More than 80 percent of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed the limits set by the World Health Organization (WHO), a UN spokesman said Thursday.
While all regions of the world are affected, populations in low-income cities are the most impacted: 98 percent of cities in low- and middle-income countries with more than 100,000 inhabitants do not meet WHO air quality guidelines, Stephane Dujarric said at a daily news briefing here.
In high-income countries, that percentage drops to 56 percent, showed the latest global urban ambient air pollution database presented Thursday by the UN agency.
In the past two years, the database, which now covers 3,000 cities in 103 countries, has nearly doubled, with more cities measuring air pollution levels and recognizing the associated health impacts.
Ambient air pollution is the greatest environmental risk to health, causing more than three million premature deaths worldwide every year, the spokesman said.
"Air pollution is a major cause of disease and death. It is good news that more cities are stepping up to monitor air quality, so when they take actions to improve it they have a benchmark," said Flavia Bustreo, WHO assistant director general for family, women's and children's health.
"When dirty air blankets our cities the most vulnerable urban populations -- the youngest, oldest and poorest -- are the most impacted."
As urban air quality declines, the risk of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases, including asthma, increases for the people who live in them, WHO said.
During the five-year period from 2008 to 2013, WHO compared 795 cities in 67 countries for levels of small and fine particulate matter PM10 and PM2.5 -- particles smaller than 10 or 2.5 microns.
This included pollutants such as sulfates, nitrates and black carbon, which penetrate deep into the lungs and into the cardiovascular system, posing the greatest risks to human health. Data were then analyzed to develop regional trends.
Among the key trends from the period include that global urban air pollution levels increased by 8 percent, despite improvements in some regions, according to the agency.
In general, urban air pollution levels were lowest in high-income countries, with lower levels most prevalent in Europe, the Americas and the Western Pacific region.
The highest urban air pollution levels were experienced in low- and middle-income countries in WHO's Eastern Mediterranean and South-East Asia regions, with annual mean levels often exceeding five to 10 times the limits set by the agency, followed by low-income cities in the Western Pacific region.
