven percent of submicrometer particles were reduced by the system under static conditions. This means that greater than 87 percent of respirable dust particles should be reduced as the particle-size distribution of respirable dust particles is greater than that of submicrometer particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced, which is an important component of an effective system and minimizes the entry of particles, such as dust, into the room. The intake airflow was around 118 cfm, greater than the airflow suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) for acceptable indoor air quality. After one year, the loading of the filter caused the airflow to decrease to 80 cfm, which still produces acceptable indoor air quality. Due to the loading of the filters, the reduction efficiency for submicrometer particles under static conditions increased to 94 percent from 87 percent.

An approach to adjust standardized mortality ratios for competing cause of death in cohort studies

Purpose

The calculation of standardized mortality ratios (SMRs) is a standard tool for the estimation of health risks in occupational epidemiology. An increasing number of studies deal with the analysis of the mortality in employees suffering from an occupational disease like silicosis or coal-worker pneumoconiosis (CWP). Their focus lies not on the mortality risk due to the occupational disease itself, but on other diseases such as lung cancer or heart diseases. Using population-based reference rates in these studies can cause misleading results because mortality rates of the general population do not reflect the elevated mortality due to the occupational disease investigated. Hence, the purpose of the present paper is to develop an approach to adjust the risk estimates for other causes of death with respect to the effect of an occupational disease as a competing cause of death in occupational mortality cohort studies.

Methods

To overcome the problems associated with SMRs, the paper makes use of proportional mortality ratios (PMR), which are a further approach for the estimation of health risks in occupational epidemiology. The cause-specific SMR can be rewritten as a product of PMR times the overall SMR. The PMR can be adjusted by ignoring the competing cause of death. Hence, an adjusted cause-specific SMR can be derived by multiplying this adjusted PMR with the overall SMR. This approach is applied to studies concerning lung cancer risk in coal miners suffering from CWP.

Results and conclusions

The usual approach for calculating SMRs leads to an underestimation of the real lung cancer risk in subgroups of miners suffering from CWP. The same effect can be observed in workers exposed to respirable silica already suffering from silicosis. The presented approach results in more realistic risk estimation in mortality cohort studies of employees suffering from an occupational disease. It is easily calculable on the basis of usually published values of observed cases and the corresponding cause-specific SMR.

Ceramics manufacturing contributes to ambient silica air pollution and burden of lung disease

Inhalation of silica (SiO2) in occupational exposures can cause pulmonary fibrosis (silicosis), lung function deficits, pulmonary inflammation, and lung cancer. Current risk assessment models, however, cannot fully explain the magnitude of silica-induced pulmonary disease risk. The purpose of this study was to assess human health risk exposed to airborne silica dust in Taiwan ceramics manufacturing. We conducted measurements to characterize workplace-specific airborne silica dust in tile and commodity ceramic factories and used physiologically based alveolar exposure model to estimate exposure dose. We constructed dose-response models for describing relationships between exposure dose and inflammatory responses, by which health risks among workers can be assessed. We found that silica contents were 0.22-33.04 % with mean concentration ranges of 0.11-5.48 and 0.46-1763.30 μg m(-3), respectively, in commodity and tile ceramic factories. We showed that granulation workers in tile ceramic factory had the highest total SiO2 lung burden (∼1000 mg) with cumulative SiO2 lung burden of ∼4 × 10(4) mg-year. The threshold estimates with an effect on human lung inflammation and fibrosis are 407.31 ± 277.10 (mean ± sd) and 505.91 ± 231.69 mg, respectively. For granulation workers, long-term exposure to airborne silica dust for 30-45 years was likely to pose severe adverse health risks of inflammation and fibrosis. We provide integrated assessment algorithms required to implement the analyses and maintain resulting concentration of silica dust at safety threshold level in the hope that they will stimulate further analyses and interpretation. We suggest that decision-makers take action to implement platforms for effective risk management to prevent the related long-term occupational disease in ceramics manufacturing.

Laryngeal cancer and silica dust exposure: a systematic review and meta-analysis

BACKGROUND

Individual epidemiological studies generally lack the power to examine the association between silica exposure or silicosis and laryngeal cancer. We summarized pertinent evidence from published literature by using meta-analysis.

METHODS

A systematic literature search was performed to identify cohort and case-control studies, and the method of meta-analysis was used to combine standardized mortality ratios (SMRs) or standardized incidence ratios (SIRs) from cohort studies and odds ratios (ORs) from case-control studies.

RESULTS

A significantly increased risk of laryngeal cancer (pooled OR = 1.39, 95% confidence interval (95% CI): 1.17-1.67) among workers exposed to silica dust was observed by combining six case-control studies with adjustment for smoking and alcohol consumption. A similarly increased but statistically non-significant risk estimate was observed from cohort studies, with a pooled SMR of 1.38 (95% CI: 0.79-1.96) for silicosis cases; and a pooled SMR of 1.13 (95% CI: 0.82-1.45) and a pooled SIR of 1.50 (95% CI: 0.59-2.42) for workers with silica dust exposure.

CONCLUSION

This systematic review demonstrated a weak association between silica or silicosis and laryngeal cancer. Owing to the inherent limitations of the original studies, interpretation of the results of this meta-analysis should be cautious.

[Laryngeal carcinoma: epidemiology, risk factors and survival]

Laryngeal cancer is one of the most frequent types of head and neck cancer. The incidence is decreasing for men but still increasing for women. The incidence in Germany is about 5-7/100,000 persons/year for men and 0.6-0.8/100,000 persons/year for women. Due to the increased life expectancy, the average age of patients diagnosed with laryngeal cancer is increasing. Nevertheless, adequately prepared older patients treated by standard protocols can have the same survival and complication rates as younger patients. Tobacco and alcohol are still the primary risk factors responsible for disease in at least 80% of the patients. Despite the many new diagnostic tools, still more than half of the patients are diagnosed at an advanced tumor stage. Survival rates have not improved significantly in the last 10 years in Germany, and the average 5-year overall survival rate is about 60%. However, a decrease in the survival rate, as observed in the USA, cannot be confirmed for Germany.