Natural Radiation
When people talk about radiation, they usually picture Chernobyl and a mushroom cloud. But the reality is that radiation is everywhere, and it has always been here—long before we arrived, and even before the Earth was formed. Today, we’ll tell you where it can be found most abundantly in nature.
Where radiation comes from
Remember: everything we see around us is made up of tiny particles called atoms. Atoms, in turn, have even smaller particles: protons and neutrons.
Different chemical elements are simply made up of different numbers of protons in an atom. But neutrons are more complicated: the same element may have more or fewer neutrons than the «norm». Such atoms are called isotopes.
And most isotopes are unstable. This means that the lack, or excess, of neutrons disturbs the processes in the atom, and the atom «wants» to return to equilibrium. Over time, this leads to the disintegration of the atom, in the process of which particles are emitted—this is radiation.
A major source of radiation within the solar system. Photo: NASA / Unsplash
It turns out that radiation is the emission of particles by unstable atoms as they decay. And it just so happens that these particles are dangerous to the health of all living things.
The most dangerous of all is radiation in space, generated in the extreme processes inside the stars, where, amidst the enormous pressure and chaotic collision of nuclei, atoms are constantly gaining and losing neutrons. Because of all of this activity, space is literally teeming with radioactive particles, and every spacecraft needs serious protection.
The Earth is protected from the endless space storm of dangerous particles by its magnetic field, the atmosphere, and the ozone layer. But the planet itself has enough radiation sources of its own, without space radiation.
Radiation 🤝 Microplastics
On Earth, you can get small doses of radiation in any number of places—from air travel, the air, food, water, and soil. What’s more: even our body emits a small amount of radiation, as isotopes accumulate in our bones and our teeth. In this sense, radioactivity is like microplastics—it is everywhere.
The dose of radiation received is usually measured in microsieverts. There are other values, but for convenience, we will use microsieverts.
For comparison:
- The average annual human exposure to radiation from all sources on Earth is 2400 microsieverts.
- The minimum known dose for cancer is 100,000 microsieverts.
- You can get radiation sickness from 1 million microsieverts.
Let’s go through these in order. The atmosphere protects you from dangerous particles from outside, but the higher you are (i.e. the closer you are to space), the more rarefied the air becomes, and the higher your chance of getting a dose of cosmic radiation.
Astronauts get the most radiation: over the course of six months on the International Space Station, you can be exposed to 72 thousand microsieverts. Photo: NASA / Unsplash
In an airplane, people receive an average of 4 microsieverts per hour in the air. But measurements after long flights, for example, from Northern Europe to Japan, the maximum exposure was 70 microsieverts, which is 3% of the annual norm. Pilots and stewardesses can accumulate from 3000 to 5000 microsieverts during a year, significantly above the norm.
The next source of terrestrial radiation is the Earth itself. There are many radioactive isotopes left inside the planet’s interior from the time of the planet’s formation, which is why we can mine uranium.
But isotopes are also found in ordinary rocks like granite, so the radiation background is slightly elevated at points where the granite comes out to the surface. The results of decay also accumulate underground, and come to the surface in the form of radioactive radon gas, which can regularly be found even in ordinary apartments.
In addition, there are radioactive isotopes in all kinds of food, as plants absorb radiation from the water in the ground, and animals absorb isotopes when they eat these plants. Here are a few examples:
- A single Brazil nut will irradiate you by 2-3 microsieverts (potassium-40, radium-226 and radium-228 isotopes)
- One banana will expose you to 0.1 microsieverts (potassium-40 isotopes)
- A potato has 0.02 microsieverts (potassium-40 isotopes)
Living with radiation
We realize it sounds scary. But as you have probably noticed, all these radiation microdoses are insignificant. To get a full day’s worth of radiation at one time, you need to eat 100 bananas—not an easy task.
The «banana isotope», potassium-40, is found in almost every food that humans have consumed for thousands of years. While you were reading the previous paragraph, not one or two, but probably thousands of potassium-40 isotopes have decayed in your body—and it has not had any noticeable effect on you, so it will never cause any harm in such small doses.
Radon can be considered more dangerous. It is regularly found in apartments, as well as in building materials (bricks, for example), tap water, household gas, and even in the pipes of coal-fired power plants.
In the early twentieth century, when the nature of radioactivity was not fully understood, radon baths had become popular. It was believed that if you bathed in a pond or lake where radon came to the surface, you could recover and improve your health. This method has not been proven effective when compared to a placebo; however, we have learned a lot about the harm of excessive radiation exposure over time.
But even in the situation with radon, there is nothing irreversibly terrible: the doses are insignificant, and to reduce them, it is enough to regularly ventilate a room, and filter the water, which is to say, just follow your usual routines and rules. Meanwhile, in the mountains, where there are many granite deposits, scientists have not been able to detect an increase in cancer incidence, so running away to the lowlands is also hardly worth it.
In general, we can say that you should not be afraid of natural radiation, when your exposure is within the norm. And everyone can avoid unnecessary microsieverts, at least by not taking regular radon baths.
We’ll talk more about the theme of solar radiation, which has a huge impact on the weather, in a future article.
Text: Jason Bright, a journalist, and a traveler
Cover photo: Manav Jain / Unsplash
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