Some time ago, the "Customs Release" released such a news:
Dalian Zhoushuizi Airport Customs, a subsidiary of Dalian Customs, supervised inbound flights, an inbound passenger triggered an alarm when passing through the fixed nuclear radiation monitoring door of the customs, and after on-site customs officers reviewed, the passenger carried a bag of "health stones" nuclear radiation exceeding the standard, with a radiation dose of 105 microsieverts per hour, exceeding the background value of the scene by 1050 times. Instrumental analysis revealed the radioactive substance thorium-232, which is listed as a Group 1 carcinogen by the World Health Organization's International Agency for Research on Cancer.
Image source: Customs release
In addition to "health care stones", some people will buy "health care belts", "health bracelets" and so on, thinking that they can "adjust feng shui to keep peace" and have health care effects, but in fact, these items with excessive radiation values are not only not healthy, but may also be harmful to the body.
If the radiation value exceeds the standard, how much harm is it to the human body
In order to facilitate everyone to better understand the impact of these items with excessive radiation on the human body, let's first explain the two words mentioned in the news: "microsieverts" and "background value".
Microsieverts: One of the units of calculation of a radioactive dose. 1 microsievert (μSv) = 0.001 millisievert (mSv).
Background value: generally refers to the relevant value generated by the natural environment itself without external human interference.
The global average person receives about 2,400 microsieverts of background radiation per year. The national standard of the mainland stipulates that the public should not exceed 1,000 microsieverts per year in addition to the natural background radiation. For those working with radioactivity, the maximum radiation dose per year is 50,000 microsieverts.
What is the concept of "health stones with a radiation dose of 105 microsieverts per hour" mentioned in the news, if you carry this bag of stones on your body for a day, the total amount of radiation will already exceed the maximum radiation value that ordinary people can accept for a year.
The harm of nuclear radiation to people and living beings is related to the dose of nuclear radiation, the time people are exposed to nuclear radiation, and the half-life of nuclear substances. Specifically:
When the short-term radiation dose is less than 100 millisieverts, there is no harm to the human body;
At 100 to 500 millisieverts of short-term radiation, peripheral vascular lymphocytes decrease;
short-term radiation dose of 500 to 1000 mSieverts, nausea and vomiting, and a decrease in white blood cells;
The amount of short-term radiation is between 2000 and 4000 millisieverts, which produces radiation diseases, such as destruction of bone marrow and bone density, extreme reduction in the number of red blood cells and white blood cells, and symptoms such as internal bleeding, vomiting, and diarrhea;
The short-term radiation dose is greater than 4000 millisievert hours, which is life-threatening.
Some people may ask, if the radiation of "power stones" is harmful to the human body, then will the medical radiation such as X-rays and CT examinations also have an impact on health?
As can be seen from the figure below, on the one hand, the amount of radiation exposed to medical treatment is within a safe range, and on the other hand, it will be further ensured by controlling the frequency of annual radiation examinations, wearing lead clothing during local inspections, and reasonably designing a phased and multi-step radiation treatment plan.
Image source: Chinese Academy of Sciences
Radioactivity is everywhere around us
It should be noted that although excessive radiation levels do cause great harm to the human body, we do not need to mention "radiation" to change color. In fact, ionizing radiation can be said to be almost ubiquitous in daily life, but some are insignificant to us, some help us to produce and live, and some threaten our life and health.
Radioactive materials can be divided into two categories: natural and artificial:
Natural radionuclides – products from the universe
In the vast universe, nuclear reactions are still taking place in many celestial bodies, such as the nearest sun, which is a huge nuclear reactor. This ancient "alchemy", which existed at the beginning of the universe, kneaded together the smallest and lightest hydrogen collisions, continuously assembled into larger and heavier nuclides, continuously produced new nuclides, and also threw out a large number of cosmic rays composed of high-energy particles and electromagnetic waves.
These rays carry a large number of particles and energy, some of which shoot new nuclides directly into the Earth, and some that interact with the atmosphere to produce new nuclides, so that the Earth has a constant supply of nuclides from the universe. These nuclides are found in every corner of nature, including living organisms, along with the circulation of air and water. Among them, the radionuclides are part of the natural radioactivity, together with the radionuclides that are already on Earth.
I don't know if you remember what you mentioned in the first part: "The mainland national standard stipulates that the public ...... in natural background radiation every year", we live in nature, are exposed to these natural radiation all the time, and also participate in the flow of these radionuclides in nature, so the radiation generated in this living environment is also called "natural background exposure".
Image source: United Nations Environment Programme, Radiation – Impacts and Sources, 2016
Some human activities in daily life can also lead to an increase in the amount of natural radiation received:
Radioactive contamination of the room due to substandard building materials
Building materials such as marble, granite, gypsum, and even earth and sand are all radioactive, among which radium (Ra), radon (Rn), thorium (Th), and potassium (K) are the radionuclides to pay attention to. In addition to producing organic pollutants such as formaldehyde and benzene, inferior building materials may also lead to excessive indoor radioactive pollution.
The combustion of high-level raw coal produces radioactive dust
Coal mines contain a certain amount of radionuclides, and the mining and burning of highly radioactive coal mines will cause radioactive dust to diffuse into the atmosphere, increasing people's exposure to background radiation. Screening of raw coal and treatment of coal ash are effective means to reduce the emission of radioactive pollutants.
"Stand taller, radiate stronger": the atmosphere and the Earth's magnetic field are important barriers against cosmic rays
The atmosphere at higher altitudes is relatively thinner, and people are exposed to higher background exposure than people at lower altitudes. Similarly, pilots of airplanes and astronauts who have been working in space for a long time are at higher risk of irradiation.
Artificial radionuclides – contemporary alchemy
Artificial radionuclides are produced by humans in the process of using ionizing radiation. Contemporary "alchemy" such as nuclear tests, accelerators, and reactors can produce a large number of artificial radionuclides, which are also an important means of discovering and researching new nuclides. These nuclides are commonly used in medical irradiation, nuclear energy production, irradiation detection, experimental research and other scenarios.
For example, technetium-99M is commonly used in medical treatment for imaging of human organs, brachyradiotherapy and extracorporeal radioanalysis of iodine-125 cancer, iodine-131 for the treatment of hyperthyroidism and thyroid cancer, and lutetium-177 combined with various targeted molecules to achieve a variety of malignant tumor diseases with systemic metastasis......
Lutetium-117 solution. Image source: China Nuclear Technology Network
In industry, cobalt-60 is the most important γ radiation source, often used in industrial disinfection, irradiation processing, irradiation breeding, non-destructive testing and other fields, and barium, bromine, iodine, tritium, sulfur and other elements of radionuclides are often used as industrial tracers......
Iridium-192 radioactive source that could be mistaken for a bracelet
Common radiation rumors in life
Can cacti protect against radiation?
Cactus, as an "ordinary" plant, does not have the ability to resist radiation. The source of the rumors about cactus' radiation resistance is likely to be that people think of its living environment, and the strong ultraviolet rays and extremely arid environment make people want to "speak" about it. Taking 10,000 steps back, even if the cactus can resist radiation, it must be plunged into the cactus pile and become a "hedgehog" in order to fully protect and reduce the risk of radiation.
There are no cacti in the radiation shielding material!
Can iodized salt protect against radiation?
After the Fukushima accident, many places in China have set off a rush to buy iodized salt, and many people try to achieve radiation protection by ingesting iodized salt, but in fact, iodized salt is not directly related to radiation protection, and there is no need to hoard.
On the one hand, sea salt accounts for only a small part of the source of salt, and even if the discharge of nuclear-contaminated water into the sea affects the production of sea salt, it will not lead to a huge gap in the supply of salt on the mainland; on the other hand, it is not advisable to replace the stable iodine tablets used to protect against radiation with iodized salt, and the iodine content of the two is very different, if it is really replaced by iodized salt, it is necessary to eat 3 kg to 4 kg of iodized salt at a time to achieve the same effect.
What are the health functions of radium, thorium and radon?
In the early days of radioactivity, people were not aware of their harm, but because of the fluorescent effect of these radioactive materials, they mistakenly believed that they carried mysterious powers. Radioactive materials such as radium and thorium are frantically added to all kinds of food supplies, cosmetics, toothpaste, toys, and even drinks and medicines within people's reach. Its only function is to bring "pure natural and additive-free" radiation to the human body, and excessive radiation makes people who are exposed to them for a long time suffer from anemia and cancer......
Today we may hear the phrase "radon hot springs for health care", but in fact there are areas with special geological structures, and the concentration of minerals and natural radionuclides in the hot spring water is slightly higher than in other areas, among which the decay of radium-226 produces radon gas, a radioactive noble gas. Proper soaking in hot springs itself can help strengthen blood circulation, relieve blood pressure, improve the body's metabolic efficiency, and enhance human immunity, but there is not enough experimental or clinical evidence to support whether the slightly increased radiation dose really has physiotherapy and health care effects.
Source: Popular Science China
Reprinted from: People's Daily WeChat public account