In this blog post, we will examine the misconceptions and truths about radiation, from its definition to its effects on the human body and how it is measured.
Since the Fukushima nuclear power plant explosion on September 11, 2011, South Koreans have become increasingly fearful of radiation. Radiation poses serious risks, such as genetic mutations and cancer, and is invisible to the naked eye. As a result, radiation has become a source of anxiety in our daily lives. However, although we have heard the term “radiation” many times, many people do not know exactly why radiation is harmful to us or how much radiation we need to be exposed to in order to suffer the damage we commonly imagine. It may be foolish to take action based solely on what the internet or the media says without knowing the facts. It is important to learn what radiation is, how it is measured, and how much damage it can cause.
In fact, research and understanding of radiation advanced rapidly in the late 19th and early 20th centuries. The existence of radiation was first discovered in 1895 by German physicist Wilhelm Röntgen, who discovered X-rays. Subsequently, in 1896, French physicist Henri Becquerel discovered natural radiation emitted from uranium, and research on radiation began in earnest. Later, Marie Curie and Pierre Curie discovered the radioactive substances radium and polonium, which led to further research on the dangers and usefulness of radiation. These discoveries led to the medical use of radiation, such as radiation therapy for cancer treatment, but at the same time, awareness of the dangers of radiation also increased.
Let’s say you are going on a trip to Japan. You will probably wonder how much radiation you will be exposed to. There is a way to measure how much radiation you are exposed to. It is by using a radiation meter. There are various types of radiation meters, but let’s learn about the principle of the GM tube measurement method, which is the most widely used.
Gases are composed of molecules, and molecules are composed of atoms.
Atoms are made up of atomic nuclei and several electrons. When high-energy electromagnetic waves, such as gamma rays, collide with these gas molecules, the electrons are knocked out. This separation of electrons is called ionization, which results in the formation of positive and negative ions. GM tubes utilize this principle.
A GM tube creates a voltage inside a tube filled with gas by inserting an electrode and connecting a wire to the outside. When radiation passes through the GM tube, the electrons in the gas are separated by the radiation, generating ions, and an electric current flows due to the voltage inside the tube and the ions. By measuring this electric current, it is possible to measure the amount of radiation.
This method is widely used for monitoring the vicinity of nuclear facilities. The type of radiation that can be measured using a GM tube is gamma rays, as shown above. There are three types of radiation: alpha rays, beta rays, and gamma rays. Alpha rays can be blocked by our skin, and beta rays do not have strong penetrating power, so they do not cause harm to the human body unless ingested. However, gamma rays are different.
Gamma rays are what we commonly refer to as harmful radiation.
Light is called visible light, which is a type of electromagnetic wave, and gamma rays are also a type of electromagnetic wave. But why does light not cause us any harm, while gamma rays have such a terrifying effect? This is because the wavelength of radiation is much shorter than that of light. The wavelength of electromagnetic waves is inversely proportional to the energy of light. Visible light has a wavelength of about 380 nm to 770 nm, while gamma rays have a wavelength of about 0.01 nm, so their energy is more than 10,000 times greater.
Have you ever wondered why light passes through glass but our bodies do not? This is because light has enough energy to pass through glass but not enough energy to pass through the human body. However, gamma rays have enough energy to pass through the human body and can destroy the genetic material and core proteins of cells in their path, causing cell death. The cells in our bodies are constantly being replaced by new cells, but when the newly created cells are killed by radiation, they cannot replace the original cells, and symptoms (hair loss, partial erythema, blisters, ulcers, necrosis, etc.) appear after a certain period of time after exposure. Furthermore, if this destruction occurs in germ cells, the chromosomes of the germ cells are mutated, and the genes of the germ cells produced are also mutated, which may cause mutations in the next generation.
So how much radiation can our bodies safely be exposed to? There are various units for measuring radiation, but the unit used as the international standard is the sievert (Sv), which indicates only the biological effects of radiation regardless of the type of radiation. This unit represents the energy of radiation received per unit mass (J/kg). To get a sense of how much Sv is, let’s use the radiation we are exposed to in our daily lives as an example. The amount of radiation we receive when we have a chest X-ray is 0.1 mSv (0.0001 Sv). The annual radiation exposure limit set by South Korean law is 1 mSv, and symptoms do not appear at levels below 200 mSv.
Real-time radiation levels can be checked on various websites. Currently, the radiation level in Tokyo, Japan, is very low at around 60 nSv/h, so traveling to Japan is unlikely to pose a health risk.
If we visit areas where radiation levels may be high, such as near nuclear power plants or when traveling to Japan, we may miss out on opportunities due to vague fears. However, nowadays, radiation detectors are widely available, and due to concerns from many people, radiation standards have been set for seafood imported from Japanese waters. Rather than being afraid of radiation, it is better to measure it if possible, and if the amount is not harmful to the human body, then there is no need to avoid places that are rumored to be dangerous.
