BATHER LOAD, UREA AND DBPSThis chart shows

urea concentration before and during the NCAA Women’s

Swimming Championships last March. The data on the right

illustrates the effects of a heavy bather load on urea composition.

Urea is the dominant form of organic nitrogen in human urine and

sweat, and as such, it is the greatest contributor to organic-N in

pools.  Urea reacts with chlorine to generate nitrogen

trichloride (aka trichloramine), which is largely responsible for

the “chlorine” odor that people associate with

(chlorinated) pools, and is a fairly powerful irritant of

respiratory tissues, eyes, etc.
BATHER LOAD, UREA AND DBPSThis chart shows urea concentration before and during the NCAA Women’s Swimming Championships last March. The data on the right illustrates the effects of a heavy bather load on urea composition. Urea is the dominant form of organic nitrogen in human urine and sweat, and as such, it is the greatest contributor to organic-N in pools.  Urea reacts with chlorine to generate nitrogen trichloride (aka trichloramine), which is largely responsible for the “chlorine” odor that people associate with (chlorinated) pools, and is a fairly powerful irritant of respiratory tissues, eyes, etc.

Water in swimming pools, waterparks, spas and sprayparks (together referred to here for simplicity as “pools”) is disinfected to reduce the risk of illness from contact with various pathogens that are brought into the water. These pathogens are mostly introduced into pool water by swimmers themselves from body fluids and fecal matter.

The pathogens include bacteria, viruses and protozoa. Reported illnesses include skin rashes, eye, ear and respiratory infections, nausea, cramps, fever, body aches, fatigue, vomiting and diarrhea. Though it is rare, pool pathogens can even cause death.

In any given year, hundreds to thousands of people report illnesses associated with pool pathogen exposures. Clearly, disinfection to inactivate pool pathogens is essential to the health of swimmers.

Disinfectants not only kill pathogens but also react with substances such as organic matter already in the water, producing chemicals referred to as disinfection byproducts, or DBPs. The specific DBPs formed depend on factors such as the type of disinfectant used and the chemicals already present in the pool. Chemists have been able to analyze hundreds of DBPs in pool water and have shed light on the complexity of the chemical mixtures in pools.

People who swim, play or even stay at poolside are exposed to DBPs because DBPs are not only in the water itself, but also in the air near swimming pools. People are exposed to DBPs from inhaling volatile DBPs, ingesting DBPs when swallowing small amounts of water and by skin contact with pool water. While most of the attention has been on DBPs formed from chlorine-based disinfectants, simply switching to another type of disinfectant will not prevent DBP formation because all disinfectants produce DBPs — it is just the types and relative amounts of DBPs that change. Unfortunately, compared with chlorine, we know relatively little about DBPs from other disinfectants such as bromine, ozone, copper/silver and UV disinfection.

So why should we care about DBPs? Over the past 1½ decades, many scientists have been conducting studies that have looked for links, or associations, between exposure to DBPs and adverse health effects. The results of these studies have caused concern among swimmers and generated considerable media attention. What have these studies found?

Studies conducted in the 1990s by a research group in Belgium first reported associations between infant and childhood exposure to DBPs in pools and allergic illness, pulmonary integrity and asthma. These studies brought attention to the issue of childhood exposure to DBPs at pools and possible adverse health effects, which stimulated research on this topic by other researchers. However, several newer large studies have not found associations between pool attendance and childhood asthma.

Research on this topic continues. More recently, researchers have begun to examine whether exposure to DBPs at pools may be linked to development of bladder cancer, but as of now, there are no definitive answers to this question.

While scientists have not yet been able to completely answer questions about DBPs and health, we do know there are ways to reduce DBP exposures to swimmers now, while at the same time ensuring that pools are properly disinfected.

What can be done to simultaneously keep pools disinfected and reduce DBP exposure? An important first step is to make sure that pool operators and swimmers understand the link between their actions at pools and the formation of DBPs. Here are some facts and tips:

Fact: Pool operators are responsible for adding disinfectants (for example, chlorine) to pools and for maintaining appropriate disinfectant concentrations in pool water. Most of the organic compounds that react with chlorine (and other disinfectants) to produce DBPs are introduced by swimmers.

Tip: Pool operators can help keep DBP formation to a minimum by taking certain precautions, such as ensuring they understand how to properly use disinfectants (for example, maintaining appropriate disinfectant concentrations in a pool); obtaining training and national certification; improving their

record-keeping on pool maintenance and their pool quality monitoring. They can also provide opportunities for bathroom breaks (for example, closing pools for brief periods every hour) and working to educate swimmers on the importance of showering.

Fact: Urine and sweat in pool water create several problems. These body fluids react with disinfectants, leading to DBP production and disinfectant usage. Such fluids contain nitrogen, which in combination with disinfectants, produce DBPs that are thought to be responsible for many reported health effects at pools.

Contrary to popular belief, most body fluids are not sterile, and can introduce pathogens to the water, again meaning more disinfectant and more DBPs.

Tip: The public (including recreational swimmers and competitive swimmers) must no longer accept poor pool hygiene, in particular the notion that urinating in pools is OK. According to a survey conducted by the Water Quality and Health Council, one in five swimmers admits to “peeing” in the pool. Swimmers, coaches and lifeguards must be better educated on the importance of bathroom breaks.

Fact: Not only urine, but skin cells, residual stool, sweat and personal care products all react with disinfectant to produce DBPs and require the use of greater amounts of disinfectant. According to the same WQHC survey, about one-third of swimmers pass the shower without stopping, and three-quarters say their fellow swimmers fail to shower before swimming.

Tip: Swimmers must be better educated about showering before entering pools. In addition, pools can be designed to increase the likelihood that swimmers will shower before swimming.

The science of pools and DBPs is advancing and the aquatics industry needs to be aware of evolving research on DBPs and health so that it is prepared to answer questions from the swimming public and the media.

There is also a dearth of support for essential research on DBP formation and exposure. The industry needs to support practical research on this topic.

At a recent workshop held during the 2010 World Aquatic Health Conference, a research agenda was developed that would address critical gaps in our understanding of DBP formation and exposure.

For information on how you can help, please contact Ann Mason, managing director, Research Foundation for Health and Environmental Effects amason@rfhee.org, or Thomas Lachocki, chief executive officer, National Swimming Pool Foundation tom.lachocki@nspf.org.