Does swimming in chlorinated pools cause asthma in children? In 2003, a Belgian research team proposed the increased exposure of children to chlorinated swimming pools could be responsible for rising rates of asthma among children in developed nations. But many other scientists (see below) challenge the “pool chlorine hypothesis,” as it is called, and since we last wrote about this topic, there is more information to ponder.
Belgian Superior Health Council Conclusions
Based on the Belgian research, that government’s Superior Health Council (BSHC), a group of scientific experts, was asked by the Minister of Public Health in 2009 for detailed scientific advice on the matter of asthma development in children who swim. The BSHC responded in February, 2011 with a report stating that although a relationship between swimming pool attendance and childhood asthma has not been confirmed, it cannot be excluded. Importantly, the BSHC concluded that the available evidence does not support advising children against swimming in chlorinated pools. The BSHC underscored the advantages of physical exercise during swimming. They noted swimming is especially well-tolerated by asthmatics–and they concluded that there is no good reason to keep children out of properly managed chlorinated pools.
What Causes Childhood Asthma?
There has been much research on the potential causes of asthma in children. In addition to the research on pool swimming, many other factors have been investigated including: respiratory infection in infancy, air pollution, maternal smoking, fast food ingestion, exposure to cockroaches and a lack of exposure to environmental microbes, aka the “hygiene hypothesis.”
The Belgian Minister of Public Health requested further information from the scientific body in 2011, this time asking for advice on baby swimming and different methods of swimming pool disinfection. That report found no real benefits to baby swimming from 0 to 12 months old as inter-limb coordination is not acquired before the ages of three to four. For older children, however, the BSHC concluded swimming remains highly advisable, even in the case of asthma. The BSHC said the advantages of swimming under good hygienic conditions in monitored pools outweigh any potential risk of toxicity linked to chlorinated swimming pools. Furthermore, the BSHC stated that chlorine is the best disinfectant available in a properly-managed pool.
Other Investigators’ Conclusions
In 2008, Goodman and Hays conducted a “meta-analysis” of scientific research examining the association of swimming and asthma. They found no consistent association between asthma development and swimming pool use during childhood. Last year a Spanish research team similarly concluded that: “the body of evidence in children indicates that asthma is not increased by swimming pool attendance.” Overall, “…the health benefits of swimming outweigh the potential health risks of chemical contamination. However, the positive effects of swimming should be enhanced by minimizing potential risks.”
The Common Thread: Swimmer Hygiene and Pool Maintenance
A common thread running through all expert opinions on the swimming pool and asthma question is this: Both swimmers and pool managers have important roles to play in maintaining healthy pools. Swimmers have a responsibility to shower before swimming and not treat the pool as a toilet. Poor swimmer hygiene uses up chlorine and contributes to the production of irritating byproducts. Pool managers have a responsibility to maintain appropriate treatment chemical levels so that germs will be destroyed and pool water will remain comfortable. When things go haywire—swimmers pee in the pool and pool managers neglect their duties—pools become unhealthy, raising the possibility of unintended health consequences. Whether childhood asthma is among those consequences is doubtful, given the weight of evidence from the scientific literature, but why not do all we can to keep the “healthy” in “healthy pools”?
Ralph Morris, MD, MPH, is a Physician and Preventive Medicine and Public Health official living in Bemidji, MN.