Health Effects of High Chlorine in Swimming Pools

Yes, the lap pool at your favorite gym is often full of chemicals, but those chemicals — namely, chlorine — help protect you from nasty bacteria in the water (and you know exactly how much bacteria you need protection from if you've ever smelled the locker room). The health effects of high chlorine in swimming pools are commonly mild, and normal chlorine levels are usually quite safe, though. So know what to look for and don't let fear stop you from reaping the numerous benefits of a good swimming routine, which range from toning the muscles to pumping the lungs and working the heart.

Chlorine is mostly safe and helpful, but too much can cause irritation. (Image: JaySi/iStock/GettyImages)

Tip

Chlorine doesn't normally have an adverse affect on health, though over-chlorinated pools may lead to irritation.

Addressing Over-Chlorination

If you're a pool owner or otherwise in charge of maintaining a swimming pool, the best bet for assessing over-chlorination is to check the chlorine level in parts per million (ppm) using chlorine test strips or a chlorine testing kit. If the pool's combined chlorine level exceeds 4 ppm, the water is over-chlorinated. At this point, you can employ a variety of tactics to get the water back to an ideal level of 3 ppm:

  • Stop adding chlorine to the pool.
  • Remove any existing chlorine tablets.
  • Allow the pool to soak up about two to three hours worth of direct sunlight, as ultraviolet rays can deplete up to 90 percent of water's chlorine levels.
  • Add a neutralizing chemical, such as sodium thiosulfate or sodium sulfite.
  • Replace a portion of the pool water.

Warning

Avoid swimming in water with chlorine levels above 10 ppm, which can cause serious skin and eye irritation.

Chloramines and pH Balance

Unfortunately, if you're just a swimmer, you'll likely only notice over-chlorination when you experience its effects . As it turns out, you can't really smell over-chlorination, despite what the urban myths say.

That strong "chlorine" smell is actually the ammonia-based compound chloramine, which is produced when chlorine oxidizes bacteria and oil. Basically, it means that the chlorine is doing its job and neutralizing the bad stuff.

Those chloramines are also what cause the potential health effects of high chlorine in swimming pools, as they affect the water's pH balance, turning it into a mild irritant. The good news is that the effects of chlorine in water on the human body usually tend to err on the "annoying" side rather than the "go to the hospital" side.

Chlorine and Eye Irritation

By and large, the health effects of high chlorine in swimming pools aren't too dire. One of the most readily apparent effects of a mildly over-chlorinated pool is eye irritation. Often known as swimmer's eye, the chemical reaction that occurs as chlorine mixes with organic matter may cause slight redness in the eyes, as blood vessels near the eye surface become enlarged or dilated.

In cases of common over-chlorination, swimmer's eye will usually fade on its own once you're out of the pool.

Skin and Hair Irritation

Swimming pool chlorine affects the skin too. As Dr. Ana Duarte, dermatology director at Nicklaus Children's Hospital of Miami, tells LiveScience in a 2018 interview, "too much chlorine can cause a lot of [skin] irritation." This irritation may include redness, itchiness, bumps or hives, and it's caused by what is known as irritant dermatitis — basically, a very mild chemical burn from the increased acidity of an over-chlorinated body of water.

Some of the effects of an over-chlorinated pool might not set in until you've been out of the water for a bit. For instance, when an excess of chlorine strips the skin of its natural oils, you may experience dry skin or increased irritation of existing dermatitis conditions. Those with particularly sensitive skin may experience rashes, tenderness, lesions or scaling.

For the same oil-stripping reasons, dry hair sometimes becomes an issue. Likewise — while this isn't exactly an adverse effect on your health — too much chlorine can cause color-treated hair to take on a greenish tint (if the chlorine used contains copper, that is).

Chlorine and Respiration

On the more serious — but also far less common — end of the spectrum, over-chlorination may trigger an asthma attack due to the release of vapor on the water's surface. For this to happen, though, the pool would have to be extremely over-chlorinated.

Since too much chlorine can irritate or sensitize the respiratory tract, it may increase the risk of developing asthma and similar respiratory allergies over time. According to the American College of Allergy, Asthma and Immunology, this is typically only a risk for those who experience long-term chlorine exposure, such as lifeguards or Olympic swimmers.

While there's no such thing as a chlorine allergy, some people may be more sensitive to chlorine reactions than others.

About Chlorine Poisoning

On a more immediate level, chlorine poisoning may occur in extremely over-chlorinated pools. Signs of chlorine poisoning include:

  • Sudden nausea or vomiting
  • Burning in the throat
  • Shallow breathing
  • Dizziness
  • Wheezing or coughing
  • Dull pains in the chest
  • Chest tightness

According to CareWell Urgent Care, "Unless you or your kids have just swum in a pool that was filled with more chlorine than water, odds are that these symptoms aren't life-threatening." Typically, light or moderate chlorine poisoning and its effects will fade without treatment within 24 hours of exposure. However, it's best to visit a care facility if you experience signs of chlorine poisoning, just to be on the safe side.

Read more: Chlorine & Eczema

What You Can Do

When dealing with an over-chlorinated pool, chlorine's side effects on humans are usually easily addressed. It's always a good idea to hit the shower directly after your swim to wash away any lingering chlorine, then apply a moisturizer to help restore your skin's natural oils — moisturizing creams with ceramides are particularly helpful. By the same token, a few lubricating saline eye drops can help ease mild chlorine irritation in the eyes.

Of course, prevention is often the best remedy. To save yourself from potential eye irritation, don't forget to strap on a pair of goggles during your swim. If your hair is prone to drying out, treat your locks with a light hair oil or put on a swim cap before your dip to keep chlorine from penetrating your coif.

Keep your swim safe by testing chlorine levels, taking common-sense preventive measures and practicing proper post-swim hygiene, and you'll benefit from adding a few laps to your regimen without having to worry about over-chlorination.

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