Traffic fumes may trigger asthma in children who are genetically susceptible to the disease, according to a study published in the journal Thorax last week. The researchers, based at the University of Southern California, found that children who carried variations in the gene GSTP1, coupled with elevated levels of the enzyme EPHX1, were up to nine times more likely to have developed asthma if they lived near a busy road.
'This study is very promising as it is one of the first to look specifically at how genetic susceptibility to respiratory disease and environmental traffic fumes can cause childhood asthma', Leanne Male, Asthma UK's assistant director of research, told the BBC.
To assess the affect of each of the risk factors on asthma risk, the researchers looked for variations in the GSTP1 gene and also measured levels of the EPHX1 enzyme in the body, in some 3,000 children affected by asthma.
The gene and the enzyme both appear to be involved in purging harmful chemicals breathed into the body, say the researchers, and confer varying levels of risk depending on the combination of risk factors carried. Estimates showed that children who have elevated levels of the EPHX1 enzyme, combined with living within 75 metres of a busy road, are three times more likely to have asthma. However, if a child also inherits variations in the GSTP1 gene from either or both parents, they were up to nine times more likely to have asthma.
The effects of pollution on asthma risk have been in question for many years. Leanne Male hopes that the research may one day provide an explanation: 'People with asthma tell us that traffic fumes make their asthma worse and, although this research only looks at individuals with a certain genetic make-up, we await further robust research in this new and exciting area to help us find better ways to treat asthma'.