Background information on urban outdoor air pollution
What are the most polluted cities in the world? Does WHO rank or compare cities on urban outdoor air quality?
Many cities in the world, including some expected to be among the most polluted, do not collect information or report on its outdoor air quality. WHO therefore cannot compare cities based on their levels of outdoor air pollution.
Rather, WHO has brought together information on urban outdoor air pollution collected by cities worldwide in order to raise awareness and facilitate adequate responses to protect public health from the adverse impacts of outdoor air pollution.
Cities that collect and disseminate information on outdoor air quality need to be praised for their action. This is the first crucial step to identify if there is an outdoor air pollution problem and to begin to take corrective action. The cities which have invested in the capacity to regularly monitor and report the local air quality measurements have already demonstrated a commitment to starting to address air quality issues and public health.