Obese children are more vulnerable to the harmful effects of air pollution than their slimmer classmates, according to a study.
Researchers at the Harvard School of Public Health, Boston, found fat youngsters five times more likely to be vulnerable to traffic fumes and industrial smog.
Dr Heike Luttmann-Gibson, who led the study, said: "Given the epidemic of obesity in children, it might be we are developing a population that is more susceptible to air pollution."
Her findings come from a study of 611 primary children aged nine and 10. The team measured air pollution each day and compared it to the lung function of their volunteers.
The 10 per cent of children who were classed as obese were two to five times more susceptible to air pollution.
The team is unsure why overweight children are more at risk. However fatty tissue is known to release chemicals involved in inflammation.
"Since air pollution also leads to inflammation of the airways, we think there is a multiplier effect that makes obese children more sensitive to air pollution."
Dr Heike Luttmann-Gibson added: "The higher the air pollution on a given day, the lower the children's lung function was on the following day, with a much greater effect being seen in the obese children.
"Obesity in childhood causes a host of medical conditions and problems, including increased risk of diabetes, heart problems and asthma."