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Indoor Swimming, Asthma Link?

July 17, 2006 - Indoor swimming pools may give kids asthmaasthma, Belgian researchers warn.

The researchers -- toxicologists Alfred Bernard, PhD, and Marc Nickmilder, PhD, of Brussels' Catholic University of Louvain -- say there is often a buildup of chlorine byproducts around indoor pools. These toxic gasses, they suggest, are hurting children's lungs.

Is there any proof this is so? No. But Bernard and Nickmilder assembled data on how many indoor pools are in each country in Europe. They find that areas with the most pools per child have the highest rates of childhood asthma.

"Our study shows that the prevalence of wheezingwheezing and of ever [having had] asthma across Europe is associated with the availability of indoor chlorinated swimming pools," Bernard and Nickmilder conclude.

They report their findings in the current issue of Occupational and Environmental Medicine.

The researchers found the rate of wheezing rose by 3.39% -- and the rate of asthma rose by 2.73% -- for every additional indoor chlorinated swimming pool per 100,000 area residents.

Bernard and Nickmilder note their "pool chlorine hypothesis" may seem paradoxical. After all, many people with asthma find swimming -- particularly swimming in the hot and humid air of an indoor pool -- to be a good way for them to exercise.

But the researchers note that chlorine reacts with organic matter to form a gas called nitrogen trichloride or trichloramine. That, they explain, is "the gas which gives indoor pools their typical smell." It is, they say, "one of the most concentrated air pollutants to which children in Europe are regularly exposed."

The Belgian researchers call for more study of the issue. In the meantime, they urge regulation of pool chlorination and strongly recommend proper ventilation of indoor pools.