More than 80 percent of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed the World Health Organization limits, according to its latest report.
Globally, outdoor air pollution has increased by 8 percent from 2011 until 2015. All regions of the world are affected, but populations in low-income cities are the most impacted.
The PM2.5 micro-particles, classed as a Group 1 carcinogen by WHO, are tiny particulate matter that can cause stroke, heart disease, and chronic respiratory diseases.
Four of the 10 most polluted cities are in India, topped by one in Iran. However, the chart of big cities with more than 14 million inhabitants where air quality is the worst, based on 2016 WHO database, looks quite different.