Children who make regular visits to an indoor pool may develop damage to a type of lung cell that helps prevent airway inflammation, a new study suggests.

The researchers speculate that repeated exposure to chlorine byproducts in the air around indoor pools may harm these respiratory cells, known as Clara cells.

A number of past studies have found elevated rates of airway inflammation and asthma among competitive swimmers, with researchers attributing it to inhalation of chlorine gas and its byproducts. In addition, research has suggested that trained swimmers may have poorer Clara cell function.

“We suspect that chlorinated compounds in the air of swimming pools may influence the lungs and airways so that the children might have an increased risk for getting asthma,” Dr. Birgitta Json Lagerkvist, the study’s lead author, told AMN Health.

More research, however, is needed to confirm that suspicion, said Lagerkvist, of Umea University in Sweden. Children in this study, she added, showed normal lung function, regardless of their pool use.

Lagerkvist said she would not advise parents against taking their children to swimming pools based only her team’s study.

The findings are published in the December issue of the journal Environmental Health Perspectives.

For the study, the investigators measured lung function and blood levels of an anti-inflammatory protein, known as CC16, produced by Clara cells in 57 children living in Umea. Nearly 40 percent of the 10- to 11-year-olds had visited an indoor pool for at least an hour a month for the previous six months or more; they were considered “regular” indoor pool users.

The researchers found that compared with their peers, children who regularly used these pools had a lower average CC16 concentration, which suggests damage to Clara cells.

Sodium hypochlorite, which contains one percent chlorine, was used to disinfect the pools. According to Lagerkvist and her colleagues, this makes it likely that the surrounding air contained elevated levels of nitrogen trichloride, or NCl3, which forms when chlorine reacts with organic matter, such as sweat. High levels of NCl3 in the air have been shown to irritate the eyes and throat.

“Our results,” the researchers report, “indicate that repeated exposure to chlorination byproducts in the air of indoor swimming pools has an adverse effect on the Clara cell function in children, such that the anti-inflammatory role of CC16 in the lung could be diminished.”

Lagerkvist said that one way to reduce the chance of harming lung cells is to use indoor pools with good ventilation - ones that, for instance, do not recycle the air in order to save energy.

SOURCE: Environmental Health Perspectives, December 2004.