IT IS undisputed that hospital admission for asthma has increased steadily in Britain over the past 20 years; for children, the admissions graph goes uphill at 45 degrees. One in 10 suffer from asthma, a huge increase over the past few years. Nitrogen dioxide from exhaust fumes has been similarly increasing in the air: twice as high as 20 years ago.

Children on bicycles, engulfed in a cloud of exhaust smoke from a passing bus, accompany worried articles about our smelly and damaged world. It is surprising, then, to hear from two world experts that the incidence of asthma is no higher in cities than it is in the country. A recent survey in Scotland found that it was just as bad in Skye as in the centre of Aberdeen. Another survey compared post-Cold War industrial East Germany to clean West Germany and, again, found levels just the same.

And as for the hated ozone layer, Peter Barnes, Professor of thoracic medicine at the Royal Brompton Hospital, says: “You’d expect the ozone level to be higher in cities, but it’s not. Ozone is formed by nitrogen dioxide and oxygen coming together, catalysed by sunlight. In the city, the ozone reacts again with the nitrogen dioxide to form oxygen. So the levels of ozone are actually higher in the country.”

Really knowledgeable people, like Professor Barnes and Dr Andy Bush, Senior Lecturer in Paediatrics at Royal Brompton, are willing to admit ignorance. The underlying cause of asthma remains a mystery, and the two experts do not pretend otherwise. “There are two issues,” said Dr Bush. “What is causing asthma in the first place; and if you’ve got asthma, what makes it worse?

“There’s quite a lot of evidence that pollutants can make asthma worse if you’ve got it, but I suspect they’re not actually causing asthma.” But the disorder attracts theories from the under-informed as irresistibly as cot death, anorexia, ME or any other mysterious medical horror of modern life.

Anti-pollutionists blame the increase on exhaust fumes; anti-smoking campaigners point to women smoking during pregnancy; anti-stress obsessives say it is overwork and anti-central-heating fanatics blame house-dust mites, a warm, modern house being a breeding paradise.

In trying to find answers, volunteers – asthmatic and non-asthmatic – undergo grim tests. They endure up to six hours in various kinds of polluted air in an exposure chamber, sometimes working on an exercise bicycle. “The tests are controversial,” said Professor Barnes, “because to get any effect you have to use high levels of pollution. If you do tests with nitrogen dioxide, you can’t detect the effects; but what seems to happen in real air is that if you have nitrogen dioxide mixed with sulphur dioxide, then you do have an effect.

“That’s the concern: pollutants are amplifying each other, and the combinations are what cause trouble.”

WHAT is clear is that asthmatics are all different and no one theory will account for all cases. Sylvia Dowding is south-east regional organiser for the National Asthma Campaign. Its aims are to fund research, build awareness and offer support. Her son, 25, had severe childhood asthma which is now controlled. Mrs Dowding feels that pollution can be a trigger. “If asthma is there already, pollution can bring it on. But when my son was young he had to spend a night in London for some tests. We thought the city air might be dreadful for him, but actually we had one of the best nights ever. It just shows how individual the problem is.”

The pollution theory is positively harmful, she says. “People might think, well, there’s nothing to be done, and give up taking medication, or give up trying to find the true reasons for it.”

Her son has been a smoker since he was 15, with no ill-effects on his asthma. “You need a tube to soothe the tube” as the wry asthmatic Joe Follows says to the hero of Ferdinand Mount’s novel Of Love and Asthma – a charming love story written by a man who knows just what it is like to be “a member of the great community of the bronchially strangulated”. The smoking asthmatic, like the chocolate-eating fatty or the one-lunged long-distance cyclist, is simply putting two fingers up to health theorists. Surely a good thing, even if it is medically slightly mad?

Dr Bush, though, has a thing about smoking and is convinced – though it is still only a theory – that passive smoking is an underlying cause of asthma. He cites a study in the Isle of Wight which showed that women who smoke in pregnancy are more likely to have babies with childhood asthma. In the second half of pregnancy, the baby’s tubes increase in size, but they don’t if the mother smokes. “The Government has breathtaking hypocrisy when campaigning for the health of the nation while allowing cigarette advertising,” he says. “Smoking in front of a child is a form of child abuse. My 15-year-old son tells me that about three-quarters of his friends are smoking.”

What the great doctor says may well be true, but there is a whiff of the hobby horse in his words.

Asthma is also being diagnosed more than it used to be and doctors admit that this is part of the reason why numbers are going up. ‘A lot of grown-ups say, ‘I always had a bad chest’,” said one south London GP. ‘Now almost any child who gets slightly wheezy at night is said to have asthma.” PROFESSOR Barnes said: ‘But an attack is an attack. You can’t hide it. And the increase in hospital admissions shows that asthma is getting worse.” In the waiting room at Dr Bush’s paediatric clinic, there were different things said about the pollution question.

The mother of Toni Watson, 16, from Shoreham-by-Sea, said: ‘We moved to the coast: we thought it would be the end of Toni’s asthma. But it’s been far worse. Perhaps it’s the main roads nearby, or the factories. We don’t know. We took Toni to Disney World in Florida in 1993 and for that whole fortnight she was fine. My other daughter has no problems with allergies in London, but when she stays with us she’s always coughing and sneezing.” The mother of Esther Grew, 13, said: ‘I do believe pollution makes it worse. We live at Wallington in Surrey. It used to be a village, now it’s so busy with cars going through to Croydon, it’s disgusting.”

Mike Lacey, father of nine-year-old Rasmus, said: ‘We live at Heston, three-quarters of a mile from the runway at Heathrow. We moved from Denmark last year. Rasmus hadn’t had any trouble there but it’s been really bad here.”

Farah, 11, who goes to Graveney School in Tooting, added: ‘I always take my inhaler before games: swimming and PE bring my attacks on. My asthma’s about the same in the town and in the country. But I’m allergic to cats.’ Mrs Turner, mother-of-three from Chingford, said: ‘My son has hay fever, my daughter Robin has asthma and the baby has the first signs of eczema. I’ve asked the doctor, ‘Where should we live? I want to get rid of this’. But there’s no simple answer. And you can’t get a doctor to tell you that traffic pollution’s bad for asthma. Perhaps it’s a conspiracy, to stop everyone moving out of towns into the country.”

The diary of a sufferer JOE Pitura-Riley (now three) would shout, scream and cough at night, and awaken at least six times, writes Caroline Phillips. His mother Annette was exhausted and could never sleep more than two hours for being at her son’s side.

If ever Annette or husband David, a corporate video presenter, allowed Joe into the chilly garden, he’d be wheezy and chesty. If Joe even ran to the bottom of the garden, he would gasp and rasp. And whenever he caught a cold, it would go straight to his chest and he’d have to be hospitalised. Joe was admitted to Guy’s hospital six times between the ages of 18 months and eight years.

The first time Annette took him to hospital, he was eight months old. She was traumatised. ‘I asked the doctor whether Joe was going to die,” says Annette, 33, a literature student.‘He had started to turn blue and looked so scared. I felt so helpless for this little baby who couldn’t get air into his lungs.”