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



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.



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.



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.
Department of Occupational & Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.|Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.
Satiavani
S
Poinen-Rughooputh
Department of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.
Mahesh Shumsher
MS
Rughooputh
Department of Occupational & Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.|Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.
Yanjun
Y
Guo
Department of Occupational & Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.|Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China.
Yi
Y
Rong
Department of Occupational & Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China. wchen@mails.tjmu.edu.cn.|Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430030, China. wchen@mails.tjmu.edu.cn.
Weihong
W
Chen
D002273:Carcinogens / Q000633:toxicity*; D004391:Dust; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008175:Lung Neoplasms / Q000209:etiology* / Q000401:mortality; D008297:Male; D009784:Occupational Diseases / Q000209:etiology* / Q000401:mortality; D016273:Occupational Exposure / Q000009:adverse effects*; D012044:Regression Analysis; D012307:Risk Factors; D012822:Silicon Dioxide / Q000633:toxicity*; D012829:Silicosis / Q000150:complications / Q000401:mortality
D002273:Carcinogens; D004391:Dust; D012822:Silicon Dioxide
Exposure-response analysis; Heterogeneity; Lung cancer; Meta-analysis; Meta-regression; Silica; Silicosis