Dr. Elissa B. Gartenberg once had a patient who had been swimming competitively for years. A teenage girl, she was strong, fit, and dedicated, but her asthma continually flared up during indoor practices. At first, Gartenberg thought the flare-ups were just the usual exercise-induced symptoms, but they got worse. The patient started wheezing almost every time she swam, even when she wasn’t pushing herself too hard.
She eventually figured out that it wasn’t just the exercise—but the pool itself. The chlorine fumes from the indoor facility were irritating the girl’s lungs. Poor ventilation made it worse, and the buildup of chemical byproducts in the air triggered her symptoms. Once she switched to an outdoor pool and used her controller inhaler more consistently, the difference was night and day.
“That experience opened my eyes to how overlooked indoor air quality can be, even in places meant for health and fitness,” Gartenberg said.
While swimming is good exercise, the chemicals used to kill germs in pools pose health risks that can affect the eyes, skin, lungs, and other body parts. Showering and other precautions can reduce the potential for harm.
Health Risks
A 2021 study published in the European Journal of Allergy and Clinical Immunology states that common swimming pool disinfectants, such as chlorine and bromine, form disinfection byproducts when combined with materials in the water. Such materials include human body excretions of sweat, urine, and saliva, pharmaceuticals such as painkillers, and personal care products, such as sunscreens, cosmetics, and lotions. The following are health risks associated with the byproducts:
Eye Effects
Swimming in chlorinated pools can result in several eye problems, largely related to exposing the eye surface to chlorine, Dr. Jovi Boparai, an ophthalmic surgeon at CorneaCare, told The Epoch Times in an email.
Chlorine exposure to the eyes can lead to conjunctivitis, a condition that causes inflammation of the thin membrane that covers the white part of the eyes and lines the inner part of the eyelids. Symptoms of conjunctivitis include eye irritation, redness, stinging, and burning.
“Exposure may lead to dry eyes, a condition that presents with dryness, wateriness, redness, irritation, and blurred vision. Chlorine can disrupt the tear film, which lubricates the eyes and allows clear, comfortable vision,” Boparai said.
Prolonged exposure to chlorine may even lead to keratitis, which is inflammation of the cornea, he said. Symptoms of keratitis include pain, light sensitivity, and blurred vision.
Other Effects
Swimming in indoor pools with poor ventilation can result in asthma flare-ups and dry, itchy skin, according to Gartenberg, who practices family medicine in Scottsdale, Arizona.
High levels of chlorine can trigger asthma even in those without a previous history of the disease. Ammonia and chloramine are other irritants found in pools.
Some people report stomach issues from swallowing pool water, especially if it contains chlorine-resistant bugs such as cryptosporidium, she said. Every summer, public pools and water parks close for decontamination because of a cryptosporidium outbreak, which is a common cause of diarrhea and can be hard to treat.
Teeth Effects
The chlorine in pools can cause a buildup of brown tartar, or calculus, on the front teeth, according to Dr. Calvin Eastwood, a dentist at Summerbrook Dental & Implants in Fort Worth, Texas.
“The bleach causes saliva to break down and stick to the teeth, causing the buildup,” he told The Epoch Times in an email. “Also, if the pool is acidic due to poor management, it will cause erosion of the enamel on the front teeth.”
Eastwood said these maladies happen when water seeps through the lips onto the teeth, which is why the stain occurs only on the fronts of the front teeth. Due to increased exposure, dentists see it more in competitive swimmers and divers than in leisure swimmers.
Bladder Cancer
Researchers examined lifetime water-related habits and exposure to the disinfection byproduct trihalomethanes among 1,219 people with bladder cancer and 1,271 controls. A comparison between the groups indicated that swimming in pools with the chemical was associated with an increased risk of bladder cancer.
Risk Factors
A complex interaction exists between the pool environment, the agents within the pool that can cause harm, and the different physiological routes of exposure that contribute to health risks.
The 2021 study lists factors that increase risks:
- Inhalation: Studies suggest that the exposure dose increases with a higher intensity of physical activity, indicating that more vigorous swimmers receive higher exposure than less vigorous ones.
- Ingestion: People can inadvertently swallow water, and this occurs more often in children than adults and in adult men than in adult women.
- Skin absorption: Some research indicates that young children are especially at risk. Early life exposure may promote the development of childhood asthma.
Tips to Minimize Risks
“People can take several proactive steps to protect their eyes when considering swimming,” Boparai said.
These include:
- Avoid swimming in questionable or poorly monitored pools.
- Wear protective goggles to protect the eyes from direct contact with the water.
- Never wear contact lenses when swimming. Doing so significantly increases the risk of contact-lens-associated complications, such as infections.
- Rinse the eyes with artificial tears after swimming.
- If any eye symptoms develop after swimming, consult an eye doctor right away.
Gartenberg offers the following recommendations:
- Shower before and after swimming. Rinse off thoroughly, taking care to wash away all fecal material from you and your child’s body.
- Moisturize after swimming and rinsing off.
- Encourage kids to take regular breaks.
- Try not to swallow pool water.
- Use a double swim diaper for small children or incontinent adults.
- If your child has sensitive skin or asthma, stick to outdoor or well-ventilated indoor pools when possible.
- Avoid swimming if you or your child is sick, especially with gastrointestinal symptoms.
Alternative Pools
“When families ask me what type of pool is safest, I usually recommend saltwater,” Gartenberg said.
The salt in the water breaks down into sodium and chloride, so it still has chlorine, but the amounts are lower. For this reason, the water tends to be much gentler on the skin and lungs.
Pools that use ultraviolet light or ozone gas systems with minimal chlorine are also a great option when available, she said. Both methods can remove germs.
Natural swimming pools are appealing because they don’t use chemicals, according to Gartenberg.
“Instead, they rely on plants and biological filtration to keep the water clean. However, these systems are very difficult to maintain at the level of safety needed for small children or immunocompromised individuals,” she said.
Unlike traditional pools, natural pools don’t consistently kill off harmful bacteria, parasites, or viruses, she said. Children are particularly vulnerable to infections because they’re more likely to swallow water while playing, and their immune systems aren’t fully developed. Even low levels of contamination can lead to serious illness in anyone with a weakened immune system, such as cancer patients.
“Unless you can verify that the pool is maintained to strict safety standards, I don’t recommend these for families with young kids or anyone at higher risk,” Gartenberg said.
Natural Bodies of Water
Although swimming in natural bodies of water may avoid chlorine exposure, there are other risks.
“Swimming in lakes and oceans can feel like a great escape, but I always remind families that natural water is not filtered, treated, or predictable,” Gartenberg said.
Oceans can carry jellyfish, algae blooms, and bacteria that cause serious skin infections or worse. Lakes can be even riskier, especially when the water is warm and shallow. That is when parasites, amoebas, and harmful bacteria thrive, she warned.
“It is easy to forget these risks when the water looks clean and peaceful, but I have seen how quickly things can go wrong,” Gartenberg said. “Years ago, while I was in medical school, I cared for a young boy who had gone swimming in a lake during a hot summer day. He was active, bright, and full of life. A few days later, he came down with a fever and complained of a headache.”
What started as something that looked like a simple virus quickly spiraled into something terrifying, she said. He became confused, had trouble speaking, and then began having seizures. Gartenberg and her team discovered that an amoeba had entered through his nose while he was swimming and made its way to his brain. It was Naegleria fowleri, an incredibly rare but almost always fatal infection. He was hospitalized, but despite aggressive treatment, the disease progressed fast. He died within a week.
“I still think about him, and this is why I always tell families to avoid diving or letting lake water shoot up the nose, especially in the summer when the risk is highest,” she said. “I recommend using nose clips or skipping those lake swims entirely if the water is warm and untreated. It is a rare danger, but when it strikes, it is devastating.
“Swimming can be a wonderful activity for families, and with the right precautions, it can stay that way. We just have to be smart about where and how we do it.”
