Chloramine & Chloramine Removal for Ferments & Cultures


Problems Reaching Breakpoint

Although rarely a problem in outdoor pools, since sunlight destroys chloramines, and the objectionable odors blow away, many pools operators have a great deal of difficulty ridding their indoor pools of chloramines. Unfortunately, HOCl also reacts with UV light (sunlight) and becomes an inactive chloride ion or salt (Cl–).

Some pools have enormously high bather load to water volume ratios, resulting in heavy organic loading, and high levels of ammoniated impurities in the water. Spray features at amusement parks, health club spas, therapy pools, swim school pools, and children’s wading depth pools with interactive play features, for example, often have chlorine levels unfathomable to operators of more traditional swimming pools. It is not surprising to find that an 18,000 gallon swim school pool maintained at 94° Fahrenheit having a bather load of 300 pre–school aged children per day, will have a continuing problem with chloramines. Ten thousand gallon children’s wading pools at successful commercial waterparks may have bather loads exceeding 2,000 children per day. It is not unusual to find amusement park water spray features with interactive fountains that have more users coming into contact with the water than number of gallons of water in the water feature. These same pools often have problems reaching breakpoint or keeping chloramines within acceptable levels.

If a chloramine residual persists in a pool in spite of the operator following proper breakpoint chlorination techniques, and continues to be a chronic nuisance, some of the following suggestions should be tried.

Regular Dilution

Drain and replace with 30 liters (approximately 8 gallons) of fresh water per user per day, as recommended in the German DIN (Deutsch Industrie Normen) Standard 19,643: “Treatment & Disinfection of Swimming & Bathing Pool Water”. The DIN Standard has been adopted by the European Community, and FINA requires water standards compatible with the DIN standard during international swimming competition.

Increase Exposure Time and Chlorine Concentration

You may be successful in reaching breakpoint by superchlorinating for longer periods of time with higher levels of chlorine.

Draw Water from the Pool Surface

Chloramines are concentrated near the surface of the water, as are most organic contaminants. During breakpoint chlorination, turn off the valve which draws water from the main drains and direct all the water through the perimeter overflow system. By circulating only through the skimmers or gutters, you will speed up the process by removing the water where chloramines are concentrated first.

GAC Filtration

Install secondary granulated activated carbon (GAC) filters and remove ammonia through filtration. GAC filters can be used to treat a slip–stream of water continually drawn off the main effluent line, or to treat source water prior to its being added to the pool. Many pools in areas of the country where municipal water utilities are adding ammonia to the source water to prevent trihalomethane formation in drinking water are installing GAC filters to pre–treat fill water to keep ammonia levels below 0.02 ppm. Chloramination has become a common practice by water utilities in order to comply with U.S. EPA water quality standards for drinking water to prevent formation of chloroform, a known carcinogen. Since chloramines do not react with raw water organic precursors which form when vegetation decays, monochloramines are commonly being used to treat water which has been stored in reservoirs. This practice is causing havoc in swimming pools.Non Chlorine OxidizersPotassium peroxymonosulfate (AKA: monopersulfate), can be used instead of chlorine to shock , or oxidize chloramines and other organic contaminants from the water. The product is a buffered chemical compound which utilizes oxygen to prevent or destroy the eye irritation and odor qualities of pool water by reacting with ammonia to produce chloride and nitrogen. Sold under various trade or brand names, the product has be successfully marketed to homeowners, and is beginning to make inroads into the commercial pool market.

Unlike chlorine which must reach a “breakpoint”, any amount of potassium peroxymonosulfate added to water will oxidize some material. Normally though, between 5 ounces and one pound per ten thousand gallons of water is added on a weekly basis to pools, and daily basis to spas. Non chlorine oxidizers will not raise chlorine levels, are totally soluble, do not cause bleaching, and they don’t affect water balance or pH. Monopersulfates are especially recommended for pools or spas with high bather load to water volume ratios where total dissolved solids and ammonia normally build–up at a rapid pace.

The pool owner should be cautioned however, that regular use of non chlorine oxidizers may irritate bathers causing them to itch. Also, potassium peroxymonosulfate is known to have an effect on DPD reagents in both liquid and tablet form, causing water samples to turn dark red, and may cause a false high free available chlorine reading. DPD reagent #3 is oxidized by monopersulfate so the test actually reads the monopersulfate residual preventing an accurate reading which distinguished between free and total chlorine. Some test kit manufacturers sell FAS–DPD reagents that eliminate monopersulfate interference.

Some pools maintain a residual of monopersulfate to help eliminate bather waste and the build–up of organic contaminants, as a preventative rather than corrective treatment. One manufacturer (U.S. Filter) has patented a continuous breakpoint halogenation and peroxygenation system. Potassium peroxymonosulfate doesn’t react with chlorine, but rather oxidizes contaminants and reduces the demand on the sanitizer. It should be noted though that not all products sold as non chlorine oxidizers contain the active ingredient potassium monopersulfate. For example, sodium percarbonate (AKA: sodium carbonate peroxyhydrate) releases or produced hydrogen peroxide, and reacts with chlorine.

Eliminate the Chlorine to Eliminate the Chloramines

Hydrogen peroxide or sodium thiosulfate can be added to the pool to drop the chlorine level to zero. This eliminates the free chlorine residual by converting chlorine back to chlorine salt. When chlorine is eliminated from the water, chloramines will also be eliminated. However, when chlorine is reintroduced, it will start combining with the ammonia which is still present in the water and form chloramines, but hopefully in a gradual manner and as a less objectionable monochloramine rather than nitrogen trichloride.

A word or two of caution – don’t overdo the amount of hydrogen peroxide or sodium thiosulfate you add to the water or you will create a chlorine demand and have a difficult time reestablishing a chlorine residual. Also, do not add products containing hydrogen peroxide to a pool which utilizes diatomaceous earth filters, since hydrogen peroxide reacts with and dissolves D.E.


Zeolites with a high (at least 80%) percentage of clinoptilolite can be used as a filter media instead of #20 silica sand in sand filters. Zeolites are a family of granular, extremely porous volcanic minerals capable of removing ammonia from the water as well as particles down to 5 microns in size, equivalent to the filtering capabilities of a diatomaceous earth filter. Zeolites for swimming pool filtration are marketed under various trade names by Neptune Benson (Clinopure 80), British Zeolite Co. (Zeoclere–30), Innovative Water Science (Zeo–Pure 90), Eco Smarte (Hydroxite #2), and others.

When a layer of 10% sodium chloride (table salt) is added to the filter bed an ionic reaction occurs which causes the absorption and removal of ammonia as the water passes through the filter, thereby reducing chloramine formation. The pool operator must regenerate filter media every 6 months by backwashing, shocking with a salt solution, allowing the bed to reactivate for 24 hours, agitating the media, then backwashing. Zeolites supplied by a reputable distributor should have a life expectancy 5 to 7 years.

Corona Discharge Ozone Systems

Organic contaminants are slightly reactive with ozone, but after being partially oxidized, microflocculation allows their removal by filtration. Inorganic contaminants such as ammonia react significantly with ozone when the pH is maintained below 9.0. Ozone constantly oxidizes monochloramines to form chloride and nitrate ions. Unfortunately, ozone also destroys high free chlorine residuals in the process of destroying chloramines, so chlorine lost in the process must be constantly replaced.

Ultraviolet LightUV light whether from natural sunlight or from UV light sanitation systems can be used to destroy chloramines and aerosolized chlorine compounds. If natural sunlight cannot be brought into the natatorium, UV light sanitation systems can be installed to provide supplemental sanitation and destroy chloramines.

UV light systems are installed in–line and are used in combination with either hydrogen peroxide or chlorine which provides a residual sanitizer and oxidizer in the pool water. The system consists of a treatment chamber installed on the filter effluent line, control box and power supply. Photolytic liners are permanently attached to the internal surfaces of the treatment chamber. Water flows through clear, quartz glass or Teflon tubes through the treatment chamber, passes the UV lamps (arc tubes) and pathogens are destroyed. UV kills microorganisms by destroying the DNA in the cells. There is no change in water color, temperature, taste, pH or chemical composition, however, turbid water will absorb UV light and make UV less effective as a disinfectant.

Disinfectant level is related to light intensity and exposure time. UV dosage is measured in either microwatt seconds per square centimeter (MWS/cm2). You may also see intensity and exposure time expressed in millijoules per square centimeter (mJ/cm2) instead. Six thousand to 10,000 MWS/cm2 or a minimum of 60 mJ/cm2are needed to destroy pathogenic organisms.

There are two types of UV lamps: low pressure (with an electromagnetic spectrum between 185 and 254 nanometers); and more commonly used today, medium pressure high intensity (with a wider electromagnetic spectrum between 180 and 400 nanometers, and not affected by water temperature). UV is most germicidal in wavelengths between 240 and 280 nanometers. Organic compounds are best photo oxidized by hydroxyl radicals in wavelengths below 230 nanometers. The bond between chlorine and nitrogen is broken, and chloramine destruction is most effective in the range of 245 and 340 nanometers, making low pressure bulbs a poor choice for chloramine destruction.

Increase Airflow Over the Water SurfaceIt is not possible to superchlorinate below a pool blanket or inside an enclosed pipe. By definition, oxygen is needed for oxidation to occur and off gassing into the air must take place. If there isn’t enough oxygen over the pool, breakpoint will not be achieved. Think of a fire. If the fuel is present but oxygen is lacking, combustion will not occur. Do whatever you can to get more air moving over the pool. So open the windows and doors, turn on the exhaust fans to move large volumes of air.

Unfortunately, as you speed up the removal of chloramines from the water, you release them into the air in the natatorium. Since like an outdoor pool, you do not have the ever present wind to blow away the odors and irritants, the air handling system must be designed to take the place of nature.

Chloramines are very volatile and easily vaporized into the air surrounding the pool. You can reduce the chloramine concentration in the air, by increasing the percentage of outside air brought into the natatorium and diluting the objectionable chloramine odors and irritants with fresh air. There should be at least 8 complete air exchanges per hour. Open air dampers to permit 100% fresh air to be brought in especially during breakpoint chlorination. During regular operation, as little as 15% fresh air may be permitted by code, but a minimum of 40% is recommended (up to 100%) depending on usage patterns, natatorium design, and equipment installed. For instance, pools that have water features installed that agitate water or aerosolize water vapor, particulates, or pathogenic organisms should exchange more air.

The location and placement of supply registers and return/exhaust ducts should be such that air is supplied low, moved across the water surface at a velocity less than 25 feet per minute to move the heavier than air gasses concentrated and settled directly over the pool, and exhausted high near ceiling level. Pollutants travel from positive to negative pressure areas, so natatoriums should be positively pressured in relation to the out of doors, and negatively pressured in relation to surrounding occupied spaces.

The air handling system installed should be capable of providing thermal environmental temperatures acceptable to 80% or more of the primary/priority facility users, averting sick building syndrome problems, and preventing discernible odors, without evident drafts, stratification of air, thermoclines or temperature gradients.

Air-stratification Leads to “Sick Pool Syndrome”

“Sick Pool Syndrome” is a phrase that is relatively unfamiliar to the HVAC community. However, if there is a high school or college in your area with an indoor pool where swimmers train, there is a good chance that some of those swimmers suffer from Sick Pool Syndrome’s consequences: extreme shortness of breath or asthma events.

Correcting the problem holds opportunities for contractors interested in natatorium work. From the HVAC perspective, the problem is not just excessive humidity and corrosion from chlorine (although those considerations could be helpful in obtaining the necessary funding for the work).

The IAQ problem is caused by air stratification, which creates dead air at the water’s surface, where swimmers inhale what is essentially chlorinated air.


Swimming has been considered a healthy sports alternative for young people with asthma. In addition to easier breathing than higher-impact land sports, the deep breathing of swimming has even been considered beneficial to asthmatics. So it was not surprising that after a swim meet or during rigorous workouts, some members of the swim team would use their inhalers — there were just more asthmatics on the swim team, right?

According to Paul Richards, aquatics director at Dickinson College, Carlisle, PA, asthmatic members of his swim team routinely use their inhalers before swimming laps to prevent asthma events. The situation in Dickinson’s natatorium became alarming when those swimmers had to stop in the middle of exercising and use “rescue inhalers” because they couldn’t breathe.

Depending on how the pool water is cleaned, dead air at the water’s surface could be carrying chlorine gases. Richards explained that pool chlorine breaks down into hypochloric and hydrochloric acids and other compounds broadly called “chloramine,” which become trapped in that dead space 10 to 12 inches over the water’s surface. Swimmers inhale just above the water’s surface, where the chemicals are concentrated.

Even though the amount of chlorine measured at the water’s surface is relatively low, over the course of a workout, a swimmer breathes in much more of the chemicals, resulting in exercise-related asthma (bronchospasm), according to Drobnic, Freixa, Casan, Sanchis, and Guardino in their paper, “Exercising Increases the Toxicity of a ‘Safe’ Chlorinated Pool Atmosphere” (Medicine and Science in Sports and Exercise, 1996).

Still more alarming: In 2000, Dr. Stephen J. McGeady from Thomas Jefferson University, Wilmington, DE, measured the lung function of competitive swimmers in swimming pool and lab settings. He and his colleagues heard that many non-asthmatic university team swimmers had to use inhalers. This proved to be true. Richards said he was not surprised to hear it.

Richards said that ideally, air return intakes should be positioned to direct airflow so as to eliminate dead areas. However, he noted, “Ventilation [of natatoriums] was not a design issue for a long time.”

Dickinson College’s poor natatorium IAQ was remedied with an overhead trunk fabric duct design (above) and a heat recovery dehumidifier (below).


Coach Richards joined Dickinson College in 1994. In addition to his coaching and teaching duties, Richards oversees the operations of Dickinson’s year-round aquatics facility. His background includes the study of natatorium mechanics.

There was no doubt in his mind that his natatorium suffered from Sick Pool Syndrome. In fact, he recounted that when he first arrived, the ventilation system was completely shut off because as he was told, “The chlorine odor was too strong in the parking lot.” He got that situation changed immediately, but the problems continued.

Swim practice was periodically interrupted by team members with breathing problems caused by stagnant, chloramine-laden air near the pool surface. While all of these team members were already known to have asthma, he agreed that “anyone with restricted airway disease” is susceptible to Sick Pool Syndrome. He was not surprised to hear of the reports of non-asthmatics suffering bronchospasms while swimming.

The 23-year-old Dickinson natatorium was built in the 1980s. It was originally designed with a commercial air conditioner. Its air distribution consisted of two 4- by 4-foot wall grille returns in one location, and a series of five 3- by 1-foot wall diffuser air supplies in only one wall. Consequently, air stratification was significant in more than 50% of the pool area. Air movement was particularly dead at the pool’s surface level, where heavy chloramine gases became trapped.

In addition, 80% humidity levels had taken a toll on many parts of the 10,000-square-foot natatorium structure, as well as the roof and metal amenities of Kline Athletic Center, a 78,000-square-foot field house.

Ongoing roof problems in the adjacent field house eventually led school officials to appropriate $248,000 for repairs. These included a complete retrofit for Dickinson’s eight-lane, 25-yard-long pool natatorium. Richards, who has a masters degree in sports sciences with a specialization in aquatics maintenance, management, and design, researched natatorium technology with the help of Durwin Ellerman, supervisor of mechanical and electrical trades at Dickinson.

Natatorium environments are most effective with a combination of under-deck and overhead air supplies, according to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

However, this was not feasible with the school’s budget.

Rich Munkittrick, vice president of manufacturers representative H&H Sales, Mechanicsburg, PA, provided drafting and engineering assistance. Since under-deck ductwork was not economically feasible, Richards and Ellerman conceived of a main, 52-inch-diameter trunk line spanning 120 feet down the center of the natatorium. Their design incorporated a heat recovery dehumidifier from Dectron Internationale (Roswell, GA) and fabric duct from DuctSox (Dubuque, IA), which could improve the pool’s indoor air quality (IAQ) while staying within budget.


The trunk line delivers approximately 15% of the airflow through the fabric’s natural porosity, according to its manufacturer. The remaining air is delivered through a linear diffuser and four 20-inch-diameter, perpendicular branches that spray the windows and the spectator section with 82 degree F air.

Air distribution at the pool’s surface level, which was a major concern of Richards because of swimmers’ health issues, now relies on new returns at the shallow end to draw the conditioned air down from the supply duct to mix with evaporating chemicals and then return them to the dehumidifier.

For the best air distribution and aesthetics, Richards said he wanted the trunk line at the center of the roof’s peak; however, existing lighting fixtures would have been blocked by the duct.

Ellerman conceived of a fixture retrofit that would allow both the trunk and the lighting to hang at the center. He lowered the lighting below the trunk line by extending the ceiling-mounted conduit pendants into an “O” shape that encircles the duct and connects to the fixture below the duct.

Another important factor is the temperature differential between the air and water (which now measure 82 degrees and 80 degrees, respectively). Previously, the differential between the 75 degree air and the 80 degree water caused additional humidity problems. The current relative humidity is maintained at 50%, thanks to the improved air-to-water temperature differential and the addition of the heat recovery dehumidifier.

Richards said that the conditions now are ideal. And the dehumidifier recaptures condensate, “a complete pool fill per year,” said Richards.

“I guess the jury is still out,” on how well the fabric ducts will stand up to the corrosive environment, he said. “I think it will last a lot longer than metal.” He also pointed out that it was “very easy to install,” hence, very easy to replace. And it can be taken down by hand and washed.


The most important consideration, of course, is the swimmers’ health. These days, inhaler use is minimal at practices, according to Richards.

Visiting spectators and opposing teams regularly make positive comments on humidity levels and IAQ during swim meets held at Dickinson, he said. “We did a survey in our regional conference. Based on chemical evidence and anecdotally, we were certainly not the exception” for Sick Pool Syndrome.

He suspects a significant number of natatoriums nationwide may need complete retrofits or serious fine-tuning to their air-handling and chemical systems, as well as their operating procedures.

However, knowledge of poor IAQ in natatoriums may be lacking among high school and college administrators. Even in his own school’s case, it was the roof deterioration that finally got funding approval for the field house.

HVAC contractors may need to educate aquatics directors on humidity control, air stratification, and the role they play in Sick Pool Syndrome.

“Colleges and universities tend to hire swim coaches and then name them aquatics directors,” Richards said. “Unfortunately, a large percentage of swim coaches have little or no training in facilities management and know very little about water chemistry. So then those responsibilities are left to physical plant engineers, who many times don’t have aquatics facility training either.”

Sidebar: It All Starts With Good Design

When mechanical contractors design an enclosed swimming pool, they have to keep in mind how to correctly distribute the air throughout the space and how to remove air from the room efficiently, in order to avoid air stagnation or stratification in the natatorium.

Controlling humidity in a natatorium presents many challenges. Special attention and careful consideration must be given to the location of supply air ducts, the location of the air return grille, the use of moisture barriers, and door and window insulation values, according to Pat Reynolds, president of PoolPak Inc.

Obviously, a well-designed dehumidifier is only one step toward effective climate control in a pool space.

According to Reynolds, “Efficient dehumidification of a pool enclosure requires well-balanced and properly placed ducting systems. Ducts should never be positioned in a manner such as would result in the short cycling of the supply air. Short cycling is caused when the location of the return duct is too close to, or directly in line with, the supply duct causing warm, dry air to recycle prematurely.”

The return intake(s) should be positioned so that all of the moist, warm air flows efficiently back to the dehumidification system, eliminating dead areas where air stagnation can occur, Reynolds stated. “In most instances, a single return duct is ideal in the pool area. The desirable location for the return is at a point high enough to capture the warm, humid air that naturally rises.” Normally, this is about 10 to 15 feet above the floor, or the surface of the pool.

“Airflow should never be directed over a pool surface or over any concentration of water,” Reynolds said. “Should air flow over or too close to the water, it will speed evaporation and limit the effectiveness of the dehumidification system. The greater the velocity of the air currents, the greater the evaporation process.”

Typically, an indoor pool requires space air heating 70% to 90% of the year. Therefore, the most effective air distribution system is one that takes advantage of hot air’s natural tendency to rise. This type of system will supply the air “low” and return it “high,” Reynolds pointed out. “When this is not possible, a ceiling supply arrangement is necessary.”

The supply air grille should be located close to the windows, preferable within 12 inches from the surface to sufficiently bathe the cold glass with a blanket of warm, dry air. The majority of the supply air (80%) should be directed down the walls. The remaining 20% should be directed along the ceiling to break up any stratification and stagnation that might occur there.

Where skylights are present, it is best to utilize supply ductwork to flood the glass with warm, dry air. Another method to deal with skylights is to install ceiling fans, running in reverse, to draw up the warm air against the glass surface. This, however, is not as reliable as a direct flow of air from ducts.

Reynolds points out another important factor: “You can correctly build the enclosure and have a very good dehumidification system, but if you do not maintain your equipment, you cannot control the humidification adequately.”

Publication date: 08/12/2002

WHO Aquatic Safety Guidelines 4. Chemicals

Chemical hazards
Chemicals found in pool water can be derived from a number of sources: the source
water, deliberate additions such as disinfectants and the pool users themselves (see
Figure 4.1). This chapter describes the routes of exposure to swimming pool chemicals,
the chemicals typically found in pool water and their possible health effects.
While there is clearly a need to ensure proper consideration of health and safety
issues for operators and pool users in relation to the use and storage of swimming pool
chemicals, this aspect is not covered in this volume.
Figure 4.1. Possible pool water contaminants in swimming pools and similar environments
4.1 Exposure
There are three main routes of exposure to chemicals in swimming pools and similar
• direct ingestion of water;
• inhalation of volatile or aerosolized solutes; and
• dermal contact and absorption through the skin.
Chemicals in pool,
hot tub and spa water
Source water-derived:
disinfection by-products;
pH correction chemicals;
lotions (sunscreen, cosmetics,
soap residues, etc.)
Disinfection by-products:
e.g. trihalomethanes;
haloacetic acids;
nitrogen trichloride
4.1.1 Ingestion
The amount of water ingested by swimmers and pool users will depend upon a range
of factors, including experience, age, skill and type of activity. The duration of exposure
will vary signifi cantly in different circumstances, but for adults, extended exposure
would be expected to be associated with greater skill (e.g. competitive swimmers),
and so there would be a lower rate of ingestion in a comparable time than for
less skilled users. The situation with children is much less clear. There appear to be
no data with which to make a more detailed assessment. A number of estimates have
been made of possible intakes while participating in activities in swimming pools and
similar environments, with the most convincing being a pilot study by Evans et al.
(2001). This used urine sample analysis, with 24-h urine samples taken from swimmers
who had used a pool disinfected with dichloroisocyanurate and analysed for
cyanurate concentrations. All the participants swam, but there is no information on
the participant swimming duration. This study found that the average water intake
by children (37 ml) was higher than the intake by adults (16 ml). In addition, the
intake by adult men (22 ml) was higher than that by women (12 ml); the intake by
boys (45 ml) was higher than the intake by girls (30 ml). The upper 95th percentile
intake was for children and was approximately 90 ml. This was a small study, but
the data are of high quality compared with most other estimates, and the estimates,
are based upon empirical data rather than assumptions. In this volume, a ‘worst case’
intake of 100 ml for a child is assumed in calculating ingestion exposure to chemicals
in pool water.
4.1.2 Inhalation
Swimmers and pool users inhale from the atmosphere just above the water’s
surface, and the volume of air inhaled is a function of the intensity of effort and time.
Individuals using an indoor pool also breathe air in the wider area of the building
housing the pool. However, the concentration of pool-derived chemical in the pool
environment will be considerably diluted in open air pools. Inhalation exposure will
be largely associated with volatile substances that are lost from the water surface, but
will also include some inhalation of aerosols, within a hot tub (for example) or where
there is signifi cant splashing. The normal assumption is that an adult will inhale approximately
10 m3 of air during an 8-h working day (WHO, 1999). However, this
will also depend on the physical effort involved. There will, therefore, be signifi cant
individual variation depending upon the type of activity and level of effort.
4.1.3 Dermal contact
The skin will be extensively exposed to chemicals in pool water. Some may have a
direct impact on the skin, eyes and mucous membranes, but chemicals present in pool
water may also cross the skin of the pool, hot tub or spa user and be absorbed into the
body. Two pathways have been suggested for transport across the stratum corneum
(outermost layer of skin): one for lipophilic chemicals and the other for hydrophilic
chemicals (Raykar et al., 1988). The extent of uptake through the skin will depend
on a range of factors, including the period of contact with the water, the temperature
of the water and the concentration of the chemical.
4.2 Source water-derived chemicals
All source waters contain chemicals, some of which may be important with respect
to pool, hot tub and spa safety. Water from a municipal drinking-water supply may
contain organic materials (such as humic acid, which is a precursor of disinfection
by-products), disinfection by-products (see Section 4.5) from previous treatment/
disinfection processes, lime and alkalis, phosphates and, for chloraminated systems,
monochloramines. Seawater contains high bromide concentrations. In some circumstances,
radon may also be present in water that is derived from groundwater. Under
such circumstances, adequate ventilation in indoor pools and hot tubs will be an
important consideration. WHO is considering radon in relation to drinking-water
quality guidelines and other guidance.
4.3 Bather-derived chemicals
Nitrogen compounds, particularly ammonia, that are excreted by bathers (in a number
of ways) react with free disinfectant to produce several by-products. A number of
nitrogen compounds can be eluted from the skin (Table 4.1). The nitrogen content
in sweat is around 1 g/l, primarily in the form of urea, ammonia, amino acids and
creatinine. Depending on the circumstances, the composition of sweat varies widely.
Signifi cant amounts of nitrogen compounds can also be discharged into pool water
via urine (Table 4.1). The urine release into swimming pools has been variously estimated
to average between 25 and 30 ml per bather (Gunkel & Jessen, 1988) and be
as high as 77.5 ml per bather (Erdinger et al., 1997a), although this area has not been
well researched.
The distribution of total nitrogen in urine among relevant nitrogen compounds
(Table 4.1) has been calculated from statistically determined means of values based on
24-h urine samples. Although more than 80% of the total nitrogen content in urine
is present in the form of urea and the ammonia content (at approximately 5%) is
low, swimming pool water exhibits considerable concentrations of ammonia-derived
compounds in the form of combined chlorine and nitrate. It therefore appears that
there is degradation of urea following chemical reactions with chlorine.
Sweat Urine
Portion of total
nitrogen (%)
Portion of total
nitrogen (%)
Urea 680 68 10 240 84
Ammonia 180 18 560 5
Amino acids 45 5 280 2
Creatinine 7 1 640 5
80 8 500 4
Total nitrogen 992 100 12 220 100
a Adapted from Jandik, 1977
Table 4.1. Nitrogen-containing compounds in sweat and urinea
In a study on the fate of chlorine and organic materials in swimming pools using
analogues of body fl uids and soiling in a model pool, the results showed that organic
carbon, chloramines and trihalomethanes all reached a steady state after 200–500 h
of operation. Only insignifi cant amounts of the volatile by-products were found to
be lost to the atmosphere, and only nitrate was found to accumulate, accounting for
4–28% of the dosed amino nitrogen (Judd & Bullock, 2003). No information is
available on concentrations of chemicals in actual swimming pool water from cosmetics,
suntan oil, soap residues, etc.
4.4 Management-derived chemicals
A number of management-derived chemicals are added to pool water in order to
achieve the required water quality. A proportion of pool water is constantly undergoing
treatment, which generally includes fi ltration (often in conjunction with coagulation),
pH correction and disinfection (see Chapter 5).
4.4.1 Disinfectants
A range of disinfectants are used in swimming pools and similar environments. The
most common are outlined in Table 4.2 (and covered in more detail in Chapter 5).
They are added in order to inactivate pathogens and other nuisance microorganisms.
Chlorine, in one of its various forms, is the most widely used disinfectant.
Some disinfectants, such as ozone and UV, kill or inactivate microorganisms as
the water undergoes treatment, but there is no lasting disinfectant effect or ‘residual’
that reaches the pool and continues to act upon chemicals and microorganisms in the
water. Thus, where these types of disinfection are used, a chlorine- or bromine-type
disinfectant is also employed to provide continued disinfection. The active available
disinfectant in the water is referred to as ‘residual’ or, in the case of chlorine, ‘free’ to
distinguish it from combined chlorine (which is not a disinfectant). In the case of
a Usually used in combination with residual disinfectants (i.e. chlorine- or bromine-based)
Table 4.2. Disinfectants and disinfecting systems used in swimming pools and similar environments
Disinfectants used
most frequently in large,
heavily used pools
Disinfectants used
in smaller pools
and hot tubs
Disinfectants used
for small-scale and
domestic pools
• Gas
• Calcium/sodium
• Electrolytic generation
of sodium hypochlorite
• Chlorinated isocyanurates
(generally outdoor pools)
Chlorine dioxidea
• Liquid bromine
• Sodium bromide +
Lithium hypochlorite
Hydrogen peroxide/
bromine, as the combined form is also a disinfectant, there is no need to distinguish
between the two, so ‘total’ bromine is measured.
The type and form of disinfectant need to be chosen with respect to the specifi c requirements
of the pool. In the case of small and domestic pools, important requirements are
easy handling and ease of use as well as effectiveness. In all cases, the choice of disinfectant
must be made after consideration of the effi cacy of a disinfectant under the circumstances
of use (more details are given in Chapter 5) and the ability to monitor disinfectant levels.
1. Chlorine-based disinfectants
Chlorination is the most widely used pool water disinfection method, usually in the
form of chlorine gas, sodium, calcium or lithium hypochlorite but also with chlorinated
isocyanurates. These are all loosely referred to as ‘chlorine’.
Practice varies widely around the world, as do the levels of free chlorine that are
currently considered to be acceptable in order to achieve adequate disinfection while
minimizing user discomfort. For example, free chlorine levels of less than 1 mg/l are
considered acceptable in some countries, while in other countries allowable levels may
be considerably higher. Due to the nature of hot tubs (warmer water, often accompanied
by aeration and a greater user to water volume ratio), acceptable free chlorine levels
tend to be higher than in swimming pools. It is recommended that acceptable levels
of free chlorine continue to be set at the local level, but in public and semi-public
pools these should not exceed 3 mg/l and in public/semi-public hot tubs these should
not exceed 5 mg/l. Lower free chlorine concentrations may be health protective when
combined with other good management practices (e.g. pre-swim showering, effective
coagulation and fi ltration, etc.) or when ozone or UV is also used.
Using high levels of chlorine (up to 20 mg/l) as a shock dose (see Chapter 5) as a
preventive measure or to correct specifi c problems may be part of a strategy of proper
pool management. While it should not be used to compensate for inadequacies of
other management practices, periodic shock dosing can be an effective tool to maintain
microbial quality of water and to minimize build-up of biofi lms and chloramines
(see Sections 4.5 and 5.3.4).
Chlorine in solution at the concentrations recommended is considered to be
toxicologically acceptable even for drinking-water; the WHO health-based guideline
value for chlorine in drinking-water is 5 mg/l (WHO, 2004). Concentrations signifi –
cantly in excess of this may not be of health signifi cance with regard to ingestion (as
no adverse effect level was identifi ed in the study used), even though there might be
some problems regarding eye and mucous membrane irritation. The primary issues
would then become acceptability to swimmers.
The chlorinated isocyanurates are stabilized chlorine compounds, which are widely
used in the disinfection of outdoor or lightly loaded swimming pools. They dissociate
in water to release free chlorine in equilibrium with cyanuric acid. A residual of cyanuric
acid and a number of chlorine/cyanuric acid products will be present in the water.
The Joint FAO/WHO Expert Committee on Food Additives and Contaminants
(JECFA) has considered the chlorinated isocyanurates with regard to drinking-water
disinfection and proposed a tolerable daily intake (TDI) for anhydrous sodium dichloroisocyanurate
(NaDCC) of 0–2 mg/kg of body weight (JECFA, 2004). This would
translate into an intake of 20 mg of NaDCC per day (or 11.7 mg of cyanuric acid per
day) for a 10-kg child. To avoid consuming the TDI, assuming 100 ml of pool water is
swallowed in a session would mean that the concentration of cyanuric acid/chlorinated
isocyanurates should be kept below 117 mg/l. Levels of cyanuric acid should be kept
between 50 and 100 mg/l in order not to interfere with the release of free chlorine,
and it is recommended that levels should not exceed 100 mg/l. However, although no
comprehensive surveys are available, there are a number of reported measurements of
high levels of cyanuric acid in pools and hot tubs in the USA. Sandel (1990) found
an average concentration of 75.9 mg/l with a median of 57.5 mg/l and a maximum of
406 mg/l. Other studies have reported that 25% of pools (122 of 486) had cyanuric
acid concentrations greater than 100 mg/l (Rakestraw, 1994) and as high as 140 mg/l
(Latta, 1995). Unpublished data from the Olin Corporation suggest that levels up to
500 mg/l may be found. Regular dilution with fresh water (see Chapter 5) is required
in order to keep cyanuric acid at an acceptable concentration.
2. Chlorine dioxide
Chlorine dioxide is not classed as a chlorine-based disinfectant, as it acts in a different
way and does not produce free chlorine. Chlorine dioxide breaks down to chlorite and
chlorate, which will remain in solution; the WHO health-based drinking-water provisional
guideline value for chlorite is 0.7 mg/l (based on a TDI of 0.03 mg/kg of body
weight) (WHO, 2004), and this is also the provisional guideline for chlorate. There is
potential for a build-up of chlorite/chlorate in recirculating pool water with time. In order
to remain within the TDI levels of chlorate and chlorite, they should be maintained
below 3 mg/l (assuming a 10-kg child and an intake of 100 ml).
3. Bromine-based disinfectants
Liquid bromine is not commonly used in pool disinfection. Bromine-based disinfectants
for pools are available in two forms, bromochlorodimethylhydantoin (BCDMH)
and a two-part system that consists of sodium bromide and an oxidizer (usually hypochlorite).
As with chlorine-based disinfectants, local practice varies, and acceptable
total bromine may be as high as 10 mg/l. Although there is limited evidence about
bromine toxicity, it is recommended that total bromine does not exceed 2.0–2.5 mg/l.
The use of bromine-based disinfectants is generally not practical for outdoor pools and
spas because the bromine residual is depleted rapidly in sunlight (MDHSS, undated).
There are reports that a number of swimmers in brominated pools develop eye
and skin irritation (Rycroft & Penny, 1983). However, Kelsall & Sim (2001) in a
study examining three different pool disinfection systems (chlorine, chlorine/ozone
and bromine/ozone) did not fi nd that the bromine disinfection system was associated
with a greater risk of skin rashes, although the number of bathers studied was small.
4. Ozone and ultraviolet
Ozone and UV radiation purify the pool water as it passes through the plant room,
and neither leaves residual disinfectant in the water. They are, therefore, used in conjunction
with conventional chlorine- and bromine-based disinfectants. The primary
health issue in ozone use in swimming pool disinfection is the leakage of ozone into
the atmosphere from ozone generators and contact tanks, which need to be properly
ventilated to the outside atmosphere. It is also appropriate to include a deozonation
step in the treatment process, to prevent carry-over in the treated water. Ozone is a
severe respiratory irritant, and it is, therefore, important that ozone concentrations in
the atmosphere of the pool building are controlled. The air quality guideline value
of 0.12 mg/m3 (WHO, 2000) is an appropriate concentration to protect bathers and
staff working in the pool building.
5. Other disinfectants
Other disinfectant systems may be used, especially in small pools. Hydrogen peroxide
used with silver and copper ions will normally provide low levels of the silver and copper
ions in the water. However, it is most important that proper consideration is given
to replacement of water to prevent excessive build-up of the ions. A similar situation
would apply to biguanide, which is also used as a disinfectant in outdoor pools.
4.4.2 pH correction
The chemical required for pH value adjustment will generally depend on whether
the disinfectant used is itself alkaline or acidic. Alkaline disinfectants (e.g. sodium
hypochlorite) normally require only the addition of an acid for pH correction, usually
a solution of sodium hydrogen sulfate, carbon dioxide or hydrochloric acid. Acidic
disinfectants (e.g. chlorine gas) normally require the addition of an alkali, usually a
solution of sodium carbonate (soda ash). There should be no adverse health effects
associated with the use of these chemicals provided that they are dosed correctly and
the pH range is maintained between 7.2 and 8.0 (see Section 5.10.3).
4.4.3 Coagulants
Coagulants (e.g. polyaluminium chloride) may be used to enhance the removal of
dissolved, colloidal or suspended material. These work by bringing the material out
of solution or suspension as solids and then clumping the solids together to produce
a fl oc. The fl oc is then trapped during fi ltration.
4.5 Disinfection by-products (DBP)
Disinfectants can react with other chemicals in the water to give rise to by-products (Table
4.3). Most information available relates to the reactions of chlorine, as will be seen from
Tables 4.4–4.11. Although there is potentially a large number of chlorine-derived disinfection
by-products, the substances produced in the greatest quantities are the trihalomethanes
(THMs), of which chloroform is generally present in the greatest concentration, and
the haloacetic acids (HAAs), of which di- and trichloroacetic acid are generally present in
the greatest concentrations (WHO, 2000). It is probable that a range of organic chloramines
could be formed, depending on the nature of the precursors and pool conditions.
Data on their occurrence in swimming pool waters are relatively limited, although they
are important in terms of atmospheric contamination in enclosed pools and hot tubs.
When inorganic bromide is present in the water, this can be oxidized to form
bromine, which will also take part in the reaction to produce brominated by-products
such as the brominated THMs. This means that the bromide/hypochlorite system of
disinfection would be expected to give much higher proportions of the brominated
by-products. Seawater pools disinfected with chlorine would also be expected to show
a high proportion of brominated by-products since seawater contains signifi cant levels
of bromide. Seawater pools might also be expected to show a proportion of iodinated
by-products in view of the presence of iodide in the water. In all pools in which free
halogen (i.e. chlorine, bromine or iodine) is the primary disinfectant, no matter what
form the halogen donor takes, there will be a range of by-products, but these will be
found at signifi cantly lower concentrations than the THMs and HAAs. The use of
ozone in the presence of bromide can lead to the formation of bromate, which can
build up over time without adequate dilution with fresh water (see Chapter 5).
While chlorination has been relatively well studied, it must be emphasized that
data on ozonation by-products and other disinfectants are very limited. Although
those by-products found commonly in ozonated drinking-water would be expected,
there appear to be few data on the concentrations found in swimming pools and
similar environments.
Both chlorine and bromine will react, extremely rapidly, with ammonia in the water,
to form chloramines (monochloramine, dichloramine and nitrogen trichloride)
and bromamines (collectively known as haloamines). The mean content of urea and
ammonia in urine is 10 240 mg/l and 560 mg/l, respectively (Table 4.1), but hydrolysis
of urea will give rise to more ammonia in the water (Jandik, 1977). Nitrogencontaining
organic compounds, such as amino acids, may react with hypochlorite to
form organic chloramines (Taras, 1953; Isaak & Morris, 1980).
During storage, chlorate can build up within sodium hypochlorite solution, and this
can contribute to chlorate levels in disinfected water. However, it is unlikely to be of con-
a UV is a physical system and is generally not considered to produce by-products
Table 4.3. Predominant chemical disinfectants used in pool water treatment and their
associated disinfection by-productsa
Disinfectant Disinfection by-products
Chlorine/hypochlorite trihalomethanes
haloacetic acids
chloral hydrate (trichloroacetaldehyde)
chloropicrin (trichloronitromethane)
cyanogen chloride
Ozone bromate
carboxylic acids
brominated acetic acids
Chlorine dioxide chlorite
trihalomethanes, mainly bromoform
bromal hydrate
cern to health unless the concentrations are allowed to reach excessive levels (i.e. >3 mg/l),
in which case the effi cacy of the hypochlorite is likely to be compromised.
Ozone can react with residual bromide to produce bromate, which is quite stable
and can build up over time (Grguric et al., 1994). This is of concern in drinking-water
systems but will be of lower concern in swimming pools. However, if ozone were
used to disinfect seawater pools, the concentration of bromate would be expected to
be potentially much higher. In addition, bromate is a by-product of the electrolytic
generation of hypochlorite if the brine used is high in bromide. Ozone also reacts
with organic matter to produce a range of oxygenated substances, including aldehydes
and carboxylic acids. Where bromide is present, it can also result in the formation of
brominated products similar to liquid bromine.
More data are required on the impact of UV on disinfection by-products when
used in conjunction with residual disinfectants. UV disinfection is not considered to
produce by-products, and it seems to signifi cantly reduce the levels of chloramines.
4.5.1 Exposure to disinfection by-products
While swimming pools have not been studied to the same extent as drinking-water,
there are some data on the occurrence and concentrations of a number of disinfection
by-products in pool water, although the data are limited to a small number of
the major substances. A summary of the concentrations of various prominent organic
by-products of chlorination (THMs, HAAs, haloacetonitriles and others) measured
in different pools is provided in Table 4.4 and Tables 4.9–4.11 below. Many of these
data are relatively old and may refl ect past management practices. Concentrations
will vary as a consequence of the concentration of precursor compounds, disinfectant
dose, residual disinfectant level, temperature and pH. The THM found in the greatest
concentrations in freshwater pools is chloroform, while in seawater pools, it is usually
bromoform (Baudisch et al., 1997; Gundermann et al., 1997).
1. Trihalomethanes
Sandel (1990) examined data from 114 residential pools in the USA and reported average
concentrations of chloroform of 67.1 μg/l with a maximum value of 313 μg/l. In hot
spring pools, the median concentration of chloroform was 3.8 μg/l and the maximum
was 6.4 μg/l (Erdinger et al., 1997b). Fantuzzi et al. (2001) reported total THM concentrations
of 17.8–70.8 μg/l in swimming pools in Italy. In a study of eight swimming
pools in London, Chu & Nieuwenhuijsen (2002) collected and analysed pool water
samples for total organic carbon (TOC) and THMs. They reported a geometric mean1
for all swimming pools of 5.8 mg/l for TOC, 125.2 μg/l for total THMs and 113.3 μg/l
for chloroform; there was a linear correlation between the number of people in the pool
and the concentration of THMs. The pool concentrations of disinfection by-products
will also be infl uenced by the concentration of THMs and the potential precursor compounds
in the source and make-up water.
THMs are volatile in nature and can be lost from the surface of the water, so they
will also be found in the air above indoor pools (Table 4.5). Transport from swimming
pool water to the air will depend on a number of factors, including the concentration
in the pool water, the temperature and the amount of splashing and surface
1 Mean values in Table 4.4 are arithmetic means.
disturbance. The concentrations at different levels in the air above the pool will also
depend on factors such as ventilation, the size of the building and the air circulation.
Fantuzzi et al. (2001) examined THM levels in fi ve indoor pools in Italy and found
mean concentrations of total THMs in poolside air of 58.0 μg/m3 ± 22.1 μg/m3 and
concentrations of 26.1 μg/m3 ± 24.3 μg/m3 in the reception area.
Strähle et al. (2000) studied the THM concentrations in the blood of swimmers
compared with the concentrations of THMs in pool water and ambient air (Table
4.6). They showed that intake via inhalation was probably the major route of uptake
of volatile components, since the concentration of THMs in the outdoor pool water
was higher than the concentration in the indoor pool water, but the concentrations in
air above the pool and in blood were higher in the indoor pool than in the outdoor
pool. This would imply that good ventilation at pool level would be a signifi cant
contributor to minimizing exposure to THMs. Erdinger et al. (2004) found that in
a study in which subjects swam with and without scuba tanks, THMs were mainly
taken up by the respiratory pathway and only about one third of the total burden was
taken up through the skin.
Studies by Aggazzotti et al. (1990, 1993, 1995, 1998) showed that exposure to
chlorinated swimming pool water and the air above swimming pools can lead to an
increase in detectable THMs in both plasma and alveolar air, but the concentration in
alveolar air rapidly falls after exiting the pool area (Tables 4.7 and 4.8).
2. Chloramines, chlorite and chlorate
Exposure to chloramines in the atmosphere of indoor pools was studied in France by
Hery et al. (1995) in response to complaints of eye and respiratory tract irritation by
pool attendants. They found concentrations of up to 0.84 mg/m3 and that levels were
generally higher in pools with recreational activities such as slides and fountains.
Erdinger et al. (1999) examined the concentrations of chlorite and chlorate in
swimming pools and found that while chlorite was not detectable, chlorate concentrations
varied from 1 mg/l to, in one extreme case, 40 mg/l. Strähle et al. (2000)
found chlorate concentrations of up to 142 mg/l. The concentrations of chlorate
in chlorine-disinfected pools were close to the limit of detection of 1 mg/l, but the
mean concentration of chlorate in sodium hypochlorite-disinfected pools was about
17 mg/l. Chlorate concentrations were much lower in pools disinfected with hypochlorite
and ozone, and the chlorate levels were related to the levels in hypochlorite
stock solutions.
3. Other disinfection by-products
A number of other disinfection by-products have been examined in swimming pool
water; these are summarized in Tables 4.9–4.11. Dichloroacetic acid has also been
detected in swimming pool water. In a German study of 15 indoor and 3 outdoor
swimming pools (Clemens & Scholer, 1992), dichloroacetic acid concentrations
averaged 5.6 μg/l and 119.9 μg/l in indoor and outdoor pools, respectively. The mean
concentration of dichloroacetic acid in three indoor pools in the USA was 419 μg/l
(Kim & Weisel, 1998). The difference between the results of these two studies may
be due to differences in the amounts of chlorine used to disinfect swimming pools,
sample collection time relative to chlorination of the water, or addition or exchanges
of water in the pools.
Disinfection by-product concentration (μg/l)
type Reference
Chloroform BDCM DBCM Bromoform
Mean Range Mean Range Mean Range Mean Range
Poland 35.9–99.7 2.3–14.7 0.2–0.8 0.2–203.2 indoor Biziuk et al., 1993
Italy 19–94 indoor Aggazzotti et al., 1993
93.7 9–179 indoor Aggazzotti et al., 1995
33.7 25–43 2.3 1.8–2.8 0.8 0.5–10 0.1 0.1 indoor Aggazzotti et al., 1998
USA 37.9 indoor Copaken, 1990
Armstrong &
Golden, 1986
4–402 1–72 <0.1–8 <0.1–1 outdoor
3–580 1–90 0.3–30 <0.1–60 indoor
<0.1–530 <0.1–105 <0.1–48 <0.1–183 hot tub
Germany 14.6 2.4–29.8 indoor Eichelsdörfer et al., 1981
43 14.6–111 outdoor
Lahl et al., 1981
Ewers et al., 1987
198 43–980 22.6 0.1–150 10.9 0.1–140 1.8 <0.1–88 indoor
0.5–23.6 1.9–16.5 <0.1–3.4 <0.1–3.3 indoor
<0.1–32.9 <0.1–54.5 <0.1–1.0 <0.1–0.5 hydrotherapy
<0.1–0.9 <0.1–1.4 <0.1–16.4 2.4–132 hydrotherapy
3.6–82.1 1.6–17.3 <0.1–15.1 <0.1–4.0 outdoor
94.9 40.6–117.5 4.8 4.2–5.4 1.8 0.78–2.6 indoor Puchert et al., 1989
80.7 8.9 1.5 <0.1 indoor Puchert, 1994
74.9 11.0 3.0 0.23 outdoor
.3–27.8 0.69–5.64 0.03–6.51 0.02–0.83 indoor Cammann & Hübner, 1995
1.8–28 1.3–3.4 <0.1–1 <0.1 indoor Jovanovic et al., 1995
Schössner & Koch, 1995
Stottmeister, 1998, 1999
8–11 indoor
14. 0.51–69 2.5 0.12–15 0.59 0.03–4.9 0.16 <0.03–8.1 indoor
30. 0.69–114 4.5 0.27–25 1.1 0.04–8.8 0.28 <0.03–3.4 outdoor
4.3 0.82–12 1.3 0.19–4.1 0.4 0.03–0.91 0.08 <0.03–0.22 hydrotherapy
3.8 6.4 (max.) spa Erdinger et al., 1997b
7.1–24.8 indoor pool Erdinger et al., 2004
Denmark 145–151 indoor Kaas & Rudiengaard, 1987
Hungary 11.4 .<2–62.3 2.9 <1.0–11.4 indoor Borsányi, 1998
UK 121.1 45–212 8.3 2.5–23 2.7 0.67–7 0.9 0.67–2 indoor pools Chu & Nieuwenhuijsen, 2002
Table 4.4. Concentrations of trihalomethanes measured in swimming pool water
BDCM = bromodichloromethane; DBCM = dibromochloromethane
4.5.2 Risks associated with disinfection by-products
The guideline values in the WHO Guidelines for Drinking-water Quality can be used to
screen for potential risks arising from disinfection by-products from swimming pools
and similar environments, while making appropriate allowance for the much lower
quantities of water ingested, shorter exposure periods and non-ingestion exposure. Although
there are data to indicate that the concentrations of chlorination by-products
in swimming pools and similar environments may exceed the WHO guideline values
for drinking-water (WHO, 2004), available evidence indicates that for reasonably
well managed pools, concentrations less than the drinking-water guideline values can
be consistently achieved. Since the drinking-water guidelines are intended to refl ect
tolerable risks over a lifetime, this provides an additional level of reassurance. Drinking-
water guidelines assume an intake of 2 litres per day, but as considered above,
ingestion of swimming pool water is considerably less than this; recent measured data
(Section 4.1.1) indicate an extreme of about 100 ml (Evans et al., 2001). Uptake via
skin absorption and inhalation (in the case of THMs) is proportionally greater than
from drinking-water and is signifi cant, but the low oral intake allows a margin that
can, to an extent, account for this. Under such circumstances, the risks from exposure
to chlorination by-products in reasonably well managed swimming pools would be
considered to be small and must be set against the benefi ts of aerobic exercise and the
risks of infectious disease in the absence of disinfection.
Levels of chlorate and chlorite in swimming pool water have not been extensively
studied; however, in some cases, high chlorate concentrations have been reported,
which greatly exceeded the WHO provisional drinking-water guideline (0.7 mg/l)
and which would, for a child ingesting 100 ml of water, result in possible toxic effects.
Exposure, therefore, needs to be minimized, with frequent dilution of pool water with
fresh water, and care taken to ensure that chlorate levels do not build up in stored
hypochlorite disinfectants.
The chloramines and bromamines, particularly nitrogen trichloride and nitrogen
tribromide, which are both volatile (Holzwarth et al., 1984), can give rise to signifi
cant eye and respiratory irritation in swimmers and pool attendants (Massin et
al., 1998). In addition, nitrogen trichloride has an intense and unpleasant odour at
concentrations in water as low as 0.02 mg/l (Kirk & Othmer, 1993). Studies of subjects
using swimming pools and non-swimming attendants have shown a number of
changes and symptoms that appear to be associated with exposure to the atmosphere
in swimming pools. Various authors have suggested that these were associated with
nitrogen trichloride exposure in particular (Carbonnelle et al., 2002; Thickett et al.,
2002; Bernard et al., 2003), although the studies were unable to confi rm the specifi c
chemicals that were the cause of the symptoms experienced. Symptoms are likely to be
particularly pronounced in those suffering from asthma. Yoder et al. (2004) reported
two incidents, between 2001 and 2002, where a total of 52 people were adversely affected
by a build-up of chloramines in indoor pool water. One of the incidents related
to a hotel pool, and 32 guests reported coughs, eye and throat irritation and diffi culty
in breathing. Both incidents were attributed to chloramines on the basis of the clinical
syndrome and setting. Hery et al. (1995) found that complaints from non-swimmers
were initiated at a concentration of 0.5 mg/m3 chlorine species (expressed in units
of nitrogen trichloride) in the atmosphere of indoor pools and hot tubs. It is recommended
that 0.5 mg/m3 would be suitable as a provisional value for chlorine species,
Table 4.5. Concentrations of trihalomethanes measured in the air above the pool water surface
Disinfection by-product concentration (μg/m3)
Pool type Reference
Chloroform BDCM DBCM Bromoform
Mean Range Mean Range Mean Range Mean Range
Italy 214 66–650 19.5 5–100 6.6 0.1–14 0.2 indoor1) Aggazzotti et al., 1995
140 049–280 17.4 2–58 13.3 4–30 0.2 indoor1) Aggazzotti et al., 1993
169 35–195 20 16–24 11.4 9–14 0.2 indoor1) Aggazzotti et al., 1998
Canada 597–1630 indoor Lévesque et al., 1994
Germany 65 9.2 3.8 indoor1) Jovanovic et al., 1995
36 5.6 1.2 indoor2)
5.6 0.21 outdoor1)
2.3 outdoor1)
3.3 0.33–9.7 0.4 0.08–2.0 0.1 0.02–0.5 <0.03 outdoor1) Stottmeister, 1998, 1999
1.2 0.36–2.2 0.1 0.03–0.16 0.05 0.03–0.08 <0.03 outdoor2)
39 5.6–206 4.9 0.85–16 0.9 0.05–3.2 0.1 <0.03–3.0 indoor1)
30 1.7–136 4.1 0.23–13 0.8 0.05–2.9 0.08 <0.03–0.7 indoor2)
USA <0.1–1 <0.1 <0.1 <0.1 outdoor3) Armstrong & Golden, 1986
<0.1–260 <0.1–10 <0.1–5 <0.1–14 indoor3)
<0.1–47 <0.1–10 <0.1–5 <0.1–14 hot tub3)
BDCM = bromodichloromethane; DBCM = dibromochloromethane
a Measured 20 cm above the water surface
b Measured 150 cm above the water surface
c Measured 200 cm above the water surface
Table 4.6. Comparison of trihalomethane concentrations in blood of swimmers after a 1-h
swim, in pool water and in ambient air of indoor and outdoor poolsa
THM concentration (mean, range)
Indoor pool Outdoor pool
Blood of swimmers (μg/l) 0.48 (0.23–0.88) 0.11 (<0.06–0.21)
Pool water (μg/l) 19.6 (4.5–45.8) 73.1 (3.2–146)
Air 20 cm above the water surface (μg/m³) 93.6 (23.9–179.9) 8.2 (2.1–13.9)
Air 150 cm above the water surface (μg/m³) 61.6 (13.4–147.1) 2.5 (<0.7–4.7)
a Adapted from Strähle et al., 2000
Table 4.7. Concentrations of trihalomethanes in plasma of 127 swimmersa
THM No. positive/no. samples
Mean THM
Range of THM
Chloroform 127/127 1.06 0.1–3.0
BDCM 25/127 0.14 <0.1–0.3
DBCM 17/127 0.1 <0.1–0.1
a Adapted from Aggazzotti et al., 1990
Table 4.8. Comparison of trihalomethane levels in ambient air and alveolar air in swimmers prior
to arrival at the swimming pool, during swimming and after swimminga
THM levels (μg/m3) at various monitoring timesb
Ambient air 20.7 ± 5.3 91.7 ± 15.4 169.7 ± 26.8 20.0 ± 8.4 19.2 ± 8.8
Alveolar air 9.3 ± 3.1 29.4 ± 13.3 76.5 ± 18.6 26.4 ± 4.9 19.1 ± 2.5
Ambient air n.q. 10.5 ± 3.1 20.0 ± 4.1 n.q. n.q.
Alveolar air n.q. 2.7 ± 1.2 6.5 ± 1.3 2.7 ± 1.1 1.9 ± 1.1
Ambient air n.q. 5.2 ± 1.5 11.4 ± 2.1 n.q. n.q.
Alveolar air n.q. 0.8 ± 0.8 1.4 ± 0.9 0.3 ± 0.2 0.20 ± 0.1
Ambient air n.q. 0.2 0.2 0.2 n.q.
Alveolar air n.q. n.q. n.q. n.q. n.q.
a Adapted from Aggazzotti et al., 1998
b Five competitive swimmers (three males and two females) were monitored A: Prior to arrival at the pool; B: After 1 h resting at poolside
before swimming; C: After a 1-h swim; D: 1 h after swimming had stopped; and E: 1.5 h after swimming had stopped. D and E
occurred after departing the pool area. n.q. = not quantifi ed
Table 4.9. Concentrations of haloacetic acids measured in swimming pool water
MCAA = monochloroacetic acid; MBAA = monobromoacetic acid; DCAA = dichloroacetic acid; DBAA = dibromoacetic acid; TCAA = trichloroacetic acid
Disinfection by-product concentration (μg/l)
type Reference
Mean Range Mean Range Mean Range Mean Range Mean Range
Germany 26 2.6–81 0.32 <0.5–3.3 23 1.5–192 0.57 <0.2–7.7 42 3.5–199 indoor Stottmeister & Naglitsch, 1996
32 2.5–174 0.15 <0.5–1.9 8.8 1.8–27 0.64 <0.2–4.8 15 1.1–45 hydrotherapy
26 2.5–112 0.06 <0.5–1.7 132 6.2–562 0.08 <0.2–1.3 249 8.2–887 outdoor
30 hot tub Lahl et al., 1984
25–136 indoor
2.3–100 indoor Mannschott et al., 1995
Disinfection by-product concentration (μg/l)
type Reference
Mean Range Mean Range Mean Range
Germany 6.7–18.2 indoor Puchert, 1994
Stottmeister, 1998, 1999
<0.5–2.5 outdoor
13 0.13–148 2.3 <0.01–24 1.7 <0.01–11 indoor
9.9 0.22–57 0.62 <0.01–2.8 1.5 <0.01–7.8 hydrotherapy
45 <0.01–0.02 2.5 <0.01–16 1.3 <0.01–10 outdoor
24 indoor Baudisch et al., 1997
49 seawater
Table 4.10. Concentrations of haloacetonitriles measured in swimming pool water
DCAN = dichloroacetonitrile; DBAN = dibromoacetonitrile; TCAN = trichloroacetonitrile
Table 4.11. Concentrations of chloropicrin, chloral hydrate and bromal hydrate measured in swimming pool water
Disinfection by-product concentration (μg/l)
type Reference
Chloropicrin Chloral hydrate Bromal hydrate
Mean Range Mean Range Mean Range
Germany 0.1–2.6 indoor Schöler & Schopp, 1984
0.32–0.8 indoor Puchert, 1994
<0.01–0.75 outdoor Stottmeister, 1998, 1999
0.32 0.03–1.6 indoor
0.20 0.04–0.78 hydrotherapy
1.3 0.01–10 outdoor
265 indoor Baudisch et al., 1997
230 seawater Baudisch et al., 1997
0.5–104 indoor Mannschott et al., 1995
expressed as nitrogen trichloride, in the atmosphere of indoor swimming pools and
similar environments. However, more specifi c data are needed on the potential for
exacerbation of asthma in affected individuals, since this is a signifi cant proportion of
the population in some countries. There is also a potential issue regarding those that
are very frequent pool users and who may be exposed for longer periods per session,
such as competitive swimmers. It is particularly important that the management of
pools used for such purposes is optimized in order to reduce the potential for exposure
(Section 5.9).
4.6 Risks associated with plant and equipment malfunction
Chemical hazards can arise from malfunction of plant and associated equipment. This
hazard can be reduced, if not eliminated, through proper installation and effective
routine maintenance programmes. The use of gas detection systems and automatic
shutdown can also be an effective advance warning of plant malfunction. The use of
remote monitoring is becoming more commonplace in after-hours response to plant
and equipment malfunction or shutdown.
4.7 References
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exposure to trihalomethanes in indoor swimming pools. Science of the Total Environment, 217: 155–163.
Armstrong DW, Golden T (1986) Determination of distribution and concentration of trihalomethanes in
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Baudisch C, Pansch G, Prösch J, Puchert W (1997) [Determination of volatile halogenated hydrocarbons in
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Vorpommern (in German).
Bernard A, Carbonnelle S, Michel O, Higuet S, de Burbure C, Buchet J-P, Hermans C, Dumont X,
Doyle I (2003) Lung hyperpermeability and asthma prevalence in schoolchildren: unexpected associations
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in swimming pool water. International Journal of Environmental Analytical Chemistry, 46: 109–115.
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uptake in swimming pools. International Journal of Hygiene and Environmental Health,
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ingested by recreational swimmers. Paper presented to 2001 Annual Meeting of the Society for Risk Analysis,
Seattle, Washington, 2–5 December 2001.
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trihalomethanes in indoor swimming pools. Science of the Total Environment, 17: 257–265.
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seawater and saline pools”.] Kiel, Institut für Hygiene und Umweltmedizin der Universität Kiel (in German).
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34: 248–250 (in German).
Hery M, Hecht G, Gerber JM, Gendree JC, Hubert G, Rebuffaud J (1995) Exposure to chloramines in the
atmosphere of indoor swimming pools. Annals of Occupational Hygiene, 39: 427–439.
Holzwarth G, Balmer RG, Soni L (1984) The fate of chlorine and chloramines in cooling towers. Water
Research, 18: 1421–1427.
Isaak RA, Morris JC (1980) Rates of transfer of active chlorine between nitrogenous substrates. In: Jolley
RL, ed. Water chlorination. Vol. 3. Ann Arbor, MI, Ann Arbor Science Publishers.
Jandik J (1977) [Studies on decontamination of swimming pool water with consideration of ozonation of nitrogen
containing pollutants.] Dissertation. Munich, Technical University Munich (in German).
JECFA (2004) Evaluation of certain food additives and contaminants. Sixty-fi rst report of the Joint FAO/
WHO Expert Committee on Food Additives (WHO Technical Report Series No. 922).
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water, air and in swimmers and lifeguards in outdoor and indoor pools”.] Stuttgart, Landesgesundheitsamt
Baden-Württemberg (in German).
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51(9): 869–879.
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water.] Paper presented to the 3rd Symposium on “Problems of swimming pool water hygiene”, Reinhardsbrunn
(in German).
Kelsall HL, Sim MR (2001) Skin irritation in users of brominated pools. International Journal of Environmental
Health Research, 11: 29–40.
Kim H, Weisel CP (1998) Dermal absorption of dichloro- and trichloroacetic acids from chlorinated water.
Journal of Exposure Analysis and Environmental Epidemiology, 8(4): 555–575.
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& Sons, p. 916.
Lahl U, Bätjer K, Duszeln JV, Gabel B, Stachel B, Thiemann W (1981) Distribution and balance of volatile
halogenated hydrocarbons in the water and air of covered swimming pools using chlorine for water disinfection.
Water Research, 15: 803–814.
Lahl U, Stachel B, Schröer W, Zeschmar B (1984) [Determination of organohalogenic acids in water
samples.] Zeitschrift für Wasser- und Abwasser-Forschung, 17: 45–49 (in German).
Latta D (1995) Interference in a melamine-based determination of cyanuric acid concentration. Journal of
the Swimming Pool and Spa Industry, 1(2): 37–39.
Lévesque B, Ayotte P, LeBlanc A, Dewailly E, Prud’Homme D, Lavoie R, Allaire S, Levallois P (1994)
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swimming pool water.] Zentralblatt für Hygiene und Umweltmedizin, 197: 516–533 (in German).
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Städte-Hygiene, 35: 109–112 (in German).
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Forum Städte-Hygiene, 46: 354–357 (in German).
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Cranfi eld University, Cranfi eld, UK.
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Yoder JS, Blackburn BG, Craun GF, Hill V, Levy DA, Chen N, Lee SH, Calderon RL, Beach MJ (2004)
Surveillance of waterborne-disease outbreaks associated with recreational water – United States, 2001–
2002. Morbidity and Mortality Weekly Report, 53(SS08): 1–22.

National Aquatic Health Conference: Indoor Air Quality Standards

Proposal from the CDC


Trichloramine prevention
remains better than cure
Recreation is the first UK publication to feature new
research from Germany that is relevant to anyone involved
in managing, working in or using indoor swimming pools
This German research, published here for
the first time in the UK, provides an
important step forward in our
understanding of the relationship between
chlorine levels in pools and the production
of trichloramines. Essentially, high
combined chlorine levels do not
automatically mean high trichloramine
The key precursor for the formation of
trichloramines (nitrogen trichloride) is urea
from urine, sweat and skin cells. Best
practice remains largely unchanged: that
the concentration of urea in pool water
must be minimised.
Keys to minimising urea concentration:
● Educate pool users: prevention is better
than cure. Comprehensive pre-swim
hygiene measures including using the
toilet (elimination of the urine source)
and washing thoroughly prior to pool use
(the skin source) will help greatly.
● Remove urea by water treatment through
ozone-activated carbon treatment or
● Reduce the urea concentration by dilution
(adding 30 litres of fresh water per pool user).
● Provide good pool hall ventilation, ideally
without re-circulation or at least 30 per
cent fresh air.
solubility, it readily escapes from swimming and
bathing pool water and may consequently accumulate
in the air of indoor pools and then lead to breathing
problems and eye irritations. The irritating effects
are similar to those of chlorine gas [2].
Belgian researchers hypothesised that the
exposure of schoolchildren to trichloramine during
visits to indoor chlorinated swimming pools
adversely affected the lung epithelium permeability
of the children and could lead to an increased risk
of developing asthma [3].English scientists reported
asthma symptoms in lifeguards and swimming
teachers caused by chloramines [4].More recent
studies corroborate the above hypothesis [5, 6].
In summer 1999, the German Federal
Environmental Agency, as a precaution, started to
measure trichloramine in the air of indoor pools as
part of scientific investigations into the formation
and minimisation of undesirable by-products of
swimming and bathing pool water chlorination.
The object was to obtain initial information as to
whether and to what extent the air in German
indoor swimming pools is contaminated by this
compound.No such information was available for
German indoor pools at the time.
The following is a report on the formation and
properties of trichloramine and its analysis. First
measurement results are presented and discussed.
2. Urea and formation of trichloramine in
pool water
Considerable amounts of urea are introduced to
swimming and bathing pool water by pool users.
The sources are the skin, urine and sweat.Urea is
the main final product of the protein metabolism
of humans. About 90 per cent is excreted via the
kidneys (urine), the remainder via sweat and
intestinal secretions. It also forms during skin
Urea is a chemical compound with the following
formula:H2N-CO-NH2. In its pure form, it forms
colourless and odourless crystals which are readily
soluble in water. The presence of urea in
chlorinated pool water leads to the formation of
Urea sources: skin, urine and sweat
The skin is the largest organ of the human body,
with a surface area of approximately 1.5 to 2m2.
Urea is a product of the degradation of the amino
acid arginine during skin hornification [7]. It
belongs to the natural factors that keep the skin
The urea content in the horny layer (stratum
corneum) of healthy skin is about 8 μg per cm2 of
skin surface, for both men and women. 2m2 of
skin surface would thus contain about 0.16 g of
urea. Pool water readily removes water-soluble
organic and inorganic constituents including urea
from the skin of pool users.Assuming that all urea
in the stratum corneum is fully washed into pool
water in this way, then 1,000 pool users would
release about 160g of urea into pool water.
Thorough washing and showering by pool users
prior to pool use removes about 75 to 97 per cent
of the urea contained in the stratum corneum and
is thus a very effective way to prevent urea input
into pool water (Figure 1). Substantial amounts
of urea and other nitrogen compounds may also
be introduced into pool water through urine and
sweat.Table 1 lists average concentrations of urea
in urine, sweat and the horny layer of the
Different figures are given in the literature as
regards urine and sweat input to pool water [9 –
13].Assuming a urine input of 35 ml per pool user
as determined by Gunkel and Jessen [9], the input
of urea to pool water would be about 0.8g per pool
user. The amount of sweat released to pool water
per pool user depends on many factors, such as
water temperature, air humidity, physical
condition and activity of the pool user. The expert
literature indicates that an active swimmer, for
example, may excrete up to one litre of sweat per
hour [14].Urea input with one litre of sweat would
amount to about 1.5g per pool user and hour.
Trichloramine formation mechanism
In the scientific literature, the mechanism of
trichloramine formation from urea is discussed
from three different directions:
• Enzymatic degradation of urea, by the enzyme
urease which is contained in various bacteria, to
ammonia or ammonium, and reaction of the latter
with free chlorine to trichloramine.According to
Jessen and Gunkel [13], this process does not occur
in chlorinated pool water;
• Hydrolysis (cleavage by the action of water) of
urea,with formation of ammonia or ammonium,
and subsequent reaction with free chlorine to
trichloramine. This occurs only at temperatures
of more than 65C and is not, therefore, relevant to
pool water;
• The decisive mechanism for the formation of
trichloramine in pool water is the step-by-step
March 2006 recreation ● 31
Figure 1: Influence of washing on the urea content in the stratum corneum, after (8).
Table 1: Average concentration of urea in urine,
sweat and the horny layer of the epidermis.
Shower gel + water
Urea content in skin after washing
35% Test person A
Test person B
Test person C
Test person D
8 μg/cm_
Table 3: Henry’s law constants (H).
Hypochloric acid 0.069
Monochloramine 0.45
Dichloramine 1.52
Trichloramine 435
1) Eichelsdörfer et al. [16] ; 2) Spon [17]
Table 2: Properties of chlorine and chloramines.
Free chlorine Mono Dichloramine Trichloramine
No eye irritation in rabbits1) 0-8 0-2 No data No data
Distinct eye irritation 30 4 No data No data
in rabbits1)
Odour and taste threshold2) 20 5 0.8 0.02
O = C + 2 HOCl 2 NCl3 + CO2 + H2O
1,1,3,3- hypochloric acid trichloramine
tetrachlorourea ➞ ➞
reaction of the urea introduced by pool users with
free chlorine to 1,1,3,3-tetrachlorourea and finally
to trichloramine, as described in the literature [15].
Properties of trichloramine
Trichloramine is an undesirable by-product of
disinfection,which has a strong irritating effect on
the eyes, nose, throat and bronchial tubes. Its
odour is similar to that of chlorine. The odour and
taste threshold in water is very low, at 0.02 mg/l.
A threshold concentration for eye irritation caused
by the presence of trichloramine in pool water has
not been established to date.
Eichelsdörfer et al. [16] demonstrated for free
chlorine and monochloramine that distinct eye
irritation in rabbits does not start at a
concentration lower than about 30 mg/l and 4
mg/l, respectively. The value for trichloramine
ought to be markedly lower. Table 2 summarises
the literature data.
Previously, it had long been assumed that
trichloramine forms only at a pH less than or equal
to 4.4. However, this view has had to be revised;
trichloramine is also formed at higher pH values
such as occur in pool water, and is rather stable
under such conditions. Investigations have shown,
for example, that a diluted aqueous trichloramine
solution has a half-life of 218 minutes at a pH of
7. This means that 50 per cent of the substance
decomposes in water during that time [18]. For
example, when the trichloramine concentration
in pool water is 0.1 mg/l, then it would be 0.05
mg/l after 218 minutes, if one ignores gaseous
emissions of the compound to air.
The outgassing behaviour of a substance
dissolved in pool water can be estimated using the
air/water partition coefficient (= Henry’s law
constant, H). The lower the Henry’s law constant,
the more soluble is the substance in pool water.
The higher its Henry’s law constant, the more
readily it escapes from pool water to air. The
Henry’s law constants of mono-, di- and
trichloramine and hypochloric acid have been
determined experimentally by Holzwarth et al.
[19] (Table 3).
The H values show that trichloramine escapes
from pool water 966 times faster than
monochloramine and 286 times faster than
dichloramine. It ‘feels’ 435 times ‘more
comfortable’ in indoor pool air than in pool water.
This and its odour and taste threshold (Table 2)
are the main reasons for the typical chlorine-like
smell in swimming pool halls. The H value of
dichloramine is only of theoretical interest, as the
compound is not stable and decomposes very
quickly in pool water [20].
Water attractions such as waterslides, water
geysers, flood showers and water fountains
accelerate the release of trichloramine to air.
Comparing, for example, the outgassing behaviour
of trichloramine to that of chloroform, which
belongs to the substance group of
trihalomethanes, trichloramine escapes from pool
water three times faster than that substance.
3.1 Measurement in pool water
There is currently no simple on-site method for
the selective determination of trichloramine in
pool water. One laboratory method to reliably
differentiate between and quantify the various
inorganic chloramines – mono-, di- and
trichloramine – is membrane introduction mass
spectrometry (MIMS), whose use remains
reserved to specialised water analysis laboratories.
The detection limit for trichloramine is reported
to be 0.06 mg/l [21].
4.2 Measurement in the air of indoor
swimming pools
The German Federal Environmental Agency,
Department for Drinking and Swimming Pool
Water Hygiene, began measuring trichloramine
in the air of indoor swimming pools in summer
1999, for precautionary and the following other
reasons: no data whatsoever was available on
trichloramine concentrations in the air of German
swimming pool halls; the French INRS (Institut
National de Recherche et de Sécurité) has
published a validated method for the
determination of trichloramine in air [22], which
was adopted by the Federal Environmental Agency
to ensure comparability with INRS measurement
data and which is, to this day, the only existing
method for determination of trichloramine in air;
a health-based guideline value of ≤ 0.50 mg/m3
has been proposed in France for trichloramine in
indoor pool air [2, 22]. This value can be used as
a basis for assessment of the measurement results.
The principle of the analytical method is shown
in the flow chart, left.
5. Selected results
Table 4 presents selected measurement results on
trichloramine in the air of indoor swimming pools
for different pool types and compares them with
32 ● recreation March 2006
Table 5: Influence of air renewal on trichloramine concentration in indoor pool air
Flow chart: the principle of the analytical method.
Contribution of fresh air to Trichloramine Chloramines (expressed as
ingoing air mass flow in air combined chlorine) in pool water
% mg/m3 mg/l
0 0.52 0.15
30 0.37 0.15
1) according to INRS [22] ; 2) according to the German standard DIN 19643-1 [23]
Table 4: Trichloramine concentrations in the air of indoor swimming pools and corresponding
concentrations of combined chlorine in pool water.
Pool type Trichloramine Chloramines (as combined chlorine)
in indoor pool air in pool water
mg/m3 mg/l
Leisure 0.13 0.07
Leisure 0.16 0.13
Leisure 0.37 0.80
Leisure 2.2 0.12
Conventional 18.8 0.25
Hydrotherapy 0.19 0.01
Hydrotherapy 0.14 0.05
Exercise pool 0.05 0.03
Guideline values 0.501) 0.202)
Chloride concentration
per sample volume
➞NCl3 concentration
per m3 of air
➞ ➞ ➞ ➞
NCl3, NH2Cl,
HOCl, etc.)
isolation of NCl3 by
trapping soluble
chlorine compounds
in an adsorption tube
Concentration of
NCl3 and chemical
transformation to
chloride in a special
treated filter cassette
of chloride and
by ion
‘Water attractions such as
waterslides, water geysers,
flood showers and fountains
accelerate the release of
trichloramine to the air’
the corresponding measurement data for
combined chlorine in pool water.
The values in Table 4 show that measured
trichloramine concentrations in the air of indoor
swimming pools do not correlate with the values
for combined chlorine. There may be cases where
the concentration of combined chlorine in pool
water, at 0.80 mg/l, exceeds by far the upper value
of 0.20 mg/l recommended by the German
standard DIN 19643-1 while the trichloramine
concentration in the indoor pool air, at 0.37
mg/m3, is below the recommended guideline value
of 0.50 mg/m3.
Conversely, there are cases where concentrations
of combined chlorine in pool water comply with
(0.12 mg/l) or are just slightly above (0.25 mg/l)
the recommended upper value while the
corresponding results for the trichloramine
concentration in indoor pool air (2.2 and 18.8
mg/m3) exceed the guideline value, in the one case,
by a substantial amount. This means that a DINcompliant
concentration of combined chlorine in
pool water is not automatically linked with
trichloramine concentrations in the indoor pool
air that are safe for human health.
For this reason, care must be taken to ensure
that the ventilation system is designed so that
during pool operating hours the proportion of
fresh air fed to the air circulating in the pool hall
is adjusted to the pool capacity utilisation rate, as
prescribed by the technical rule VDI 2089-1 [24].
When the pool is used to maximum capacity (for
example,with very high bather loads and with all
water attractions switched on) the proportion of
fresh air should be at least 30 per cent of the
ingoing air mass flow.An example of the influence
of air renewal via the contribution of fresh air to
the ingoing air mass flow is presented in Table 5.
While the upper value in DIN 19643-1 for
combined chlorine in pool water is complied with,
at 0.15 mg/l, trichloramine can build up in the
indoor pool air to exceed the guideline value of
0.50 mg/m3 if there is no air renewal by a defined
proportion of fresh air (no dilution effect).
6. Discussion and conclusions
No direct correlation exists between the
trichloramine concentration in the indoor pool
air and the corresponding value for the chemical
parameter ‘combined chlorine’ in pool water.This
is because the measurement result for this sum
parameter does not, unfortunately, indicate how
much of the total content is trichloramine. A
simple and reliable on-site method for specific
measurement of trichloramine as an individual
substance in pool water does not yet exist.
A DIN-compliant concentration of combined
chlorine in pool water is no automatic guarantee
that the trichloramine concentration in the air of
the indoor pool will be tolerable from a health
perspective. In addition, this means that, during
pool operating hours, the airborne trichloramine
should be diluted by air renewal via a defined
contribution of fresh air to the ingoing air mass
flow in accordance with the generally accepted
technical standards (VDI 2089 Blatt 1) [24]. This
will prevent trichloramine accumulating in the air
of the pool hall to an extent as to exceed the
guideline value of 0.50 mg/m3.
The concentration of urea in pool water must
be minimised, since its reaction with free chlorine
in pool water results in the formation of
trichloramine, among other substances. This may
be achieved by the following:
• With the help of pool users: by using the toilet
(elimination of the urea source ‘urine’) and
washing themselves thoroughly (elimination of
the urea source ‘skin) prior to pool use;
• Removal of urea by water treatment (e.g. ozoneactivated
carbon treatment [25] [26], photooxidation
[27]); and
• Reducing the urea concentration by dilution
(adding 30 litres of fresh water per pool user).
If these hints are observed, there need be no
concern, according to present knowledge, that
trichloramine in indoor swimming pool air may
pose a health risk.
March 2006 recreation ● 33
1) DIN EN ISO 7393-2, Publication date:
2000-04, Water quality-
Determination of free chlorine and
total chlorine – Part. 2: Colorimetric
method using N,N-diethyl-1,4-
phenylendiamin, for routine control
purposes, English version, Beuth-
Verlag Berlin.
2) Gagnaire, F., Axim, S., Bonnet, P.,
Hecht, G. and Hery, M.: Comparison of
the sensory irritation response in mice
to chlorine and nitrogen trichloride. J
Appl Toxikol 14, 405-409 (1994).
3) Bernard, A, Carbonnelle, S., Michel,
O., Higuet, S., de Burbure, C., Buchet,
J.-P., Hermans, C., Dumont, X. and
Doyle, I.: Lung hyperpermeability and
asthma prevalence in schoolchildren:
unexpected associations with the
attendance at indoor chlorinated
swimming pools. Occup Environ Med
60, 385-394 (2003).
4) Thickett, K.M., McCoach, J.S., Gerber,
J.M., Sadhra, S. and Burge, P.S.:
Occupational asthma caused by
chloramines in indoor swimmingpool
air. Eur Respir J 19, 827-832
5) Lagerkvist, B.J., Bernard, A.,
Blomberg, A., Bergstrom, E., Forsberg,
B., Holmstrom, K., Karp, K.,
Lundstrom, N.-G., Segerstedt, B.,
Svensson, M., Nordberg, G.:
Pulmonary Epithelial Integrity in
Children – Relationship to Ambient
Ozone Exposure and Swimming Pool
Attendance. Environ Health Perspect
112 (17), 1768-1771 (2004).
6) Bernard, A., Carbonnelle, S.,
Nickmilder, M., de Burbure, C.: Noninvasive
biomarkers of pulmonary
damage and inflammation:
Application to chidren exposed to
ozone and trichoramine. Toxicol Appl
Pharmacol 206 (2), 185-190 (2005).
7) Jacobi, O.: Die Inhaltsstoffe des
normalen Stratum corneum und
Callus menschlicher Haut. Arch Derm
Forsch 240, 107-118 (1971).
8) Häntschel, D., Sauermann, G.,
Steinhart, H., Hoppe, U. and Ennen, J.:
Urea analysis of extracts from
stratum corneum and the role of
urea-supplemented cosmetics. J
Cosmet Sci 49, 155-163 (1998).
9) Gunkel, K. und Jessen, H.-J.:
Untersuchungen über den
Harnstoffeintrag in das Badewasser.
Acta hydrochim hydrobiol 14, 451-461
10) Borneff, J.: Hygiene. Georg Thieme
Verlag Stuttgart, New York, 5.
Auflage, 213, 1991.
11) Erdinger, L., Kirsch, F. und Sonntag,
H.-G.: Kalium als ein Indikator der
anthropogenen Belastung von
Schwimmbadwasser. Zbl Hyg 200,
297-308 (1997).
12) Gunkel, K. und Jessen, H.-J.: Zur
Harnstoffproblematik im
Z gesamte Hyg 34, 248-250 (1988).
13) Jessen, H.-J. und Gunkel, K.: Zur
Problematik des Urineintrags in das
Badewasser. A. B. Archiv des
Badewesens Nr. 6, 273-274 (1995).
14) Roeske, W.: Schwimmbeckenwasser.
1. Auflage, Verlag Otto Haase,
Lübeck, 1980.
15) Robson, H.L.: Chloramines. In:
Encyclopedia of Chemical
Technology, Kirk, R.; Othmer, D.F. ed.,
2nd ed., Vol. 4, 908-928, John Wiley
& Sons, New York, 1993.
16) Eichelsdörfer, D., Slovak, J., Dirnagl,
K. und Schmid, K.: Zur Reizwirkung
(Konjunctivitis) von Chlor und
Chloraminen im
Schwimmbeckenwasser. Vom
Wasser 45, 17-28 (1975).
17) Spon, R.: Do You Really Have A Free
Chlorine Residual? How to Find Out
and What You Can Do About It. RR
Spon & Associates, PO box 222,
Rescoe, IL 610973, USA, 2002.
18) Cooper, W.J., Roscher, N.M., Slifker,
R.A.: Determining free available
chlorine by DPD-colorimetric, DPDSteadifac
(colorimetric), and FACTS
procedures. Journal AWWA, 362-368
19) Holzwarth, G., Balmer, R.G. and
Sony, L.: The fate of chlorine and
chloramines in cooling towers.
Henry’s law constants for flashoff.
Water Res 18, 1421-1427 (1984).
20) Hand, V.C. and Margerum, D.W.:
Kinetics and Mechanism of the
Decomposition of Dichloramine in
Aqueous Solution. Inorg Chem 22,
1449-1456 (1983).
21) Shang, C. and Blatchley, E.R.:
Differentiation and Quantification of
Free Chlorine and Inorganic
Chloramines in Aqueous Solution by
MIMS. Environ Sci Technol 33, 2218-
2223 (1999).
22) Héry, M., Hecht, G., Gerber, J.M.,
Gendre, J.C., Hubert, G. and
Rebuffaud, J.: Exposure to
chloramines in the atmosphere of
indoor swimming pools. Ann Occup
Hyg 39, 427-439 (1995).
23) DIN 19643-1, Publication date: 1997-
04, Treatment of the water of
swimming-pools and baths – Part 1:
General requirements, English
version, Beuth Verlag Berlin
24) Technical rule (draft) VDI 2089 Blatt
1, Publication date: 2005-03 Building
services in swimming baths – Indoor
pools, English version, Beuth Verlag
25) Eichelsdörfer, D. und v. Harpe, T.:
Einwirkung von Ozon auf Harnstoff
im Hinblick auf die
Badewasseraufbereitung. Vom
Wasser XXXVII, 73-81 (1970).
26) Jentsch, F.: Erfahrungen mit der
Ozon-Aktivkohle-Behandlung von
Schwimmbad-Meerwasser. Zbl Bakt
Hyg, I. Abt Orig B 164, 485-491
27) Kaas, P.: Beckenwasser-
Aufbereitung mit Photooxidation.
Paper presented at the seminar
“New Concepts and Technologies”,
Dr. Jentsch Fachberatung
Schwimmbeckenwasser, Baunatal,
16 September 2003.
Dr Ernst Stottmeister and
K Voigt are from the
German Federal
Environmental Agency.

Chlorine and Chloramine Removal with Activated Carbon

Municipalities routinely began
using chlorine to treat drinking
water starting in 1908 with
Jersey City, NJ. Its use has helped to virtually eliminate diseases
like typhoid fever, cholera and dysentery in the US and other
developed countries. Globally the World Health Organization
(WHO) estimates that 3.4 million people in underdeveloped
countries die every year from water-related diseases.
Use of chlorine in water can produce an undesirable taste;
therefore, many consumers prefer to remove it. Disinfection
byproducts (DBPs) may also unintentionally form when chlorine
and other disinfectants react with natural organic matter that is
in the water. To reduce DBP formation, many municipalities are
switching to monochloramine.
Monochloramine treatment was first used in Ottawa,
Ontario, Canada in 1916 and in Denver, CO in 1917. Use of
monochloramine took a downturn during World War II due to
ammonia shortages. Currently the US EPA estimates more than
30 percent of larger US municipalities use monochloramine.
It’s a common misperception that activated carbon removes
chlorine and monochloramine from water by adsorption.
Understanding how activated carbon
removes chlorine and monochloramine
from water is critical to the design and
operation of such systems.
Chlorine formation and
Use of chlorine is the most common
method to disinfect public water
supplies. Chlorine is a powerful germicide,
killing many disease-causing
microorganisms in drinking water, reducing
them to almost non-detectable
levels. Chlorine also eliminates bacteria,
molds and algae that may grow in
water supply systems.
US EPA’s maximum residual disinfection levels (MRDLs) are
four mg/L for chlorine; however, chlorine may cause problems
that activated carbon can help resolve. The addition of chlorine
to disinfect water is accomplished by one of three forms: chlorine
gas (Cl2), sodium hypochlorite solution (NaOCl) or dry calcium
hypochlorite, Ca (OCl)2.
The addition of any of these to water will produce
hypochlorous acid (HOCl). This disassociates into hypochlorite
ions (OCl-) to some degree. (The reaction is summarized
Cl2 + H2O → HOCl + H+ + Cl–
HOCl – → H+ + OCl+
The ratio of hypochlorous acid and hypochlorite ion in water
is dependent upon pH level and, to a much lesser degree, water
temperature. The ratio of hypochlorous acid and hypochlorite ion
at various water pH and temperature is shown in Table 1.
It is important to understand the ratio of hypochlorous
acid and hypochlorite ion in water. First,
it has been estimated that hypochlorous
acid is almost 100 times more effective
for disinfection than hypochlorite ion. Secondly, activated
carbons more readily remove hypochlorous acid compared to
the hypochlorite ion.
Chlorine concentrations greater than 0.3 ppm in water can be
tasted. Activated carbon is very effective in removing free chlorine
from water. The removal mechanism employed by activated
carbon for dechlorination is not the adsorption phenomena that
occur for organic compound removal.
Dechlorination involves a chemical reaction of the activated
carbon’s surface being oxidized by chlorine. There are reactions
when hypochlorous acid and hypochlorite ion react with activated
carbon (shown below).
Carbon + HOCl → C*O + H+ + Cl–
Carbon + OCl– → C*O + Cl–
C*O represents the oxidized site of activated carbon after
reacting with chlorine; the chlorine has been reduced to chloride
ion (Cl-). These reactions occur very quickly.
Factors impacting
When designing an activated
carbon dechlorination system, several
process factors must be considered. If
the system is being designed for organic
removal and dechlorination, design
criteria for organic removal will override
design criteria for dechlorination.
Since organic adsorption onto activated
carbon is a slower process than
dechlorination, a system that has been
properly designed for organic removal
will work well for dechlorination.
When the design is strictly for dechlorination, consideration
must be given to any dissolved organics that may be present
in the water. These organics can reduce the capacity of carbon
for dechlorination by occupying the available sites used for
Particle size of activated carbon is the most important factor
impacting effective dechlorination. The smaller the activated
carbon particles, the faster the dechlorination rate. A disadvantage
of smaller particles is greater pressure drop within the media bed
and, therefore, must be given careful consideration in the overall
system design.
A 20×50 mesh size granular activated carbon (GAC) will be
more effective than a 12×30 or 8×30 mesh GAC. Carbon block
filters are made with fine mesh powder activated carbon with
particle sizes predominantly between 50 and 325 mesh.
Carbon block filters, therefore, are very effective for
dechlorination because of their very small activated carbon
particle size. If a GAC dechlorination system was designed for
20×50 mesh GAC and it was replaced with 12×40 mesh GAC, it
Chlorine and Chloramine Removal
with Activated Carbon
By Robert Potwora
Table 1. Percentages of HOCl and OCl –
% HOCl % OCl – % HOCl % OCl –
pH 32°F 32°F 68°F 68°F
4 100.0 0.0 100.0 0.0
5 100.0 0.0 97.7 2.3
6 98.2 1.8 96.8 3.2
7 83.3 16.7 75.2 24.8
8 32.2 67.8 23.2 76.8
9 4.5 95.5 2.9 97.1
10 0.5 99.5 0.3 99.7
11 0.05 99.95 0.03 99.97

Using free chlorine to disinfect, however,
can cause problems. Free chlorine can
react with naturally occurring organics in
the water, like humic and fulvic acids, to
form total trihalomethanes (TTHMs) and
haloacetic acids (HAAs).
Trihalomethanes in water are generally
composed of chloroform and, to a
lesser extent, bromodichloromethane, dibromochloromethane
and bromoform. To minimize TTHM
and HAA formation, many municipalities have
switched to alternate disinfection methods, the most
common being monochloramine.
Chloramines are formed by adding ammonia to chlorinated
water. The reactions are:
HOCl + NH3 → NH2Cl + H2O (monochloramine)
HOCl + NH2Cl → NHCl2 + H2O (dichloramine)
HOCl + NHCl2 → NCl3 + H2O (trichloramine)
The chloramine formed is dependent upon water pH. At
pH less than 4.4 trichloramine is formed. Between pH 4.4 – 6.0,
dichloramine is formed. At pH above 7, monochloramine is the
most prevalent.
Since most municipalities have a pH greater than 7, monochloramine
is the only chlormaine to be concerned about. Monochloramine
may impact taste and odor, but to a lesser extent
than chlorine. It is toxic to tropical fish and may cause anemia in
patients being treated with kidney dialysis.
Removal by activated carbon, therefore, is becoming more
common. How monochloramine is removed by activated carbon
is summarized in these reactions.
GAC + NH2Cl + H2O → NH3 + H+ + Cl- + CO*
CO* + 2NH2Cl → N2 + H2O + 2H+ + 2Cl + C
CO* represents a surface oxide on the GAC
The preferred reaction is the second one because nitrogen
and chloride are the end products. With a new bed of traditional
GAC, the first reaction occurs to some degree with ammonia
being formed. Over time with traditional GAC, the second reaction
will occur.
GAC systems designed for free-chlorine removal may need to
be retrofitted for monochloramine removal. The reaction rate for
monochloramine removal is considerably slower than removing
free chlorine using traditional GAC.
At least two to four times more EBCT will be required for
monochloramine removal with traditional GAC. Regulatory
authorities and some standards may require 10 minutes EBCT
when removing monochloramine from water for kidney dialysis.
Percent reduction
Carbon contact elapsed time (minutes)
0 1 2 3 4 5 6 7 8 9 10
Competitive surface-enhanced
Spartan coconut surface-enhanced
Standard coconut AC
Figure 3.
Removal of monochloramine
Information on treating water for hemodialysis may be found in
ANSI/AAMI Standard RD 62:2006, “Water Treatment Equipment
for Hemodialysis Applications.”
Surface enhanced activated carbons
To compensate for poor performance of traditional GAC
for monochloramine removal, manufacturers have developed
surfaced-enhanced activated carbons. These activated carbons
have surface reaction sites enhanced during the manufacturing
process. They are superior for monochloramine removal compared
to traditional GAC. For surface-enhanced GAC, an EBCT of three
minutes will be sufficient to remove monochloramine from water.
A coconut shell-based, surface-enhanced GAC can be compared to
a bituminous coal-based, surface-enhanced
activated carbon (Table 2).
In addition to excellent monochloramine
removal with surface-enhanced coconut
shell-based GAC, its higher iodine
number means it has superior volatile
organic chemical (VOC) capacity. It also
has lower ash content and higher hardness,
resulting in less dust.
A quick bench-scale test is used to
evaluate how well different types of activated
carbons perform for monochloramine
removal. In a beaker containing 400 mL
water and four-ppm monochloramine,
0.2 grams of pulverized activated carbon
is added.
With constant stirring, reduction in
monochloramine is monitored over time. Different types of
surface-enhanced activated carbons can be compared with a
traditional activated carbon (Figure 3). The surface-enhanced,
coconut shell-based activated carbon proved superior.
Based upon field studies for surface enhanced GAC, a
minimum EBCT of three minutes is recommended. For traditional
GAC, a minimum EBCT of 10 minutes is recommended. Using the
recommended EBCT for each type of GAC, the volume of GAC
required for various flow rates may be compared (Table 3). Surfaceenhanced
GAC costs more, but based upon the lower volume
requirements, it is cost effective compared to traditional GAC.
About the author
 Robert Potwora is Technical Director for Carbon Resources, LLC. He
has 30 years experience in the activated carbon industry and is currently
Vice Chairman of the ASTM D28 Committee on Activated Carbon.
Potwora may be reached by phone at (760) 630-5724 or by email at
About the company
 Carbon Resources, based in Oceanside, CA, is a quality supplier of
activated carbon products and services that is backed by technical support
and individualized customer service. The Carbon Resources management
team has over 85 years of experience in the activated carbon industry and
offers an unmatched line of the most diverse activated carbon products
on the market. The Sabre-series®, Spartan-series® (the surface-enhanced
coconut shell-based activated carbon used in Table 2), Guardian Adsorberseries
® and newly introduced Sentry-series® activated carbon products
are widely recognized in the industry. For more information, please visit