Ozone causes asthma, suggests new study

High ozone levels may cause asthma, not just exacerbate it as previously thought, according to a study carried out by a team from Keck School of Medicine of the University of Southern California (USC) and published in The Lancet this week.

The study tracked 3535 children from 12 communities in southern California for up to five years, none of which were asthmatic at the onset if the investigation. The communities were chosen partly on the basis of their levels of ozone concentration, six had high levels with the other six being low ozone communities.

Two hundred and sixty-five new cases of asthma were reported in these children in the follow-up of the investigation, and it was noted that children who exercised heavily – thereby increasing the amount of ozone getting into their lungs – in areas of high ozone were 3.3 times more likely to develop asthma. The study reported that children playing highly active sports in low ozone areas were at no greater risk from developing asthma than children who did not participate in sports in the same environment. However, the study indicated that in areas where ozone levels were higher and other pollutant levels were low, contraction of asthma in children exercising vigorously was increased to 4.2 times.

Asthma has been on the increase over the past decades in developed countries; in UK adults alone, cases have more than doubled in the past 20 years (see related story), although reasons for this are unclear. In the past it has been recognised that air pollution exacerbates asthma. However this new study allows a link to be drawn between high exposure to ozone and the initial development of the disease.

Dr. Rob McConnell from the USC School of Medicine, a member of the group which conducted the study, said “our study provides evidence that ozone is involved in the development of new onset asthma in children who exercise heavily”. However he does stress that “it is by no means conclusive proof that air pollution causes asthma”. The study offers asthma investigators “a piece of the complicated asthma puzzle” Dr. McConnell told edie, stating that he is satisfied that his work and that of his colleagues is “progress in the right direction”.

The Asthma Audit 2001, published by the National Asthma Campaign, estimated that 5.1 million people in the UK – one in 13 adults and one in eight children – were now asthma sufferers and every year serious asthma conditions cause 74,000 emergency hospital admissions.

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