The effect of silica exposure on the risk of lung cancer: A dose-response meta-analysis

Background: The relationship between silica and the risk of developing lung cancer has been established in previous literature, but how much the level of exposure to silica can increase the risk of lung cancer is a question that has been addressed in this review. Methods: Three electronic databases, including MEDLINE, Scopus, and Web of Science were searched for relevant literature. For the dose-response relationship between exposure to silica and developing lung cancer, we performed a meta-analysis using the random-effects model. For each level of exposure, we calculated the overall risk ratio (RR) with 95% confidence intervals (CI). Results: Nineteen studies were included in the meta-analysis. There was a positive and significant increasing dose-response trend between silica exposure and the risk of developing lung cancer as follows: < 0.50 mg/m(3) 1.14 (95% CI: 1.05, 1.23; I-2 = 79%), 0.50-0.99 mg/m(3) 1.34 (95% CI: 1.05, 171; I-2 = 45%), 1.00-1.99 mg/m(3) 1.14 (95% CI: 1.00, 1.30; I-2 = 70%), 2.00-2.99 mg/m(3) 1.47 (95% CI: 1.05, 2.06; I-2 = 57%), 3.00-3.99 mg/m(3) 1.44 (95% CI: 0.99, 2.11; I-2 = 58%), and >= 4.00 mg/m(3) 1.64 (95% CI: 1.20, 2.24; I-2 = 88%). The heterogeneity across studies was mild to moderate. Conclusions: The presence of a dose-response relationship favors the causal relationship between exposure to silica and developing lung cancer.