Radiation is a general term for alpha, beta, and gamma rays generated by the decay of radioactive isotopes, cosmic rays from outer space, and particle rays and electromagnetic waves artificially generated by X-ray generators such as X-ray tubes, accelerators, and nuclear reactors. For more information, see "What is the difference between radioactivity, radiation, and radioisotope?" for more information.
When a person is exposed to radiation, the effects are divided into stochastic and deterministic effects. When a person is exposed to radiation, the ionizing effect of the radiation damages the DNA of the cells. If the amount of radiation received is small, the human body has the ability to repair the DNA when the cells are reproducing. If the amount of radiation received is very small, most of the damage will be repaired without any problem.
However, there are cases where the DNA of the cell is incompletely repaired during the repair process. This can cause the cells to mutate and turn into cancer cells or cause genetic effects. This is a stochastic effect.
Since DNA damage can be caused not only by radiation but also by smoking, drinking, diet, and chemical substances, it is difficult to say that radiation is the cause of cancer in each individual case.
Therefore, there is no boundary that says, "If you are exposed to more than this, symptoms will appear. However, the risk of cancer due to exposure can be studied by comparing the cancer rates of a group of people who have been exposed to radiation and a group of people who have not.
In terms of stochastic effects, the risk of cancer from receiving 100-200 mSv of radiation is said to be the same as that from lack of vegetables, and the risk of cancer from receiving 200-500 mSv of radiation is said to be the same as that from lack of exercise. The higher the amount of radiation received, the higher the risk, but the symptoms are not severe.
On the other hand, if a person is exposed to a large amount of radiation at one time, the number of cells whose DNA is damaged and cannot be reproduced will exceed the number of cells that can be reproduced, and cell repair will not be able to keep up. This is called a deterministic effect.
There is a boundary between the definite effects and the symptoms that will appear if the exposure is higher than the threshold. This boundary is called the threshold. In definite effects, the cells themselves are not damaged, but rather the reproduction of cells is affected, so there are few visible symptoms immediately after exposure.
However, depending on the location and amount of radiation received, symptoms such as hair loss, infertility, and cataracts may appear. The higher the dose, the more severe the symptoms become.
|Effects on the human body
|Gamma radiation acute collection dose threshold (Gy)
|Temporary infertility (testes)
|Decreased hematopoiesis (bone marrow)
|Cataract and vision loss (eye)
|Permanent infertility (ovary)
|Temporary hair loss (skin)
|Skin redness (skin)
|3 to 6
|Skin burns (skin)
|5 to 10
|Permanent infertility (testis)
People are exposed to small amounts of radiation even in their natural lives. The radiation we receive naturally comes from rocks on the ground, food, and the air we take into our lungs, and this is called "natural radiation.
The annual exposure dose from natural radiation varies depending on the food you eat, but the average dose in Japan is about 2.1 mSv.
Some natural radiation is emitted from space and is called cosmic rays. When you fly in an airplane, you receive more cosmic rays than on the ground due to the higher altitude.
However, even if you fly from Japan to Europe to the United States and back, the amount of exposure you receive is only about 0.1 mSv. For the average person, this figure is sufficiently small compared to the annual exposure in normal life that there is no effect on health.
However, in the case of airplane crews, the annual exposure dose from cosmic rays increases because they have so many opportunities to fly. For this reason, guidelines have been established to strive to keep the annual exposure within 5 mSv.
Although there are some regions where the annual natural radiation dose exceeds 5 mSv due to the higher amount of radioactive materials contained in natural rocks than others, no special health problems have been reported so far, so it is safe to assume that there is no particular problem with the annual exposure dose for aircrews.
X-rays are one type of radiation that is widely used in our daily lives. X-rays, which are commonly used in hospitals, are used to visualize the inside of the body by irradiating the body with X-rays and using the difference in transmittance between areas with high density and areas with low density.
Since X-rays are emitted, radiation exposure occurs. However, there is no health risk because the exposure dose for a single medical chest X-ray is very low at 0.02-0.1 mSv.
Medical CT, which uses X-rays in the same way as X-rays, used to have an exposure dose of about 5 to 30 mSv, but in recent years, by using image processing technology, low exposure CT has been developed to reduce the exposure dose to about 1/10 of the conventional dose.
In addition to medical x-rays, industrial x-ray equipment used for non-destructive testing is subject to the Industrial Safety and Health Law, which stipulates how to handle and manage such equipment. For example, people who use radiation equipment are required to wear dosimeters and record the results, as well as undergo medical examinations every six months.
Furthermore, depending on the size of the X-ray equipment, it must be installed in a radiation equipment room equipped with shielding walls. Unlike water, radiation cannot be seen with the naked eye, so it is important to have proper knowledge of its use and to handle it in accordance with the established rules.
Medical x-rays and industrial x-ray machines do not have radioactive materials inside them. X-rays are produced by the power of electricity. Therefore, there is no danger of radiation leaking out of X-ray equipment, unless it is energized.
Matsusada Precision offers X-ray non-destructive inspection systems as described in the following pages.
List of Matsusada Precision X-ray non-destructive inspection systemsX-ray non-destructive inspection
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Reference (Japanese site)
- Japanese source page 「放射線の人体への影響とX線装置の安全性を解説」
- 環境省ホームページ: 「様々な影響のしきい値」