As disgusting as it is, we all know that when you go swimming there's a high chance that somebody's relieved themselves in the pool. Yack.
Now a new study has found that urine could be the least of your worries, as more harmful chemicals could be floating around in your local swimming haunt including insect repellant, caffeine and flame retardants.
All of these have the potential to be ingested by swimmers and pose a hazard to their health.
Previous research has shown that urine in pools can react with chlorine to create potentially hazardous chemicals.
Now, a study by Purdue University has revealed that chlorine could be reacting with body care products to create a similar effect.
Professor Ernest Blatchley from the Division of Environmental and Ecological Engineering said: "The motivation for examining pharmaceuticals and personal care products is that there is this unknown potential for them to bring about undesired or unexpected effects in an exposed population."
"There are literally thousands of chemicals from pharmaceuticals and personal care products that could be getting into swimming pool water."
Samples of water were taken from a variety of indoor swimming pools in the US.
Using a technique, which was developed by professor Ching-Hua Huang, of Georgia Institute of Technology, they were able to identify and quantify 32 pharmaceuticals and personal care products in water.
Out of the 32 chemicals investigated, researchers found that there were three which showed up more regularly.
These included Deet (which is found in insect repellants), caffeine and tri(2-chloroethyl)-phosphate (TCEP) - a type of flame retardant.
"Swimmers are exposed to chemicals through three different routes: You can inhale, you can ingest and it can go through your skin. So the exposure you receive in a swimming pool setting is potentially much more extensive than the exposure you would receive by just one route alone," Blatchley added:
He noted that he's unsure of what the consequences of this are for the human body.
The study is published in the journal Environmental Science and Technology Letters.
We don't know about you, but we're thinking it's time to ditch the swimming pool in favour of one of these...
[H/T Daily Mail]