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Breathing easy: Study targets improving air quality at indoor aquatic facilities

Volatile disinfection byproducts in indoor aquatic facilities

Researchers have identified at least 11 volatile disinfection byproducts common to chlorinated pools (see Table 1). These include inorganic chloramines, like trichloramine, along with several trihalomethanes, several halogenated nitriles, and at least one organic chloramine compound. The volatile compounds form when free chlorine reacts with certain precursor compounds in the water—mainly urea, uric acid, creatinine, and amino acids (mostly associated with sweat and urine).


Table 1

Type Compound
Inorganic Chloramines NCl3, NHCl2, NH2Cl
Organic Chloramines CH3NCl2
Halonitriles CNCl, CNBr, CNCHCl2
THMs CHCl3, CHBrCl2, CHBr2Cl, CHBr3

Volatile disinfection byproducts become most harmful to respiratory health when they transfer from liquid to gas form. There are multiple factors that increase the potential for this transfer to occur. One is the water quality, or the concentration of the volatile disinfection byproducts in the water. As the concentration builds up in the water, so does the potential for the transfer of the compounds from a liquid to a gas phase.

Mixing of water and air in an indoor aquatic facility also increases the transfer of volatile compounds to the air. The mixing processes are affected by several aspects of pool operations, including:

  • the water circulation system;
  • the number of swimmers in the pool at any given time that provide mechanical mixing of the water and the air;
  • the presence of water or spray features that accomplish effective mixing of water and air; and
  • the characteristics of the air handling system.

Swimmers and water or spray features are more effective than routine water circulation at transferring compounds from liquid to gas phase. This is one of the reasons why the concentration of volatile compounds in the air is often higher right after an increase in the number of swimmers.

 Health symptoms associated with volatile disinfection byproducts

Breathing in volatile compounds can lead to a variety of health issues—not only for swimmers, but also for spectators, or those working at the facility. These may include:

  • respiratory symptoms such as nasal irritation, coughing, and wheezing;
  • shortness of breath and chest tightness;
  • sore throat;
  • asthma attacks;
  • red, stinging eyes; and
  • skin irritation and rashes.
Water or spray features effectively mix water and air in an indoor pool.
Water or spray features effectively mix water and air in an indoor pool.

These health issues can be particularly harmful to children, people with existing respiratory illnesses, or others who are immunocompromised, with resulting visits to emergency rooms and intensive care units.

The design and operation of indoor pool water treatment and air handling systems should provide a healthy and safe environment for the swimmers, workers, and spectators. However, existing design and operational criteria are not keeping up with current use, activities, aquatic features, and building construction requirements to provide this healthy environment. More research is needed to determine how to best prevent these types of adverse health events from occurring at indoor aquatic facilities.

The study: Monitoring and control of gas-phase trichloramine in indoor pool facilities

The Council for the Model Aquatic Health Code (CMAHC) has partnered with Purdue University and Michigan State University to conduct a study that will identify operating conditions for indoor pools that will help prevent the buildup of volatile compounds in the air and lead to air quality measurements known to be safe for swimmers and patrons. CMAHC’s indoor aquatic facility ventilation design and air quality ad hoc committee, comprised of leaders in the public health and the aquatic industry, saw a widening gap between existing ventilation standards in indoor aquatic facilities and growing aquatic needs. The committee is working with Ernest R. Blatchley III, Lee A. Rieth, professor in environmental engineering at Purdue University and principal investigator of the study, to collect data that will illustrate relationships between the operational features of indoor pool facilities and air quality.

Specifically, the study will focus on identifying design and operational characteristics that will allow indoor pools to stay at or below the safe concentrations of trichloramine in the air. The physical and chemical characteristics of trichloramine dictate it will behave similarly to other volatile compounds in indoor aquatic facilities. Therefore, it is likely the conditions that lead to effective control of trichloramine will also effectively control other volatile compounds.

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