Diesel exhaust exposure and risk of non-Hodgkin lymphoma: A meta-analysis

Objective We aimed at carrying out a systematic review and meta-analysis of epidemiological studies on the association between occupational and non-occupational exposures to diesel exhaust and risk of non-Hodgkin lymphoma. Methods We conducted a systematic search of the literature and identified 16 cohort studies and 7 case-control studies that analyzed non-Hodgkin lymphoma alone or combined with Hodgkin lymphoma or multiple myeloma, from which we extracted 29 independent risk estimates. We performed random-effects meta-analyses for ever-exposure to diesel exhaust, overall and after stratification for outcome and study design. Results The meta-relative risk of non-Hodgkin lymphoma was 0.97 (95% confidence interval, 0.93-1.01; P-heterogeneity = 0.43). The meta-relative risk of results of cohort studies was 0.97 (95% confidence interval, 0.94-1.01) that of case-control studies was 1.00 (95% confidence interval, 0.84-1.17). Similar results were obtained when the meta-analysis was restricted to studies that analyzed only non-Hodgkin lymphoma. There was no indication of publication bias. Conclusion Our meta-analysis provided no overall evidence of an increased risk of non-Hodgkin lymphoma in subjects exposed to diesel exhausted.