Research reports indicate that if the concentration of chlorine used for disinfection in swimming pools is too high, it may cause exercise-induced asthma. Experts caution that swimmers should not overlook the harm this factor poses to the respiratory system while exercising.

When the chlorine concentration in pool water is below 0.5 ppm, fewer than 20% of people experience bronchoconstriction—a rate similar to that of “exercise-induced bronchoconstriction” caused by other land-based sports activities. However, when the chlorine concentration reaches 1.0 ppm, the percentage of swimmers experiencing bronchoconstriction rapidly rises to over 60 percent; regardless of their prior respiratory health, this can trigger exercise-induced asthma.

Researchers point out that these findings warrant particular attention, as swimming is often recommended as an effective form of exercise for people with asthma. Experts advise that while enjoying the pleasure and health benefits of swimming, participants should also be aware of this potential hazard posed by chlorine in swimming pools. If the chlorine concentration in the pool water complies with regulations, there should be no choking odor; if swimmers detect a pungent smell, it indicates that the chlorine concentration has exceeded the standard.

In some swimming facilities, the chlorine odor may be stronger due to the chlorine in the footbaths used for disinfection before entering the pool (as required by regulations, chlorine levels in footbaths must be kept high); swimmers should be mindful of this distinction.

作者：Michael Chiu，MWS，CI
本文原載於《明報日報》。