Review
Biol. Sport 2010;27:233-240
P O T E N T I A L N E G AT I V E E F F E C T S O F
C H LO R I N AT E D S W I M M I N G P O O L
ATTENDANCE ON HEALTH OF SWIMMERS
AND ASSOCIATED STAFF
AUTHORS: Zarzoso M.1, Llana S.2, Pérez-Soriano P.2
1
2
Accepted
for publication
24.09.2010
Reprint request to:
Manuel Zarzoso
46010 Valencia, Spain
E-mail: [email protected]
Department of Physiology. University of Valencia, Valencia, Spain
Department of Physical Education and Sports. University of Valencia, Valencia, Spain.
ABSTRACT: Swimming is a recommended activity to achieve good health and to prevent certain pathologies of
the circulatory, pulmonary and locomotive systems. However, recent research has focused on the possible hazard
of chlorinated swimming pools. Chlorine reacts with organic compounds found in the water, giving way to
the formation of disinfection by-products (DBPs). DBPs enter the human body by water ingestion, inhalation and
dermal absorption. The most important DBPs are trihalomethanes, like chloroform, and chloramines, mainly
trichloramine. Acute problems by accidental exposure to chlorine and its DBPs were reported years ago but their
chronic effects have only been known since the beginning of the 21st century. Recent studies connect swimming
in chlorinated pools with the prevalence of panting, asthma and hay fever. Besides, several DBPs are volatile
and can be inhaled, not only by swimmers but also by those near the swimming pool. Although there are other
environmental factors that could contribute to the increase of respiratory disorders, some authors have given
rise to the so-called „chlorine hypothesis” which postulates that the increase in asthma in developed countries
can be explained, in part, by the effects of DBPs present in chlorinated swimming pools. In order to constrain
their potential negative effects, it is necessary (a) to control the amount of chemical agents used in swimming
pools, (b) not to raise water temperature excessively, (c) to maintain effective ventilation and (d) to have strict
hygiene rules for swimmers. However, the best way to avoid these problems would be using alternative disinfection
systems.
KEY WORDS: swimming, chlorine, health, disinfection by-products
INTRODUCTION
Swimming has been recommended to people to keep healthy and
operators. Finally, some recommendations are presented to preserve
fit since, at least, the Roman Empire. Nobody questions today
the benefits of swimming and to reduce potential harming effects as
the beneficial effects of physical exercise in water, so that swimming
much as possible.
the locomotive system -especially of the spine [27], circulatory
Swimming pool disinfection
problems [7] and it is even prescribed as the most appropriate sport
The large number of people going to the pools causes water to have
for asthmatic children [59].
a great deal of organic (hair, sweat, epithelial cells, urine, etc.) and
However, in recent years numerous papers have been published
inorganic substances (dirt in nails and skin folds, solid waste from
warning about health risks of swimming pool -and similar settings,
different sources, etc.), making the maintenance of physical and
e.g. spas- attendance [16,79]. Such risks are related to the use of
chemical properties within certain values necessary. Batjer et al. [9]
chemical agents for disinfection, particularly chlorine and its
pointed out that, even under strict hygienic conditions, each swimmer
disinfection by-products (DBPs). Therefore, the aim of this article
contributes a few grams of organic matter into the pool.
was to review the available publications in the peer-reviewed scientific
Water in swimming pools is not free from potentially dangerous
literature to provide insight into how chlorinated swimming pool
substances. Already in the 1970s, studies conducted by Rook [66-
attendance could affect the health of swimmers and associated staff.
68] showed that treated water for human consumption contained
After describing the substances resulting from water chlorination and
certain chemical substances that could be dangerous. The reaction
different ways of exposure, this article will discuss the effects of
of a number of polluting elements existing in water with chemicals
chlorine derivatives on the populations exposed to chlorine and its
used in disinfection results in numerous toxic substances generically
DBPs: recreational and competition swimmmers, technical staff and
grouped as disinfection by-products (DBPs).
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is recommended to prevent and treat some pathologies of
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Zarzoso M. et al.
Swimmers are exposed to these products in three ways [29,59] :
varies across countries but it should not exceed 3 mg/l (up to 5 mg/l
1) Water ingestion: all swimmers swallow water to a greater or
in drinking water) in public swimming pools [79]. Yet, many facilities
lesser extent depending on variables such as age, sex, technical skills,
use regular “shock doses” consisting of 20 mg/l as a preventative
swimming style, intensity and duration. The only study that has
measure.
experimentally measured water ingestion is that of Evans et al. [32],
Due to its large oxidising capacity, apart from disinfecting, free
reporting an average ingestion of 26.5 ml of water per session,
chlorine reacts with nitrogenated organic compounds found in water,
although considerable differences were found depending on
giving way to potentially hazardous products for swimming pool
age (37 ml in children versus 16 ml in adults) and gender (45 ml
users.
in boys, 30 ml in girls, 22 ml in men and 12 ml in women).
The main sources of nitrogenated organic compounds are urea
2) Inhalation: many of the DBPs are volatile and as such they are
and ammonia and, to a lesser extent, creatinine and different amino
inhaled by swimmers. This is actually the way most DBPs enter
acids present in sweat and urine. All these compounds react to
the body, 66% of the total. The amount of air ventilated by swimmers
hypochlorite forming chloramines [42,46,71]. It must be noted that,
depends on their swimming pace, this way in intense swimming up
even when chlorine and chlorinated compounds are used correctly,
to 100 l/min can be ventilated while in a more relaxed activity
reactions leading to DBPs formation are inevitable [3]. The DBPs
5 l/min are ventilated. Drobnic et al. [26] estimated chlorine inhalation
known at present are shown below [21,57,80]:
in a group of swimmers training in an indoor pool. In a two-hour
training period, swimmers could be exposed to a chlorine amount
over the recommended level for a worker after 8 hours exposure
(from 4 to 6 g.). On the other hand, the concentration of volatile
substances varies largely depending on the treatment and the type
of pool (indoor or outdoor). For instance, in indoor pools trihalomethane
concentration is 100 µg/l while in outdoor pools it does not exceed
10 µg/l [22,33,69].
3) Dermal absorption: the irritating effect of chemicals in water
is well-known by swimmers, especially in the eyes and mucosa, but
these substances can penetrate the skin too. Raykar et al. [64] have
pointed out that some lipophilic and lipophobic products can go
through the stratum corneum of the epidermis and spread into the
body. This is considered to be the least important pathway but nobody
FIG. 1. CLASSIFICATION OF CHLORINATION DBPs.
has yet measured the amount of products that penetrate the organism
in this way.
1) Trihalomethanes (THMs). These are the DBPs produced in
The substances swimmers are exposed to depend on the chemical
larger quantities. Chloroform (CHCl3) is the most representative and
treatment used. In the disinfection of swimming pool water, chlorine
it is used to measure THM exposure in indoor swimming pools [74].
is the most commonly used product. But, apart from that, it is also
It is classed in group 2B of the IARC (International Agency for Research
the substance causing the most problems as a result of the DBPs it
on Cancer) as a carcinogenic agent [41]. Nevertheless, very few
generates, as will be explained next.
studies on the effects on human health caused by environmental
exposure over long periods have been conducted [2].
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Water chlorination
Since chlorine (Cl-) was discovered in 1774 by the German chemist
the water surface and are therefore inhaled not only by swimmers
Carl Wilhelm Scheele, its compounds have been used in different
but also by any other users or technical staff [33]. From all
applications, i.e. explosives, pesticides, for whitening, refrigerating
the variables affecting the THM level in indoor pools, the most relevant
and of course for water disinfection. Several products derived from
is the number of swimmers, existing a linear correlation between
chlorine are used in water disinfection, grouped as follows [79]:
their number and THM concentration [22]. As for their concentration,
a) products derived from non-stabilised chlorine like chlorine gas,
it is not uniform: greater concentration has been measured on the
sodium hypochlorite or calcium hypochlorite and
surface, with a gradual decrease taking place as the distance from
b) products derived from stabilised chlorine, mainly isocyanydes
the water sheet grows [50].
-
-
(sodium dichloroisocyanurate and trichloroisocyanuric acid).
-
Due to their volatile nature, THMs are released into the air from
Analyses performed in indoor pools in the United States [69],
From all such products, sodium hypochlorite (NaOCl) and
Italy [33] and England [22], indicate that THM concentrations in
dichloroisocyanide are the most widely used [22,46]. Regardless of
water are about 100 µg/l, ranging from 17.8 µg/l. to 313 µg/l.
the product used, the free or residual chlorine portion is responsible
In outdoor swimming pools, amounts range between 3.8 µg/l and
for disinfection. The amount of free chlorine allowed by the regulations
6.4 µg/l, which stresses the importance of having adequate ventilation.
234
Potential negative effects of chlorinated swimming pool attendance on health of swimmers and associated staff
On the other hand, Fantuzzi et al. [33] have shown that THMs spread
swimmers meant a 0.40 mg/m3 rise. They were also significantly
all around the premises in a swimming pool, reporting concentrations
associated (p<0.01) to the levels of trichloramine, the free chlorine
3
of 26.1±24.3 µg/m even in the reception desk.
in water and the ceiling height.
With regard to concentrations in users, Aggazzotti et al. [3] pointed
3) Haloacetic acids (HAAs). Among them, trichloroacetic acid
out that, after swimming for one hour, THM absorption is seven times
(CCl3COOH) is a strong carboxylic acid. Clemens and Scholer [23]
higher than values while resting. They also noticed a negative
analysed 15 indoor pools in Germany, reporting mean concentrations
correlation between chloroform values and age, which suggests that
of 119.9 µg/l. In turn, Kim and Weisel [47] studied three indoor
younger individuals absorb chloroform faster. The elimination of
swimming pools in the US, reporting much higher concentrations,
the absorbed chloroform is quick and complete after 10 hours.
419 µg/l on average. On the contrary, with outdoor swimming pools,
Levesque et al. [53] studied chloroform exposure in water in indoor
concentrations hardly ever exceed 10 µg/l [23]. Once more, these
swimming pools and found that 1 hour swimming meant a chloroform
findings underline the importance of adequate ventilation in pools to
dose of 65 μg/kg/day, 141 times the dose of a 10 minute shower
avoid dangerous concentrations.
and 93 times the exposure by drinking water ingestion; they also
4) Other substances. This category includes known DBPs which
found out that, when chloroform levels in water are kept between
there is little information about, substances like haloketones,
150 and 300 ppb, the body concentration after 35 minutes swimming
trichloroaldehydes, trichloronitromethane and cyanogen chloride.
is equivalent to 55 minutes, reaching a balance between absorption
and elimination. However, at levels over 500 ppb a balance is no
The “chlorine hypothesis”
longer possible and the chloroform load rises with longer swimming
The consequences of accidental chlorine and DBPs exposure are
periods, which evidences the saturation of biotransformation
well-known [1,17,24], but the harmful effects of chronic DBPs
mechanisms. Recently, Caro and Gallego [21] performed a study on
exposure in swimming pool at typical concentrations have only recently
workers’ and swimmers’ exposure to THMs, analyzing urine samples
been determined. The link between swimming and respiratory health
and measuring the concentration of chloroform and
has been first investigated in Belgium with a study conducted with
bromodichloromethane as an index of exposure to these compounds.
school children [13]. Surprisingly, their findings showed that
Their results showed that THM uptake in swimmers was higher after
the increase in the permeability of the pulmonary epithelium caused
1 hour of exercise than that of workers after 4 hours of work.
by DBPs can make children more prone to asthma, which is rather
2) Chloramines. These DBPs are responsible for the typical
paradoxical if we bear in mind that swimming has traditionally been
“swimming pool smell”, eye and mucosa soreness and skin dryness
recommended to asthmatic subjects due to the warm, humid
[58]. These inorganic compounds are volatile and highly reactive
atmosphere of swimming pools.
[40]. The most abundant chloramines are monochloramine (NH2Cl),
Disorders in the function of clara cells -whose main mission is to
dichloramine (NHCL2) and trichloramine (nitrogen trichloride, NCl3).
protect the pulmonary epithelium- have also been reported. Lagerkvist
The latter is the most irritating and generates a stronger odour [40],
et al. [49] used the plasma concentration of the protein secreted by
noticeable at concentrations as low as 0.02 mg/l [48].
these cells (CC16) to examine the response produced by exercising
Hery et al. [39] reported that discomfort caused by chloramines
in environmental air and in the atmosphere of chlorinated swimming
-
-
3
starts with concentrations of just 0.3 mg/m , while the levels recorded
pools. The results proved that there were no significant changes in
in swimming pools were 0.84 mg/m3.
the mean CC16 concentrations before and after open-air exercising;
In outdoor pools chloramines and THM tend to dissipate into
yet, children regularly going to chlorinated pools had significantly
the air. However, in indoor pools, a constant production of chloramines
lower CC16 levels. Therefore, regular exposure to DBPs in the air in
may result in high concentrations that can be dangerous [58].
indoor swimming pools could exert negative effects on the proper
Mean values recorded in France, Belgium and Germany swimming
function of clara cells in children.
pools shifted between 0.2 and 0.9 mg/m3 [40,60], chloramines thus
Regarding air concentrations of NCL3 and pulmonary damage,
being one of the most concentrated air pollutants (the rest of pollutants
Carbonelle et al. [20] observed that air concentrations of NCL3
the population is exposed to hardly ever exceed 0.3 mg/m3) [60].
between 355 and 490 µg/m3 induced changes in the levels of CC16
Chloramine concentration grows with the number of users, water
and surfactant protein A (SP-A) and B (SP-B) in trained and
temperature and the turbulence caused by swimmers.
recreational swimmers, showing epithelial cell injury. On the other
That explains why in leisure centers chloramine concentration is
hand, a recent research conducted by Carbonelle et al. [19]
higher than in public swimming pools [58].
has shown that exercise performed in indoor swimming-pool
-
Recently, Jacobs et al. [43] measured the presence of trichloramines
3
in 38 pools, finding mean concentrations of 0.56 mg/m and
term changes in the serum level of SP-A, SP-B, CC16 and Krebs
maximum of 1.34 mg/m . A regression analysis of the data proved
von den Lunge-6 (KL-6), another marker of pulmonary epithelial
that the number of users in the water was significantly associated to
cell injury, showing the importance of an adequate control of NCL3
the trichloramine level, in such a way that an increase of 50 additional
concentration.
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3
containing less than 300 μg/m3 of NCL3 in air does not induce short
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Zarzoso M. et al.
Recent studies reported on the relationship between swimming
the fact that they use more the “splash pools”, kept at a higher
in indoor [11,60] and outdoor [14] chlorinated pools and
temperature and subsequently with larger amounts of DBPs. Besides,
the prevalence of panting, asthma, hay fever, rhinitis and atopic
when children play or learn to swim they inhale and swallow more
eczema, giving way to the so-called “chlorine hypothesis”. This
gases and water. Bernard et al. [12] evaluated the impact of infant
hypothesis postulates that childhood asthma rise in industrialized
swimming on the allergic status and respiratory health of 341
countries would be caused, at least partly, by the increasing and
schoolchildren aged from 10 to 13 years, measuring aeroallergen-
largely uncontrolled exposure of young children to chlorination by-
specific immunoglobulin E (IgE), exhaled nitric oxide (eNO) and
products contamining the air of indoor swimming pools [13], mainly
the serum concentration of CC16. They reported that children who
trichloramine [11]. However, this is a controversial hypothesis and
swam as infants showed clara cell damage and permeability changes
some researchers have questioned the findings of Bernard et al.
of the lung epithelial barrier, effects that are associated with higher
They argue several methodological [6,28,65] and political [65]
risk of asthma and recurrent bronchitis. On the other hand, they
aspects, among which the limitations of an ecological study design
did not find differences in the levels of IgE and eNO. Recently,
stand out. Therefore, until a clear cause-effect relationship between
a study conducted by Voisin et al. has shown that swimming in
chlorinated swimming pool attendance and asthma development
indoor and outdoor pools during infancy is associated with a dose-
has been established using prospective longitudinal studies, this
dependent increase in the risk of bronchiolitis. This effect independent
hypothesis should be considered with caution. In addition, it is
of other risk factors as exposure to tobacco or smoke, day-care
difficult to evaluate how the pool chlorine hypothesis could explain
attendance or antecedents of atopic diseases and could increase
the variation of asthma prevalence because there is insufficient
the risk of asthma and respiratory allergies later during childhood
information to distinguish the effects associated with DBPs exposure
[76].
and their contribution from other variables such as swim exercise
itself or other environmental and societal risk factors such as dust
Effects on competition swimmers, technical staff and operators of
and air pollution [43], obesity [4], smoking [36], microbial infections
swimming facilities
[44], nutritional status [30] and others.
In addition to the effects described earlier, abundant research has
If this hypothesis is taken into account, special attention must
focused on other populations exposed to chlorine and its DBPs, not
be paid to baby swimming. In these early ages the body is in full
only swimmers who spend hours exercising in water but also technical
development, being very sensitive to interactions with chemicals.
staff and operators in contact with the environment of the swimming
In the last years, this has been a matter of great concern and some
pool.
studies have been carried out to evaluate the effects of early
swimming in the respiratory health of children.
Regarding the incidence of asthma and bronchial hyperreactivity
in athletes, studies conducted on US top level athletes [77,78] noticed
Some researchers found that baby swimming increases the risk
a higher incidence of asthma in endurance disciplines such as cycling,
of infection in the respiratory tract and the middle ear, particularly
swimming, rowing or long-distance skiing. These studies concluded
in genetically predisposed children [62]. Evidence presented by
that the higher prevalence could be attributed to the prolonged
Nystad et al. [61] suggests that some children could have an
hyperventilation and higher exposure to allergenic and irritating agents
increased risk of wheeze from 6 to 18 months if they take part in
while training, underlining that the environment where the activity
baby swimming during the first 6 months of life; on the other hand,
is performed can be an important factor influencing the appearance
the risk of lower respiratory tract infections or otitis media was not
of asthma or airway problems. Along these lines, Langdeau et
increased. Finally, in Germany, Schoefer et al. [70] found an
al. [51] found that elite swimmers and subjects who practised winter
association between swimming pool attendance and higher rates
sports had a higher airway hyperreactivity prevalence than sedentary
of diarrhoea, but they did not find any connection between attendance
individuals of the same age, being the incidence of asthma and airway
of chlorinated swimming pools and allergic outcomes. However,
hyper-responsiveness more frequent or more marked in swimmers
the results of this study were conditioned by the different
than in cold air athletes.
the studies have been performed) and Germany, with chlorine levels
of swimming pools could be an important factor in the development
of such airway lesions. For this purpose, several researches have
10 times lower.
The results obtained by Bernard and Nickmilder [15], Bernard
studied bronchial hyperreactivity and airway inflammation in
et al. [11] warned that the use of indoor chlorinated pools, especially
swimmers. Helenius et al. [38] found out that bronchial hyperreactivity
by children, can interact with the state of atopy that in the respiratory
was more present in swimmers (48%) than in non swimmers (16%)
system produces rhinitis and asthma. The authors reported that
and, after analysing the characteristics of the subjects’ sputum noticed
the risk is greater in children who swim in indoor chlorinated pools
that the amount of eosinophil and neutrophil leukocytes was
regularly before they are 6-7 years old. Children of these ages seem
significantly higher in swimmers. Similarly, swimmers with bronchial
to be more sensitive to DBPs, an aspect that is enhanced by
hyperreactivity had a greater amount of eosinophils (responsible for
-
-
-
-
Taking into account the aforementioned, environmental conditions
-
recommended levels of chlorine between Belgium (where most of
236
Potential negative effects of chlorinated swimming pool attendance on health of swimmers and associated staff
pro-inflammatory reactions like allergies) than those without
Other effects
symptoms, as well as a significantly higher bronchial hyperreactivity
Apart from the described effects of chlorine and its DBPs on
to histamine. In contrast, Belda et al. [10] found that the inflammation
the respiratory system, several studies have analysed the effects on
could be mediated by neutrophils, rather than eosinophils, and could
other parts of the body.
be related to the duration of training, perhaps due to exposure to
chlorine derivatives.
group (60.2%) than in controls (12.9%) and strong correlation was
a high asthma incidence and other respiratory symptoms induced
found with competition swimming so that the more hours of training
by exercising, asthma and hay fever occurring more frequently in the
per week in the pool, the greater the incidence of dental stains; this
group of international swimmers (19% and 21% respectively) [37].
relationship was not linear, as a brusque increase was found in
These authors concluded that the most important risk factors for
training periods longer than 6 hours a week.
-
Swimmers usually suffer from dry skin or xerosis [34]. Atopic
Likewise, an important proportion of swimmers often refer to
[45,56,73] and contact [52,63] dermatitis have occasionally been
irritating symptoms on eyes and throat, and headaches when
identified. Less frequent is an increased production of grease, known
swimming in indoor pools. In this respect, Levesque et al. [55]
as “swimmer´s shine” [8], caused by prolonged skin hyperhydration.
compared the prevalence of health problems in young swimmers and
As far as the effects on the nose and nose physiology are regarded,
footballers and observed that the presence of respiratory symptoms
Deitmer and Scheffler [25] found that swimmers had greater
as coughing, sore throat, sore eyes and outer ear otitis was greater
obstruction, itching, nasal discharge, sinusitis and allergies. Besides,
in swimmers than in indoor soccer players. They concluded that
swimmers often referred to an “allergy to chlorinated water”.
the incidence of these symptoms could potentially be reduced by
This term was subsequently used by Bonini et al. [18] to describe
limiting exposure to chlorination by-products.
a clinical case characterised by nasal obstruction, liquid nasal
In the case of coaches, instructors, lifeguards or maintenance staff,
-
competition swimmers. Prevalence was higher in the swimmers
Later studies carried out in competition swimmers showed
asthma were age and the amount of training done in the pool.
discharge and sneezing.
DBPs inhalation is not negligible and after an hour’s exposure in
The relationship between chronic exposure and chlorinated
a ‘typical’ 100 μg/m3 atmosphere, a THM concentration of 30 μg is
compounds has also been explored using oxidative stress indicators
found in alveolar air [2]. Massin et al. [58] studied the occurrence of
in swimmers. Varraso et al. [74] evaluated DBPs exposure measuring
eye and respiratory symptoms in lifeguards working in indoor swimming
chloramine concentration in the pool’s water and THMs in
pools to investigate the relationship with trichloramine concentrations.
the swimmers’ blood. Cu2, Zn3, superoxide dismutase (SOD), and
According to the results, there was a high prevalence of irritation in
glutathione peroxidase (GSH-Px) were the biological markers of
eyes and nose, regardless of sex, which significantly increased with
the oxidative stress response. The results confirmed that the oxidative
greater trichloramine concentrations. They also found a direct
stress found was not exclusively due to exercising and part of it was
relationship between trichloramine concentration and temporary
caused by the toxicity of chlorine and its DBPs. In this case, chloroform
bronchial hyperreactivity, which could indicate that lifeguards can
seemed to be the main factor.
develop asthma as an occupational disease. Along the same lines,
Other research lines have attempted to asses potential health
a few years later Thickett et al. [72] identified the first cases of
risks of chloroform exposure in swimmers. The highest concentration
occupational asthma in lifeguards. The results of their study evidenced
they found in competition swimmers was 10.000 times smaller than
a relationship between trichloramine exposure and asthma development
that required for tumours to appear in animals and, for that reason,
in swimming pool workers. This is a very relevant finding, as it was
the authors concluded that swimmers have a large safety margin
previously thought that it only caused transient symptoms and
[54]. Nonetheless, ascertaining what actually occurs in repetitive
discomfort.
and long-term exposure to this product is still pending.
Recently Jacobs et al. [43] estimated trihalomethane exposure
Aiking et al. [5] studied the hepatotoxic and nephrotoxic effects
at work in 624 indoor pool workers. The results showed that these
of chlorinated compounds in 18 competition swimmers, finding out
individuals were more likely to develop conditions related to
that B2 microglobulin, and indicator of kidney damage, was
the upper airways (sinusitis, chronic colds, and a sore throat).
significantly higher in the urine samples of younger swimmers.
Those employees who, apart from working in the pools, also used
Recently, Villanueva et al. [75] tried to determine whether the risk
them as swimmers had a greater occurrence of respiratory
of developing bladder cancer was related to THMs exposure while
symptoms associated with rhinitis, nasal congestion, sneezing,
showering, bathing or using indoor swimming pools, since studies
and sore and tearful eyes. In addition, when the temperature and
conducted in drinking water had so pointed out. Their findings support
humidity were too high, the ventilation was not adequate and the
experimental and epidemiological evidences that THMs, and possibly
workers reported discomfort caused by the presence of chemicals,
other DBPs, are associated with a higher risk of bladder cancer, not
the prevalence of respiratory and allergic symptoms was 1.4 to
only through drinking water but also through ingestion, inhalation
4.6 times greater.
and dermal absorption in closed environments like swimming pools.
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Escartín et al. [31] studied the incidence of dental stains in
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Zarzoso M. et al.
Chlorine has also been attributed the whitish or greenish colour
To avoid the possible harmful effects, heated swimming pools
of the hair of some swimmers. This pigmentation change is reversible
should ideally use disinfection systems producing minimum DBP
and is only worrying from an aesthetic point of view, being
amounts. Apart from chlorine, there are other disinfection treatments:
the consequence of prolonged exposure to swimming pool water and
bromine, active oxygen, polyhexamethylene biguanide hydrochloride
sunlight. A whitish pigmentation is indeed caused by the decolouring
(PHMB), electrophysical systems (electrolytic copper and electrolytic
power of chlorine but the greenish colour is caused by copper ions
silver), ozone and ultraviolet disinfection, seeming these last two
in water [8].
the most recommendable methods. All these water disinfection systems
have appeared in recent decades as a counterpoint to chlorination but
CONCLUSIONS
they have not managed to take over. This could be explained by three
The review of the literature conducted shows the effects of chlorination
main reasons 1) chlorine’s great disinfecting efficiency, 2) the great
used in indoor swimming pools and similar settings for different
optimisation and cheap price of chlorination systems, with almost
functional systems of the human body. From all the possible harmful
a century worth of research and development, and 3) the lack of
effects reported, those affecting the respiratory system are the most
knowledge and/or the uncertainty of using new systems [55].
noticeable, to the extent that they have given way to
Based on the above, authors like Nemery et al. [59] have pointed
the “chlorine hypothesis” which postulates that swimming in
out the need to lay down air quality standards for swimming pools.
a chlorinated pool from an early age could be an important
In any case, attempts should be made to control the amount of DBPs
environmental factor for asthma in children. Likewise, in 2002
in the facilities. The goal should be to preserve the benefits of swimming
the first documented cases of occupational asthma were reported in
and to reduce potential harming effects as much as possible. To that
lifeguards. However, there are some dissenting opinions making this
end, special attention must be paid to the precise control of chemicals
a topic which needs further investigation, since it is well established
used in swimming pools, the avoidance of too high water temperature,
that there are other environmental and social factors that could
an effective ventilation of the facilities and the establishment of strict
contribute to the rise of respiratory disorders.
hygienic rules for swimmers before swimming [55].
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-
-
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-
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