BI Answers: Is it OK to pee in the ocean?
If you’ve been to the beach this summer, chances are you probably had to pee, decided not to get out of the water, and just peed in the ocean.
Don’t worry, you’re not alone. Two-thirds of people surveyed by Proctor & Gamble (the company that makes Charmin toilet paper) said that they have peed in the ocean and almost half said they had done it more than once.
And after doing the deed, you may have had second thoughts because, at some point during your childhood, someone probably told you that pee attracts sharks. And you kind of believed them.
Does pee attract sharks?
We asked David Shiffman, a marine biologist who studies shark feed and conservation (also known by his Twitter handle @WhySharksMatter), about whether or not sharks are attracted to human urine.
His response was pretty blunt.
We were hard pressed to find academic research papers on the subject (although there are a whole bunch of papers written about shark kidneys), but we found some other accounts that support Shiffman’s statement.
Vic Peddemores, senior research scientist, from the New South Wales Department of Fisheries in Australia told The Sydney Morning Herald: “I would have been dead a long time ago — there is no evidence that urine attracts sharks. I have been in the water close to large sharks like a tiger shark and have [p]eed, and it makes no difference.”
National Geographic ran a series of experiments with sharks and divers to debunk several shark-related myths. They placed 2 divers in water, one holding a bottle of urine that slowly seeped into the water and another diver, in a separate area, without any urine:
Experiment Result: No reaction from sharks
We couldn’t find peer-reviewed evidence, but it seems that when it comes to peeing in the water, you are probably fine as far as sharks are concerned.
Does pee pollute the ocean?
According to a recent video produced by American Chemical Society, it is A-OK to pee in the ocean.
Here’s the quick chemistry lesson:
Human urine is 95 per cent water. It also contains sodium (Na) and chloride (CL) ions — these are the same components that make up regular table salt (NaCL).
The ocean too is made up mostly of water (more than 96 per cent) and an even higher concentration of sodium and chloride ions.
Both the ocean and urine also contain potassium (K).
One compound found in urine that is not found in the ocean is urea. It is an carbon-based compound that helps the body rid itself of nitrogen. But, as the video notes, the nitrogen in urea can combine ocean water to produce ammonium, a compound that acts as food for ocean plant life. You might even say that peeing in the ocean is actually GOOD for the plants and animals there.
Another point made in the video is that all of the animals that live in the ocean also pee in the ocean, including fin whales, which produce 250 gallons of pee each day. Even if every human on earth peed in the ocean at the same time, it would only create a tiny concentration of urea.
What about in the pool?
There are chemical reasons *not* to pee in the pool, according to a study published in Environmental Science and Technology. As Professor Ernest Blatchley of the Purdue University Engineering department explains in another YouTube video produced by the American Chemical Society, uric acid, which is found in human urine, interacts with chlorine (a disinfectant found in most pools) to create two dangerous compounds: cyanogen chloride and trichloramine. There is a little bit of evidence to show that these two compounds may contribute to respiratory problems and skin irritation in swimmers.
Though, a very thorough analysis from Ars Technica throws much of that chemistry out the window: The chemicals in the pool would have to be a much higher concentration — which would be very dangerous in itself — to make the reaction happen at a high enough level to make enough toxic byproducts that it would be dangerous. According to Casey Johnston:
In the end, we need a pool that is two parts water to one part chlorine and would probably burn the eyeballs out of your sockets and make your skin peel away from your bones (this calls for a pool boy who can only be criminally sadistic). If you and three million other people could get at this pool and unload your pee into it before your bodies melted, before the crowd crushed you to death, and before you drowned from the massive tidal wave of pee… yes, you could feasibly die of cyanogen chloride poisoning originating from chlorinated water and pee.
Where not to pee
Coral reefs! As with the relationship between human urine and sharks, it is difficult to find academic research on the impact of human urine on coral reefs. However, there is anecdotal evidence to suggest that it may be an issue. CNN interviewed Paul Sanchez-Navarro, Director of Centro Ecologico Akumal, an organisation that monitors the impact of development on the reefs that thrive off the coast of Mexico’s Quintana Roo province:
Pollution spilled into the sea by the thousands of hotels on the Mexican Riviera is “stressing” the coral reefs. “There are a lot of nutrients going into the ground water caused by treated water from the hotels and municipal waste water treatment plants,” [Sanchez-Navarro] explains. “They inject the water into the ground and that makes its way into the aquifer… We’ve found way too many nutrients — nitrates and phosphates — and that comes from human waste, mostly urine.” The result, says Sanchez-Navarro, is increased algae growth that effectively suffocates the coral, impeding its growth.
Small bodies of water! In 2012, TIME reported that a lake in northern Germany had been closed due to an “an algae bloom that poisoned over 500 fish,” which some researchers thought was due to “a significant amount of human urine [in the lake].”
The bottom line? Pee in the ocean (but not on coral reefs) and it’s unlikely that sharks will bother you. But don’t pee in freshwater or small bodies of water because anecdotally, bad things might happen.
This post is part of a continuing series that answers all of your “why” questions related to science. Have your own question? Email [email protected] with the subject line “Q&A”; tweet your question to @BI_Science; or post to our Facebook page.