Detecting Pee in a Pool Thanks to Sweet Science

shutterstock_138187181We can’t be the only ones looking forward to taking a dip in the swimming pool this summer while enjoying an ice cold drink. Fingers crossed, your swimming pool of choice is urine free, but if we are being honest, that’s likely not the reality. Luckily, the sanitation of pools can be controlled with chemicals such as chlorine. As a testing lab, we remain consistently curious about how analytical science can be used to produce answers to nagging questions. Let’s take the question of pee in the pool—how much is there? How would you even begin to assess this?

Foundationally, it is worth considering how urine would even be detected since the chemicals used to make the pool sanitary destroy common compounds found in urine, urea for example. Scientists at the University of Alberta decided to tackle this analytical challenge and come up with a way to quantify urine in the pool. They started with a widely consumed compound, acesulfame-K (ACE).

ACE is present in common artificial sweeteners. When ACE is consumed it enters the stomach and the rest of the food gets digested. However, ACE leaves your stomach and passes through your blood unchanged. From there, it gets filtered into the kidneys, still unchanged. Next, it enters the urine stream, (can you guess what comes next?) still unchanged. If the person happens to be in a pool when they urinate (yes, that is so gross), it enters the pool still unchanged.  Based on this knowledge, researchers discovered that if they could test for the presence of ACE in a swimming pool, they could extrapolate the amount of urine present based on other research efforts done to establish the average amount of ACE in urine.

The amount of ACE within swimming pools is measured on the nanograms per liter order, which means roughly a part per trillion level. In order to accomplish analysis this sensitive an incredible instrument was required—one we are fortunate to have on site—Liquid Chromatography/Mass Spectrometry (LC/MS). LC/MS has extreme sensitivity and is suited for an analysis of this nature.

Chromatography, in general, is the right choice when trying to separate out mixtures, like pool water full of chemicals and possibly urine. LC-MS rather than Gas Chromatography-Mass Spectrometry (GC-MS) was used because ACE is a non-volatile compound. In order to analyze a sample with GC-MS it must be heated and the volatiles are then analyzed, ACE doesn’t have a boiling point, it degrades when temperatures are high enough. Mass-spectrometry is what allows for the identification of the individual components within a mixture of compounds.

For this research, a controlled study was not conducted. The lack of a controlled study was one known limitation and resulted in conducting this research based on a variety of assumptions. However, can you imagine what a controlled study related to urine in pools would be like? Potentially lots of people drinking lots of diet drinks and then taking a dip in the pool. Science can be strange, that’s for sure.

A vulnerability of this study is that ACE in a swimming pool could be the result of something other than urine. For example, if someone accidentally dropped a diet soda into the pool it would immediately give false-positive results for copious amounts of urine. Based on the calculations and information provided in this study, if you dropped 8-ounces of soda in a pool it would give results of 56 liters or urine in the swimming pool.

So what can we conclude from this strangely fascinating scientific study? Many things! Once again, we are able to see the everyday application of specialized analytical techniques, like LC-MS. We are also struck by the curious minds that endeavored to measure urine in the swimming pool in the first place. We can conclude above all else, science is anything but dull.

5 Comments


  1. um, doesn’t this assume that only people consuming ACE will show positive results? what about all those kids who don’t drink diet drinks? this does not seem to be a very good predictor unless some sophisticated algorithm is incorporated.

    Reply

    1. Hi Ronald,

      Yes, you’re absolutely right with these questions. There are many factors to keep in consideration when pursuing valid data. We did have internal discussions about the limitations of this study based on the many assumptions made but felt there was still value in what these scientists accomplished. Admittedly, we also really liked this one because of the use of LC-MS. Since we just got this instrumentation it is heavy on our radar and this unique use piqued our attention. I still think it would be “interesting” to do a controlled study on this one.

      Thank you!

      Caitlyn

      Reply

  2. As a daily swimmer in a YMCA pool I have significant exposure to swimming in urine. I would be interested in the biostatistics of urine in pools as broken down into geographical regions, principal pool uses (fitness, children’s entertainment, education, therapy).
    I am also interested in knowing as much as possible about likely pathogens sourced from urine.
    I would be interested in a random sampling of pool water and LC/MS assessment of urine content
    FTW

    Reply

  3. I got hung up on the statement that ACE passes through the body unchanged. Does that mean you could pee in your coffee to sweeten it? That you would only need to use one packet of sweetener for a week if you just “recycled” it?

    Reply

    1. Hi Jeff,

      Great (and unique) question! Unfortunately, we aren’t too sure about an answer for that one. However, if you ever try to sweeten your coffee through that manner please let us know the results – hah! Stay curious!

      Best wishes,
      Ashlyn Davidson

      Reply

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