What are the dangers of a high chlorine pool level?

Written by melissa lewis
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What are the dangers of a high chlorine pool level?
(High chlorine levels is more dangerous in indoor pools. engindeniz: sxc.hu)

Chlorine is added to pools to keep them clean and free from dangerous bacteria. However, if swimmers are exposed to high levels of chlorine too frequently, especially in indoor pools, they may be exposing themselves to other health risks. For this reason, some pool owners use alternatives to chlorine such as salt and copper-silver disinfectant.

Chemical Balance

Chemical balance is imperative to keeping swimming pools safe. If you use chlorine to disinfect your pool, the proper chlorine levels, along with the right pH levels, are essential to keep the water free from dangerous bacteria and algae. Fortunately, there are test strips available that test pH and chlorine levels. Adding chemicals based on those results and following manufacturer directions are crucial to keeping your pool safe for swimmers.


High chlorine levels in pools have been linked to not only causing asthma, but triggering its symptoms including wheezing, coughing and shortness of breath, especially in children. In a 2009 Belgian study conducted by Alfred Bernard, research director and professor of toxicology at Catholic University of Louvain in Brussels, indicated that teens who spent more the 1000 hours in chlorinated pools were eight times as likely to suffer from asthma compared to those who swam in pools with copper-silver disinfectant. Bernard states that when chlorine is used properly, it is a safe disinfectant, but when there is too much chlorine--as there often is--or if chlorine builds up in the air of an indoor pool, the "irritating effects may be detrimental to the airways of regular swimmers."


Not only does high chlorine irritate the airways and trigger asthma, it also irritates the eyes and skin. Red, itchy and burning (stinging) eyes, along with a skin rash are caused by too much chlorine. While usually not severe, if you notice a rash or your eyes start to bother you, you and all the other swimmers should get out of the pool until the chlorine levels can be tested and corrected, if necessary.


Chlorine added to drinking water has been linked to the increased occurrence of some cancers. There is also indication that frequent exposure to high chlorine levels in pools can also increase the risk of some cancers, including breast, bladder and rectal cancers. The suspected carcinogen is not from the chlorine itself, but from substance, trihalomethanes (THMs), formed from a chemical reaction between the chlorine and organic matter, such as skin cells and body lotions. THMs are absorbed into the skin, swallowed and breathed in.

Pregnant Women

There may be a link between miscarriage and birth defects if exposed to high chlorine levels. It is the same THMs that cause cancer that scientists in London are concerned about. Dr Neiuwenhuijsen of Imperial College in London states that chlorine levels should be kept as low as possible in pools and that further study is needed since, according to him, "swimming pools could be a major pathway for the uptake of trihalomethanes among pregnant women who go swimming often."

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