A study has found that urinating in swimming pools is more than just unsanitary - it can also produce poisonous chemicals when urine and chlorine react.
One in five Americans have admitted to relieving themselves in swimming pools, while US Olympic swimmer Michael Phelps described peeing in a pool as "kind of a normal thing to do for swimmers" because chlorine destroys bacteria in water
But now research is suggesting it could actually be a health hazard (as well as disgusting).
Researchers from the China Agricultural University and Purdue University found that when uric acid, a compound in urine, and chlorine mix it can produce substances that could cause health problems - namely trichloramine and cyanogen chloride.
The latter is listed as a classified substance under the US Chemical Weapons Convention because it could potentially be used in chemical warfare.
Trichloramine has been linked to breathing problems and cyanogen chloride can affect the lungs, heart and nervous system.
Scientists have not yet identified all of the specific ingredients in sweat and urine that could cause these potentially harmful compounds to form.
A study published in the journal of Environmental Science and Technology looked at what happens when urine reacts with chlorine.
Lead authors Jing Li and Ernest Blatchley found that when they mixed uric acid and chlorine both of the potentially harmful compounds formed within an hour. They calculated that more than 90 per cent of the compound in pools comes from urine.
Uric acid accounted for 24 to 68 percent of the byproduct cyanogen chloride in the pool water samples.
According to The Atlantic, a person leaves about 30 to 80 millilitres of urine behind each time they visit a swimming pool.
Mr Blatchley said that if a lot of people are in a swimming pool at one time and urinate in the pool, there is the potential for a lot of cyanogen chloride to form and deplete the chlorine in the pool.
Cyanogen chloride would normally decay rapidly, but less chlorine could allow it to stay present in the water for longer.
However the amounts of cyanogen chloride generated are highly unlikely to meet the World Health Organisation's 'danger zone' of 70 micrograms per litre.
Ars Technica were also quick to point out that dying of cyanogen chloride poisoning originating from chlorine in water and urine is extremely unlikely - think three million swimmers urinating in one very chlorinated pool.
The authors concluded that swimmers might want to consider peeing outside of the water to improve swimming conditions.
“Given that uric acid introduction to pools is attributable to urination, a voluntary action for most swimmers, these findings indicate important benefits to pool water and air chemistry that could result from improved hygiene habits on the part of swimmers.”