Long-term air pollution exposure and malignant intracranial tumours of the central nervous system: a pooled analysis of six European cohorts

Background Risk factors for malignant tumours of the central nervous system (CNS) are largely unknown. Methods We pooled six European cohorts ( N = 302,493) and assessed the association between residential exposure to nitrogen dioxide (NO 2 ), fine particles (PM 2.5 ), black carbon (BC), ozone (O 3 ) and eight elemental components of PM 2.5 (copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc) and malignant intracranial CNS tumours defined according to the International Classification of Diseases ICD-9/ICD-10 codes 192.1/C70.0, 191.0–191.9/C71.0–C71.9, 192.0/C72.2–C72.5. We applied Cox proportional hazards models adjusting for potential confounders at the individual and area-level. Results During 5,497,514 person-years of follow-up (average 18.2 years), we observed 623 malignant CNS tumours. The results of the fully adjusted linear analyses showed a hazard ratio (95% confidence interval) of 1.07 (0.95, 1.21) per 10 μg/m³ NO 2 , 1.17 (0.96, 1.41) per 5 μg/m³ PM 2.5 , 1.10 (0.97, 1.25) per 0.5 10 −5 m −1 BC, and 0.99 (0.84, 1.17) per 10 μg/m³ O 3 . Conclusions We observed indications of an association between exposure to NO 2 , PM 2.5 , and BC and tumours of the CNS. The PM elements were not consistently associated with CNS tumour incidence.