THURSDAY, May 29, 2003 (HealthDayNews) -- Indoor swimming pools could be a major source of childhood asthma.
That's the conclusion of a new study by Belgian scientists who found that exposure to a byproduct of chlorine used to disinfect pools damages the lungs and could be associated with an increased risk of asthma in children who swim a lot.
Previous studies have found a link between breathing problems and swimmers and lifeguards, who spend a great deal of time in and around pools. But the latest work is the first to suggest that recreational indoor swimming might also raise the risk of asthma.
"There seems to be an association, particularly when the children are very young," says Alfred Bernard, a professor of toxicology at Catholic University of Louvain in Brussels, and leader of the research. "They can't swim, so they maximize their exposure" to the dangerous byproduct, a gas called nitrogen trichloride.
The good news, Bernard says, is that the potential problem has a simple solution -- indoor pools must have proper ventilation. "It's just a question of ventilating the pool," he says. "There is almost no gas outside."
A report on the study appears in the June issue of Occupational and Environmental Medicine, a British health journal.
Another step that could greatly cut down on the amount of nitrogen trichloride released in pools is to make sure bathers are clean before they step into the water, and to keep young children from leaving their own liquids -- urine, sweat, saliva -- behind.
"All the byproducts come from the interaction of chlorine with organic matter," Bernard says.
In Brussels, indoor public pools are closed if they fail to meet air-quality standards. Bathers are also required to shower before entering the water.
In their study, Bernard's group measured blood levels of lung and immune system proteins in 226 children without asthma who'd been swimming at indoor pools. They also looked for changes in lung proteins in a smaller group of children and adults after they went swimming at a chlorinated pool. And they compared asthma rates and pool use in almost 1,900 other children who had participated in an asthma survey in the mid and late 1990s.
Dr. James Martin, a physician at Montreal's McGill University, has studied chlorine's effects on the lungs in occupational settings, such as paper mills, where the gas is used. "Sometimes workers are accidentally exposed to chlorine, they get a blast of it, and they can get asthma permanently," he says. The latest work seems to show that indoor pools may pose a similar threat through repeated exposure to the toxin, he says.
Bernard says it's unclear how much exposure to chlorine might explain childhood asthma rates, which are climbing in industrialized countries. More studies in this area are needed, he adds.
More information
To learn more about asthma, visit the American Academy of Allergy Asthma and Immunology or the American Lung Association.
