By CHRISTINE DELL'AMORE, UPI Consumer Health Correspondent
Source: UPI
WASHINGTON (UPI) -- The rising tide of childhood asthma has again been linked to a classic American pasttime -- the swimming pool. In a new study, Belgian researchers showed that exposure to indoor swimming pools before the age of 6 is the "most consistent predictor" of childhood asthma, mostly in children already genetically predisposed to the condition.
Their study, published in the October issue of Environmental Health Perspectives, further investigates the theory that trichloramine, an irritant gas and chlorine byproduct released into the air of indoor swimming pools, can lead to asthma. The chemical irritates the upper respiratory tract, travels deep into the lung and causes cell damage.
"This is just an association, and we need to look into more chemicals," cautioned lead author Alfred Bernard, a professor of toxicology at the Catholic Unviersity of Louvain in Brussels.
Bernard and colleagues recruited 341 schoolchildren -- 172 boys and 169 girls -- between the ages of 10 to 13 from Belgian primary schools, all of whom had mandatory pool time as part of their education.
In 2002, the research team tested the students' blood to determine their genetic predisposition to allergies and administered an exercise-induced test to detect asthma. Of the total group, 32 boys and 24 girls had asthma. In Brussels, about 15 percent of children have asthma, so the study seems representative of the city's population, Bernard said.
The team concluded chlorination by-products polluting the air, such as trichloramine, actually promotes the development of asthma -- at least in young, genetically suspectible children who attend heavily polluted pools.
Bernard and colleagues also calculated the risk of developing asthma increased about 8 percent per 100 hours of exposure to pools.
The researchers speculated younger children were more at risk for several reasons: For one, young kids usually cluster in the shallow pool, which is hot and more heavily polluted than the main pool. When children learn to swim, they tend to inhale and swallow more aerosols and water droplets containing chemicals. Also, human lungs are still developing -- and thus sensitive to outside pollutants -- before the age of 6.
"In my view, this might explain why in Canada and Scotland and Ireland, (places) without much air pollution, there is such a high prevalence of asthma," Bernard said.
Childhood asthma has skyrocketed ten-fold across the developed world, particularly in the English-speaking countries of the United Kingdom, Ireland, Australia and New Zealand. In the United States, there are nearly 5 million asthma sufferers are under age 18 -- making asthma the most common chronic childhood disease.
The emphasis on stringent hygiene in these countries, as well as the popularity as indoor swimming pools, has led some to question whether pools and asthma are somehow linked.
Another major theory is the hygiene hypothesis, which says asthma and other allergic diseases are spurred by the declining exposure of children to infections during infancy.
But because asthma has so many triggers and potential causes, scientists are unable to fully explain its dramatic spike.
The Brussels study named trichloramine as the main culprit in triggering the development of asthma. Little research has focused on trichloramine and its effect on children; likewise, there is no regulation of the chemical in the United States and other developed countries. The city of Brussels recently passed air standards for trichloramine.
Although the chemical can be easily regulated by ventiliation, the process is not cheap. For that reason, many of the pool facilities studied failed to properly ventilate their indoor pools. The recommended frequency is six to eight times an hour, Bernard said.
"Children could be, in some way, the victims of this rising cost," he said.
Finding an alternative to chlorine to sterilize pools -- such as ozone, for instance -- might eliminate trichloramine, but won't necessarily cut down on costs.
Because indoor swimming pools are similar across the globe, the results can be generalized to U.S. children, Bernard said.
"There's no reason to believe this is specific to Belgium," he said.
There were limitations to the study; namely, the small sample size. The results will have to be repeated in a much larger cohort. The team also did not study outdoor pools. (Bernard and colleagues are currently studying outdoor pools to determine whether the chlorine byproducts harm children through contact with the skin, or only when inhaled.)
Also, it's possible asthmatic children swim more than non-asthmatics. That's because doctors often recommend asthmatic children swim for exercise, as the steamy, hot atmosphere aids breathing.
The trichloramine theory is an important area of research, Dr. Raoul Wolf, section chief of pediatric allergy and immunology at the University of Chicago Comer Children's Hospital, told EcoWellness.
Yet Wolf is hesitant to put much stock in the possibility of the chemical actually causing asthma. There's no question exposure to chlorine is a trigger for children who have asthma, he said. But it's too easy to jump to the conclusion swimming and asthma are connected causally.
Proving causation is particularly tricky with a multi-faceted disease such as asthma.
"This doesn't mean if you avoid swimming pools, you're going to avoid asthma," Wolf said.
Bernard stressed his study should not scare parents away from signing their kids up for swimming lessons. But they should be aware of how their local pool is ventilated.
"This has nothing to do with swimming -- this has to do with air quality," he said. |
