Children who swim regularly in chlorinated pools are five times more likely to develop asthma, research has found.
Swimming is recommended as a good form of exercise for asthmatics because the warm humid air is less likely to trigger attacks than other physical activities.
But mounting research is suggesting that the chlorine used to keep the pools clean could be contributing to the development of the condition.
It is thought the chlorine fumes floating around the surface of the pool may help to trigger the condition by irritating the upper airways.