Air quality deteriorating in world’s cities
Written by Deborah Ritchie
Air quality in the majority of cities worldwide that monitor outdoor (ambient) air pollution fails to meet WHO guidelines for safe levels, putting people at risk of respiratory disease and other health problems. Only 12% of the people living in cities reporting on air quality reside in cities where this complies with WHO air quality guideline levels. About half of the urban population being monitored is exposed to air pollution that is at least 2.5 times higher than the levels WHO recommends.
WHO’s urban air quality database covers 1,600 cities across 91 countries. In most cities where there is enough data to compare the situation today with previous years, air pollution is getting worse. Many factors contribute to this increase, including reliance on fossil fuels such as coal fired power plants, dependence on private transport motor vehicles, inefficient use of energy in buildings, and the use of biomass for cooking and heating.
But some cities are making notable improvements – demonstrating that air quality can be improved by implementing policy measures such as banning the use of coal for space heating in buildings, using renewable fuels for electricity production, and improving efficiency of motor vehicle engines.
Health risks caused by air pollution
The latest available data have prompted WHO to call for greater awareness of health risks caused by air pollution, implementation of effective air pollution mitigation policies; and close monitoring of the situation in cities worldwide.
“Too many urban centres today are so enveloped in dirty air that their skylines are invisible,” said Dr Flavia Bustreo, WHO assistant director-general for Family, Children and Women's Health. “Not surprisingly, this air is dangerous to breathe. So a growing number of cities and communities worldwide are striving to better meet the needs of their residents – in particular children and the elderly."
In April 2014, WHO issued new information estimating that outdoor air pollution was responsible for the deaths of some 3.7 million people under the age of 60 in 2012. The Organisation also emphasised that indoor and outdoor air pollution combined are among the largest risks to health worldwide.
There are many components of air pollution, both gaseous and solid. But high concentrations of small and fine particulate pollution is particularly associated with high numbers of deaths from heart disease and stroke, as well as respiratory illnesses and cancers. Measurement of fine particulate matter of 2.5 micrometres or less in diameter (PM2.5) is considered to be the best indicator of the level of health risks from air pollution.
In high-income countries, 816 cities reported on PM2.5 levels with another 544 cities reporting on PM10, from which estimates of PM2.5 can be derived. In low- and middle-income countries, however, annual mean PM2.5 measurements could be accessed in only 70 cities; another 512 cities reported on PM10 measurements.
“We can win the fight against air pollution and reduce the number of people suffering from respiratory and heart disease, as well as lung cancer,” said Dr Maria Neira, WHO director for public health, environmental and social determinants of health. “Effective policies and strategies are well understood, but they need to be implemented at sufficient scale….Copenhagen and Bogotà, for example, have improved air quality by promoting ‘active transport’ and prioritizing dedicated networks of urban public transport, walking and cycling.”
The report notes that individual cities can take local action to improve air quality and thus go against regional trends. And good air quality can go hand in hand with economic development, as indicated by some major cities in Latin America which meet, or approach, the WHO air quality guidelines.
“We cannot buy clean air in a bottle, but cities can adopt measures that will clean the air and save the lives of their people,” said Dr Carlos Dora, coordinator, Interventions for Healthy Environments, WHO Department of Public Health, Environmental and Social Determinants of Health.
Measures include ensuring that houses are energy efficient, that urban development is compact and well served by public transport routes, that street design is appealing and safe for pedestrians and cyclists, and waste is well managed. Such activities not only clean the air but can also serve as a catalyst for local economic development and the promotion of healthy urban lifestyles.