Archive for the ‘Facts’ Category

Smells Like Chlorine?

Friday, January 20th, 2017
Smells Like Chlorine

The nose is an extremely sensitive “detector” that sends information to the brain where it is interpreted.

They say “the nose knows,” but I say the nose can be confused. Chlorine odors are a good example. Several different chlorine odors can arise from various chlorine-based substances and in different circumstances. They are not all simply due to “chlorine.” A prime example is the irritating smell commonly attributed to chlorine around some poorly managed swimming pools. That smell is from a couple of chemical compounds in the chloramine family. Some chloramines form when chlorine disinfectants react chemically with nitrogen-based substances from the bodies of swimmers, including urine. The poolside pronouncement of “too much chlorine in the pool” may be more aptly described as “too much peeing in the pool.” Ironically, the odor could signal that more chlorine is needed in the pool.

Not One Chloramine

Chloramines start out as ammonia— NH3— which looks like a three-legged stool with the nitrogen atom as the “seat” and a hydrogen atom at the end of each “leg.” Ammonia is common in the environment, and Ammoniaalthough household ammonia has a very sharp odor, ammonia has no odor at the very dilute levels typically found in water. When chlorine is added to water in sufficient amounts, it breaks ammonia down into nitrogen (N2) gas and hydrogen (as water or H2O). But if the amount of nitrogen increases (from peeing in the pool, for example), the balance between chorine and nitrogen is disturbed and the ammonia is only partially deconstructed.

TrichloramineWhen three chlorine atoms replace the hydrogen atoms on the ammonia molecule, the resulting compound is trichloramine, a pungent, irritating compound that is often mistaken for “too much chlorine” in the pool, even at very low concentrations. Trichloramine and its sister chemical dichloramine (with two chlorine atoms and one hydrogen forming the “legs”) are responsible for the odor you might smell when you enter an enclosed pool area in which there is poor airflow through the building. Besides just smelling bad, these same two chemicals can also turn swimmers’ eyes red.

DichloramineThe problem with trichloramine and dichloramine goes beyond that irritating smell. When trichloramine is present in the pool, the level of “free chlorine” available to disinfect the water and protect swimmers from microbial disease is greatly diminished. That’s why it’s important to check pool water regularly for the pH and the presence of free chlorine1. Pool managers are obliged to do just that, and pool patrons can do the same with easy-to-use pool test strips.

MonochloramineTrichloramine and dichloramine have a third sister – monochloramine. As the name suggests, in this compound, only one of the hydrogen atoms on the ammonia has been replaced with chlorine. This chemical, however, carries no odor and is an effective disinfectant that has been used successfully by many water treatment plants for many decades. What a difference a minor change in a chemical formula can make!

Monochloramine is typically formed in source water by first adding chlorine to break down any ammonia (into nitrogen and water) and then adding back trace amounts of ammonia in carefully monitored amounts to produce only monochloramine.

Bleach Smell

Unlike the chloramine family of compounds, chlorine bleach is a solution of water and sodium hypochlorite with the chemical formula NaOCl [bleach contains sodium (Na), oxygen (O) and chlorine (Cl)]. The odor of bleach (bleach that is not infused with a fragrance) is not nearly as pungent as that of di- and trichloramines. When the chlorine in bleach combines with nitrogen-based substances, however, smelly di- and trichloramines can form by chemical reaction. This could happen in the swimming pool environment, for example.

Chlorine Gas

Chlorine is a common, naturally occurring element, but due to its reactivity, it usually occurs in nature combined with other elements, such as sodium in common table salt, NaCl. It is also produced industrially as part of the “chlor-alkali” process in which both chlorine and sodium hydroxide (NaOH) are generated by applying electricity to salty water. In that process, chlorine is produced as a gas consisting of twin atoms chemically bound together, and is represented by chemists as “Cl2.” Both chlorine and sodium hydroxide are used to help produce hundreds of everyday products, including water treatment chemicals, PVC pipes, pharmaceuticals, paper, aluminum, silicon chips for computers and even the titanium metal used in joint replacements.

Chlorine gas is a respiratory irritant that the human nose can detect at very low levels (0.2-0.4 parts per million in air; just for reference, one part per million is equivalent to four drops of ink in a 55-gallon barrel of water). At these low concentrations, chlorine gas smells very much like household bleach. When levels rise to the range of 1-3 ppm, however, mild mucous membrane irritation is noted and higher level exposure becomes increasingly dangerous.2 That is why the chlor-alkali industry takes extensive measures to ensure the safe production, handling and transportation of chlorine gas and even the less reactive sodium hypochlorite and calcium hypochlorite.

Not Just One Chlorine Compound

Chlorine is a reactive element that is found in many different compounds exhibiting different but sometimes similar properties, including odor. It is credited to have dramatically improved public health over the past 100 years through its ability to disinfect water.  I hope this discussion helps to clarify “the smell of chlorine.” Now your nose knows! 

Stephan A. Hubbs retired from water treatment operations at the Louisville Water Company in 2004. He was involved in the development of the first chlorine by-products regulation in 1975-1979 and remains an active volunteer in the drinking water community today.

Click here to download this article.

1 Hypochlorous acid, or HOCl, for you chemists!

2 The Chlorine Institute, Inc., Pamphlet 63: First Aid, Medical Management/Surveillance and Occupational Hygiene Monitoring Practices for Chlorine, Edition 8, June, 2011.

“Doggy”- Paddle to Health

Monday, August 15th, 2011

Aquatic rehab: Not just for the dogs

Jake in the Under Water TreadmillHow cute is that? Little Jake over there is undergoing aquatic rehabilitation in an underwater treadmill after paralyzing his rear limbs in an unfortunate accident. One veterinarian’s initial prognosis was that Jake would not be able to walk again. But after physical therapy and the underwater treadmill, Jake is back on his feet and happier than ever.

Canines are not the only species that can benefit from aquatic therapy. Whether it is used to help people recover from acute injuries or to maintain health in the face of chronic disease, hydrotherapy is regarded as having “broad rehabilitative potential” that is relatively underused (Becker, 2009).

Water: An ideal medium for exercise.

Swimming is widely recommended by medical experts for its healthful benefits*. According to the American Red Cross, the buoyancy of water results in less stress on the joints, helping to reduce swelling and tissue damage. Warm water can increase circulation, decrease pain, and increase muscle relaxation and soft tissue flexibility.

Patients (and puppies) looking to strengthen muscles should exercise in pools with some turbulence.
Aquatic exercise: Benefits galore

  • Lower risk of death In a 2009 Washington State University study of over 40,000 men, exercise swimmers had less than half the mortality risk of sedentary men, and exercise swimmers had half the mortality risk of exercise walkers and runners.
  • Aids patients with COPD A 2009 study of patients with chronic obstructive pulmonary disease (COPD) found the swimming pool a “feasible and positive alternative venue for pulmonary rehabilitation”.
  • Asthma Many studies have found swimming improves asthma symptoms; LaKind et al. cite Welsh et al. 1, who reviewed the relevant scientific literature. According to LaKind et al., Welsh et al. note that most studies find “positive effects of swim training on fitness as measured by improved aerobic efficiency, physical working performance, and recovery heart rates.”
  • Heart healthy Aquatic exercise strengthens the heart muscle and improves oxygen delivery to the muscles.
  • Reduces water and sodium retention Animal data collected in Brazil 2 indicate exercise in water might be prescriptive for patients with hypertension, obesity and/or mild renal disease as it reduces water and sodium retention.
  • Hand eye coordination and balance According to a study done in Taiwan, swimming can improve hand eye coordination and balance in the elderly, which could lower a senior’s risk of a falling-related injury.
  • Bone health Aquatic exercise can maintain or improve bone health in post-menopausal women.
  • Better flexibility and range of motion According to the American Red Cross, when accompanied by good stretching habits, aquatic exercise can greatly improve flexibility and aid range of motion.
  • Improved mood Swimming can improve the mental state of both men and women, the elderly and women with fibromyalgia, mothers, and parents of children with developmental disabilities.

Swimming may be the BEST and most enjoyable form of exercise, so give it a try!

*The American Red Cross recommends a health assessment from your health care provider before you begin an exercise program.

Ralph Morris, MD, MPH, is a Physician and Preventive Medicine and Public Health official living in Bemidji, MN.

1. Welsh, L.; Kemp, J. G.; Roberts, R. G. Effects of physical conditioning on children and adolescents with asthma Sports Med. 2005, 35 ( 2) 127– 141

2. Fabri et al.,(2010). Aquatic and Land Exercise Training Affects Renal Function in Rats Under Isosmotic Volume Expansion, Journal of Exercise Physiology, vol. 13, no. 2.

Swimming in the News

Monday, August 1st, 2011

by the Water Quality & Health Council

With high temperatures plaguing much of the country, the pool seems like the best bet to beat the heat. This blog highlights two interesting and entertaining resources recently found in the media that can help keep swimming healthy and enjoyable.

1. CDC’s Healthy Swimming 2011 Video Contest Winner’s Video!

This summer, the Centers for Disease Control and Prevention (CDC) challenged the public to create a short video to help educate swimmers about pool safety.  The winners, David and Aaron Mathews, worked with friends and family to develop “Recreational Water Illness Police,” a clip that uses humor to inform viewers about the most common recreational water illness—diarrhea. Roger that.

2. Quiz:  Is It Safe To Pee In The Pool … And Other Water Safety Questions

Want to test your water safety knowledge? A Huffington Post online quiz emphasizes key swimming safety issues, some of which are often overlooked, such as showering before entering the pool.  It is important that swimmers shower with soap (especially swimmer “bottoms”) before swimming so they do not introduce harmful bacteria into the pool.  This fact is lost on all but 25 percent of parents according to a recent report.  And no, it is not safe to pee in the pool.


This Summer: Dip before You Dive to Help Avoid Recreational Water Illnesses

Monday, May 23rd, 2011

It’s nearing the end of May, which means: it’s time to get back into the water!  Yes, pool season unofficially starts Memorial Day weekend and there is nothing more fun than spending a day at the pool.

But before diving in, it may be a good idea to know just what you are diving into.  Most pools are properly maintained, allowing swimmers to simply enjoy the water.  However, last summer, the Centers for Disease Control and Prevention (CDC) reported pool inspection data from 13 states indicated about one in eight public pool inspections resulted in pools being closed immediately due to serious code violations.

Dip before You Dive!

How do you know if a pool is properly maintained? There are hardly enough pool inspectors to go around, so CDC recommends swimmers take matters into their own hands and test pool water before getting in the pool.  It’s easy and free and will only take you a minute. Before swimming, dip a color-coded test strip into the water and check to see if the pH and chlorine readings are at appropriate levels. The pH should register between 7.2 and 7.8, and the free chlorine level should be between 1.0 and 4.0 parts per million (ppm).  If levels are out of those ranges, pool staff should be notified immediately. Pool staff should ascertain and correct the problem; if swimmers are unsatisfied with the pool staff response, CDC recommends they contact their local health department.

Swimmer’s Ear:  Listen up

New “swimmer’s ear” statistics provide a good reason to check pools for adequate pH and chlorine levels.  The May 20 Morbidity and Mortality Weekly Report (MMWR) notes that “swimmer’s ear” accounts for 2.4 million doctor visits and nearly $500 million in health care costs annually.  According to CDC, pools with proper pH and chlorine levels are less likely to harbor the bacteria that can cause “swimmer’s ear” and other germs that cause recreational water illnesses, including diarrhea and various skin infections.

Free Pool Test Kit Offer

This summer, the Water Quality & Health Council is offering free pool test kits to swimmers across the country. These can be requested online at Kits include three pool test strips and a pamphlet of information, including CDC’s tips for preventing “Swimmer’s Ear.”  We are asking swimmers to return to to upload their pool chemistry results, contributing to an informal survey of pool health across the country.  We’ve even developed a convenient smart-phone application on that webpage to enable swimmers to upload data poolside.

What We Did Last Summer

Last summer, the Water Quality & Health Council provided more than 43,000 free pool test strips to individuals who requested them via the Healthy Pools website.  Data submitted last summer by close to 800 swimmers who had requested the strips indicated that 40 percent of pools had either unacceptable pH or chlorine readings.  We look forward to this summer’s results and further raising awareness of the importance of proper pool chemistry.

Check for more summer swimming tips.

For more information on preventing recreational water illnesses, please visit the CDC website at

Chris Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.

Almost Half of Surveyed Americans Admit Unhygienic Pool Behavior

Monday, June 8th, 2009

Do you know what’s in your public pool? A recent Water Quality and Health Council survey found that almost half (47%) of respondents admit to one or more behaviors that contribute to an unhealthy pool.  One in five (17 percent) say they’ve urinated in the pool – and eight in ten (78 %) are convinced their fellow swimmers are guilty. As far as showering goes – forget it. Roughly one third (35%) pass the shower without stopping and three quarters (73%) say their fellow swimmers fail to shower before swimming.

Why Worry? Unclean water can lead to recreational water illnesses (RWIs) – diarrhea, respiratory illness, and ear and skin infections. According to the CDC, these illnesses are on the rise. Between 2005 and 2006, 78 outbreaks were reported in 31 states –the largest number of outbreaks ever in a two-year period. Close to 4,500 people were affected.

However, most respondents (63%) are unaware of illnesses associated with contaminated pool water. In fact, less than one quarter consider the frequency of pool cleaning and chemical treatment (23%) and even less (16 %) think about chlorine levels to maintain clean pool water. Remember, using your senses and following the CDC’s six simple swimming steps will help lead to a healthy and fun swimming summer.