Regional city‐population weighted comparisons in annual mean PM for a three‐year period, by region, for cities present in both versions of the AAP database. The mean for the World is based on weighting by regional urban population. Source: WHO. Click to enlarge. Air quality in most cities worldwide that monitor outdoor (ambient) air pollution fails to meet World Health Organization (WHO) guidelines for safe levels, putting people at additional risk of respiratory disease and other health problems, according to WHO’s expanded ambient (outdoor) air pollution (AAP) in cities database 2014 . WHO’s 2014 AAP database consists mainly of urban air quality data—annual means for PM10 and/or PM2.5—and covers 1,600 cities across 91 countries. Only 12% of the people living in cities reporting on air quality reside […]