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Indoor Pools May Raise Child Asthma Risk

Increased Exposure to Chlorine Byproduct Is Culprit, Study Shows
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WebMD Health News

May 29, 2003 -- Children who regularly swim in crowded indoor pools may be increasing their chances of developing asthma. Early research suggests a link between asthma and a byproduct of the chlorine used to keep pool water clean.

If confirmed, the link could help explain an epidemic rise in childhood asthma cases in the British Isles, New Zealand, and portions of Canada and the northern United States, the study's authors say. Due to climate, indoor swimming is more common in these areas.

"We have no direct proof that indoor pools are the cause of this asthma increase, but I think it is something that we definitely have to look at closer," toxicologist and lead researcher Alfred Bernard, PhD, tells WebMD. "Children with asthma are often told that swimming in indoor pools is good for them because of the hot, humid air. But it could be that this is the worst place for them."

Last year, British researchers published a study finding an increase in asthma risk among lifeguards working at indoor pools. The researchers identified the chemical trichloramine as the potential cause of this occupational risk.

Trichloramine is produced when chlorine reacts with polluting proteins from swimmers' bodies, such as sweat and urine. The amount of trichloramine present in the air is determined by how crowded a pool is, the personal hygiene of the swimmers, how often the water is changed, and how well ventilated the area is.

In this study, Bernard and colleagues from Belgium's Catholic University of Louvain investigated whether indoor swimming could be a factor in childhood asthma. They measured levels of lung proteins associated with cellular damage in blood samples from 226 school children who swam regularly at indoor pools. Blood samples from 16 children and 13 adults were also taken before and after indoor pool swimming sessions, to test for immediate effects from exposure.

They concluded that regularly swimming in indoor pools was associated with damage to the normal barriers within the lung, making them more permeable, or leaky, which could increase the vulnerability to the passage of allergens. The more frequently the study participants swam in the indoor pools, the worse the damage, Bernard and colleagues noted. The findings are published in the latest issue of the journal Occupational and Environmental Medicine.

It may take years to determine whether an association between indoor pool exposure and childhood asthma exists, but Bernard says there are simple steps that should be taken now to reduce potential risk.

"There is no reason why the air quality in these pools cannot be checked for this chemical," he tells WebMD. "[Trichloramine] is a well known lung irritant, and swimming in indoor pools in the presence of this irritant can't be good for anybody."

Asthma researcher Larry Borish, MD, tells WebMD that it is unlikely that indoor pool exposure, or any other single exposure source, can explain the rise in childhood asthma cases. Different people may have different asthma triggers, he says, adding that researchers working to find answers need to look at the broader picture.

"People are too busy focusing on the epidemic of asthma when the real epidemic is with autoimmune diseases in general," he says. "Rheumatoid arthritis, multiple sclerosis, and Crohn's disease -- all of these immune diseases are at epidemic levels, and I have no doubt that this is all related."

The authors suggest it may be prudent to switch to non-chlorine based disinfectants and reinforce water and air quality control in indoor pools.

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