By Jeremy Appleton, ND, CNS

Healthnotes Newswire (December 21, 2006)—Swimming in private and public swimming pools is a favorite pastime for many families, especially during the hot summer months. However, this activity is not without risks, especially in younger children who frequently use heavily chlorinated pools. A new study from Germany has found that use of chlorinated pools is associated with an increased risk of developing hay fever later in life.

“The most sensitive populations for environmental factors are babies and young children,” said Yvonne Kohlhammer, MD, of the National Research Center for Environment and Health in Neuherberg, Germany, and the new study’s lead author. “At that age the body is more vulnerable to toxins because development, especially of the lungs and immune system, is not yet completed.”

Researchers interviewed 2,606 adults between ages 35 and 74 to obtain information on swimming pool attendance, medical history, and the occurrence of allergic diseases. Specifically, they were looking for any associations between hay fever and swimming pool attendance, taking into account various influences that could confuse results such as age, gender, region, education, and smoking.

Children who were frequently exposed to pools at school age were 74% more likely to develop hay fever; those who were ever exposed to chlorinated pools had a 65% increased risk. Adults were also susceptible to chlorination’s ill effects. There was a 32% increased risk of hay fever in those study participants who had attended chlorinated pools in the last 12 months. The strongest associations were found for the youngest children: in that group, the risk of hay fever increased with increasing current and school-age pool attendance.

Chlorine and many of its byproducts are known toxic agents. In this study, pool attendance was used as a way to measure contact with chlorine and its byproducts. Chlorine compounds, which are used to disinfect swimming pools, can react with swimmers’ urine and sweat, producing potentially harmful fumes at the water’s surface. These fumes have been shown previously to damage the inner lining of the lungs, called the epithelium, a delicate area where oxygen is delivered. Chronic irritation of the lung epithelium has been shown in many other studies to predispose people to allergic diseases and to sensitize their bodies to common allergens.

One limitation of this study is that the data were collected retrospectively, meaning that researchers considered only events that occurred in the past (pool attendance, hay fever, and allergy symptoms). Studies designed this way are less likely to produce definitive answers because they rely on study participants’ memories, rather than tracking outcomes as the study progresses.

“Hay fever is a disease with numerous potential influencing aspects, including lifestyle changes, environmental factors, allergen exposure, and immunology,” said Dr. Kohlhammer. “Contact with chlorine might not be the leading reason for hay fever, especially in adults, but it appears to be an important contributor.”

Chlorination in swimming pools might not be as harmless as earlier thought. Although toxicity resulting from chlorine gas inhalation was well known in industrial accidents, chlorine has been generally regarded as a safe disinfectant in pool treatments, provided that free chlorine levels are kept within acceptable ranges (optimally less than 1 mg per liter). However, even at these low levels, there is no evidence that it does not contribute to allergies.

Based on the results of this study, parents should limit the exposure of babies and very young children to highly chlorinated pools. Children and adults already suffering from allergic diseases—such as asthma, eczema, and hay fever—might do well to avoid chlorinated pools altogether. Alternative pool-cleaning methods that require little or no chlorine to keep swimming pools disinfected are available.

(Allergy 2006;61:1305–09)

Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.

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