Swimming pool chlorine raises asthma, allergy risks: study

NEW YORK (Reuters Life!) - Swimming in chlorinated pools may increase the risk of a child getting asthma and respiratory allergies like hay fever, according to a Belgian study.

Researchers from the Catholic University of Louvain in Brussels, Belgium, found that teenagers who spent more than 100 hours swimming in chlorinated pools were up to six times more at risk of having asthma than other teens.

"The impact of these chemicals on the respiratory health of children and adolescents appears to be much more important -- at least by a factor of five -- than that associated with secondhand smoke," toxicology professor Alfred Bernard told Reuters Health.

"There is little doubt that pool chlorine is an important factor implicated in the epidemic of allergic diseases affecting the westernized world."

In the study, Bernard and his colleagues compared the health of 733 teenagers aged 13 to 18 who swam in chlorinated pools for various amounts of time with that of 114 teenagers who swam mostly in pools sanitized with a mix of copper and silver.

Among "sensitive" adolescents, the odds for hay fever were between three and six times higher for those who swam in chlorinated pools for more than 100 hours, the researchers reported in the journal Pediatrics.

The odds of allergic rhinitis were increased two to three times among those who logged more than 1,000 hours in chlorinated pools.

Among children and teens who swam in chlorinated pools for between 100-500 hours, 22 children out of 369, or six percent, had current asthma, compared with only 2 of 144, or 1.8 percent, of those who had spent less than 100 hours in chlorinated pools.

The proportions with asthma rose with longer exposure, to 14 out of 221, or 6.4 percent, who had been swimming for 500-1,000 hours, and 17 out of 143, or 11.9 percent, for those who swam for more than 1,000 hours.

The risk of asthma and allergy was not influenced by swimming in copper-silver sanitized pools and children without allergic tendencies were not at increased risk of developing allergies.

"The only plausible explanation" for these observations, the researchers said, is that the chlorine-based toxic chemicals in the water or hovering in the air at the pool surface caused changes in the airway and promote the development of allergic diseases. "It is probably not by chance that countries with the highest prevalence of asthma and respiratory allergies are also those where swimming pools are the most popular," said Bernard.

(By Megan Brooks of Reuters Health, Editing by Belinda Goldsmith)