Quirks & Quarks

Dear Canada, you are peeing in the pool and we have proof

An artificial sweetener provides evidence that we go wee in the pool.
Lesson one - don't pee in the pool. ( U.S. Air Force photo by Senior Airman David L. Minor)

Artificial sweeteners, and one in particular, are found in many of the foods we eat, especially low-calorie treats. A recent study by Lindsay Blackstock, a Phd student in Analytical & Environmental Toxicology at the University of Alberta focused on acesulfame potassium (ACE) as a way of measuring the amount of urine in swimming pools and hot tubs.

The following interview has been condensed and edited for clarity.   

Bob McDonald : No one's surprised to hear that people pee in pools. Why did you want to know how much is actually in the water?

Lindsay Blackstock: We wanted to apply this concept of using an artificial sweetener as an indicator of urine in recreational waters. So this concept's been applied before for environmental water bodies -- rivers, lakes, groundwater. The presence of those sweeteners in different water types have given researchers information that those waters could be impacted by human waste.

BM: Well tell me about these sweeteners. How are they an indicator of how much pee is in water?

LB: Artificial sweeteners essentially pass through our body unchanged. We don't metabolize them at all. That makes them really good indicators of human waste. So we chose acesulfame potassium — I'm going to call it "ACE" for short — in particular because of its stability, and also because it's excreted exclusively in urine. So we thought that would be the best sweetener to look at in swimming pools and hot tubs.

Now this sweetener has been found in processed baked goods, different drinks and many other things you might not expect if you are getting a low-calorie food option. It might be in there. It's also a flavouring agent common in baking mixes or pudding mixes, for example.

BM: Well, tell me about your experiment. How did you use the sweetener to find pee in pools?

LB: The first thing we had to do was collect samples from as many willing facilities that have swimming pools and hot tubs. We collected 29 different hot tub and swimming pool samples from two Canadian cities, and we analyzed those samples and found the occurrence of this sweetener in 100 per cent of the samples.

BM: Boy! So how much urine does that represent in the pool?

LB: Right. So we looked at two different sized swimming pools, one of which was about a third of a size of an Olympic size swimming pool. So around 840,000 litres and the second smaller pool was half that size. And we monitor the concentration of the sweetener over three weeks. We also looked at 20 different Canadian urine samples, mixed them all together, and measured the average concentration of the sweetener in urine. Once we had those two values, and we also knew the volumes of the pools, we were able to estimate the volume of urine required to read to the concentration of sweeteners that we found.

BM: And what did you come up with?

LB:  So in the smaller pool we estimated 30 litres of urine. And in this larger pool 75 litres of urine.

BM: Holy smokes. That sounds like a lot. What is that compared to the volume of the pool?

LB: Incredibly small. Keep in mind that's 75 litres in 840,000 litres. And again we weren't actually detecting urine. We were detecting the sweetener. And to put that concentration into perspective, we were detecting parts per trillion.

BM: OK, but you're still talking about a considerable amount of urine to do that. Were you surprised by your findings?

LB: We were actually quite surprised that people were indeed peeing in the pools, even though it's a taboo subject. Clearly people must be peeing for this artificial sweetener to be showing up.

BM: Now you say that you also looked at hot tubs. How do they compare?

LB: We found the concentration to be much higher than what was in the swimming pools. So to give a little bit of perspective, that doesn't necessarily mean there's more urine, but each urination event would have a much bigger impact on the concentration because it would be diluted in a much smaller volume of water.

BM: What are the real health implications of having urine in pools?

LB: So urine itself is essentially considered to be sterile. Not a big concern, but there are a few minor risks inherent to the disinfection process of the compounds present in urine. So they can react with chlorine, for example, to form disinfection byproducts like trichloramine. They're associated with eye irritation and irritation to the lungs as well, so some people might find after they go swimming that they get red eyes and some research has indicated that trichloramine could be the cause of that.

BM: Are you more afraid of swimming pools?

LB: No definitely not. We're really not worried about it at all. It's really great to swim and keep healthy that way.

BM: So the bottom line here is keep the pee out of the pool.

LB: Absolutely. We want to reiterate the benefits of maintaining a healthy lifestyle through swimming far outweigh any of the potential risks associated with disinfection byproducts that can be formed if you go swimming one time.

Research paper in Environmental Science & Technology Letters:  Sweetened Swimming Pools and Hot Tubs