Surreal illustration of hidden chemical reactions in swimming pool water.

Is Your Pool Water Safe? The Hidden Dangers Lurking Beneath the Surface

Theo Raines in Health & Wellness December 2025 • 4 min read.

"Uncover the surprising chemical reactions in swimming pools and how they might affect your health."

Summer is synonymous with swimming pools, offering a refreshing escape from the heat. But have you ever stopped to consider what's actually in the water besides chlorine? While chlorine is essential for disinfection, it can react with organic matter introduced by swimmers, leading to the formation of disinfection by-products (DBPs).

These DBPs, formed from the interactions of chlorine with urine, sweat, and personal care products, are a growing concern for public health. The central question is whether these chemical by-products pose a significant risk to swimmers' health, and what measures can be taken to minimize potential harm.

This article dives deep into the science behind pool water chemistry, exploring the formation of DBPs, the latest research on their health effects, and practical tips for ensuring a safer swimming experience. Understand the science so you can protect yourself and your family this pool season.

The Chemistry of Pool Water: What's Really Going On?

Surreal illustration of hidden chemical reactions in swimming pool water.

Chlorine's primary role in swimming pools is to eliminate harmful bacteria and viruses, keeping the water safe for swimmers. However, when chlorine interacts with organic compounds like urea (found in urine and sweat), it creates a variety of DBPs. Two of the most common and concerning DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs).

The concentration of these DBPs can vary widely depending on factors such as the number of swimmers, the amount of organic matter present, water temperature, and pH levels. Indoor pools, with less ventilation, often have higher concentrations of DBPs compared to outdoor pools.

Trihalomethanes (THMs): These are formed when chlorine reacts with organic matter. Chloroform is a common THM found in swimming pools.
Haloacetic Acids (HAAs): Similar to THMs, HAAs are created through the reaction of chlorine and organic compounds.

While chlorine effectively disinfects pool water, the formation of DBPs raises concerns about potential health risks associated with swimming.

Practical Steps for a Safer Swim

While the science surrounding the long-term health effects of DBPs is still evolving, there are several practical steps swimmers and pool operators can take to minimize exposure:

<ul><li>Shower Before Swimming: Rinsing off before entering the pool removes sweat, urine, and personal care products, reducing the amount of organic matter that can react with chlorine.</li><li>Avoid Urinating in the Pool: This directly reduces the amount of urea in the water.</li><li>Support Proper Pool Maintenance: Encourage pool operators to maintain proper chlorine and pH levels, ensure adequate ventilation (especially in indoor pools), and consider alternative disinfection methods.</li><li>Swim in Well-Maintained Pools: Choose pools that are known for their cleanliness and adherence to safety standards.</li></ul>

By understanding the chemistry of pool water and taking proactive steps, you can enjoy a refreshing swim while minimizing potential health risks.

About this Article -

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Everything You Need To Know

What happens when chlorine interacts with things in the pool?

Chlorine is used to disinfect pool water by killing harmful bacteria and viruses. However, it can react with organic matter introduced by swimmers, such as urine, sweat, and personal care products. These reactions create disinfection by-products (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). These DBPs are a growing concern because of their potential health impacts.

What are disinfection by-products (DBPs) and how are they formed?

Disinfection by-products (DBPs) are created when chlorine, used to disinfect pool water, interacts with organic matter like urine, sweat, and personal care products. Two common types of DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). The levels of DBPs depend on several factors, including the number of swimmers, the amount of organic matter present, water temperature, and pH levels. Indoor pools tend to have higher concentrations of DBPs because of less ventilation. These DBPs are a significant issue because of potential health risks.

What are trihalomethanes (THMs) and haloacetic acids (HAAs) and why are they important?

Trihalomethanes (THMs) and haloacetic acids (HAAs) are types of disinfection by-products (DBPs) formed when chlorine interacts with organic matter in pool water. Chloroform is a common example of a THM. The presence of these DBPs is important because they are linked to potential health risks for swimmers. The concentration of these DBPs in pool water can vary, influenced by the number of swimmers, the amount of organic matter, water temperature, and pH. It is essential to understand the formation of these DBPs to ensure a safer swimming experience.

Why should I be concerned about disinfection by-products (DBPs)?

The potential health effects of disinfection by-products (DBPs) are a growing concern. Although the article does not specify all the health risks, it highlights the need for ongoing research. Swimmers can take practical steps to minimize exposure to DBPs, such as showering before swimming and using the restroom frequently. The article emphasizes the importance of understanding the science behind pool water chemistry to protect yourself and your family.

What can I do to make swimming safer?

Several practical steps can be taken to minimize exposure to disinfection by-products (DBPs). Showering before swimming removes organic matter that can react with chlorine. Using the restroom frequently reduces the amount of urea (found in urine) that can contribute to DBP formation. Proper pool maintenance by operators, including adequate ventilation and monitoring of water chemistry (pH levels), is also important for reducing DBP concentrations. These steps collectively contribute to creating a safer swimming environment by minimizing the formation and exposure to harmful DBPs.