The World Health Organization says 98 percent of residents in large cities of low- and middle-income countries are facing excessively high air pollution.
Overall, the Geneva-based health agency says its database shows more than four in five urban dwellers worldwide live in cities that don't meet WHO air quality guidelines, including 56 percent of city dwellers in high-income countries.
The agency on Thursday released new information from its Global Urban Ambient Air Pollution Database, which covers 3,000 cities in 103 countries and is based partly on country reports.
The agency said global urban air pollution levels rose 8 percent "despite improvements in some regions." WHO noted that people face a higher risk of strokes, heart disease, lung cancer and respiratory diseases as air quality worsens.