Chlorinated pools may have an adverse affect on those working in and around them. A recent Dutch study finds that, because of the way chlorine reacts with substances like sweat, it creates byproducts in the air that may eventually cause breathing problems in those regularly exposed to it.

The most dangerous byproducts are chloramines, which irritate the respiratory tract. At the 38 pools they surveyed, researchers found that swimming instructors -- or, those who had the most regular exposure to chloramines -- were nearly 2 1/2 times as likely to suffer from sore throats and nearly 3 1/2 times as likely to suffer from chronic cold when compared with other pool workers.

Fortunately, this doesn't appear to affect those who use the pools -- although these users are thought to be the source of the problem. Subsequently, researchers suggest that improved hygiene amongst swimmers might work to improve the air quality for instructors, and other at-risk employees.