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.
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).
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.
The presence of a dose-response relationship favors the causal relationship between exposure to silica and developing lung cancer.
- • The relationship between silica exposure and the risk of lung cancer previously has been established.
- • There is a dose-response relationship between silica exposure and the risk of lung cancer.
- • Policymakers can provide programs to reduce the exposure with silica in the workplace and outdoors.
Lung cancer is a multifactorial disease and one of the most fatal cancer worldwide. Lung cancer is the most often diagnosed malignancy worldwide including 2.1 million new cases, equal to 11.6% of the total incidence of cancer in 2018 . There are several risk factors for lung cancer; including smoking, air pollution, family history of lung cancers, previous lung diseases, and exposure to secondhand smoke . In addition, occupational exposures to asbestos and silica are among risk factors for developing lung cancer .
According to the International Agency for Research on Cancer (IARC) Report, silica is classified as a human lung carcinogen . Exposure to silica is one of the most important modifiable risk factors for lung cancer . However, the results of the original studies investigating the relationship between silica exposure and the risk of lung cancer show different results . One of the best and reliable methods to make a robust conclusion is to conduct a meta-analysis. Based on the latest meta-analysis conducted by Pelucchi et al. in 2006, there was no significant association between silica exposure and the risk of lung cancer . In 2009, Lacasse et al. performed a dose-response meta-analysis and concluded that the increased risk of lung cancer was particularly apparent when the cumulative exposure to silica was beyond the level of exposure limit recommended for a prolonged period . This updated systematic review and dose-response meta-analysis was conducted to assess how the risk of lung cancer changes as the level of long-term exposure to silica increases.