More than 80 per cent of people living in urban areas that monitor air pollution are exposed to levels that exceed the World Health Organization (WHO) guidelines. All regions of the world are affected, but people in low-income cities suffer the worst effects. Some 98 per cent of cities in low- and middle-income countries with more than 100,000 inhabitants do not meet the WHO air quality guidelines. In high-income countries, that figure decreases to 56 per cent of cities.
These figures come from the WHO’s recent update of its global urban ambient air pollution database. Data from a total of 795 cities in 67 countries was compared for levels of small and fine particulate matter (PM10 and PM2.5) between 2008 and 2013. Over these six years, global urban air pollution levels increased by eight per cent, despite improvements in some regions.
PM10 and PM2.5 include pollutants such as sulphates, nitrates and black carbon, which penetrate deep into the lungs and into the cardiovascular system, posing the greatest risks to human health.
According to the database, levels of PM2.5 are highest in India, which has 16 of the world’s 30 most polluted cities. China has improved since 2011 and now has only five cities in the top 30. Nine other countries, including Pakistan and Iran, have one city each in the worst 30.
“It is crucial for city and national governments to make urban air quality a health and development priority,” said Dr Carlos Dora, co-ordinator of the WHO’s Interventions for Healthy Environments programme. “When air quality improves, health costs from air-pollution-related diseases shrink, worker productivity expands and life expectancy grows.”
The WHO database, including a summary, is at: www.who.int/phe/health_topics/outdoorair/databases/cities/en