A Canadian study has revealed some swimming pools can contain up to 75 litres of urine.

Researchers from the University of Alberta analysed more than 250 samples from 31 pools and tubs in two Canadian cities.

This was done by identifying the synthetic sweetener acesulfame-K (ACE) – which is widely consumed - and examining its excretion in urine.

The study say this makes it an ideal urinary marker. The ACE sweetener was present in all samples.

Artificial sweeteners are consumed in large quantities because of their negligible calories and low impact on blood sugar.

ACE, used in prepackaged foods, is not metabolised by humans and is completely absorbed and excreted in urine.

Researchers examined the levels of ACE over three weeks in two different sized pools - 11,0000 and 22,0000 gallons.

They used the average ACE level to estimate the urine present as 30 litres and 75 litres respectively.

The average urine excretion per swimmer in pools is approximately 70 mL.

Although considered a taboo, 19% of adults have admitted to having urinated in a swimming pool at least once.

Researchers say: “Human urinary input into swimming pools is a public health concern, although urine itself is sterile.

"Urine contains many nitrogenous compounds such as urea, ammonia, amino acids, and creatinine.

"These compounds can react with disinfectants (e.g., chlorine) in swimming pools to form DBPs (disinfection byproducts), including trihalomethanes, haloacetic acids, haloamines, and halonitromethanes."

The study has been published in the journal Environmental Science and Technology Letters.