A WARNING from the WHO on the dangers of air pollution has provoked a fierce struggle between industry and government officials in Europe. A panel of WHO experts has concluded that thousands of Europeans who are exposed to airborne particles common in cities will suffer or die.
The WHO panel, drawn from 11 countries and chaired by Robert Maynard, head of air pollution at the Department of Health in London, says that there “may be large” health implications from particles known as PM10s. The particles get their name because they measure less than 10 micrometres across. They come mostly from diesel vehicles.
In the report, which recommends new European safety standards for air pollutants, the WHO experts decline to propose a safe limit for PM10s “because there is no evident threshold for effects on morbidity and mortality”. For the first time, the WHO panel has abandoned its practice of lumping particles together with sulphur dioxide. It has also estimated how many people will be harmed by PM10s alone (see Table).
The panel says that a three-day episode with PM10 concentrations at 50 micrograms per cubic metre causes a great deal of extra suffering. In a sample of 1 million individuals, 1400 extra people need their asthma inhalers, six more than usual are admitted to hospital with respiratory problems, and four more die. In most British cities, levels of PM10s rise above 50 micrograms per cubic metre on up to 40 days a year. The highest level in 1993 – the latest year for which figures are available – was 163 micrograms per cubic metre.
Next week, the British government’s expert panel on air quality standards is expected to recommend that people should not be exposed to more than 50 micrograms of PM10s per cubic metre over 24 hours. The WHO report implies that exposure at this level over three days in Greater London would force 1400 asthmatics to reach for their inhalers, send 40 more than usual to hospital with respiratory problems and kill an extra 27.
“The government will have to make a political decision about how many people it allows to choke or croak,” says Tim Brown from the National Society for Clean Air. The same dilemma is facing the European Commission’s technical working group on particles, which met for the first time two weeks ago. According to insiders, it is studying a PM10 limit between 30 and 100 micrograms per cubic metre.
But the oil and transport industries, which were represented at the working group’s meeting, are mounting stiff resistance to strict limits on PM10s. They fear they will be forced to invest heavily to reduce particle emissions from vehicles. They say the American epidemiological studies on which the WHO report is based reveal an association but not a causal link between particles and ill-health. “To say that particles are dangerous is emotive and irresponsible,” says one oil industry scientist who wishes to remain anonymous.
The WHO experts regard the US studies as sound and dismiss criticisms from industry as predictable and irrelevant. “This is an issue of high public health importance,” says Michal Krzyzanowski, a panel member from the WHO’s European Centre for Environment and Health at Bilthoven in the Netherlands. Another panel member says that understanding the health effects of particles “represents the biggest change in air pollution toxicology in the last 20 years”.