No, it is not safe to swim in a pool with chlorine levels that are too high. Probably because chlorine is used to clean our drinking water, we tend to think of it as safe. However, the reason that chlorine is so useful for water treatment is that it kills bacteria, viruses and other pathogens so successfully. It does so by breaking down cell membranes, and we have cell membranes too.

Small enough levels of chlorine appear to be fine for larger organisms like us. But as chlorine levels increase, risks and health impacts increase. Direct exposure to chlorine in a puck form can obviously be harmful, but what about those medium cases: a pool with too much chlorine or long-term exposure to chlorinated pool water?

Short Term: Irritation

When you’re in a pool with chlorine levels that are too high, the most likely immediate result is irritation. Chloramine, a byproduct of chlorine, tends to hang around in the mist just above the water. Here, it hurts your eyes even if you keep your eyes closed under the water. Chlorine and chloramine will also irritate your lungs and your skin.It will also dry out your hair and nails. The higher the chlorine levels, the more intense the irritation.

Short Term: Risk of Serious Reaction

Some people are more sensitive to chlorine than others. In a pool with just slightly too high levels, there is a risk that these people will suffer more severe irritation in their skin, eyes, lungs or other exposed parts of their bodies. If you have a known sensitivity to chlorine, you should talk to your doctor about whether or how you can swim safely.

Short Term: Chlorine Poisoning

In pools with chlorine levels that are much too high, you can get chlorine poisoning. Symptoms include:

  • Blurred vision
  • Red/blistered skin
  • Nausea
  • Vomiting
  • Burning nose, throat, eyes
  • Coughing
  • Difficulty breathing

Long Term: Cancer Risk

According to SafeWater, there are risks of too much exposure to chlorine in drinking water, never mind the higher chlorine exposure even in a properly-maintained pool. Drinking water chlorine is associated with increased risks of bladder, colon and rectal cancer. This is mostly due to exposure to the chlorine byproducts trihalomethanes, which are carcinogenic. Haloacetic acids, another chlorine byproduct, may also be a risk, but research into both is ongoing.

Due to this increased cancer risk, some areas in Europe have stopped using chlorine in their water treatment plants. Other areas feel that the benefits of using chlorine for drinking water outweighs these risks.

Swallowing pool water regularly, even if it is chlorinated to an appropriate level, may increase your risk of developing cancer, but research has not been completed on the subject.

Long Term: Asthma, Tooth Decay

There has also been some research conducted into long-term exposure to properly chlorinated pool water, specifically for children and professional swimmers. Babies may develop asthma from exposure to normally chlorinated pools. Professional swimmers may suffer the same and may also lose tooth enamel. Research into these effects is still ongoing.