Focus: New link between asthma and diesel fumes shows the campaign must go on

For two years this newspaper has helped raise awareness of a disease that affects 5.2 million people in Britain. Policies and lives have changed, but there is still much to do. Severin Carrell and Geoffrey Lean report on a crisis in research funding and dramatic new science that shows pollution from exhaust fumes can cause asthma

Major new scientific findings suggest that air pollution from vehicles can cause asthma in previously healthy people as well as triggering attacks in people with the disease.

Major new scientific findings suggest that air pollution from vehicles can cause asthma in previously healthy people as well as triggering attacks in people with the disease.

Until now, scientists had believed traffic fumes simply worsened everyday life for asthmatics. But research on both sides of the Atlantic now suggests that tiny "particulates" from exhausts can sidestep the body's natural defences and set off asthma.

Diesel, which is being heavily promoted by ministers as a "green" fuel that can help combat global warming, is most to blame.

"These microscopic particles are a major threat to human health," said Professor Stephen Holgate, one of the Government's most senior advisers on air pollution, who is opening a major conference on asthma backed by The Independent on Sunday on 28 April (see below).

"There is a strong suspicion that particulates in air pollution are playing a much greater role in the causation of asthma than has previously been realised," said Professor Holgate, who chairs the official Expert Panel on Air Quality Standards.

"The latest scientific evidence suggests that particulates are now the most important type of air pollutant that threatens human health."

The new findings raised serious questions about the safety of diesel cars, said Professor Holgate. He was talking ahead of a new effort to push asthma to the top of the Government's agenda later this month, when some of Britain's top asthma experts and campaigners will meet at London's Royal Society of Medicine for a conference on the disease.

The event is being co-sponsored by the IoS as part of its ongoing asthma campaign, which began two years ago when scientific evidence of a definite link between pollution and asthma emerged.

The campaign raised the profile of asthma in the UK dramatically and caused ministers and the European Commission to reappraise official policies on ozone pollution. Now the conference will focus on the latest research and try to set new scientific priorities - one of the most significant gaps in the Government's strategy.

A global survey confirmed the UK's status at the top of the world's asthma league table, last month with GPs seeing 20,000 new cases each week. Yet the burden of investigating and reversing this phenomenon is shouldered almost entirely by charities such as the National Asthma Campaign (NAC), which can only afford £2m a year on research, and the pharmaceutical companies, whose main interest is to sell drugs, not cures.

Professor Martyn Partridge, the NAC's chief scientist, described government res- earch spending on respiratory illnesses as "lamentable". Ministers, he said, had failed to fund any - admittedly expensive - projects to stop people getting asthma.

In the light of his latest findings, Professor Holgate, who has published 400 papers on asthma and allergies and sits on the Royal Commission on Environmental Pollution, called for greater efforts to design much more effective "particulate traps" to be fitted to diesel exhausts.

The Chancellor, Gordon Brown, has led a government push to increase the use of diesel cars in Britain by introducing lower taxes for the fuel and for the cars that use it. As a result, sales of diesel cars have leapt by a third in recent years. This is presented as a "green" policy because diesel engines emit much less carbon dioxide - the main cause of global warming - than petrol-powered engines. But they also emit far more of the particulates.

Professor Holgate's warnings were backed by a leading US expert due to speak at the conference, Dr Rob McConnell, who said ministers should "think twice" about their support for diesel. "It helps reduce CO2, but I think there's increasing literature that suggests diesel exhaust particles have some serious respiratory effects."

The findings will increase pressure on ministers and car-makers to tackle traffic pollution as part of efforts to combat an asthma epidemic which affects 5.2 million Britons, giving the UK the world's highest incidence of the disease.

Pioneering research in 2002 by a team at the University of Southern California led by Dr McConnell suggested that ozone in the atmosphere, created by the interaction of sunlight on car exhausts, caused asthma in children who regularly played open-air sports.

Now both Dr McConnell and Professor Holgate believe a major research effort is needed into the damage being caused by particulates. Britain and the EU lag far behind the US in investigating their impact on human health, said Professor Holgate, who is based at Southampton General Hospital.

He will tell the conference that air pollution is emerging as a key area for asthma research. Studies have made it more clear that microscopic particles are a trigger for asthma attacks, and could work beside pollen to set off severe attacks by inflaming the lungs, he said.

But the latest findings also show particulates are so small that they can sneak through the lungs' natural defences and damage the body's cells, causing asthma and other respiratory illnesses in susceptible people. The same mechanism, he said, was now being linked to heart attacks and coronary thrombosis.

Professor Holgate stressed that other environmental and genetic factors played a greater role in causing asthma, such as poor diet during pregnancy and a lack of exposure to allergens during infancy. Unhealthy eatingincreased the risks that particulates would damage the vulnerable, he said, because their bodies' natural defences would be far weaker.