Diesel engine fumes 'make asthma worse'

Heavy London traffic makes it harder for asthmatics to breathe, a study has shown.

Researchers from Imperial College discovered that people with breathing problems who walked along Oxford Street lost six per cent of their lung capacity and saw an increase in other symptoms.

They blamed diesel vehicles which can emit 100 times more particulates - minute particles of dust, dirt, soot and smoke - than their petrol equivalents.

It took hours for the 60 subjects, who had mild or moderate asthma, to start breathing normally again.

In Hyde Park the asthmatics experienced some of the same symptoms but to a much lesser degree. Previous studies have shown that almost 90 per cent of traffic-generated particulate matter in cities is from diesel exhausts.

Study co-author Professor Fan Chung said it should "not necessarily" deter people from shopping in Oxford Street but called for better controls of traffic levels.