Around 99 percent of the global population breathes air that exceeds World Health Organization's air quality limits, with people in low and middle-income countries being most exposed to pollution, according to the UN agency's latest database.

The agency's report includes data on air pollutants such as particulate matter and nitrogen dioxide - both of which are found in fossil fuel emissions and blamed for some respiratory and heart conditions - for the years between 2010 and 2019 and covers over 6,000 cities in 117 countries.