2007 June issue of Pediatrics.new European study has found that infants who were regularly exposed to the chlorinated air of indoor swimming pools were more at risk for developing asthma than were infants who didn’t swim indoors.

“Our data suggest that infant swimming practice in chlorinated indoor swimming pools is associated with airway changes that, along with other factors, seem to predispose children to the development of asthma and recurrent bronchitis,” wrote the Belgian researchers. They also found the effect was stronger for babies who swam indoors and were also exposed to environmental tobacco smoke.

The researchers found that children who went swimming indoors as infants were 50 percent more likely to report wheezing, almost four times as likely to experience chest tightness, and had more than double the risk of experiencing shortness of breath, compared to the children who hadn’t been regular swimmers as infants.

The study also found that exposure to passive smoke alone didn’t seem to increase a child’s risk of asthma, but when coupled with indoor swimming, the risk of developing lung problems was even higher.

The study authors suggest that the risk might be higher because exposure to chemicals, such as chlorine, may alter the lining of the lungs, predisposing youngsters to airway disease.