released Thursday found that air quality levels exceed WHO limits for 80% of those living in urban areas that track air pollution, putting people more at risk for respiratory diseases, stroke, heart disease and lung cancer.
Global air pollution also rose 8% from 2008 to 2013.
"Urban air pollution continues to rise at an alarming rate, wreaking havoc on human health," says Dr. Maria Neira, the WHO director of the Department of Public Health, Environmental and Social Determinants of Health. "At the same time, awareness is rising and more cities are monitoring their air quality. When air quality improves, global respiratory and cardiovascular-related illnesses decrease."
The data was particularly worrisome for poorer cities -- 98% of those in "low- and middle-income" countries with more than 100,000 people didn't meet the WHO guidelines, compared to 56% in "high-income"countries.
The WHO estimates that air pollution causes upwards of 3 million premature deaths every year.
However, the report did note some positive trends.
About 30 percent of cities tracked had decreasing levels of pollution.
Half of the cities in high-income countries and more than a third in low-income and middle-income countries reduced pollution levels by 5% in five years.
And, 3,000 cities in 103 countries are now tracking pollution statistics. That's double the number of cities compared to two years ago.
The study tracked the growth in the two different sizes of particulate matter, PM10 and PM2.5, per cubic meter of air.
PM2.5 particles are fine, with a diameter of 2.5 micrometers (µm) to more than 40 micrometers, according to the Environmental Protection Agency.
PM10 particles are less than or equal to 10 micrometers in diameter.