Air pollution is responsible for half a million premature deaths annually in the WHO European Region, primarily due to noncommunicable diseases, such as ischaemic heart disease, stroke, lung cancer and chronic obstructive pulmonary disease. On this International Day of Clean Air for blue skies, 7 September, WHO/Europe is calling to step up action "together for clean air", highlighting the urgent need for stronger partnerships, increased investment, and shared responsibility for overcoming air pollution.