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Swimming in chlorinated pools could increase risk of asthma, allergies among atopic teens, study suggests

Thursday, September 17 2009 | Comments

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What's This? Children with atopy who swim in chlorinated pools appear to have a higher risk of asthma and respiratory allergies, according to a new study.

The study included 847 students aged 13 to 18 years who went swimming using indoor or outdoor chlorinated pools at various rates over their lifetime (<100 hours; 100-500 hours; 500-1,000 hours; >1,000 hours). The students who had swam <100 hours in chorinated pools over their lifetime (n=114) served as a reference group (they mainly swam using indoor pools sanitized with copper and silver).

Researchers assessed the students for allergies by measuring total and aeroallergen-specific immunoglobulin E (IgE) in serum, and also screened them for exercise-induced bronchoconstriction. Parents of the children were also asked to complete a questionnaire related to the health of their child, risk factors for asthma and allergic diseases, and the estimated time their child spent in outdoor or indoor chlorinated pools. Questions about respiratory symptoms and allergic diseases were derived from the International Study of Asthma and Allergy in Childhood.

Researchers defined sensitization against specific aeroallergens as serum concentrations of specific immunoglobulin E (IgE) that were >0.35 kIU/L.

The findings revealed that compared with atopic children who had <100 hours of chlorinated pool exposure, atopic children who had spent >1,000 hours in chlorinated pools had a significantly increased likelihood for ever asthma and current asthma. Specifically, among children who had aeroallergen sensitization, the odds ratio (OR) for ever having asthma was 7.11 (95% CI, 1.83-27.5) for children with >1,000 hours versus <100 hours chlorinated pool exposure, and among children with a total IgE level >30 kIU/L, the OR was 7.82 (95% CI, 2.11-29.1). The likelihood of current asthma was even higher: The OR was 12.6 (95% CI, 1.52-105) for children with aeroallergen sensitization and 14.9 (95% CI, 1.85-120) for children with a total IgE level >30 kIU/L.

These risks significantly increased as exposure to chorinated swimming increased.

In addition, a greater likelihood of having positive exercise-induced bronchoconstriction test results was also evident among students with >1,000 hours of exposure to chlorinated pools relative to those with <100 hours. Among the children with a total IgE level >30 kIU/L, the risk was almost twice as high (OR, 1.71; 95% CI, 0.70-4.20), and of those with aeroallergen sensitization, the risk was almost 4 times as high (OR, 3.67; 95% CI, 0.93-14.6). However, the trend for increasing exposure to chlorinated pools being more likely to lead to exercise-induced bronchoconstriction was not statistically significant.

Meanwhile, adolescents with atopy who spent >100 hours in chlorinated pools had a greater risk of hay fever, and those with swimming of >1,000 hours had a greater risk of allergic rhinitis. However, these associations did not exist among children without atopy or those who had swam in a pool sanitized with copper and silver.

Lastly, the investigators reported that when atopy was defined on the basis of total serum IgE levels, the population-attributable risks for chlorinated pool-related ever-diagnosed asthma, hay fever, and allergic rhinitis were 63.4%, 62.1%, and 35.0%, respectively.

"These findings reinforce the need to pursue research in this area and to enforce regulations concerning the levels of these chemicals in water and air of swimming pools," they concluded.

The study was published online Sept. 14 by Bernard A, et al. in the journal Pediatrics.

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