In pseudo-scientific articles and posts with “interestingfacts ”you probably came across the statement that house dust is as much as 70% of dead skin. In fact, this is just a myth that has become entrenched in the minds of people only because it sounds disgusting. Just think - every moment we breathe particles of complete strangers to us, just disgusting! The air around us is indeed saturated with dust with particles of dead skin, but in fact there are not so many of them. After all, if the dust were mostly particles of human skin, abandoned buildings would be perfectly clean. So what, then, does the dust that surrounds us almost everywhere consist of and regularly enters our bodies? It is not so easy to find a definite answer on the Internet, therefore, within the framework of this material, we will try to finally get to the bottom of the truth.
- 1 Refutation of myths
- 2 What is dust?
- 3 How does a person change their skin?
- 4 How much leather is in house dust?
- 5 What is in the air besides dust?
Refutation of myths
The most detailed analysis of the composition of house dustrecently posted by the author of the YouTube channel Veritasium. He carried out an in-depth study, in the course of which he found at least two advances in the myth that dust is 70% dead skin. In 2012, the scientific publication Livescience confirmed that there is indeed human skin in the dust, but there is definitely not as much of it as many articles say. According to the authors of the note, such a concentration of skin particles in the dust could only be in the old laboratory of Professor Frankenstein, who was trying to create a monster. The second denial of the myth was published in Science Focus magazine - house dust contains more dirt from the street and scraps of thread than human skin. In fact, even meteorite particles can be part of the dust, that is, we literally breathe in space objects. Dust can be anything as long as it meets certain specifications.
What is dust?
The term "dust" is usually understood as tinythe size of particles that can float in the air for a long time when the wind blows. But how tiny must these particles be, and how long must they be in the air before they can be called dust? This definition of the term is very vague and requires clarification. Nobody knows exactly what size the dust particle is, because all sources give different numbers:
- the International Organization for Standardization (ISO) defines dust as particles with a diameter not exceeding 75 micrometers, which is approximately equal to the thickness of a human hair;
- the terminological dictionary of atmospheric chemistry calls dust particles with a diameter of about 100 micrometers;
- some other scientific documents call dust particles up to 2000 micrometers, which is equal to 2 millimeters.
But why is the information on the size of dust particles inall sources are different? The point is that size is not the main characteristic of dust. From a scientific point of view, of greater interest is the sedimentation rate, which shows how long particles spend in the air. A metal ball with a diameter of 100 micrometers will quickly fall to the surface, so it cannot be called dust. But a piece of filament 2000 micrometers long soars in the air for a long time and is undoubtedly considered a dust particle. The same applies to a light particle of human skin, the diameter of which does not exceed 30 micrometers - this is also dust.
See also: How dangerous is house dust?
How does a person change their skin?
We do not notice it, but in fact all peopleshed, that is, shed their old skin like snakes. Only it does not happen periodically, but constantly. And we do not shed old skin completely at one time, but gradually. Our wrists and other open areas of the body get rid of old skin particles most actively, but the skin layer of the back and especially the abdomen is renewed much more slowly. Scientists learned about this during an experiment in which containers were leaned against and glued to different parts of the bodies of people to collect the fallen skin particles. After several days of wearing, the researchers examined the contents of the containers. The ones that were glued to the bellies were the least full.
Old human skin sheds becauseevery hour our bodies create about 20 million skin cells. The human body is not rubber and there is a limited amount of space in it, so new cells push old ones out, from which an outer protective layer is formed. Over time, dead cells begin to flake off one by one and get into the air. In the course of the experiment described above, it was found that every hour about 1000 skin cells fall off from each square centimeter of the human body. If we consider that the area of the skin of an adult is approximately 2 square meters, it turns out that every hour a person loses 20 million dead cells per hour.
Just imagine: a person sheds 480 million dead cells per day!
According to the calculations of the author of the Veritasium channel, for onea day a person releases 1-2 grams of their skin into the air. It turns out that in a year we shed about half a kilogram of skin, which is about 180 billion dead cells. There are as many stars as there are in our Milky Way galaxy! But this does not mean at all that all our skin becomes dust and penetrates into the bodies of other people through the respiratory tract. Absolutely not, because we wash off most of the dead skin with water while taking a shower or bath, leave it outside while walking and rub it into clothes, which are then washed in the washing machine.
How much leather is in house dust?
So, we figured out that a person still produces dust. But if house dust does not contain 70% of skin particles, then how much? In addition to humans, there are a lot of dust sources in nature:
- flowers scatter pollen through the air, which often causes allergies in some people;
- dirt from the street also gets into our homes and easily scatters through the air;
- tiny particles are also falling from the sky, and not just anything, but real meteorites that burn up in the atmosphere of our planet.
In fact, the exact percentagehuman skin in house dust was published in the 1981 book The Biology of House Dust. One chapter states that about 53% of dust particles up to 100 micrometers in diameter are fragments of human skin. This was found out in an experiment in which scientists studied dust collected from bed linen under a microscope. It turns out that there are still a lot of skin fragments in house dust, but definitely not 70%. However, this indicator depends on the room - if there are few people in it, the percentage will be lower.
Most of the "leather" dust accumulates onbeds and sofas. After all, it is there that we spend most of our free time and rub our skin against bed linen. About 20 years ago, a myth even appeared among the people that due to dead skin and the abundance of dust mites that feed on them, our pillows and blankets become twice as heavy in a decade. But this is also just a myth that has become entrenched in the minds of people because of its abomination. According to scientists, even if two people sleep in a bed for decades, fallen skin and ticks will increase the weight of bed linen by a maximum of 3 kilograms. Plus, if you regularly make your bed, skin particles will be lifted into the air. If before that 21,000 skin particles hovered in a square meter of air, then after shaking the laundry in a square meter there are up to 107,000 particles.
What is in the air besides dust?
Besides dust, from the surface of the human bodybacteria, fungi and mites scatter. Every hour, millions of different bacteria enter the air from our body, forming a cloud up to one meter in diameter. If a person is allowed into a clean room, he will leave behind an individual trail, by which his personality can even be recognized. The fact is that the ratio of microbes, fungi and mites is different for each person - the difference is almost the same as between fingerprints. Therefore, it is believed that someday it will even be possible to find criminals and solve even the most mysterious crimes based on "microbial prints".
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The book "The Biology of House Dust" statesan amazing list of particles that can be found in dust. These include wood fibers, rubber, human hair particles, tissue scraps, dandruff, cigarette ash, and so on. Dust, by the way, is not only on Earth, but also on the Moon. It is noteworthy that moon dust is much more dangerous for our body and scientists are even developing a "moon vacuum cleaner". You can read about the dangerous dust on the moon and how astronauts will get rid of it in this article. Enjoy reading!