Outdoor air pollution is a major environmental health problem affecting everyone in low, middle and high income countries. Ambient (outdoor) air pollution in both cities and rural areas was estimated to cause 4.2 million premature deaths worldwide per year in 2019; this mortality is due largely to exposure to fine particulate matter, which causes cardiovascular and respiratory disease, and cancers. The World Health Organisation (WHO)¹ estimated that in 2019, some 37% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke, 18% and 23% of deaths were due to chronic obstructive pulmonary disease and acute lower respiratory infections respectively, and 11% of deaths were due to cancer within the respiratory tract. WHO also states that 99% of the world’s population breathe air that exceeds their maximum recommended level of pollutants. People living in low and middle income countries disproportionately experience the burden of outdoor air pollution with 89% of the 4.2 million premature deaths occurring in these areas. The greatest burden is found in the South-East Asia and Western Pacific Regions.