Chlorinated Outdoor Pools May Increase Risks of Asthma and Allergy in Kids

There is probably no better place than an outdoor swimming pool to refresh and relax on hot days. A backyard pool is also a lot of fun for kids who can spend hours playing and swimming in the pool during summertime. A new study from Brussels, Belgium, suggests that despite their natural ventilation outdoor pools can pose similar asthma and allergy risks  as indoor pools. Chlorine vapors floating at the surface of the pool along with chlorinated water  penetrating the upper airways are the suspected cause of these respiratory effects.

The Belgian team, led by Alfred BERNARD, examined a total of 847 secondary school students with a mean age of 15 years. After their parents had given their written approval, adolescents were examined in schools. They provided blood samples for allergy tests and underwent lung function tests.  Parents were asked to fill a detailed questionnaire about the respiratory health of their child and his exposure traditional risks factors of asthma and allergies (tobacco smoke, pets, indoor and outdoor pollution,..).. The questionnaire also included very specific questions about swimming pool attendance, which allowed researchers to estimate the total number of hours each adolescent had spent during his life in outdoor chlorinated pools, at home or during holidays

Researchers found that asthma risk increases almost linearly with the number of hours adolescents had spent in outdoor swimming pools, at one our during holidays.  Children with the highest outdoor attendance (more than 500 hours, the equivalent of one hour per week for 10 years) were 5  times more likely to be asthmatic than  those who had never swum in an outdoor pool.

Looking more closely at their data, the researchers found that asthma risk largely stems from an interaction between pool attendance and the atopic status as evaluated on the basis of total serum IgE (a test reflecting the predisposition to develop allergies). However, as this interaction was triggered from relatively low level of serum IgE (25 kUI/), asthma risk concerns nevertheless more than 60 % of the children regularly attending outdoor pools.

The research team also found that kids having regularly attended a backyard pool before the age of seven were more likely to be allergic to cat or dust mite than those who had never attended an outdoor pool so early.

The researchers advice parents not to overchlorinate their own pool and not to send too frequently their children in poorly managed outdoor pools with a strong chlorine smell floating at their surface. 

Press Release Reproduced With the Kind Permission of Professor Alfred Bernard, Catholic University of Louvain, Brussels, Belgium

Page created: 29 September 2008