A recent Irish study, released by the Department of Pediatrics at University College Cork found a link between years spent swimming and the development of asthma in 121 boys. A greater occurrence of the condition was found in boys who began swimming around age 5 and swam in indoor, chlorinated pools about once a week.

The authors believe the introduction of organic materials such as sweat or urine into chlorinated water may create a setting conducive to asthma development.

Another report, released last year in the British Journal of Sports Medicine notes that nearly all of 50 elite swimmers studied had inflamed lung tissue. All the cases began after they took up swimming, and those that spent more time in the pool had more damage. 70 percent of swimmers surveyed for the European Respiratory Journal suffered from airway hyper-responsiveness, a precursor to asthma. These cases are attributed to indoor pool environments and chloramine exposure.