Occupational exposure to polycyclic aromatic hydrocarbons and lymphatic and hematopoietic neoplasms : a systematic review and meta-analysis of cohort studies

Data on the risk of lymphatic and hematopoietic neoplasms among workers whose jobs entail high exposure to polycyclic aromatic hydrocarbons (PAH) are sparse, and mainly based on small-size studies. We carried out a systematic review of occupational cohort studies that reported results on incidence or mortality from Hodgkin lymphoma (HL), non-Hodgkin lymphoma (NHL), leukemia or multiple myeloma (MM) among workers exposed to PAH. We computed meta-analytic estimates using a random effect model. Meta-relative risk (meta-RR) was computed separately by each type of neoplasm, job or industry. We identified 41 studies (12 in iron and steel foundries, 11 in aluminum plant, 6 in cokeries, 6 in carbon electrode manufacturing, 2 on asphalt workers, 2 on creosote-exposed workers, 1 on tar distillery workers and 1 evaluating both tar distillery workers and roofers). No significant excess risk of any lymphatic and hematopoietic neoplasms was found among workers employed in jobs or industries entailing high PAH exposure. Among 18 meta-analytic estimates by job or industry and type of neoplasm, 16 were close to unit, i.e., between 0.72 and 1.27, whereas the meta-RR was 1.38 [95 % confidence interval (CI) 0.95–2.01] for HL in foundry workers and 2.01 (95 % CI 0.96–4.22) for NHL in workers exposed to creosote. There was no association between occupation entailing high PAH exposure and risk of MM or leukemia.