Do you want to pee as soon as you enter the swimming pool? ! How much urine is there in the swimming pool?

This summer, the heat is unbearable all over the country, and swimming pools have become everyone’s “summer resort”. Have you gone swimming in a swimming pool?

Have you gone? Then answer the following question:

Do you always feel the urge to pee soon after entering a swimming pool? Even if you didn't drink water before entering the water, do you still feel this way soon after entering the swimming pool?

Don't deny it, when it comes to peeing in the pool, you are basically on the same level as "Flying Fish" Phelps, because he once admitted that he often pees in the pool, and so do his partners.

The Xicheng District Center for Disease Control and Prevention in Beijing conducted sanitary monitoring of swimming pools in Xicheng District for three consecutive years from 2016 to 2018. The results showed that the overall qualified rate of swimming pool water quality was 87.3%, and one of the main unqualified indicators was urea .

Image source: Journal of Environmental Health

However, it is really not your fault or your bladder's fault that you pee in the pool. It is just a physiological reaction .

It's all because of stress.

You may feel like peeing soon after entering the swimming pool. This somewhat embarrassing physiological phenomenon has a special name, called "Immersion Diuresis".

When we enter the swimming pool, in order to reduce oxygen consumption underwater, a diving reflex will occur (a series of physiological reactions stimulated when organisms are immersed in water to help improve diving). The diving reflex slows down our heartbeat, constricts blood vessels, and forces blood back into the heart.

As the heart fills with more and more blood, the pressure in the atria increases. The heart is forced to send a "cry for help" to the atrial volume receptors.

In order to lower blood pressure, the atrial volume receptors instruct the kidneys to convert part of the blood into urine. Because the atrial volume receptors are slow, you may feel the urge to urinate after being in the water for a while.

In addition, temperature is also an "accomplice" of urine . We know that the temperature of water in swimming pools is generally lower than our body temperature. When most of the human body enters the water, the blood vessels will contract due to the stimulation of cold water, and the amount of blood will decrease accordingly. In this way, there will be "extra" blood in the blood vessels, and the pressure receptors in the human body will also send signals to the kidneys to convert blood into urine.

In addition, there is also speculation that the sound of running water in the swimming pool may stimulate your urethral sphincter , making you want to "pee" involuntarily.

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How much urine is in the swimming pool?

Since everyone pees in the swimming pool, are you curious about how much urine is in the swimming pool? Professor Xingfang Li of the University of Alberta in Canada has the same problem as you. In order to find the answer to the question, she and her team conducted a study on the amount of urine in the swimming pool.

How to detect how much urine is in the swimming pool?

We know that 95% of human urine is water, and the remaining 5% is urea, inorganic salts and other substances. So, can we infer the amount of urine by the urea content in the swimming pool? The answer is no, because in addition to urine, there is also urea in human sweat . Obviously, the result obtained in this way is not very accurate.

So, Professor Li Xingfang chose acesulfame potassium. Acesulfame potassium, scientifically known as potassium acetylsulphonate, is an artificial sweetener that is widely found in beverages and foods. Yes, it is in your favorite Happy Fat House Water.

Artificial sweeteners are not metabolized and decomposed after entering the human body, but are excreted through urine. They are very stable in water and cannot be degraded. Therefore, acesulfame potassium can be used as a measure of urine content in swimming pools.

Professor Li Xingfang sampled swimming pools with capacities of 420,000 liters and 840,000 liters in a city in Canada, six times a day for three weeks.

The results showed that the concentration of acesulfame potassium in the water sample of the small swimming pool was 156 nanograms per liter, and the concentration of acesulfame potassium in the large swimming pool was 210 nanograms per liter, while the average concentration of acesulfame potassium in adult Canadian urine was 2.36 nanograms per liter. In other words, there were about 30 liters and 75 liters of urine in these two swimming pools!

Image source: Environmental Science and Technology

In a commercial swimming pool of about 800 cubic meters, the urine content is as high as 75 L! What is the concept of 75 L? It is equivalent to 140 bottles of 550 ml mineral water!!!

Now, let me tell you a cruel fact. The fresh smell you smell in the swimming pool is not just the smell of disinfectant. It is actually the "trichloramine" formed by the reaction of chlorine used in disinfectant and urea in the swimming pool. The stronger this "fresh" smell is, the more...

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Moreover, trichloramine may cause pink eye, diarrhea, otitis media, upper respiratory tract infection, etc. So, if you find your eyes are red after swimming, it is likely that trichloramine is to blame.

How to choose a clean swimming pool

What should you do if you want to swim in the summer but there is no swimming pool at home and you can only go to a swimming pool? Don't worry, just pay attention to the following points when choosing a swimming pool.

Check the health permit

Generally speaking, regular swimming pools have health licenses. The Regulations on Public Place Hygiene Management and Their Implementing Rules require that operators should hang the health licenses in a conspicuous place.

Look at the hygiene level

The public place health reputation level refers to the level of health supervision departments' comprehensive evaluation of the place's health facilities and health management, which can objectively reflect its health conditions. The higher the level, the more reliable the apparent health environment.

For example, grade A indicates excellent hygiene conditions and is accompanied by a smiley face logo; grade B indicates good hygiene conditions; grade C indicates average hygiene conditions and is accompanied by a crying expression logo.

Check swimming pool water quality

When choosing a swimming pool, pay attention to whether the pool water is clear, whether there are any floating objects, whether the color has changed, etc.

According to the requirements, swimming pools must conduct self-tests every four hours and be inspected by an agency every year. The self-test data and inspection reports must also be posted in a conspicuous place.

The weather is getting cooler, so friends who love swimming should hurry up and take advantage of the opportunity to have a swim. But remember, don’t pee secretly!

Review | Wu Xinsheng, Associate Chief Physician, Department of Gastroenterology

Source: Digital Beijing Science Center

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