Air pollution is a major threat to health, says WHO The World Health Organization says that its new guidelines on air quality could help save as many as 300 000 lives around the world each year. The guidelines call for much tougher standards for emission levels of pollutants in cities.

"By reducing air pollution levels we can help countries to reduce the global burden of disease for respiratory infections, heart disease, and lung cancer which they otherwise would be facing," said Maria Neira, WHO's director of public health and environment.

The agency says that air pollution continues to pose "a significant threat" to health worldwide and is estimated to cause more than two million premature deaths each year. More than half of this disease burden is borne by people in developing countries. The guidelines published on 5 October provide-for the first time-uniform targets for air quality in all regions of the world on four common pollutants: particulate matter, ozone, nitrogen dioxide, and sulphur dioxide.

The new criteria are based on a revision and expansion of the air quality guidelines for Europe issued in 2000 and on consultations with 80 leading scientists. They also draw on thousands of recent scientific studies from all regions of the globe.

"We look forward to working with all countries to ensure that these guidelines become part of national law," said Robert Bertollini, director of the special programme for health and environment at WHO's regional office for Europe.

Under the stricter guidelines the average annual levels of "PM10," the particulate matter that enters the respiratory tract and mainly comes from burning fossil and other fuels, should be less than 20 micrograms per cubic metre. In many cities PM10 levels currently exceed 70 micrograms per cubic metre, WHO notes. "By reducing particle matter pollution from 70 to 20 micrograms per cubic metre as set out in the new guidelines, we estimate that we can cut deaths from air pollution by around 15%," said Dr Neira.

WHO recommends that the daily level of ozone should be below 100 micrograms per cubic metre, down from the previous guideline of 120. The level for sulphur dioxide is reduced from 125 to 20 micrograms per cubic metre. The guideline's levels for nitrogen dioxide remain unchanged, however, at 40 micrograms per cubic metre.