How much pee is in your pool? It’s a question that’s long concerned scientists and swimmers alike. And now, reports Steph Yin for The New York Times, there’s a new way to find out using artificial sweetener.

In a paper published in the journal Environmental Science & Technology Letters, a team of Canadian researchers reveals that an artificial sweetener called acesulfame potassium can help estimate the amount of urine in a body of water.

The idea is simple: Since the human body can’t metabolize the sweetener, it shows up in the urine. And since human urine shows up in pools so pervasively, it’s a great proxy for pee.

The sweet-tart additive is known as “non-nutritive,” meaning it doesn’t add any calories to food. So it’s become increasingly popular since it was approved by the FDA in 1988. Environmental scientist Bill Chameides calls it “the most-used sweetener you’ve never heard of,” and it can be found in everything from Kool-Aid to soda and even prescription meds.

When the scientists went looking for it in pools in Canadian cities, they found the substance in every single one they studied. They used a method called high-performance liquid chromatography to separate out all of the chemical components in the liquid and then used mass spectrometry to figure out how much acesulfame potassium was in each gallon of water. Based on the average concentration of that artificial sweetener in urine and the volume of each pool, they could finally calculated the amount of pee present.

The results were…interesting. Though the amounts of urine varied by pool, there was a lot of pee. One 110,000-gallon swimming pool had 7.9 gallons of urine; another 220,000-gallon pool had nearly 20 gallons.

That number might seem alarming—especially given the fact that pool pee can cause both lung problems and irritated eyes when it mixes with chlorine. But a less horrifying way to view it is by percentage; the concentrations cited above both come in at less than a whopping 0.01 percent.

Still, that’s no excuse to skip the bathroom—and according to a 2012 survey, 19 percent of swimmers are guilty of contributing to those pee percentages. Artificial sweetener might help scientists figure out how much urine is inside a public pool, but it would be even sweeter if more could practice basic hygiene and refrain from peeing in the pool.