A study of more than 400 Belgian 5-year-olds found that children who had spent more than 20 hours in a chlorinated indoor pool before the age of 2 were almost 3.5 times as likely to have come down with a case of bronchiolitis at an early age compared with non-swimming children. (Bronchiolitis is an infection of the lungs' small airways, usually caused by the respiratory syncytial virus—RSV.)
Published online by the European Respiratory Journal on January 14, 2010, the study found that children who had spent that much time at an outdoor pool showed a two-fold increase in their risk of lower respiratory tract infection. Researchers speculate that airway irritation from chlorine byproducts may make babies more vulnerable to bronchiolitis. In some cases, the infection and continued chlorine exposure appeared to lead to other health problems. Among infant swimmers who had contracted bronchiolitis, 15 percent had developed asthma by age 5. The asthma rate among young swimmers with no history of the infection was only 4 percent.
Does this mean it's time to cancel the mommy-and-me swim class? According to researchers, parents should not necessarily keep their young children away from all swimming pools, but should try to avoid taking Baby to swim in pools that are heavily chlorinated. Some clues to over-chlorination include an overwhelming chlorine smell (especially in indoor pool areas), and eye, skin, and throat irritation.
"Parents should ... not lose sight that chlorine-based disinfectants and their derivatives are strong irritants not only for the skin but also the airways," says lead researcher Dr. Alfred Bernard, of Catholic University Louvain in Brussels, Belgium, in an interview with ABC News/Reuters Health. Bernard also noted that parents can look for public pools that use alternative disinfecting methods, like ozone treatment, which has long been used in Europe and is becoming more common in the US.