The World Health Organization released a new global air quality data report this week, saying that urban air quality around the world has failed to meet its health standards, leaving millions of people facing the threat of respiratory diseases, lung cancer and other serious chronic diseases.
The report said that about half of the residents living in the cities it mentioned are exposed to air pollution at least 2.5 times higher than the WHO air quality guidelines.
The new urban air quality database covers more than 1,600 cities in 91 countries, more than 500 cities more than the 2011 database, which shows that more and more cities are aware of the health hazards of air pollution and have begun to monitor outdoor air quality.
The database covers the period from 2008 to 2013, with most of the data coming from 2011 and 2012. Comparing the air quality of cities with sufficient data today and in the past shows that the air quality of most cities is deteriorating.
The most polluted cities include Dakar, Senegal; Mexico City, Mexico; Karachi, Pakistan; Delhi, India; Ulaanbaatar, Mongolia; and Seoul, South Korea.
WHO officials point out that many factors contribute to the deterioration of air quality, such as the predominance of electricity from fossil fuels, reliance on private vehicles for travel, and inefficient energy use in buildings.
However, some cities have made progress, which shows that air quality can be improved by banning coal heating, using renewable or clean energy for electricity, and increasing the power of vehicle engines.
Dr. Maria Neira, WHO's director of public environmental health, told Environmental News Service: "People need to not only know about effective policies and measures, but also make full use of them."
"Cities such as Copenhagen and Bogota have improved local air quality by encouraging 'active travel', designing urban public transportation and walking and cycling network systems," she said.
WHO hopes that people will pay attention to the health hazards caused by air pollution, take effective measures to reduce air pollution, and closely monitor the situation of urban air around the world.
Air pollution comes from gases and solids, with high concentrations of fine particles being the most likely to cause death from heart disease, stroke, respiratory disease and cancer.
WHO officials say PM2.5 is one of the most visible indicators of health risks from air pollution.
816 cities in high-income countries reported their PM2.5 index, and 544 cities reported their PM10 index, from which PM2.5 can be inferred. But the reporting situation in low- and middle-income countries is not optimistic. Only 70 cities have annual average PM2.5 data, and another 512 cities have PM10 data.
The report points out that every city can take action to improve air quality. "We can't buy bottled fresh air, but cities can take effective measures to clean the air and save urban residents," said Dr. Carlos Dora, WHO's public environmental health coordinator. (Ma Xiaofang)