- Aug 29
- 8 min read

Toxic Chemical Exposure from Swimming Pools

Nothing screams summer like swimming, whether it's at a water park or just dipping your toes in at home. However, depending on what kind of pool it is and what chemicals are being used to treat it, you may be exposed to harmful chemicals. These can be absorbed through the skin, inhaled in the air around the pool, and accidentally ingested. Children are at an increased risk for ingestion - on average, children swallow 37 milliliters of pool water in 45 minutes, while adults swallow 16 milliliters.

Chlorine-, ozone-, and bromine-based disinfectants can produce over 100 disinfection byproducts, including the major classes haloacetic acids (HAAs), nitrogenous disinfection byproducts (N-DBPs), and trihalomethanes (THMs). Disinfection byproducts can be formed in various ways, such as in reactions between disinfectants and natural organic matter (like from humans or plants) or chemicals introduced by humans. They can also be produced by treatment of water with UV radiation. These disinfection byproducts have been associated with a variety of cancers, asthma and other respiratory issues, DNA and cell harm, skin, nasal, and eye irritation, allergies, potentially immune harm, liver harm, neurotoxicity, some birth defects, decreased menstrual cycle and follicular phase length, hormone disruption, decreased time to pregnancy, pregnancy loss, and liver, cardiovascular, and kidney toxicity. These chemicals are taken into the body when you are around a pool or swimming. One study showed increased blood concentrations of chloroform, a carcinogenic THM, after swimming. Because of the presence of disinfection byproducts, swimming pool water as a whole has been determined to be harmful to cells, DNA, and the respiratory system.

The air around swimming pools can also be toxic. Breathing in this air can lead to various respiratory symptoms and conditions, such as asthma, because of disinfection byproducts. Many disinfection byproducts vaporize easily or can be suspended in air, so they are inhaled in the air around pools. Chlorine gas leaks around a pool from disinfection processes can also pose a hazard. Chlorine gas can damage the lungs, sometimes resulting in permanent respiratory symptoms, and harm the eyes, skin, and heart. Chlorine gas can also be inhaled from breathing in solid chlorine (swimming pool chlorinator tablets).

The levels of particular disinfection byproducts present vary depending on the disinfectants used and the kind of pool (indoor pool, outdoor pool, water park pool, covered pool, etc.). Although all chemical disinfection methods can lead to the formation of disinfection byproducts, chlorine is the biggest contributor. Lower levels of chlorine reduce disinfection byproduct concentrations, even when ozone or UV disinfection is added to supplement. UV and advanced oxidation process (AOP) disinfection (which can use ozone) can lower levels of some contaminants but raise others. Water treated with bromine-based disinfectant is more toxic to DNA than chlorine- or UV-treated water. There are pros and cons for both indoor and outdoor pools, with neither being better in all aspects. However, outdoor pools are less genotoxic than indoor pools. Seawater pools have high levels of iodide and bromide, which can react with disinfectants and organic matter to produce disinfection byproducts that are more harmful to cells and DNA than those produced without bromide and iodide.

There are some steps that can be taken to reduce levels of disinfection byproducts without changing the disinfection process, though these things will not eliminate the problem. Higher water temperature can lead to higher disinfection byproduct production, so keeping the pool cool may help. Substances on the skin, like oils and sweat, can react to form disinfection byproducts. Rinsing off for one minute before entering the pool helps with this issue. Urine can also react to produce disinfection byproducts, so not urinating in the pool lowers disinfection byproduct formation. Levels of some disinfection byproducts may be lowered by forward osmosis filtration, ultrafiltration, nanofiltration, reverse osmosis filtration, degradation by bacteria, and activated carbon treatment.

A variety of other toxic chemicals besides disinfection byproducts can be present in swimming pools. You may be exposed to washed-off UV filters and parabens from lotions and sunscreens. Chlorine and bromine can also react with sunscreen ingredients and personal care products like cosmetics and hair products to produce disinfection byproducts. Sometimes, these new compounds are more toxic than the ones they formed from. Plastic pool toys and accessories, frequently made of PVC, can also leach a variety of harmful chemicals into water. One common example is isophorone, which can lead to respiratory irritation, liver, neurological, and kidney harm, and cancer. Disinfectants can increase the leaching of these chemicals, and these pollutants can also react to form disinfection byproducts. Flame retardants, which have been linked to issues like cancer, reproductive harm, and endocrine disruption, have been detected in swimming pools as well. These may be released from swimsuits.

A wide variety of pharmaceuticals have been detected in swimming pool water as well. Due to difficulty removing these compounds during water treatment, they can be originally present in the water, or they can be introduced from topical products and urine. These chemicals can be harmful even at very low levels. Painkillers, antibiotics, antidepressants, anti-inflammatory drugs, diuretics, medication used to treat seizures, and stimulants have been found, among others. These pharmaceuticals can be genotoxic and cytotoxic, and some of the issues associated with improper use include nervous, cardiovascular, and respiratory system issues. Also, they can form disinfection byproducts.

Many alternative disinfectants pose health issues as well. Nanosilver is one of these alternative disinfectants. It has been linked to testis cell death, liver, lung, cardiovascular, intestinal, kidney, brain, immune, and spleen issues, inflammation, thyroid and testosterone disruption, and DNA, cell, and organelle (cell part) damage. Hydrogen peroxide is also not a viable substitute because it can produce singlet oxygen and hydroxyl radicals, which are very reactive, can damage cells, and have been classified as "probably carcinogenic." It also has been shown to not be an effective disinfectant. Persulfate, another disinfectant, has been linked to asthma, other respiratory issues, and skin irritation. Electrochemical disinfection can result in the production of ozone and hydrogen peroxide. Saltwater pools are still disinfected with chlorine, although this chlorine is produced from the salt rather than tablets.

One potential solution is switching to natural swimming pools. These systems use plants, physical filters, and/or microorganisms to clean water instead of harmful disinfecting chemicals. Using these methods, carbon or phosphorous levels in the water are limited to prevent algae and microorganisms from growing. Nitrogen is also often limited. There are many structures and designs for natural swimming pools. Some have filtration areas adjacent to the swimming area, while others have a separate filtration area. Different kinds of plants have been shown to limit carbon and phosphorous in the water effectively, and plankton and membrane biofilm reactors can be used as microorganism-based methods. Microorganisms and animals in the filtration area can also kill bacteria, preventing infection. Testing regularly for levels of bacteria can help ensure safety. Natural swimming pools are becoming more popular. Currently, there are over 20,000 natural swimming pools in Europe, 100 of which are public. Webber Natural Swimming Pool in Minnesota and Naturbad Riehen (Riehen Natural Pool) in Switzerland are two examples of public natural swimming pools.

Swimming can expose you to many harmful chemicals due to the disinfectants used in pools and other contaminants. If available, natural swimming pools may be a good alternative, but some advances in disinfection might be necessary before they become more widespread. For now, rinsing off before swimming and adding more filtration can help reduce disinfection byproduct levels.