WHO: Tackling the global clean air challenge

In many cities air pollution is reaching levels that threaten people's health according to an unprecedented compilation of air quality data released today by WHO. The information includes data from nearly 1100 cities across 91 countries, including capital cities and cities with more than 100 000 residents.

Over 2 million people die from indoor and outdoor air pollution

WHO estimates more than 2 million people die every year from breathing in tiny particles present in indoor and outdoor air pollution. PM10 particles, which are particles of 10 micrometers or less, which can penetrate into the lungs and may enter the bloodstream, can cause heart disease, lung cancer, asthma, and acute lower respiratory infections. The WHO air quality guidelines for PM10 is 20 micrograms per cubic metre (µg/m3) as an annual average, but the data released today shows that average PM10 in some cities has reached up to 300 µg/m3.

Main findings

The main findings contained in the new compilation are:

• Persistently elevated levels of fine particle pollution are common across many urban areas. Fine particle pollution often originates from combustion sources such as power plants and motor vehicles.
• The great majority of urban populations have an average annual exposure to PM10 particles in excess of the WHO Air Quality guideline recommended maximum level of 20 µg/m3. On average, only a few cities currently meet the WHO guideline values.
• For 2008, the estimated mortality attributable to outdoor air pollution in cities amounts to 1.34 million premature deaths. If the WHO guidelines had been universally met, an estimated 1.09 million deaths could have been prevented in 2008. The number of deaths attributable to air pollution in cities has increased from the previous estimation of 1.15 million deaths in 2004. The increase in the mortality estimated to be attributable to urban air pollution is linked to recent increases in air pollution concentrations and in urban population size, as well as improved data availability and methods employed.

"Air pollution is a major environmental health issue and it is vital that we increase efforts to reduce the health burden it creates," said Dr Maria Neira, WHO Director for Public Health and Environment. "If we monitor and manage the environment properly we can significantly reduce the number of people suffering from respiratory and heart disease, and lung cancer. Across the world, city air is often thick with exhaust fumes, factory smoke or soot from coal burning power plants. In many countries there are no air quality regulations and, where they do exist, national standards and their enforcement vary markedly. "

Greater awareness of health risks

WHO is calling for greater awareness of health risks caused by urban air pollution, implementation of effective policies and close monitoring of the situation in cities. A reduction from an average of 70 µg/m3 of PM10 to an annual average of 20 µg/m3 of PM10 is expected to yield a 15% reduction in mortality - considered a major public health gain. At higher levels of pollution, similar reductions would have less impact on reducing mortality, but will nevertheless still bring important health benefits.

"Solutions to outdoor air pollution problems in a city will differ depending on the relative contribution of pollution sources, its stage of development, as well as its local geography," said Dr Carlos Dora, WHO Coordinator for Interventions for Health Environments in the Department of Public Health and Environment. "The most powerful way that the information from the WHO database can be used is for a city to monitor its own trends in air pollution over time, so as to identify, improve and scale-up effective interventions."

Largest contributors to urban outdoor air pollution

In both developed and developing countries, the largest contributors to urban outdoor air pollution include motor transport, small-scale manufacturers and other industries, burning of biomass and coal for cooking and heating, as well as coal-fired power plants. Residential wood and coal burning for space heating is an important contributor to air pollution, especially in rural areas during colder months.

“Local actions, national policies and international agreements are all needed to curb pollution and reduce its widespread health effects" said Dr Michal Krzyzanowski, Head of the WHO European Centre for Environment and Health in Bonn, Germany. "Data from air quality monitoring that is released today, identify regions where action is most needed and allows us to assess the effectiveness of implemented policies and actions.”