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Published on March 14th, 2008 | by Stephanie Evans


The Hidden Risks of Aquatic Exercise

What could be more attractive to an aspirer of green living than a form of exercise that appears to leave the smallest of energy footprints?  After all, most energy involved in swimming is caloric, within the swimmer’s own body, right?  No wonder so many eco-friendly fitness enthusiasts have chosen swimming and other aquatic forms of exercise as their preferred workout.

Swimming has long been considered a remarkably low-impact, whole-body workout that reduces stress, improves the body’s use of oxygen, and keeps the joints safe and supple.  Other water activities like water running or water aerobics are also growing in popularity for the same reasons.  Add the relaxing effects of simply being in water and the post-swim soak in the hot tub to soothe hardworking muscles, and you’ve created the seemingly ideal exercise regimen…

Swimming -- Ideal Fitness Routine for the Body

However, this recipe for fitness success may not be as healthy as it seems.  Pool chemicals are known to spark health problems such as asthma and other respiratory conditions, swimmer’s ear, and the dreaded list of Recreational Water Illnesses (RWIs).  According to documented studies in Europe, pregnant women are very high at risk for vulnerabilities from exposure, as chlorine byproducts put the fetus at risk.

Additionally, the use of these chemicals contributes to the depletion of the ozone—most pool chemicals can actually be considered greenhouse emissions.  Also factor in the many tons of energy used to make and transport these chemicals designed to “purify” pool and spa water, at the risk of harming some very unlucky exercisers.

Alternative, less environmentally damaging methods of disinfecting pool water do exist.  First, let’s look at the role of chlorine in the management of a conventional pool and its effects on health, both positive and negative.

Chlorine: Pros & Cons

The distinctive smell of chlorine conjures up summer memories for some people and long, satisfying lap swims for others.  Unfortunately, the source of that familiar pungency is odious—chlorine, a gas, hovers over the surface of water when it is added in high concentrations, as it is in most pools and spas.  Prolonged inhalation of this gas leads to respiratory issues, as some Olympic swimmers and lifelong pool-goers can attest.

Manmade chlorine was considered somewhat of a boon when it first appeared on the market.  It was relatively cheap and highly effective.  The popularity of chlorine continued to grow as more and more people realized the cost-effectiveness of such a dependable killer of bacteria, viruses, and other water impurities like algae and mold.  And it certainly rid water of illness-causing microorganisms floating around.

But chlorine is not the perfect solution to disinfecting water, by any means.  Here are the problems:

  • The most dangerous aspects of chlorine are actually not entirely the fault of the gas itself.  The byproducts of chlorine when mixed with organic substances like hair, skin, urine, and sweat are incredibly toxic. Carcinogens like THMs trihalomethanes, nitrogen trichloride, halogenated hydrocarbons and chloroform are all byproducts of this noxious combination.

  • A study conducted in Belgium found that people repeatedly exposed to this mixture eventually developed lung problems similar to those of smokers.  Another study found that a 1 hour swim resulted in a chloroform dose 141 times the dose from a ten minute shower and 93 times greater than drinking tap water.

  • Another major problem with chlorine is its short “life span.”  Once chlorine has done its job, it is no longer useful or active but it is still present in gas form. More and more chlorine must be added to the pool or hot tubs as time passes and swimmers swim and organic material continues to accumulate in the water.  Naturally, the constant fortifying allows a good amount of chlorine exposure to bathers.
  • Also, chlorine may be powerful but it is not necessarily speedy; chlorine does not kill germs on contactc.  In addition, some germs are chlorine-resistant so when it does work, it only works somewhat effectively.  The risks of chlorine may prove to outweigh its benefits, by a significant margin.

    Additions of chlorine to pool and hot tub water mean well, but various illnesses can survive in the water and infect bathers.  Illnesses specific to public aquatic facilities are called Recreational Water Illnesses (RWIs).

    • Giardia and E.coli are two of the known RWIs that have been exposed to pool swimmers.
    • One frighteningly common bacteria, Cryptosporidum, is particularly resistant the effects of chlorine; this germ leads to gastrointestinal issues.

Hot tub enthusiasts are more at risk of respiratory RWIs, as water that may contain pathogens is aerated by water jets and then inhaled.  Skin rashes and other irritations can also afflict people who use hot tubs, thanks to the high heat that encourages more rapid evaporation of chlorine that clings to skin.


Alternatives to Chlorine

Ozone Gas

One alternative method of water purification requires treatment with ozone gas, which is made from oxygen and converted through electricity to ozone.  This technique has been

used for over a century in Europe to disinfect and purify water, control odor, and fulfill various medical purposes in hospitals.

Ozone gas works by reducing the organic load that reacts with chlorine.

  • Water treatment systems pump ozone gas into the pool.
  • The gas dissolves in the water and causes impurities to come together in filter-friendly clumps, or it simply blasts viruses and bacteria into harmless particles that can filter out.

Though using ozone gas does not totally eliminate need for chemicals, it does reduce the need for chlorine by 80%.  Ozone treatment is costly, which may explain the dearth of such systems, but it does not require any kind of chemicals to be transported or produced because the system just requires oxygen.

UV Light

Ultraviolet light is another system that reduces the need for chemicals.  It also works in conjunction with the pool filter system already in place.

  • High-energy light waves destroy bacteria within 2 seconds of the passage of water containing the contaminants through the special treatment chamber.  A filter attachment supplies the light that is powerful enough to destroy the DNA in germs.
  • The water that exits the treatment chamber almost meets specifications for drinking water but only a low percentage of water can travel through the chamber at a given time. Consequently, thorough disinfecting still requires chemicals but ultraviolet light reduces need for chlorine by 70%.

The New York Health Department has required ultraviolet light systems in some of their water parks and has said that this system is the most effective method of killing chlorine-resistant Cryptosporidum.

Salt Systems

Treatment with salt systems are not chemical-free by any means.  The difference is the source of the chemical: Salt generates its own chlorine and it disinfects in the same manner as standard chlorine from a bottle.  The concentration of disinfectant does remain more constant (unlike bottled chemicals, which need frequent administering), but the risky byproducts of organic material and chlorine are still present.

Salt systems can also damage equipment and cause scaling when the salt reacts with plaster in some poolside.  Extra cleaning is the least of one’s worries when some say salt-treated pools are the same as chlorine pools with softer water.


Baquacil is a milder chemical additive made with a base of hydrogen peroxide.  It contains no chlorine but claims to be able to protect bathers from the same contaminants.  The active ingredient is polyhexamethylene biguanide, a gentle chemical that Baquacil claims to be used in some contact lens solutions.

Off to the Pool?

The Center for Disease Control reports that occurrences of RWI outbreaks in public pools (outdoor, indoor, in gyms, and even on cruise ships) have increased in number over the last twenty years.  As a result, more and more people are becoming aware of what they can do to prevent such outbreaks.  Also, the public is more informed and equipped with knowledge that leads to asking the right questions when considering a gym membership, for example.

The practice of basic hygiene when using public pools and hot tubs goes far beyond pool etiquette…

  • Showering before entering pools and hot tubs reduces the amount of organic materials on one’s body.
  • Keeping an eye on children who are not potty-trained can protect swimmers from fecal matter, and a thorough soap-and-water scrub of backsides is a good preventative measure as well.
  • Changing diapers in the bathroom or changing room rather than on the deck of the pool is safer, as is washing hands after using the toilet.

Where to go for a safe swim?  Some states like Alabama and New York are already using alternative water treatment methods in their public swimming areas.  Disney water parks also use a lot less chlorine than they used to, as are many major pool operators in the United States.  Ask questions before using a facility if you have any doubts or concerns about the disinfecting methods used to keep bathers safe.

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