How much bisi does a swimming pool actually have?

Bisi.

What a wonderfully simple word for such a complicated subject. Because bisi, or urine, consists of many different substances. 95 percent is water, five percent is waste products that are filtered out of the blood by the kidneys, such as electrolytes, urea, creatinine, uric acid, and so on. Up to 3000 different chemicals can be detected in the urine.

Its complex composition is responsible for making scientific measurements of urine in swimming pool water difficult. To make matters worse, many of these react with the chemicals added to pool water to disinfect it. This creates so-called DNP: disinfection byproducts. There are hundreds again. What remains after decomposition of the urine no longer differs from residual products from other biological sources.

Bisi is not so easy to spot in the pool. Pee pee watchers can breathe a sigh of relief: For the same reasons, the discoloring panacea that should unmask pee pee (unfortunately) does not exist.

However, in 2017, Canadian researchers led by Professor Xing-Fang Li of the University of Alberta achieved a breakthrough in pool bisi research. They measured levels of the artificial sweetener acesulfame-K. Acesulfame-K is found in many processed foods and is excreted in the urine. The good thing about “Ace-K”: it does not react with chlorine. Li’s team was looking for this substance. They collected 250 samples from 31 different pools in two Canadian cities. They examined two pools over a longer period of time. The swimming pool with 830,000 liters of water contained an average of 75 liters of urine. That means: about 0.09 promille of the swimming pool water is bisi. We laymen can do little with those figures. Hence the conversion to drops. That is almost two drops of urine per liter of water (20,000 drops).

In half the pool (415,000 litres), the average urine concentration was even lower (0.07 per mil).

Lindsay K. Jmaiff Blackstock, the co-author of the study, which was published in “Environmental Science & Technology Letters,” told CNN that these results don’t apply to all pools. The urine content depends on many different factors. Among other things, how many people bathe in it and how often the water is changed.

Like many other experts, she recommends not peeing in the pool. Because back to the disinfection by-products, the DNPs: of the many hundreds of DNPs produced by urine in the water, not all are harmless. Some are suspected of causing asthma. Others have been found to be carcinogenic.

Therefore: Stop peeing in the pool!