Chlorine in Pools May Cause Breathing Trouble
Chlorine Levels May Pose Risks to Swimmers, People With Asthma
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
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.
Exercise-induced asthma causes narrowing of the airways and
difficulty in moving air out of the lung.
"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
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
- 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
- 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
Researchers recommend that swimmers use pools where the
chlorine concentration is kept below 0.5 PPM in order to reduce their risk of