Why exposure to chlorine in swimming pools is dangerous for children

Swimming is the sport of the 21st century! With multiple benefits for the health of the entire body, aquatic exercise trains all muscle groups, the entire skeletal system and stimulates the nervous system more effectively than any other sport. Since the early 1970s, the benefits of swimming have also become evident on the development of babies. With the passage of time, the implementation of water hygiene standards in public swimming pools has primarily aimed at water hygiene, but has not taken into account the specific needs of babies. Over the years, numerous studies have been conducted on the most used standard, chlorine, and its long-term effects on the development of babies exposed to water from chlorinated pools.

Why is chlorination of swimming pool water dangerous for the human body?

There are several methods for disinfecting water in swimming pools, but chlorination is the most common, due to its efficiency/price ratio.

Chlorination inactivates pathogens in swimming pools, but at the same time causes reactions with organic matter present in the water, from chemical to human-induced, such as urine, sweat, epithelial cells, hair, microorganisms, cosmetics and other care products, forming residual products of chlorine disinfection that can become dangerous with long-term exposure. The most dangerous residual products are trihalomethanes (THMs), which are not only present in the water, but, due to their volatility, also evaporate into the air above the pool water, persisting for a long time, being inhaled by the human body. Hence the specific smell of chlorine in public swimming pool rooms.

The World Health Organization (WHO) specifies that swimmers in indoor pools, especially those that are not properly ventilated, can be exposed to THMs in 3 ways, through oral ingestion, through epithelial contact, and through inhalation.

Hundreds of studies have shown that exposure to chlorine in swimming pools can affect human health. Several epidemiological studies have shown that population exposure to THMs through ingestion leads to high rates of colon, bladder, and rectal cancers. (Hamidin et al. 2008; Lee et al. 2009; Villanueva et al. 2015). And other animal studies have linked THM exposure to the formation of tumors in the liver and kidneys. (Ahmed et al. 2019). 

“A total of twenty-one studies evaluating the effects of chlorine and its by-products on allergic or respiratory health were included in the analysis. Exposure to chlorination by-products through swimming pool participation has shown adverse health effects on children, occupationally exposed subjects, competitive swimmers, and asthmatic subjects. These adverse effects were observed despite the presence of official directives in most countries controlling and regulating the use of chlorine for water disinfection. Contact with chlorination by-products may not be the main reason for poor respiratory health, but it may not be as harmless as previously thought. In particular, swimming by children in chlorinated pools is highly questionable.” it is specified in MINISTRY "Chlorine, chlorination products and their allergic and respiratory health effects" of the Institute of Epidemiology of the National Health Research Center in Neuherberg, Germany.

Children are most affected by exposure to chlorine in swimming pools

Children are the most vulnerable to exposure to chlorine in swimming pools. A study (Villanueva et al..-2015) demonstrated that long-term swimming in chlorine-disinfected pools increases the risk of asthma in children, and another study (Bernard et al.. (2009) added the risk of bronchiolitis to the list. Another study report (Pándics et al. (2018) highlighted the increased risk of cancer in children exposed to chlorinated swimming pools from an early age over the long term.

Dr. Alfred Bernard of the University of Louvain in Belgium and his team have undertaken the most studies on children's long-term exposure to chlorinated swimming pool water and its effects on their health later in life.

"Our data suggest that infant swimming in chlorinated indoor pools may be associated with distal airway changes that predispose children to the development of asthma and recurrent bronchitis. These effects may result from repeated inhalation of chlorination products, particularly trichloramine, the irritating gas formed when chlorine reacts with organic matter brought in by swimmers and which gives indoor pools their typical chlorine odor. We recommend caution before regularly taking infants to poorly ventilated indoor pools where there is a strong chlorine odor.", Dr. Bernard states in MINISTRY saddle "Respiratory health and swimming in babies."

Can cause asthma and airway inflammation

Dr. Bernard and his team also demonstrated through another study that in industrialized, economically developed countries, where access to swimming pools is easy, cases of childhood asthma have increased in recent years. Here's how he explains it, in MINISTRY "The presence of chlorinated swimming pools, atopy and the risk of bronchial asthma during childhood" How children are affected by exposure to chlorine in swimming pools:

"The pool factor responsible for these effects should probably be sought among the chlorination products, which can be inhaled as gas or aerosols. One of the main culprits could be trichloramine."

Our study clearly indicates that the risk of developing asthma peaks when children regularly go to an indoor chlorinated pool before the age of 6-7 years. The most logical explanation for this higher sensitivity of young children, already observed in our previous study (Bernard et al. 2003), is that children cannot really swim before this age and therefore have to go to the small pool, which is shallow, hot and more heavily polluted than the large pool. In addition, when children play or learn to swim, they inhale and swallow even more aerosols and water droplets containing hypochlorous acid and soluble chloramines. These can be transported more or less deeply into the respiratory tract, depending on the size of the aerosols and the breathing pattern (oral vs. nasal breathing). However, the most critical factor is that exposure to all these chlorination products peaks in children precisely at a time when their lungs are still developing. A significant proportion of lung development indeed occurs postnatally during a period extending to 6–8 years of age (Finkelstein and Johnston 2004). Throughout this time, the lung undergoes continuous alveolarization and morphogenesis with differentiation of the most critical epithelial cell types and structures. It is therefore not surprising that repeated exposure of the respiratory tract to high concentrations of chlorine-based oxidants during this period may induce epithelial changes that could promote the development of asthma in sensitized subjects.

In conclusion, our study shows that chlorination byproducts contaminating indoor swimming pool air may act as an adjuvant to promote the development of asthma in atopic children, especially young children who frequent small, heavily polluted swimming pools. These findings further support the “pool chlorine hypothesis,” which suggests that increasing exposure of children to pool chlorine may be an important lifestyle factor implicated in the increase in childhood asthma in the developed world.”

“Exposure to swimming pools early in life was associated with a significantly higher risk of developing preschool asthma. A dose-response relationship between swimming pool exposure and asthma was indicated in children with asthma onset at age 1 year. Children who were both sensitized and exposed were at particularly high risk.” it is also stated in MINISTRY "Early exposure to swimming pools and the onset of asthma in children – a case-control study" of the Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine at Umeå University in Sweden.

May cause allergic rhinitis

Other studies have shown that the long-term effects of exposure to chlorine in swimming pools can lead to allergic sensitization of the airways to dust particles, which can lead to lifelong allergic rhinitis.""Presence in chlorinated swimming pools early in life is associated with higher risks of neonatal airway inflammation and IgE sensitization to house dust mites, independent of other risk factors." is specified in MINISTRY "Risks of new-onset allergic sensitization and airway inflammation after swimming at a young age in chlorinated pools", also signed by Dr. Bernard's team from the University of Louvain in Belgium.

"The strongest associations with higher rates of allergic rhinitis were found for the youngest subjects and were related to current pool participation and school age. Higher rates of allergic rhinitis may be observed when school-age children are frequently exposed to chlorinated pool water during the past 12 years. Impaired integrity of the lung epithelium by exposure to chlorination byproducts could facilitate closer contact with allergens and therefore lead to higher rates of allergic rhinitis.” it concludes in another study, "Swimming pool frequency and the prevalence of allergic rhinitis later in life", of the National Research Center for Environment and Health, Institute of Epidemiology, in Neuherberg, Germany.

How can we avoid exposure to chlorine in swimming pools without giving up on children's aquatic education?

The above studies demonstrate that exposure to chlorinated pool water, especially for babies and preschoolers, can affect their health in the long term, with dramatic effects that can appear later in life. But does this mean we should give up this sport that brings so many benefits to children? Not at all! It just means choosing the pool that our child is going to frequent very carefully, so as to ensure that exposure to chlorine is as low as possible or non-existent (where chlorine-free water sanitization methods are used).

“The optimal microbiological and chemical method is water ozonation; however, due to the higher cost, this method is rarely used. In the case of using pools with chlorinated water, air circulation is crucial because it dissipates toxic compounds suspended in the air. Also important are the use of the smallest effective amounts of chlorine disinfectant, careful washing of the body by people using the pool before swimming, and the use of swimming caps to limit the delivery of organic compounds into the pool.” it is specified in the study "The influence of chlorinated water on the development of allergic diseases" Department of Gastroenterology, Metabolic and Internal Diseases and Dietetics in collaboration with the Department of Allergology, Clinical Immunology and Internal Diseases in Poland.

What details should we take into account when choosing a water club for our child:

• Imposing strict rules, both regarding the child's circuit in the club, and the mandatory immunization, the use of showers before entering the water, water diapers, and the prohibition of creams and lotions;
• Water sanitation should be done with ozone and UV or there should be a low level of residual chlorine in the water (there should be transparency in providing this information). In Romania, the level allowed by law is 0.5-1mg/l, but it is a limit imposed on normal public swimming pools. Those dedicated to children should have a much lower level;
• There should be a well-designed ventilation and air circulation system to avoid the accumulation of trichloramine in the air we breathe.

"Secondary disinfection of pool water with UV or ozone is recommended to destroy microorganisms, especially Cryptosporidium, which is resistant to chlorine. This action is particularly important, especially in the case of pools used by children, while also reducing exposure to chloramines."is specified in"Code of Practice” on 2023 of the UK Swimming Pool Water Treatment Advisory Group. In Germany, the law regarding residual chlorine in swimming pools is the strictest in the world, imposing a maximum of 0.3–0.6 mg/L. Here, complex methods of sanitizing water in public swimming pools are used to minimize to zero exposure to residual chlorine in the water and air, from the use of the UV method to flocculation methods or replacing the water as often as possible. Here too, ozone sanitization is mandatory in therapeutic pools. Therefore, as a responsible parent, when we decide to take our baby or preschooler to a swimming pool, we must also carefully monitor how the water is sanitized. The more transparency there is in this regard, the more attention the respective club pays to the correct sanitization of the water, the healthier we offer the child a healthier environment where they can swim safely and fully benefit from its miraculous effects.

Water sanitation at Acvatic Bebe Club

The swimming pools at Acvatic Bebe Club are sanitized using the latest technologies, so that the little ones have a healthy environment when they enjoy the pleasure of aquatic activities. The club uses both UV and ozone installations, which easily cope with difficult conditions and minimize the use of sodium hypochlorite for the disinfection of pool water. Thus, the reference values of the disinfected product are minimized, and the unpleasant odor or the development of trihalomethanes are prevented. UV light removes chlorine compounds from the pool water and ozone increases its clarity level without generating chemical byproducts, oxidizing chloramines and reducing their level in the water and air to zero.

Swimming is the only sport that trains the entire human body, both physically and cognitively and emotionally. That is why it is the most suitable sport for children, from 4 months old and becomes an effective form of therapy for premature babies. However, in order to enjoy all the benefits of swimming, the child must be in an adapted aquatic environment, which offers them safe conditions in terms of water hygiene.  

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