Chlorinated Swimming Pools Can Cause Asthma In Swimmers

Water Teatment Chemicals Used For Indoor Swimming Pools Could Be The Culprit

Chlorine treated indoor swimming pools can cause asthma or other breathing problems in swimmers according to research from several sources. These findings may explain why swimmers are more prone to asthma and other breathing problems than athletes in other sports. The chlorine used to sanitize the swimming pool might have harmful side effects.

"Our results show, indeed, that nitrogen trichloride (produced by Chlorine) is a cause of occupational asthma in indoor swimming pool workers like lifeguards and swim instructors," says Dr. K.

Thickett of the Occupational Lung Diseases Unit at the Birmingham Heartlands Hospital.

In Dr. Thickett's study, each of the subjects either stopped taking inhaled corticosteroids altogether, or their asthma symptoms resolved significantly once they were placed in other occupations away from the swimming pools. Dr. Thickett's study was backed up by research from other European and Australian sources.

The problem isn't the chlorine, but what chlorine turns into when combined with organics. The organics are contributed by bathers in the pool in the form of sweat, dander, urine and other organics. The chlorine reacts with the organics and produces nitrogen trichloride, aldehydes, halogenated hydrocarbons, chloroform, trihalomethanes and chloramines. If these sound like dangerous chemicals, they are. During the Olympic Games held in Australia, it was reported that more than one-quarter of the American swim team suffered from some degree of asthma.

Meanwhile, investigators in Belgium presented research showing that exposure to such chloramines greatly increases permeability of the lung epithelium, a condition associated with smoking cigarettes. In a study presented by Dr. Simone Carbonnelle, of the industrial toxicology and occupational medicine unit at the Catholic University of Louvain in Brussels, 226 otherwise healthy school children, mean age 10, were followed to determine how much time they spent around indoor swimming pools, and the condition of their lung epithelium.

The children in Dr. Carbonnelle's study were exposed to air around the school swimming pool for a mean of 1.8 hours per week.

The level of lung permeability would be the equivalent of what she would expect to see in a heavy smoker, according to Dr. Carbonnelle. "These findings suggest that the increasing exposure to chlorine-based disinfectants used in swimming pools and their by-products might be an unsuspected risk factor in the rising incidence of childhood asthma and allergic diseases," she said. The variation in lung surfactants persisted whether the children lived in a rural area or in the city, and whether they were from upper income, or less well-off families, she added.

As part of Dr. Thickett's study, three employees of a local public swimming pool who complained of asthma-like symptoms were subjected to chloramine challenge tests in which, in the lab setting, they were exposed to roughly the same amounts of chloramine as they would be exposed at work (i.e., around the swimming pool, close to the surface of the water).

Measurements of nitrogen trichloride were taken at 15 points around the pool, 1 m above the surface of the water. When exposed to equivalent amounts of the chemical in the lab, the three subjects all experienced significant reductions in forced expiratory volume in one second (FEV1), and high measurements on their Occupational Asthma Expert System (OASYS) scores, a measurement of asthma and allergy severity.

In the Belgium study, chloramines in the air around the surface of the pool were measured. In addition, three specific proteins were measured in the children: SF-A and SF-B (surfactant A and B) and Clara cell protein 16 (CC16). Surfactant A and B are lipid-protein structures which enhance the bio-physical activity of lungs lessening surface tension in the lung epithelium and preventing the collapse of the alveoli at the end of expiration. Anything that impairs the function of these surfactants will clearly impair lung function as well, because it makes the epithelium more permeable.

Both of these studies were concerned with chlorine byproducts in the air above indoor swimming pools. In the next article on the dangers of chlorinated pools, we'll look at studies related to drinking water and swimming pools.

Studies in the United States, Canada and Norway have linked chlorine byproducts in ordinary tap water to higher risks of miscarriages and stillbirths in pregnant women and increased incidences of bladder and colon cancer. Of disturbing news for indoor swimming pool patrons are studies that show much higher levels of these chemicals are found in swimmers. And the highest levels are found in the most active swimmers.

The heightened risk is linked to exposure to a contaminant found in chlorinated water called trihalomethanes (THMs) which forms when chlorine reacts with organic material. THMs are a widely recognized carcinogen.

While regulation changes in Canada and the United States have put tighter restrictions on the levels of THMs allowed in tap water, no such regulations exist for swimming pool water. This is in spite of a study that found a 1 hour swim resulted in a chloroform dose 141 times the dose from a 10 minute shower and 93 times greater than exposure by ingestion of tap water.

  • Recent Studies on THMs in tap water include:
  • A study by California health department investigators Kirsten Waller and Shanna Swann examined the records of 5,144 pregnant women from the Fontana, Santa Clara and Walnut Creek areas. They reported a 15.7% higher chance of miscarriage among women who drank 5 or more glasses of chlorinated water per day.
  • A Canadian study reports that women who drink tap water containing high levels of trihalomethanes are twice as likely to have stillbirths. This Dalhousie University study reported that pregnant women increase their risk the more they drink or bathe in water containing the compounds. This study was reported in the scientific journal Epidemiology.
  • A Norwegian study of 141,000 births over a three-year period found a fourteen percent increased risk of birth defects in areas with chlorinated water.

Despite these studies and the limited studies on swimming pool patrons, most swimming pool managers are probably unaware that they are exposing their patrons to THMs. This problem is not widely known and for the most part is ignored by the media.

In swimming pools, the most obvious and instant signs of high exposure to these chemicals is red eyes, rashes and other skin irritations or problems. And the highest exposure would appear to be for athletes and other swimmers who exert themselves physically in the water. Researchers report a mean chloroform uptake of 25.8 [micro]g/h for a swimmer at rest and 176.8 [micro]g/h) after 1 hour swimming. Other studies note that inhalation is an important route of exposure and the uptake through this route is affected by various factors including the number of swimmers, turbulence, and breathing rate. Which means that for elite athletes, the risk of exposure at water level is significantly higher than for that of a casual swimmer. And in both cases, the dosages of THMs far exceed what is considered allowable by merely drinking a glass of chlorinated tap water.

While the incidence of miscarriages and stillbirths is in itself cause for concern, other problems have been identified. Bladder cancer has been linked to chlorinated drinking water in an average of ten out of eleven studies. One of the studies in Ontario, conducted with funding from Health Canada, found that fourteen to sixteen percent of bladder cancers in Ontario showed a direct correlation to drinking water containing high levels of chlorine by-products. Chlorinated water has been linked to colon and rectal cancers in the studies, but the occurrences were not as common as those for bladder cancer.


Dr. John Marshall, of the Pure Water Association, an American consumer group campaigning for safer drinking water, states: "It shows we should be paying more attention to the chemicals we put in our drinking water and we should be looking for other alternatives to chlorination.

A number of safe, non-toxic options exist, such as treating water with ozone gas or ultra violet light."

While governments focus on tap water and reducing the levels of dangerous chlorine byproducts, it turns out there are also options that are available for swimming pool managers. In our next article, we'll look at the various options to chlorinating swimming pools.

Chlorine byproducts found in swimming pools are linked to higher incidences of asthma, lung damage, stillbirths, miscarriages and bladder cancer, according to credible research conducted in the U.S., Canada, Norway, Australia and Belgium.

One researcher noted that 10-year-old children spending an average of 1.8 hours per week in an indoor swimming pool environment suffered lung damage she would expect to see in an adult smoker.

For concientous swimming pools managers, the question this raises is are there viable alternatives to chlorine? Ozone and ultraviolet are the two most commonly cited technologies.

Dr. John Marshall, of the Pure Water Association, an American consumer group campaigning for safer drinking water, states: "It shows we should be paying more attention to the chemicals we put in our drinking water and we should be looking for other alternatives to chlorination. A number of safe, non-toxic options exist, such as treating water with ozone gas or ultra violet light."

Is Ozone viable for swimming pools? Recently a chemical-free public swimming pool was installed in Fairhope, Alabama. It uses Ozone technology and avoids the use of chlorine altogether. This is a first for public pools in North America.

The United States Navy Dolphin program has switched to Ozone technology over the last several years. A spokesman there stated that these systems have delivered the best water quality they have seen out of any systems they tried.

Numerous other private, public, commercial, waterpark and hotel and motel pools have switched to Ozone technologies as people become more concerned about chlorine and chlorinated byproducts. Other than the issue of carcinogens and other health problems, what are the relative benefits of Ozone vs. chlorine?

One of the main problems with adopting Ozone is that there is a higher initial capital cost to the swimming pool compared to chlorine. However, over the life of the pool Ozone and ultraviolet technologies reduce the on-going operating and maintenance costs. These costs can be significant. Chlorine is famous for destroying pool infrastructures, rusting out ventilation systems and destroying pool liners etc. Ozone poses no such problems.

The Ozone pool will be much cleaner, which means dirt, grease, oils, organics and other materials will wind up in the filter system much faster than with chlorinated systems. If the filter and strainer maintenance is not stepped up accordingly, the pool recirculating system will slow down and the pool will actually look dirtier than with Chlorine. However, proper maintenance of the filter system will solve this problem.

Part of the problem in adopting Ozone is that engineers, architects, pool builders and designers are not familiar with the technology. Some applications of Ozone, particularly systems installed 10-15 years ago were plagued with technical problems. Even though Ozone systems have been in regular use in Europe and other areas of the world since the 1950's, pools here have generally relied on chlorine.

Since our engineering, architectural and other technical training have all been geared to Chlorine, it takes re-education to now apply Ozone. Many people in these industries are reluctant to "shift gears" and take the time to educate themselves about the proper application of Ozone.

What is the difference in technologies? Chlorine is a complex man-made chemical that found original use in the infamous "mustard gas" of the First World War. Ozone has been in use for over 100 years, primarily in Europe and was first put to use for water purification, odor control and in medical hospitals (it is still being used medically today, though not commonly in North America).

Ozone is made from Oxygen or O2, which is converted through electricity to Ozone or O3. Ozone is a much more powerful oxidant than chlorine.

However, the "shelf life" of Ozone is limited. It must be manufactured and used on-site. This is done through Ozone Generators which convert Oxygen in the air into Ozone.

As well, Ozone is considered a "short-term" disinfectant and chlorine is considered a "long-term" disinfectant. Chlorine is also an entrenched technology. It has been widely used in North America and was first adopted at the turn of the century. It is still the reigning champion of disinfection and has many supporters in the chemical and swimming pool industries.

However, as we've seen in this series, there are numerous problems associated with chlorine. And viable alternatives do exist.

As we have seen in this series, there are credible researchers telling us that chlorine has some very serious health consequences when used as a sanitizer in swimming pools. The obvious question is why hasn't the swimming pool industry adopted alternative technologies on a much more industry-wide basis? After all, Ozone technology for swimming pools has been in regular use for over 50 years in places like Germany, France and other European nations.

Let's examine some of these issues. For drinking water or swimming pools, the European strategy is to use Ozone to reduce the organic load in water. When chlorine is required for long-term disinfection (such as distributing water through a municipal water distribution system), they use a very small amount of chlorine, thus reducing the risk for people drinking the water.

It is the organics that cause problems when combined with chlorine. By reducing the organic load, the Europeans keep the chloramines (the cancer causing substances) at a very low level. In European swimming pool systems, the same thought process prevails. In German DIN standards, for example, the strategy is to use a large "surge pool" that the public doesn't even see to apply Ozone or disinfection chemicals. The disinfection byproducts are then removed by various filtration processes prior to the water being returned to the pool with a slight dose of chlorine.

Under these standards, swimming pool water is essentially treated to drinking water standards.

The North American model developed under much different circumstances than the European. In North America, chemicals were adopted wholeheartedly around the turn of the century as the answer to the larger, more expensive European models of water treatment.

Engineers here found they could build water treatment plants and swimming pools at greatly reduced capital costs if they used what was then considered miraculous chemicals to treat water. And, for the most part, the systems did what they were designed to do and that was to kill micro-organisms that could lead to sickness and death. What they didn't anticipate was that chemicals like chlorine would have very serious byproducts that become health hazards themselves.

However, in North America we are now stuck with swimming pools that in Europe would be considered "surge tanks". The problem is to evolve an Ozone or other technology that can retrofit a large installed base of swimming pools in an economical manner. These systems are now starting to appear in the marketplace in increasing numbers.

If you consider that there have been several generations of engineers who have been taught chemical processes as a matter of course, it is not easy to persuade them that switching to this "new" (to North America) technology is the way to go. As well, some of the earlier North American produced Ozone systems were problematic and many engineers do not want to risk specifying equipment if they are not comfortable with the process.

However, time marches on and the technology is becoming very reliable. Is Ozone starting to gain a foothold in water treatment and for swimming pools in North America? Without a doubt. Some of the largest Ozonation plants in the world have been built in the United States. Major North American cities such as Los Angeles, Dallas, and Montreal, Canada have installed large Ozone plants for water treatment. Some of the major pool operators in North America including Disney's water parks use Ozone technology. The United States Navy has switched to Ozone systems for their Dolphin programs. As these technology leaders continue to push for alternatives to Chlorine, acceptance of the technology will be more favorable.

Other encouraging signs include the City of Fairhope, AL which has distinguished itself with the implementation of an Olympic-sized swimming pool that is operated as Ozone-only with only slight chemical assistance.

Many consumers are also requesting Ozone systems for their backyard swimming pools. Regulations for these pools do not require them to use Chlorine or other chemicals and many owners are now opting for Ozone systems.

Once pool owners switch, they realize that they no longer have to put up with red eye, rashes and the health consequences of chlorinated pools.

As the technology becomes more prevalent, expect to see more expertise at the local pool builder or pool maintenance companies. However, many of these companies rely on repeat sales of chemicals. These companies are likely to be highly resistant to Ozone systems as after-sales revenues will drop. However, for pool maintenance companies that are being paid to keep pool cleans, Ozone is a good thing. They should spend less time maintaining pools and the pools will be cleaner and the water more appealing. In the future, expect Ozone prices to drop and as more consumers become educated, demand for systems will definitely increase.