Healthy Swimmer, Healthy Summer: Avoiding Poolside Toxins

Ever leave the pool with that unmistakable “chlorine” scent? Believe it or not, that's often trichloramine, a volatile compound that forms when chlorine meets urine, not chlorine itself.

But trichloramine is just the tip of the iceberg. When chlorine disinfects (or when it's combined with sweat, sunscreen, dirt, and urine), it creates hundreds of disinfection by-products (DBPs), some linked to respiratory issues, bladder cancer, and oxidative stress. Here’s how to enjoy summer swimming safely this year.

Chlorine 101

Chlorine is everywhere. It’s used to disinfect drinking water, sanitize sewage, clean surfaces, and yes—kill bacteria in your local swimming pool. It works by breaking down the cell walls of microorganisms, making it highly effective for water sanitation.

But here’s the catch: chlorine doesn’t discriminate. It’s a potent oxidizing agent, which means it reacts with any organic compound in the water, including harmless (but gross) things like sweat, skin cells, and urine. And those reactions are where the real danger lies.

These interactions lead to the formation of DBPs, chemical compounds like trichloramine, chloroform, and haloacetic acids—some of which have been associated with serious health risks. In fact, some of the same chlorine compounds used in industrial processes are also used in warfare at high concentrations—like chlorine gas, once weaponized in World War I.

To be clear, the chlorine levels in pools are much lower. But the mechanism is the same: chlorine disrupts the biological integrity of organic materials, whether that’s bacteria—or the protective lining of your respiratory system. Over time, especially with repeated or prolonged exposure, these small doses can add up.

And it’s not just about what’s in the water. Most DBPs are volatile, meaning they don’t just stay in the pool—they evaporate into the air, especially in the warm, humid environments of indoor pools. That “chlorine smell” you catch when you walk into a rec center or swim school? You’re actually breathing in a mix of airborne toxins, which can irritate the lungs, eyes, and skin—and may contribute to asthma, allergies, and hormone disruption.

Why Pool Filtration Can Add Risk

Most pools recirculate water every 100 days or so, gradually accumulating DBPs. And some include UV filtration, which breaks nitrogen-chlorine bonds and can form free radicals like cyanogen chloride—a compound harmful to respiratory tissues.

So even though UV systems improve surface water quality, they can inadvertently create more dangerous airborne chemicals when used before chlorine re-dosing.

What Creates DBPs?

Disinfection by-products (DBPs) are created anytime chlorine or other sanitizers interact with organic matter. These interactions are unavoidable in public or frequently used pools. The primary contributors include:

1. Dirt & Debris: This includes skin cells, hair, grass, sand — the everyday grime that comes in with swimmers.

2. Sweat: Even if you don’t feel sweaty, your skin still excretes salt, oils, and trace toxins.

3. Urine: Studies estimate that each swimmer contributes anywhere from 30–80 mL of urine per swim. While that might seem minimal, it adds up quickly—especially in busy public pools.

Urine is one of the biggest drivers of trichloramine, a highly volatile DBP responsible for that strong “chlorine smell” — and linked to eye irritation, asthma, and chronic coughing, especially in children and athletes.

One of the most troubling findings? DBPs aren’t just floating around the pool — they’re actively absorbed into your body. A 2023 study showed significant spikes in DBP concentrations in participants’ urine and blood plasma after just 40 minutes of swimming. Unsurprisingly, levels were significantly higher in pools with poor hygiene practices (e.g., more sweat, sunscreen, and yes, urine).

Airborne DBPs: A Hidden Hazard

When volatile DBPs evaporate, they’re inhaled, bypassing skin absorption and impacting lungs and airways directly. Studies have found alarming levels of trichloramine in indoor pools, with links to asthma, bronchitis, and other respiratory irritation.

New Findings

A 2024 study also uncovered elevated levels of halobenzoquinones, by-products of lotions and sunscreens. These compounds generate high oxidative stress in cells, increasing DNA damage and inflammation more than older, well-known DBPs.

Another recent report confirmed swimmers absorb measurable DBP levels after just 40 minutes in the pool, with urine-rich pools showing even higher levels, demonstrating how quickly these chemicals enter your system.

Potential Health Effects

The long-term effects of DBP exposure are still being uncovered, but what researchers know so far is concerning.

According to the CDC, prolonged chlorine exposure has been associated with symptoms like:

• Respiratory irritation

• Chronic cough or wheezing

• Skin dryness, rashes, or sensitivity

• Red, irritated eyes

• Blurred vision

These effects are intensified in poorly ventilated indoor pools, where DBPs accumulate in the air, making inhalation the primary route of exposure. Children, athletes, lifeguards, and frequent swimmers are the most at risk.

What’s more, repeated exposure to certain DBPs—especially trihalomethanes and haloacetic acids—has been linked to an increased risk of:

• Bladder and colorectal cancers

• Endocrine disruption

• Allergic sensitization

• Coronary heart disease

For kids, exposure during the early years of immune development may set the stage for asthma and chronic allergies. In adults, particularly women, chlorine by-products may interfere with hormone balance, detox pathways, and even skin microbiome health.

And while occasional swimming isn’t likely to cause major harm for most people, genetic differences in detoxification ability can mean DBPs stay in some bodies longer, causing more oxidative stress and inflammation over time.

9 Easy Ways to Reduce Exposure

Good news: you don’t have to give up your favorite summer activity. By making a few intentional choices, you can dramatically reduce your DBP exposure.

Here’s how to swim smarter in 2025:

✔️ Before You Swim

• Rinse off in the shower first – Removing sweat, body oils, and sunscreen before entering the pool can prevent chemical reactions that create harmful DBPs.

• Choose clean skincare – Use organic or mineral-based sunscreen that’s free of phenyl-containing preservatives and synthetic fragrance.

• Hydrate well – Staying hydrated supports your body’s natural detox processes, making it easier to process and eliminate any absorbed DBPs.

✔️ While You Swim

• Avoid heavily chlorinated or poorly ventilated indoor pools – If the “chlorine smell” is strong, DBPs are likely high. Look for pools with modern filtration systems, outdoor access, or saltwater options.

• Don’t apply lotion right before swimming – It doesn’t just float on the surface; it can break down into halobenzoquinones once mixed with chlorine and UV.

• And yes—don’t pee in the pool – Urine is a major contributor to trichloramine, which leads to airborne respiratory toxins.

✔️ After You Swim

• Shower again immediately – This helps remove any lingering chlorine or DBPs from your skin and hair.

• Use gentle, antioxidant-rich skincare – Products with ingredients like vitamin C, green tea, and aloe can support barrier repair and help combat oxidative damage.

• Support detox pathways – If you swim regularly, consider adding targeted support with binders, glutathione, or sulforaphane-rich foods (like broccoli sprouts). You can also work with a functional health provider to identify genetic vulnerabilities through detox pathway testing.

In Summary

Chlorine helps keep pools safe—but it also leads to DBPs that can affect your health over time. Keep swimming in 2025—just be strategic:

• Shower before and after swimming

• Choose cleaner pool options

• Skip the lotion pre-dip

• Stay hydrated and ventilate indoor pool areas

However, for some individuals, lifestyle changes like showering before the pool will not be enough to prevent chlorine or DBP toxicity. There are genetic variations that limit or slow the detoxification process in the body, meaning they stay in the body for longer and have more time to cause adverse health effects.

For people with such genetic variation, proper supplementation and dietary changes are necessary to avoid bad side effects from too much time in the pool. For more information about genetic testing or supplementation, click here to contact us!

The Johnson Center for Health services patients in-person in our Blacksburg and Virginia Beach / Norfolk locations. We also offer telemedicine for residents of Virginia and North Carolina!