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Why The Chlorine in Swimming Pools Can Affect Your Thyroid

Before you jump into the pool, learn how chlorinated water can affect your thyroid function.
Why The Chlorine in Swimming Pools Can Affect Your Thyroid
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The sun is out, the pools are open, and you’re ready to spend your days cooling off!  As you probably know, most swimming pools use chlorine to keep them clean. But did you know that as a chemical disinfectant, chlorine can potentially harm your health, including your thyroid?

In this article, we will learn about chlorine, how it may affect your thyroid function, and how to reduce your chlorine exposure so you don’t miss all the summer fun!

What is chlorine?

As mentioned, chlorine is a chemical disinfectant that kills bacteria and viruses in the water that can make you sick if ingested. Public drinking water supplies and chlorinated swimming pools use chlorine as a disinfectant.

In chlorinated swimming pools, chlorine binds with waste products from your body. Anything that washes off or comes from inside your body is a waste product. Examples of waste products include pee, sweat, dirt, or personal care products (make-up, deodorant, hair products, etc). When chlorine and waste products combine, two things occur:

Chloramines are found in the air surrounding the swimming pool. Chloramines can cause red eyes, skin irritation, and rashes commonly associated with swimming in chlorine. Since chloramines are in the air surrounding pools, you can breathe it in, causing respiratory symptoms such as:

  • Nasal irritation
  • Coughing
  • Wheezing
  • Asthma attacks

You don’t have to be in the pool to have side effects from chloramine. Those sitting by the pool or sticking their feet in may also experience respiratory symptoms, especially in indoor pools without good ventilation. Besides affecting your lungs and skin, chlorine and chloramine may contribute to thyroid dysfunction by displacing iodine.

Chlorine, iodine, and your thyroid

Iodine is critical for maintaining the function of your thyroid because the thyroid needs large amounts of iodine to make thyroid hormone. Without enough iodine, your thyroid can’t make enough thyroid hormone, resulting in an underactive thyroid. An underactive thyroid leads to symptoms of hypothyroidism, including the following:

Iodine is naturally found in foods you eat, such as dairy products, eggs, or freshwater fish. As your body digests these foods, iodine enters your bloodstream. From here, a specialized transporter on your thyroid cells moves iodine into your thyroid.

So, how does exposure to chlorine or chloramine displace iodine in your thyroid?

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Endocrine disruption

Chlorine and DBPs are endocrine-disrupting chemicals that can interfere with your hormones and damage your cells – any interference with how your thyroid functions can result in an underactive thyroid, as described above.

Halogenated compounds, which include chlorine, may compete with iodine for transportation into your thyroid. When this occurs, your thyroid is taking up chlorine instead of iodine, effectively limiting how much iodine is available to make thyroid hormone. Specific populations –such as those with an underlying iodine deficiency – may be more susceptible to the effects of iodine displacement. But, not all studies support this link between chlorine and your thyroid.


An older study from 1986 looked at the effects of drinking chlorinated water on the thyroid. The results showed that ingestion of chlorine does not cause an iodine deficiency that would result in thyroid dysfunction.

A study from 1993 showed similar results - short-term exposure to chlorinated drinking water does not affect thyroid metabolism in healthy men and women. Results showed a slight decline in thyroid hormone levels. However, since thyroid-stimulating hormone levels remained the same, researchers concluded that chlorine does not alter thyroid function.

Most recently, a 2022 study found adverse health effects are probably unrelated to regulated DBPs like chloramines. Established guidelines exist for safe chlorine levels in pools and drinking water. When levels go outside that range, pools and drinking are unsafe, and action must be taken. Researchers concluded that unregulated DBPs may be more likely to cause adverse effects than regulated ones.

Further research is needed to fully understand the link between chlorine exposure and your thyroid function.


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Ways to reduce chlorine exposure

No one wants to miss out on pool time fun! But, at the same time, you want to keep your thyroid healthy. Here are ways to lower your chlorine exposure:

  • Take a shower or rinse off before entering the pool. This helps remove sweat and body waste, reducing chloramine formation. And when your hair and skin absorb clean water, you lower your body’s ability to absorb chlorine.
  • Apply sunscreen followed by coconut oil. Coconut oil helps your skin maintain its natural pH and provides extra protection. These two actions reduce chlorine absorption. Remember to let your sunscreen completely dry before applying coconut oil!
  • Wear goggles for underwater swimming to prevent eye irritation. Also, wear a swim cap to reduce hair dryness.
  • Shower off right after getting out of the pool. Sitting in a wet swimsuit increases skin irritation caused by chlorine. Don’t forget to rinse out your bathing suit before wearing it again.
  • Rehydrate your skin after swimming. Apply a non-fragrant lotion or cream to help moisturize and hydrate your skin. A vitamin C solution may help balance chlorine’s effects on your skin.

Swimming in outdoor pools instead of indoor ones can also lower your risk of chlorine exposure, as poorly ventilated indoor pools can increase chloramine exposure and side effects. Saltwater pools or pools that use UV or ionization for disinfection use fewer chemicals, making them promising alternatives to chlorinated pools.

A note from Paloma Health

While there is conflicting evidence supporting the link between chlorine and thyroid dysfunction, limiting your exposure to endocrine disruptors can improve thyroid function. Endocrine disruptors are found in:

  • Cosmetics
  • Personal hygiene products
  • Plastic containers
  • Cleaning products
  • Pesticides

If you are concerned that chlorine or other endocrine-disrupting chemicals are affecting your thyroid, schedule an appointment with one of our expert thyroid providers today to review your symptoms and discuss the next steps.

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CDC. Water Disinfection with Chlorine and Chloramine | Public Water Systems | Drinking Water | Healthy Water | CDC. Published November 18, 2020. Accessed June 29, 2023.

Disinfection By-products (DBPs) Factsheet | National Biomonitoring Program | CDC. Published September 2, 2021. Accessed June 29, 2023.

Chemical Irritation of the Eyes and Lungs | Healthy Swimming | Healthy Water | CDC. Published May 15, 2019. Accessed June 29, 2023.

American Thyroid Association. Iodine deficiency. American Thyroid Association. Published 2016. Accessed June 29, 2023.

Lisco G, De Tullio A, Giagulli VA, De Pergola G, Triggiani V. Interference on Iodine Uptake and Human Thyroid Function by Perchlorate-Contaminated Water and Food. Nutrients. 2020;12(6):1669. doi:

Bercz JP, Jones LL, Harrington RM, Bawa R, Condie L. Mechanistic aspects of ingested chlorine dioxide on thyroid function: impact of oxidants on iodide metabolism. Environ Health Perspect. 1986;69:249-54. doi:

Wones RG, Deck CC, Stadler B, Roark S, Hogg E, Frohman LA. Lack of effect of drinking water chlorine on lipid and thyroid metabolism in healthy humans. Environ Health Perspect. 1993;99:375-81. doi:

Sui S, Liu H, Yang X. Research Progress of the Endocrine-Disrupting Effects of Disinfection By-products. J Xenobiot. 2022 Jun 28;12(3):145-157. doi:

Pool time: How to protect against the side effects of chlorine. Accessed June 29, 2023.

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Emilie White, PharmD

Clinical Pharmacist and Medical Blogger

Emilie White, PharmD is a clinical pharmacist with over a decade of providing direct patient care to those hospitalized. She received her Doctor of Pharmacy degree from Massachusetts College of Pharmacy and Health Sciences. After graduation, Emilie completed a postgraduate pharmacy residency at Bon Secours Memorial Regional Medical Center in Virginia. Her background includes caring for critical care, internal medicine, and surgical patients.

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