A recent study has shown that swimming in chlorinated pools increases the risk of asthma. More than 300 million people around the world are affected by asthma. Symptoms of asthma are wheezing, shortness of breath, coughing and chest tightness. The study was done by researchers of the Catholic University of Louvain, Brussels, Belgium. 

For this research, researchers analyzed the data collected from 847 secondary school pupils with an average age of 15. Researchers asked their parents about exposure to asthma risks such as tobacco smoke, pets and pollution, and how much time the children had spent in chlorinated pools. 

Analysis of data showed that children who had swum for an hour in a week for ten years or more than 500 hours in total were five times more likely to be asthmatic than children who had never swum in a pool. Researchers found that in 50 percent of children predisposed to allergies, asthma was directly related to the amount of time spent in a pool. Risk of asthma increased by ten times in children predisposed to allergies, if they had swam for more than 500 hours in an outdoor pool. 

Earlier studies have shown adverse effect of chlorine on asthma. Chlorine fumes floating around the surface of the pool may facilitate to trigger asthma by irritating the upper airways. A previous study claimed that outdoor pools are safer as compared to indoor pools because in indoor pools chlorine vapors remains trapped inside an enclosed space. 

The present study has shown that outdoor pools are just as or more risky than indoor. This study was led by Prof Alfred Bernard, of the Catholic University of Louvain, Brussels, Belgium.