Dose–response meta-analysis of silica and lung cancer

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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.