Dose–response meta-analysis of silica and lung cancer

Abstract

To examine the association between occupational exposure to silica and lung cancer from a systematic review (and meta-analysis) of the epidemiologic literature, with special reference to the methodological quality of observational studies. We searched Medline, Toxline, BIOSIS, and Embase (1966-December 2007) for original articles published in any language. Observational studies (cohort and case-control studies) were selected if they reported the result of dose-response analyses relating lung cancer to occupational exposure to silica after appropriate adjustment for smoking. Ten studies (4 cohort studies and 6 case-control studies) met the inclusion criteria of the meta-analysis, nine of which contributing to the main analysis (dose-response analysis, no lag time). We found increasing risk of lung cancer with increasing cumulative exposure to silica, with heterogeneity across studies however. Posthoc analyses identified a set of seven more homogeneous studies. Their meta-analysis resulted in a dose-response curve that was not different from that obtained in the main analysis. Silica is a lung carcinogen. This increased risk is particularly apparent when the cumulative exposure to silica is well beyond that resulting from exposure to the recommended limit concentration for a prolonged period of time.