Should you be afraid of chlorine?


In times when everything considered healthy has the prefix ‘eco’, is labeled ‘natural’, or ‘no preservatives’, we are suspicious of chemicals. Chlorine is also on the list, but it is still used extensively to treat and disinfect water. Do we really need to be careful?


Chlorination is one of the most common ways of treating water, i.e. making water safe to drink. Every stick, however, has two ends. It is no different with chlorine, which on the one hand is effective in destroying dangerously pathogenic bacteria, and on the other – it is not completely harmless to higher organisms, including Homo Sapiens.




Chlorine is a chemical element in the form of a gas that is more than twice as heavy as air, and is a powerful oxidant, disinfectant, and bleaching agent. The smell of chlorine is unpleasant, suffocating, and, importantly, very poisonous. Chlorine is irritating to the respiratory system and mucous membranes, and may lead to pulmonary edema and death. It is assumed that the limit of dangerous concentration of chlorine in the air is 1000 ppm (abbreviation for ‘part per million’ – particle per million). For this reason, chlorine was used during World War I as a combat gas and chemical weapon. It is important to know that constant contact with chlorine, even in low concentrations, weakens the lungs and increases the risk of other lung diseases. On the other hand, chlorine is present in nature, and, as a macronutrient, is found in most living organisms, including people.




So why is chlorine used on such a large scale in the treatment of tap water or water in swimming pools? Chlorine disinfection is effective. Chlorine kills bacteria (e.g. strains of E. coli bacteria) as well as viruses, fungi, protozoa, and other microorganisms. Water contamination with dangerous pathogenic bacteria can be extremely dangerous and threaten not only health, but also human life. Most often, bacteria of these types lead to food poisoning, but it is possible for E. coli bacteria to cause serious infections in some people, including: cystitis, nephritis, meningitis, and sepsis. In such a context, the choice of the lesser evil is obvious – chlorine in permissible concentrations does not pose such a great threat to health, or potentially even life, as pathogenic bacteria. Moreover, chlorinated water is microbiologically pure and retains natural minerals, which is important from the consumer’s point of view. However, we deal with chlorinated water not only in the tap, but very often – in pools where the concentration of this element is much higher than in tap water. So, how does bathing and swimming in chlorinated water affect the human body?



Despite the fact that more and more swimming pools, aqua parks, and other swimming pools of various types are using alternative methods of water treatment, such as ozonation, or UV irradiation, the vast majority are still pools with chlorinated water. Usually, there is no problem recognizing which kind of pool we are in. The characteristic smell of chlorinated water is clearly noticeable even from a distance. Sometimes it is stronger, sometimes – weaker. A lot depends on if the standards have been violated. Two limiting values ​​are important according to the Ministry of Health regulation of 9 November 2015: free chlorine and combined chlorine. All pool water must be regularly cleaned and then undergo a chlorination (or other treatment) process in which two important chemical reactions take place. As a result of one of them – oxidation, i.e. oxidation, bound chlorine is formed, the components of which are, among others chloramines – ammonia based and trichloromethane (THM) – a halogen derivative of methane. It is only in the next step that the disinfecting function of chlorine is activated, i.e. the destruction of bacteria by free chlorine. In such a situation, not only the value of free chlorine is important, but most of all – combined chlorine. It is the by-products of the chlorine oxidation reaction (chloramines and trichloromethane) that may pose a threat to health, especially when the limits of combined chlorine are exceeded (above 0.3 mg/dm³).


Anyone who uses a swimming pool with chlorinated water knows very well what it means to have dry skin. The chlorine present in the water completely deprives the skin of its protective lipid layer. After immersion in chlorinated water the skin becomes rough and often irritated – this is the reason why we often take moisturizing body lotions to the pool. Chlorine also penetrates hair fibers, changing and weakening their structure, which may result in loss of shine, split ends, and even hair loss. There is no doubt that frequent swimming in a pool with chlorinated water has negative effects on your health, despite the other enormous advantages attained from this type of physical activity. Excess chlorine is harmful in direct proportion to the levels of bound chlorine. Mono-, di-, and trichloramines are absorbed directly through the skin, inhaled, and also ingested by bathers when they accidentally swallow the water. Chloramines can cause changes to the skin as well as irritation of the mucous membranes of the eyes and respiratory tract, including asthma symptoms. Equally dangerous is trichloromethane (THM), which is inhaled by swimmers because it is heavier than air and floats directly above the water. It penetrates directly through the skin and causes genetic changes that can lead to the formation of cancer cells.


At this point, you may be asking – “Maybe these statements are exaggerated?” or “Is this part of a campaign against chlorinated pools?”. Unfortunately not. According to the International Agency for Cancer Diseases, nearly 60 compounds of organic chlorine can cause cancer in humans and animals. A similar conclusion was reached by a team of researchers led by Manolis Kogevinas from the Center for Research on Environmental Epidemiology in Barcelona – swimming in chlorinated water, both indoors and outdoors, increases the risk of cancer. The World Health Organization (WHO) also warns against chlorination of water, which can lead to the formation of numerous carcinogenic compounds. Rita Schoeny, a representative of the United States Federal Environmental Protection Agency (EPA), is of a similar opinion, citing studies showing that chlorinated water, under certain conditions, has a carcinogenic potential. Also interesting, are the results of studies carried out on 40 healthy volunteers who spent 40 minutes in a public swimming pool in chlorinated water. After this time, some biomarkers indicated seven times higher levels of carcinogenic substances in the blood than before the bath. There are many examples, but that’s not all … poisonous chlorine compounds are also conducive to the development of respiratory and gastrointestinal allergies. It is for this reason that the EPA has warned parents against the use of chlorinated pools by children under the age of two. High levels of chlorine oxidation by-products may increase the risk of developing asthma in children. People prone to allergies and asthmatics (not only children) should also be careful, as chlorine may aggravate undesirable symptoms.


Certainly, chlorine is a simple and fairly cheap way to treat water. In the twenty-first century, however, we have at our disposal many other methods of purifying water in pools; methods which are as effective as, and a great deal safer than, chlorine. Along with the trends towards UV irradiation and ozonation, a third trend is emerging: to purify water in a completely natural way. Ecological swimming ponds and natural pools are not only a more pleasant, but also a healthier, alternative. Water in a properly designed and maintained ecological swimming pond or natural swimming pool meets strict sanitary requirements and is crystal clear, even though its purification takes place without the use of chlorine, ozone, and other chemicals. The use of biological and mechanical methods of water filtration enables the preservation of the biological balance in the swimming pond. In such conditions, the natural self-purification processes of water take place, supported by appropriate species of hydrophilic plants, mineral substrates and volcanic deposits, ecological bacterial preparations, as well as technologically advanced filtration devices. Importantly – the variety of ecological swimming ponds is enormous – they can come in various types, sizes, and forms and be perfectly integrated into the surroundings. It is important to remember that ecological swimming pools create enormous possibilities of use while maintaining natural water treatment. The use of the most modern construction technologies allows the use of natural swimming pools throughout the year (heated water, roofing). These types of swimming pools can also be equipped with specialized devices, incl. for hydro massage, as well as devices which completely eliminate or significantly reduce the amount of vegetation needed for binding.


By choosing an ecological swimming pond, or a natural swimming pool, we guarantee not only a more pleasant experience during use, but above all – certainty that the water we bath in is safe and does not threaten our health, which is priceless.