Feature Story

March 2017

Study Confirms: People Pee in Pools

By Chandler Garland

A doctoral student of analytical and environmental toxicology, Lindsay Blackstock, from the University of Alberta recently published findings that show people do indeed pee in public pools. Blackstock was able to determine signs of urine from trace amounts of acesulfame potassium in the water. This chemical compound is found in most artificial sweeteners.

"These sweeteners are consumed widely by the general public in processed foods, they were extremely stable and we don't metabolize them, so they pass through our bodies and are not completely broken down," said Blackstock.

In the first phase of the study, which was published in the journal Environmental Science & Technology Letters, Blackstock and her supervisor, Professor Xiang-Fang Li, tested samples from 31 pools and hot tubs in two Canadian cities. They found elevated levels of the sweetener in all cases. Concentrations ranged from 30 to 7,110 nanograms per liter, which is 570 times the amount found in the input water. They also found that the level of organic carbon dissolved in the water was greater than the input for all pools studied.

In the next phase, they tracked level of urine in two different-sized public pools—one 830,000 liters and the other 420,000 liters (110,000 and 220,000 gallons, respectively)—for three weeks. The researchers estimated that swimmers deposited 75 liters of urine into the large pool and 30 liters into the smaller pool.

"We wanted to focus on urine because where there is a fecal incident at a swimming pool, everybody knows about it. The pool has to be evacuated and then shocked," said Blackstock. "On the other hand, urination in a pool really goes unnoticed, and a lot of people might be doing it."

However, there is no feasible way to determine how many people urinate in pools.

Though urine is largely sterile, the combination of the nitrogen components in urine with the chlorine disinfectant used in pools can create chloramine byproducts, which are harmful respiratory aggregates. The most dangerous of these byproducts is trichloramine. This nitrogen-chlorine compound is the most volatile of similar substances and is easily released into the air. Vaporization of the chemical depends on the degree of chlorination, water temperature, circulation, ventilation and the amount of contamination.

Although few epidemiological surveys have examined the effects of exposure to trichloramines, long-term exposure to this chemical is linked to eye irritation and upper-respiratory problems up to and including chronic asthma, hoarseness, sinusitis and worsened existing respiratory diseases. These problems mostly affect professional swimmers and pool workers, but can pose risks to recreational swimmers.

Blackstock said that the study was not meant to criticize or demonize disinfectants in pools or persuade people to stop swimming. Swimming is an excellent form of exercise, which has health benefits that far outweigh the risks. "Our main message is about public health and good swimming hygiene. Peeing in the pool is a simple problem to fix—just don't do it."