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.