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NEW YORK (Reuters Health) - Infant swimming lessons in an indoor pool may have the unintended effect of raising some children's risk of asthma later on, new research findings suggest.
In a study of 341 schoolchildren, Belgian researchers found that the 43 children who had been enrolled in a swimming program as infants were about three times more likely to have asthma or suffer recurrent bouts of bronchitis than children who did not.
The problem, according to the researchers, is that chlorine byproducts may irritate infants' developing airways, causing changes that make them more susceptible to lung disease later in childhood.
Lead author Dr. Albert Bernard and colleagues at the Catholic University of Louvain in Brussels report the findings in the journal Pediatrics.
Past studies have found that competitive swimmers and people who work around indoor pools tend to have elevated rates of asthma. Experts suspect that the air quality around pools -- particularly indoor ones -- is to blame.
When the chlorine used to disinfect pools combines with swimmers' sweat, saliva or urine, irritating chlorine byproducts are formed. One of these is a gas called trichloramine, which is released into the air, giving indoor pool areas their distinctive "chlorine" smell. Trichloramine is known to irritate the eyes and upper respiratory tract.
To investigate the effects of early exposure to indoor pools and if it predisposes children to asthma, Bernard and his colleagues screened the children for asthma, questioned their parents about their respiratory health and took blood samples to measure particular proteins that indicate the health of the lining of the respiratory tract.
They found that in general, children who'd been in the pool as babies were more likely to show signs of damage to the respiratory tract lining. This damage, in turn, seemed to make them more susceptible to asthma and repeated bouts of bronchitis.
Still, the findings do not necessarily mean that parents should keep babies and toddlers away from swimming lessons, according to Bernard.
In cases where a young child is at relatively higher risk of drowning -- because of the family pool, for instance -- the benefits of learning to swim may outweigh the potential harm to the airways, Bernard told Reuters Health.
For other babies and toddlers, though, delaying swimming lessons might be a wiser move, according to the researcher.
Parents who do take their young children to swimming lessons should be alert for signs of over-chlorination, he noted. "If there is a very strong chlorine smell and if the swimmers complain of irritation (of) the eyes and upper respiratory tract," Bernard said, "this is an indication that water and air contain high levels of chlorination products."
Whether outdoor and residential pools present a risk to young children's lung health is not clear, according to Bernard. "This warrants further research," he said.
SOURCE: Pediatrics, June 2007.