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Peeing in Swimming Pools: Urine, Chemicals, and Health Hazards

Linda Crampton is a writer and former teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

Swimming in a pool is fun, but the condition of the water is an important factor to consider.

Swimming in a pool is fun, but the condition of the water is an important factor to consider.

The Problem With Peeing in Pools

Many people reading this article wouldn't dream of peeing in a swimming pool. According to a report published in an American Chemical Society journal, however, it's happening often enough to create a health hazard in some pools. Members of the general public and elite swimmers alike have admitted to peeing during swims. Some elite swimmers urinate in pool water frequently. There is evidence that urine is also being released into hot tub water.

The main problem with peeing in a swimming pool or hot tub is not the release of bacteria. Although urine isn't sterile (despite a rumour to the contrary), it generally contains a low level of microbes unless a person has a urinary tract infection. In addition, the water in pools and tubs usually contains disinfectants that kill bacteria and other microbes. Unfortunately, chemicals in urine react with the disinfectants to create potentially harmful products.

Swimming is good exercise, especially when the pool environment is healthy.

Swimming is good exercise, especially when the pool environment is healthy.

Experimental Evidence for Urination in Pools

In a major investigation, researchers from the University of Alberta in Edmonton collected water samples from pools and hot tubs in two Canadian cities. They tested the urine for the presence of acesulfame potassium, also known as acesulfame K or ACE. The chemical is a common artificial sweetener in soft drinks and processed food. It's even used as an ingredient in other sugar substitutes. It passes through the body and into the urine without being altered.

The researchers tested a total of 250 water samples from 31 pools and hot tubs. They also tested 90 samples of the tap water used to fill the pools and tubs. They discovered that ACE was present in every sample that they tested. They also found that the chemical was up to 570 times more concentrated in the pool and hot tub water than in tap water. Since ACE is not deliberately added to swimming pools or hot tubs and is excreted in human urine, the investigators concluded that people had urinated in the water.

The reason why a small amount of acesulfame K was found in tap water is due to its stability. Some of the chemical survives wastewater treatment. It has been found in groundwater and enters tap water, although not in sufficient quantities to make the water taste sweet.

Lest readers get the impression that only Canadians like to pee in pools, it should be noted that peeing in swimming pools is common in elite U.S. swimmers, as mentioned in the video below.

Elite U.S. Swimmers Pee in the Pool

Facts About Disinfection By-Products

Urine contains nitrogenous waste products, including urea, uric acid, ammonia, and creatinine. It has been known for some time that these react with chlorine-based disinfectants in pool water to form disinfection by-products, or DBPs. Bromine, ozone, and ultraviolet radiation are also used to disinfect the water, either on their own or in combination with another technique. This can cause the production of other by-products. This article discusses the effects of chlorine-based disinfectants, which are the most common type at the moment.

Hundreds of different DBPs can form in and around swimming pools, but some are more common than others. One researcher has said that he's found the same eleven volatile DBPs in every sample of swimming pool water that he's examined. The chemicals are produced not only from the components of urine but also from chemicals in sweat, personal care products, dirt, dead cells, and hair. In addition, they are made from the remains of medications that have entered the urine.

Swimming pools must contain disinfectants in order to prevent the transmission of disease. We have some control over the substances that enter the water from our bodies and from disinfectant by-products, however. I've chosen three common DBPs to discuss in this article–trichloramine, cyanogen chloride, and chloroform.

Disinfection by-products are present in treated tap water, including the water used to fill swimming pools. They make a relatively minor contribution to the DBP level in swimming pools, however. Most disinfection by-products in a pool are made after people have entered it and voluntarily or involuntarily released substances from their body.

Disinfection of Swimming Pool Water

Sodium hypochlorite and calcium hypochlorite are added to swimming pool water as disinfectants. Chlorine is used much less often because it's not as safe to store and apply. All three substances react with water to make hypochlorous acid, which kills bacteria.

Ammonia and related chemicals in sweat and urine react with hypochlorous acid. The reaction produces chemicals called chloramines. One of these chloramines is known as trichloramine. Trichloramine is responsible for the typical swimming pool smell, which is often wrongly attributed to chlorine.

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Trichloramine has the chemical formula NCl3 and is also known as nitrogen trichloride. It's one of the most common and annoying disinfection by-products. The chemical can cause eye and skin irritation as well as respiratory problems, including asthma. This can be true even when the chemical is at usual pool concentrations and gets worse as the concentration increases.

Although DBPs are often dangerous when they are in a concentrated form, they are safer at the low concentrations present in swimming pools. Pure trichloramine is an explosive substance. Fortunately, this isn't true for the chemical when it's present in pool water.

Even a residential pool requires some form of disinfection.

Even a residential pool requires some form of disinfection.

Cyanogen Chloride

Cyanogen chloride or CNCl is another common disinfection by-product. It can be deadly when it's concentrated. Like other DBPs, it has a relatively low concentration in and around pool water. People don't drop dead after inhaling or swallowing it when they visit a swimming pool. Nevertheless, the chemical is of concern.

Like trichloramine, cyanogen chloride is a volatile substance (one that readily turns into a gas). The concentrated chemical causes severe irritation of the eyes, skin, and airways and interferes with the body's ability to use oxygen. It can also cause fluid buildup in the lungs (edema), convulsions, loss of consciousness, and death. The chemical is highly unlikely to be sufficiently concentrated in swimming pool water to cause serious effects, though.

Don't Pee in the Pool

It's uncertain whether DBPs in pool water are sufficiently concentrated to cause any serious health effects. There are preliminary indications that some of them may be, but the discoveries need to be confirmed.


Chloroform or CHCl3 is yet another common DBP. Once again, it's a volatile chemical that is normally present at a low concentration in and around swimming pools but is of some concern.

The concentrated chemical irritates the eyes and skin. It also depresses the activity of the central nervous system and can cause a coma. It was once used as an anesthetic. It was found to be dangerous because it can trigger a deadly alteration in the rhythm of the heartbeat. Doctors also found it hard to control the dose. Concentrated chloroform inhaled over a long period damages the liver and kidneys. The chemical is a suspected carcinogen (a substance that causes cancer).

Keeping a pool as safe as possible is important for everyone.

Keeping a pool as safe as possible is important for everyone.

Swim diapers and swim pants are not a substitute for frequent diaper changing and bathroom breaks. It is recommended that swim diapers and swim pants are checked frequently and changed away from the poolside.

— Centers for Disease Control and Prevention (CDC)

Public Health Recommendations

Swimming in a pool is fun and can be great exercise. It's not necessary to avoid the fun or the exercise unless the disinfection by-products are too irritating for a swim or unless the pool maintenance program is of concern. I think that it's the responsibility of swimmers to follow public health recommendations, however, for the sake of themselves and of other swimmers. Many of these recommendations are listed below.

  • Shower with soap before entering a pool to remove sweat, personal care products, dead cells, and fecal matter from the skin. Feces can transmit disease.
  • Don't enter the water if you have diarrhea, an intestinal infection, or a urinary tract infection. Small quantities of feces and urine can be released into the water accidentally.
  • Don't swallow pool water and try to avoid getting it in your mouth.
  • Make sure that indoor pools have good air circulation, since many DBPs are volatile and enter the air as a gas.
  • Use the restroom whenever the urge to pee appears.
  • Make sure that children urinate in the restroom before entering the water and that they leave the water whenever they need to "go".
  • If children mention peeing in the pool, explain that this action is not a game and that it can affect the health of other people.
  • Make sure that babies wear good swim diapers. These retain solid feces, but unfortunately they may not retain liquids. In addition, they don't prevent harmful microbes in diarrhea from contaminating the water. They should be inspected and changed frequently.
  • Shower after a swim to remove contaminants.