Does Swimming In Chlorinated Pools Cause Iodine Deficiency?

Have you ever thought the public pools you are using to go swimming, relax, or simply enjoy yourself could be causing a potential iodine deficiency?

Yep, public pools are treated with a combination of chemicals, filtration, and regular maintenance to keep the water safe and clean. Here’s a breakdown of the process:

1. Chlorination (or other disinfectants):
   
   

• Chlorine (in liquid, granular, or tablet form) is the most common disinfectant. It kills bacteria, viruses, and algae.

• Some pools use bromine, which works similarly but is less harsh on the skin and eyes.

• Saltwater pools generate chlorine from salt through electrolysis — they’re not chlorine-free, but they tend to feel gentler.

2. pH Balance:
   
   

• The pH level is maintained between 7.2 and 7.8 to ensure chlorine works effectively and the water stays comfortable for swimmers.

• Too high or low pH can cause skin irritation, damage equipment, or make the chlorine ineffective.

3. Alkalinity and Calcium Hardness:
   
   

• Alkalinity (80-120 ppm) helps stabilize the pH.

• Calcium hardness (200-400 ppm) prevents water from becoming too corrosive or forming scale on pool surfaces.

4. Filtration System:
   
   

• Pools have a circulation system (usually a sand, cartridge, or diatomaceous earth filter) that removes debris and dirt from the water.

• Water is constantly pumped, filtered, and returned to keep it clear.

5. Shock Treatment:
   
   

• Periodically, pools are "shocked" — a high dose of chlorine or non-chlorine oxidizer is added to break down organic contaminants like sweat, oils, and urine.

6. Algaecides and Clarifiers:
   
   

• Algaecides prevent algae growth, while clarifiers help tiny particles clump together so they can be filtered out.

7. Regular Testing:
   
   

• Staff test the water daily (sometimes multiple times a day) to monitor chlorine levels, pH, and other chemical balances.

Some modern pools also incorporate UV systems, ozone generators, or hydrogen peroxide alongside chlorine to improve sanitation and reduce chemical usage.

Now that being said, with all of these treatments, the one we wanted to highlight today was of the addition of chlorine and how it can affect iodine.

First, let’s understand iodine, chlorine, bromine, and fluoride are all halogens. They can compete with each other for absorption in the body, especially in the thyroid, which relies on iodine to produce thyroid hormones (T3 and T4).

When you swim in a chlorinated pool, you absorb some chlorine through your skin and breathe in chlorinated air, particularly indoors.

Excessive chlorine (or bromine, which is sometimes added to pools or hot tubs) can block iodine uptake by the thyroid, leading to reduced thyroid hormone production — a condition that mimics iodine deficiency.

Sometimes, however, swimming too much in chlorine can cause an excess.  If your body gets overloaded with chlorine or bromine, they can displace iodine in the thyroid gland, disrupting normal thyroid function. This is called halogen displacement. Bromine is especially notorious for this — it’s more likely to interfere with iodine than chlorine is.

Also, sometimes swimming can have one ingest chlorinated water. While drinking chlorinated water is a more direct route to exposure, swimming in heavily chlorinated pools can also allow chlorine (and bromine if present) to absorb through your skin or lungs, especially if the pool isn’t well-ventilated.

So how would one fix this if they are constantly exposed to chlorinated pools yet want to prevent iodine deficiency?

Well, aside from recommending to stop going to chlorinated pools, we also understand that if you love swimming, you won’t want to give that sport up. So we always recommend taking some extra iodine with our Upgraded Formulas Iodine to help support your levels and prevent future deficiencies.