Exposure to Chemicals found in Swimming Pools, Hot Tubs and Spas
It’s summertime and families will begin to use swimming pools, hot tubs and spas for exercise and leisure activity.
Health agencies are typically concerned with the water quality due to microorganisms, aka germs. However, public concerns have been raised regarding potential adverse health effects resulting from exposure to the chemicals that are present in the pool water itself. When considering exposure to these chemicals, it is important to distinguish between exposure to pool treatment chemicals in their undiluted form and exposure to chemicals present in the pool water itself. Chemicals used to treat pool water are typically sold in very concentrated forms as they are intended to be added to large volumes of water. Pool treatment chemicals should be kept in places where children cannot access them as direct exposure can cause breathing problems or may result in burns to eyes and skin. If swallowed, undiluted pool treatment chemicals may be fatal. Always follow the provided instructions for the safe handling and use of pool treatment chemicals.
From where do chemicals found in swimming pool water come?
The most common sources of chemicals found in swimming pool water are source water-derived, bather-derived, management-derived, and disinfection by-products:
1) Source water-derived – Source water-derived chemicals refer to chemical contaminants in the water that was used to fill or re-fill the swimming pool, hot tub or spa. If the source water was from a municipal drinking-water supply, it may contain organic materials, disinfection by-products, phosphates or other residual chemicals from drinking water treatment processes.
2) Bather-derived – Bather-derived chemicals refer to the chemical contaminants contributed to the pool water by the swimmers themselves. Such chemicals are predominantly nitrogen-containing compounds found in sweat and urine including urea, ammonia, amino acids and creatinine. Other chemicals derived from swimmers may include cosmetics, sunscreen lotions and soap residues.
3) Management-derived – Management-derived chemicals refer to the chemicals directly added by the swimming pool operators to maintain the quality of the pool water. Management-derived chemicals include, but are not limited to, disinfectants, pH adjusters, coagulants and anti-scaling agents.
4) Disinfection by-products – Disinfectants added to maintain pool water quality can react with other chemicals found in the pool water to form a variety of disinfection by-products. Common types of disinfection by-products include, but are not limited to, trihalomethanes (THMS), haloacetic acids (HAAs), chloramines, haloacetonitriles, bromate, chlorite and chlorate.
How does exposure to chemicals present in swimming pool water occur?
There are three main routes of exposure to chemicals in swimming pools, hot tubs and spas:
1) Direct ingestion – The amount of water ingested by swimmers depends on a variety factors including experience, age, skill and type of activity. For example, adult competitive swimmers would be expected to have a longer duration of exposure but a lower rate of ingestion due to having greater skill as compared with a non-competitive swimmer. When evaluating the safety of certain pool chemicals, the U.S. EPA has utilized a default ingestion rate of 50 mL/hour for children (ages 7-10 years) as compared to 12.5 mL/hour for adult competitive swimmers.
2) Inhalation of vaporized chemicals – Swimmers may inhale pool chemicals that have vaporized from the pool water into the air just above the water’s surface. Inhalation exposure to pool chemicals is greater in indoor pools where such chemicals may concentrate further in the air due to inadequate ventilation. Inhalation exposure may also vary based on duration and the intensity of effort exerted while swimming.
3) Dermal contact/absorption – When swimming, pool chemicals will come into contact with the skin, eyes and mucous membranes of swimmers. The amount of the pool chemical absorbed into the body by dermal contact also depends of a variety of factors including duration of contact, water temperature and the concentration of the pool chemical in the water.
Are there adverse health effects associated with exposures to chemicals found in swimming pools, hot tubs and spas?
The most common adverse health effects from exposure to pool chemicals are eye, skin or respiratory irritation. The irritation is caused by chloramines in pool water and surrounding air. Chloramines are a form of disinfection by-products produced by the reaction of chlorine with either ammonia or other nitrogen compounds found in the pool water. Respiratory tract irritation is more common in indoor swimming pools where disinfection by-products may concentrate in the indoor air due to the enclosed space. Proper maintenance of the pool water chemistry and appropriate ventilation of indoor pool facilities may reduce the occurrence of irritation. However, some people with preexisting medical conditions may have heightened sensitivity.
Other health effects that have been studied in relation to disinfectant by-product exposure in swimming pools include respiratory changes (such as asthma), adverse reproductive effects and cancer. However, the current studies on these effects have not been conclusive. While further research is still needed in order to reach a consensus about the risks of exposure to disinfection by-products found in swimming pools, hot tubs and spas, it is acknowledged by researchers and regulators studying pool chemical safety that health benefits of swimming during childhood and adulthood outweigh the potential health risks of chemical exposure.
How can I reduce my family’s exposure to these chemicals that are present in swimming pool water?
Overall, the risks from exposure to disinfection by-products in reasonably well-managed swimming pools are considered to be small. Steps that can be taken to reduce the formation of disinfection by-products in pool water can include showering and using toilet facilities, washing off sunscreen lotions, and applying water-tight diapers prior to swimming. It may also be beneficial to increase air circulation in indoor pool settings to reduce the levels of volatile disinfection by-products.
In the end, it is important to maintain microbial disinfection while minimizing potentially harmful disinfection by-products with the goal of maintaining the positive health effects of swimming through exercise while reducing other potential adverse health risks.
Centers for Disease Control and Prevention: Health Swimming/Recreational Water
United States Consumer Product Safety Commission: Safety Education / Safety Guides
World Health Organization – Guidelines for safe recreational water environments
NSF International Toxicology Services Department