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Thursday, 4 January, 2001, 00:46 GMT
Pollution 'could cause asthma'
traffic fumes
Traffic pollution has been blamed for causing asthma
Experiments using monkeys suggest that traffic pollution could cause asthma in children, rather than simply trigger attacks.

But a British expert says there is plenty of evidence suggesting precisely the opposite.

Scientists at the University of California at Davis studied the effect of repeated exposure to ozone - a constituent of traffic smog - on rhesus monkeys.

They found that after living in an environment described as "similar to Mexico City" for only a few months, the young animals had developed symptoms of borderline asthma.

These included reduced lung capacity, and an apparently increased sensitivity to the dust mite allergen, wheezing when exposed to it for short periods.

Monkeys exposed on a regular basis to both ozone and dust mite allergen had more severe ractions, including decreased blood oxygen levels.

More mucus

Both groups of monkeys exposed to ozone had developed lung abnormalities similar to those found in asthmatics, including overactive muscle surrounding the airways, and over-production of mucus.

asthma attack
Attacks can be triggered by car fumes
Dr Ira Tager, of the University of California at Berkeley, told New Scientist magazine: "It fits well with what's known in humans about developmental effects."

But Dr Adnan Custovic, a National Asthma Campaign senior research fellow and an honorary consultant allergist at Wythenshawe Hospital in Manchester, said the weight of evidence pointed away from air pollution as a cause of asthma.

Plenty of studies had found no link between air pollution and levels of asthma, he said.

A recent study comparing children in heavily air-polluted former East Germany to those in the west following reunification found that asthma rates were actually lower in the east.

He added: "The problem with animal models of asthma is that you don't have one that is really representative of human asthma.

"That is why this kind of research is so difficult.

"It seems to be very clear that air pollution has a lot to do with triggering asthma attacks, but is not actually a cause."

In fact, he pointed out, asthma cases have soared since the introduction of the Clean Air Act - which radically decreased the amount of air pollution in the UK over the following decades.

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