Artificial sweeteners help monitor the amount of urine in pools

Artificial sweeteners are common in food and only enter pools from human waste.

Michael Phelps said everyone does it, so it should come as no surprise that researchers found pools contain pee. The interesting part it is how the team reached this conclusion: artificial sweeteners. Artificial sweeteners, which aren’t metabolized by the body, have unique characteristics that make them a great indicator of the effects of human waste on bodies of water, like pools and hot tubs. From the sweetener measurements they took, the researchers estimated that two 110,000- and 220,000-gallon pools had 30 and 75 liters of urine in them, respectively.

We spoke to Lindsay Blackstock from the University of Alberta about the study.

ResearchGate: What motivated this study?

Lindsay Blackstock: Artificial sweeteners have been identified as emerging environmental contaminants, as they have been found pervasively in environmental water bodies around the globe. In general, artificial sweeteners have unique characteristics: they are highly stable, consumed widely by the public, are not metabolized by the human body, and only enter the environment from human waste. This makes artificial sweeteners an effective indicator of human waste impact in environmental water bodies. We searched the literature and found that this concept had not yet been applied to swimming pools or hot tubs; furthermore, we could not find any existing studies that investigated the occurrence of any artificial sweetener in swimming pools or hot tubs.

RG: What exactly were you measuring?

Blackstock: We wanted to determine if the strategy of using artificial sweeteners to indicate human waste in environmental water bodies could be applied to recreational water bodies. We chose acesulfame potassium (ACE) as our target artificial sweetener. ACE is commonly added to many prepackaged foods and is therefore consumed widely among the general public. ACE is not metabolized by the human body and excreted exclusively in urine. Lastly, ACE is stable among large temperature and pH ranges. It is for these reasons we felt ACE would be an ideal indicator of urine and would most likely be detectable in pools and hot tubs.

RG: What are the health concerns associated with urine in pools?

Blackstock: First and foremost, we want to emphasize that the health benefits from maintaining a healthy lifestyle through swimming far exceed the potential risks associated with urine in swimming pools and hot tubs. Additionally, we want to remind the public that disinfection of recreational waters is essential in preventing the spread of waterborne illness.

Urine and sweat are some of the main contributors of nitrogenous compounds in swimming pools and hot tubs. These nitrogenous compounds have been found to react with disinfectants, like chlorine, to form disinfection byproducts. Exposure to volatile disinfection byproducts can lead to eye and respiratory irritation and has been linked to asthma in professional swimmers and pool workers. An increase in the number of swimmers has been found to be associated with increased formation of disinfection byproducts. The amount of exposure varies based on pool use, pool volume, and facility ventilation and maintenance practices.

RG: Why is it so difficult to monitor the amount of urine in pools?

Blackstock: The motivation to investigate ACE as an indicator of urine in swimming pools and hot tubs was not because there are no existing alternative methods. Urine input into pools has been estimated using potassium. Nitrogen in pools can be difficult to monitor, because it can react with disinfectants to form volatile compounds that can escape into the air where they can no longer be measured in a pool water sample.

RG: What did you discover as a result of this study?

Blackstock:  First, we had to determine if ACE was detectable in swimming pools and hot tubs. We collected water samples from 31 different swimming pools and hot tubs from two Canadian cities. We found ACE was present in 100 percent of the pools and hot tubs we sampled. Concentrations ranged from 30-7110 ng/L, up to 570 fold greater than the ACE present in the corresponding input tap water samples. Next, we wanted to investigate the stability of ACE in pools over time. After monitoring two different sized pools for three weeks, we found the average ACE concentration in the 110,000- and 220,000-gallon pools to be 156 and 210 ng/L, respectively. We determined the average ACE concentration in 20 Canadian urine samples to be 2360 ng/mL. Using the average concentration of ACE in the swimming pools and urine, along with the approximate pool volumes, we estimated the urine in the small and large pool to be 30 and 75 liters, respectively.

RG: How can we discourage people from urinating in the pools?

Blackstock: The best way to discourage people from urinating in pools is public education regarding appropriate swimming hygiene practices. While urine is commonly considered to be sterile it does not make it okay to urinate in the pool just because it may go unnoticed. Reducing the input of nitrogenous compounds from bodily fluids into swimming pools and hot tubs will reduce the amount of irritating disinfection byproducts that may be formed.

RG: What do you recommend for people who regularly swim regularly to avoid health issues?

Blackstock: We commend regular swimmers for their commitment to a healthy lifestyle. We recommend that all pool users should rinse off excess personal care products in the provided showers before entering public pools. Additionally, we should all be considerate of others and make sure to exit the pool to use the restroom.

Featured image courtesy of Cade Buchanan.