Parents who teach their children to take care crossing a road may be neglecting a greater danger by living next to one.

Researchers have found that young people growing up in homes within 500 metres of a major road suffer significant damage to their lungs from exhaust fumes.

Compared with those who live at least 1,500 metres away, their breathing is not as deep or vigorous and their lungs do not develop to the same degree. This puts them at greater risk from asthma, bronchitis and chronic obstructive pulmonary disease, and weakens their sporting ability, the research suggests.

The study, conducted at the University of Southern California, is the latest to show that air pollution increases the risk of respiratory disease. But few studies have examined its effect on lung growth in children.

Scientists measured the lung function of 3,677 children from the ages of 10 to 18. They found that even healthy children who did not smoke suffered ill effects.

"Since lung development is nearly complete by age 18 years, an individual with a deficit at this time will probably continue to have less than healthy lung function for the rest of his or her life," they write in the online version of The Lancet. The effect was found to be greater in boys than in girls.

Lung function was measured by checking how big a breath each child could take, and the maximum pressure they could muster when blowing out. The authors say carbon, nitrogen dioxide and ultrafine particulates - tiny particles that can penetrate deep into the lungs - are all increased near roads and could account for the damage. Diesel exhaust has been shown to be particularly damaging.

Pressure on space is forcing homes and schools to be built close to busy roadways, they say. Stephen Holgate, professor of immunopharmacology at the University of Southampton, said the study added to evidence that exhaust fumes damaged lung development in children "probably in the first five to eight years of life".

He said: "Reduced lung function in childhood is a known risk factor for the development and worsening of asthma in children and the development of chronic obstructive pulmonary disease later in life." He added: "The study adds to the conclusions made in a World Health Organisation report on the health effects of pollution in children, published in 2006, and emphasises the importance of continuing strategies to reduce pollutant hot spots as well as reducing overall air pollutant exposure."

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