June 11, 2004 -- Chlorine levels commonly found in homes and public pools may lead to breathing problems in swimmers, regardless of their history of such problems, researchers say.
A new study shows that swimmers experienced breathing problems similar to those associated with asthma after several minutes of swimming even in water with chlorine levels below the recommended level for disinfecting private pools.
The study shows that trained swimmers who swam for six to eight minutes in a pool with high levels of chlorine were three times more likely to develop exercise-induced bronchoconstriction (EIB) (commonly known as exercise-induced asthma) than when they swam in water with low chlorine levels or exercised out of the water.
"We've long suspected that chlorine has an adverse effect on the respiratory health of swimmers," says researcher Arthur J. Williams, MD, of the Sport Science Institute of South Africa, in a news release. "Now we know the likelihood increases significantly with the concentration of chlorine used. Swimmers should be aware of the concentration of chlorine exposure they receive, and those who care for pools should closely monitor chlorine levels."
Chlorine Tied to Breathing Problems
In the study, which was presented recently at the American College of Sports Medicine's annual meeting in Indianapolis, researchers compared the effects of exercise in different settings on breathing function.
Researchers randomly assigned 20 trained swimmers with no history of exercise-induced asthma and 21 with a history of exericse-induced asthma to the following four exercise tests of the same intensity and duration:
- Swimming in an indoor pool with no chlorine in the water
- Swimming in a chlorinated pool with low levels of chlorine (0.5 parts per million (PPM))
- Swimming in a chlorinated pool with high levels of chlorine (1.0 PPM)
- Running or cycling next to any of the pools
After exercise, researchers used a machine to test airflow during forced exhaling to analyze restriction of airflow in the airways.
The study showed that 60% of the participants, regardless of their history of EIB, suffered from airway constriction after swimming in the highly chlorinated pool compared with 20% after swimming in the low- or no-chlorine pool or on dry land.
Researchers say that the recommended chlorine level for disinfecting private pools can be as high as 2.0 PPM, which may be irritating to many swimmers, especially those with existing problems such as asthma.
"This research is the first to investigate how increases in chlorine concentrations in swimming pools can enhance respiratory problems," said Williams. "We hope people who appreciate swimming as a quality form of exercise will continue to reap its enormous physical benefits, but also be more aware of the potential hazards. We believe these hazards can be minimized through awareness and proper pool maintenance."
Researchers recommend that swimmers use pools where the chlorine concentration is kept below 0.5 PPM in order to reduce their risk of breathing problems.