Study links swimming pool chlorine to asthma

Dr MUIRIS HOUSTON

BOYS WHO swim frequently in swimming pools may be at increased risk of developing asthma, new research has found.

A study of 6- to 12-year-old boys carried out by Dr Tony Ryan and colleagues in the Department of Paediatrics at University College Cork found a significant association between the number of years a boy had been swimming and the likelihood of the child being wheezy in the past year. The greater the number of years a boy had been attending an indoor chlorinated pool, the greater the likelihood of him having asthma, the researchers found.

Parents of some 121 boys attending a national school in Cork city were questioned about how often the boys went swimming in chlorinated indoor pools. The results showed most boys did so once a week. They had been swimming for an average of five years at the time of the study.

No link was found between prevalence of asthma and parental smoking. But a significant link existed between the number of years spent swimming and a diagnosis of asthma, as well as whether a boy had experienced wheezing in the previous 12 months.

The research, in the current issue of the Irish Medical Journal – the journal of the Irish Medical Organisation – reflects a link identified in Belgian research in 2003.

The authors of the Irish study say a range of chlorine products are used in swimming pools, including chlorine gas. “When organic matter is introduced into chlorinated water (eg urine and sweat), a harmful mixture of by-products is created,” they say, adding that the most concentrated by-product found is nitrogen trichloride. This is a known respiratory irritant, and the authors suggest that chronic exposure to an indoor, chlorinated environment may be a risk factor in the development of asthma in boys.

While acknowledging their study is relatively small and relies on subjective responses by parents, the Cork paediatricians conclude: “Until the relationship between respiratory health and chlorination of swimming pools is investigated further and accurate information is available, every effort should be made to improve pool ventilation and enforce better swimmer hygiene.”