Scientists from the Catholic University of Louvain and the Free University of Brussels believe the chemical reacts with sweat and urine to produce damaging fumes.

The findings are based on a study of 226 healthy primary school children, from both urban and rural areas, who had used indoor pools regularly since early childhood.

The researchers took blood samples from each child – looking for lung proteins associated with cellular damage – and analyzed samples from 16 children and 13 adults before and after swimming to analyze the immediate effects of the chemical.

The researchers also analyzed data on childhood asthma prevalence among 2000 children aged between 7 and 14 undertaken between 1996 and 1999.

The team found that regular attendance (weekly or fortnightly) of indoor swimming pools was “consistently and significantly” associated with the destruction of cells that protect the deep lung, leaving them more vulnerable to allergens.

And after just one hour spent by the side of the pool, without swimming, the immediacy of the damage was evident from marker proteins in the blood.

Furthermore, chest tightness after exercise and prevalence of asthma were both linked to the amount of time spent at the pool.

The findings remained true even after taking into account a child’s living environment and exposure to environmental pollutants.

Writing in the journal Occupational and Environmental Medicine, the researchers say swimming is often recommended for asthmatics as the moisture-laden air can compensate for the effects of exercise – but not if the air is full of toxins.

They conclude that chlorinated indoor swimming pools have contributed to the rise in childhood asthma diagnosis in the developed world over the last few decades.

“The question needs to be raised as to whether it would not be prudent in the future to move towards non-chlorine based disinfectants, or at least to reinforce water and air-quality control in indoor pools in order to minimize exposure to these reactive chemicals,” they say.

Source: Occupational and Environmental Medicine

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