The study found that teenagers who spent more than 1000 hours swimming in pools that are sanitised using chlorine, either indoors or outdoors, (although indoor was the primary focus) were more than eight times as likely to have asthma than teenagers who swam mostly in swimming pools treated using alternative forms of sanitization mainly ionisation.
“Chlorinated pool attendance has a very significant impact on the prevalence of allergic diseases in the studied population,” said leading researcher Alfred Bernard, a professor of toxicology and research director at Catholic University of Louvain in Brussels, Belgium.
“When used correctly, [chlorine] is an efficient and safe disinfectant for swimming pools. However, when too much chlorine is added to water or builds up in the air of indoor pools, there is unavoidably some irritation of the organs of the bather in contact with the water and air”.
“There is now increasing evidence that these irritating effects may be detrimental to the airways of regular swimmers, especially the children who are the most vulnerable and the most frequent attendees of chlorinated pools.”
More than 5.1 million people in the UK currently have asthma. Britain has one of the worst rates of childhood asthma in the world.
Asthma, which comes from the Greek word meaning ‘Hard breathing’ can cause symptoms of wheezing, shortness of breath and coughing. The airway disease can be triggered by a number of factors, such as cold air, exercise and chemical irritants.
While chlorine has long been known to be an airway irritant and potential trigger of asthma, particularly in indoor pools,The recent study suggests that chlorinated pools might play a role in the development of asthma and allergy.
The study included 847 Belgian teenagers between the ages of 13 and 18. All had attended indoor or outdoor swimming pools, but at various rates of attendance. One hundred and fourteen children mainly attended pools that were kept clean with a copper-silver disinfect, rather than chlorine. The remainder primarily attended pools disinfected with chlorine.
The number of children who ever had asthma went up in proportion to their chlorinated pool exposure.
Teens who swam for 100 to 500 hours in chlorinated pools had an 80% increased risk of having asthma, while those who logged 500 to 1000 hours had just over twice the risk.
When teens spent more than 1000 hours swimming in chlorinated water, the risk of ever having had asthma nearly quadrupled.
The risk of currently having asthma was more than eight times higher in the group with more than 1000 hours in chlorinated pools compared to those who were rarely in chlorinated water, according to the study.
The risk of allergies also increased significantly when adolescents spent more than 100 hours swimming in chlorinated pools. In fact, the risk of hay fever and other allergies more than doubled with significant chlorinated pool exposure.