What health risks lurk in public swimming pools?
Despite disinfection, water in swimming pools can still provide an environment conducive to the growth of dangerous microorganisms. In the UK, swimming pools have repeatedly been identified as sources of parasitic and bacterial infections. What are the risks associated with using swimming pools, including those in Poland, and how can we protect ourselves?
What parasites and bacteria can be found in public swimming pools?
Even though pool water is regularly disinfected, it can still harbor parasites and bacteria that are resistant to chlorine. Cryptosporidium and Giardia lamblia are protozoa that cause severe gastrointestinal issues such as diarrhea, stomach pain, and vomiting. They are especially dangerous for children, the elderly, and people with weakened immune systems. Research findings also frequently indicate the presence of bacteria such as Staphylococcus aureus (golden staph), Escherichia coli, and streptococci.
These pathogens usually appear when an infected person enters the pool. They are introduced through sweat, saliva, urine, and skin particles. As a result, people may experience infections of the skin, mucous membranes, urinary tract, and digestive system. In extreme cases, complications such as sepsis, anaphylactic shock, or meningitis may occur. The risk increases with damaged skin, lowered immunity, and high pool usage.
Public pools as the most common source of infectious disease outbreaks in the UK
In the United Kingdom, public swimming pools have long been considered the main source of waterborne gastrointestinal disease outbreaks. Epidemiological data from England and Wales show that in the past two decades, swimming pools were the most common sites of gastrointestinal infection outbreaks.
The most frequently identified pathogen in such cases remains Cryptosporidium – a parasite highly resistant to disinfectants that can survive in chlorinated water for several days. It causes diarrhea, vomiting, stomach cramps, and general weakness. Symptoms can persist for up to two weeks, and about 40% of those infected experience a relapse after apparent recovery. In most cases, the illness is mild, but for vulnerable individuals and those with weakened immune systems, it can be dangerous.
The situation in Polish public swimming pools
In Poland, despite strict sanitary regulations, numerous pathogens are still detected in swimming pools. In March 2025, the presence of Pseudomonas aeruginosa – a bacterium particularly dangerous to immunocompromised individuals – was detected in the water of a municipal swimming pool in Chojnice. This pathogen can cause ear infections, skin conditions, gastrointestinal issues, and eye inflammations.
Although Pseudomonas aeruginosa should not be present in pool water, sanitary inspections revealed its presence in samples collected on March 25. The incident caused concern among parents of children using the facility, especially since some of them had visited the pool just before the results were released. This case confirms that even in modern, well-maintained swimming pools, health-threatening situations can occur – particularly during peak seasons when maintaining full water quality control becomes more challenging.
How to deal with bacteria in pools?
The quality of pool water depends not only on filtration and disinfection systems but also on the responsible behavior of users. Although the water undergoes regular microbiological and physicochemical testing by sanitary inspectors and facility administrators, risk cannot be completely eliminated. It exists wherever people gather.
Following basic hygiene rules is essential. Before entering the pool, one should thoroughly wash their body, remove any cosmetics, and wear a clean swimsuit, flip-flops, and a swim cap. Foot disinfection basins must also be used. It is forbidden to relieve oneself in the pool. Ignoring symptoms of illness – even temporary diarrhea – can pose a threat to others. After leaving the water, it is important to take a shower to rinse off chlorine, sweat, and potential microorganisms, thereby reducing the risk of illness.
