Bibliografisk note

Funding Information:
Conflict of interest: Z.J. Andersen reports participation on the WHO GAPH Technical Advisory Group, holds an unpaid role with the European Respiratory Society, outside the submitted work. U. Gehring has nothing to disclose. S. De Matteis has nothing to disclose. E. Melén is a member of the ERS Environmental Health Committee. A.M. Vicedo-Cabrera has nothing to disclose. K. Katsouyanni reports research grants from the EC (Horizon2020) and the US Health Effects Institute, outside the submitted work, and is a member of the WHO GAPH Technical Advisory Group. A. Yorgancioglu is the Advocacy Council Chair of ERS and receives support for travel and accommodation at ERS meetings. C.S. Ulrik reports fees for lectures from AZ, GSK, TEVA, Sanofi, Orion Pharma, Novartis and Chiesi, outside the submitted work. S. Medina is an employee of Santé publique France. K. Hansen is part of the leadership of the European Lung Foundation and the European Respiratory Society. P. Powell is an employee of ELF. B. Ward is an employee of ERS. B. Hoffmann is a member of the research committee for Health Effects Institute, Boston, USA.