Is your public pool free from urine?

Some people believe that the answer to the question posted in the title of the blog post is no. Now there is evidence to back it up. The study profiled here also gives an indication of how serious the problem of urine in the pool might be.


The study, conducted by a team of Canadian researchers, did not measure urine in pool water directly. The research team collected 250 samples from 31 pools and tubs at hotels and recreation facilities in two Canadian cities. They measured the amount of a sweetener called acesulfame-K (ACE), which is widely consumed and is completely excreted into urine.

Concentrations of ACE in the samples range from 30 to 7110 nanograms per liter (ng/L) and are up to 570 times greater than in tap water. In particular, the research team determined the levels of ACE over a 3-week period in two pools (110,000 and 220,000 U.S. gallons) and then used the ACE levels to estimate the urine concentration to be 30 and 75 liters, respectively.

Thus the researchers found that the 220,000-gallon public commercial-size pool contained about 75 liters (about 20 gallons). This estimate would translate to roughly 2.7 gallons in a typical residential pool (20 feet by 40 feet by 5 feet). So there may be close to 3 gallons of urine in a typical residential pool.

The sweetener is widely consumed in North America. ACE has been detected in other places too (e.g. China). The study seems to confirm some people’s suspicion that people are peeing in swimming pools. The peeing is frequent enough for ACE to show up in sufficient quantity.

Urine in swimming pools is obviously gross. What are the potential health hazards? Ever wonder why there is a sharp odor of chlorine after the pool has been used by a lot of people? When chlorine are mixed with urine, a host of potentially toxic compounds called disinfection byproducts are created. One such byproduct is chloramines, which give out the sharp odor that people may mistake for just the smell of chlorine. The other byproducts are more harmful, e.g. cyanogen chloride, which is classified as a chemical warfare agent, and nitrosamines, which can cause cancer. The study does not have evidence to say whether the nitrosamine levels in pools increase cancer risk. Nonetheless, this is still a striking finding.

The potential health hazards are compounded by the fact that it is not uncommon for pool water to go unchanged for years. When that is the case, the pool operator simply adds more water and more chlorine to disinfect. Such practice will lead to formation of more disinfection byproducts.

Here’s a reporting of the study from The study, published in Environmental Science & Technology Letters, was conducted by a research team from University of Alberta. Here’s a link to the actual paper.

The lead researcher in the study said that she is a regular swimmer and that the study is not meant to scare people away from a healthy activity. The intention is to promote public awareness of the potential hazards of urine in the pool and to promote best practices in using swimming pools.

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