Radioactive substances detected around Japan's nuclear power plant include iodine 13 1 and cesium 137, among which iodine 13 1 once inhaled by human body may cause thyroid diseases, while cesium 137 may cause damage to human hematopoietic system and nervous system. So when people are exposed to nuclear radiation, they may get radiation sickness. The symptoms of this disease are obvious. Within a few hours, people will feel nausea and vomiting, followed by symptoms such as diarrhea, headache or fever. After the initial symptoms have passed, there may be a short asymptomatic period, but new and more serious symptoms will appear after a few weeks. At higher radiation doses, these symptoms may appear faster and more obvious. At the same time, nuclear radiation will cause extensive and sometimes even fatal damage to human internal organs. Exposed to nuclear radiation, half of healthy adults can't bear the radiation dose of 4 Gy. In contrast, the radiation dose of radiotherapy used in cancer treatment is about 1 to 7 Gy, but it is highly controllable, and its action area is strictly limited to a small lesion. Effects of different radiation doses on people In daily life, people are often exposed to various kinds of radiation, and different radiation doses have different effects on the human body. The short-term radiation dose is lower than 100 millisieverts, which is harmless to human body. When it is higher than 4000 millisieverts, it is fatal to human body. In radiation medicine and human radiation protection, people use Siver as an international unit to measure the damage of radiation to biological tissues. Siver is a very large unit, so people usually use millisieverts and microsieverts. 1 millisieverts equals 1000 microsieverts. For people who are not exposed to radiation frequently in their daily work, the normal natural radiation (mainly radon radiation in the air) is 1000 microsieverts-2000 microsieverts every year. When the intake of short-term radioactive substances is lower than 100 millisieverts, it is harmless to human body. If this number exceeds 100, it will do harm to human body. 100 millisieverts-500 millisieverts, there is no feeling of disease, but the number of white blood cells in the blood sample is decreasing. When1000-2000 millisieverts, radiation will cause slight radiation diseases, such as fatigue, vomiting, loss of appetite, temporary hair loss, and erythropenia. At 2000-4000 millisieverts, people's bone marrow and bone density are destroyed, the number of red blood cells and white blood cells is extremely reduced, and there are symptoms such as internal bleeding and vomiting. When it is more than 4000 millisieverts, it will directly lead to death. In daily life, people fly 10 hours, which is equivalent to receiving 30 microsieverts of radiation. The hourly radiation of Fukushima nuclear power plant is 10 15 microsieverts, which is equivalent to one person receiving 10 x-rays. What harm does radiation do to the human body? Radioactive substances will release ionic radiation when they decay. This radiation can cause serious damage to the chemical environment inside the human body, and it will break the chemical bonds between various atoms and molecules in human tissues. The human body will automatically respond to this and try to repair this damage. But sometimes this kind of damage will be very extensive and serious, and it is almost impossible to repair it, and there is still the possibility of errors in the process of automatic repair. The most sensitive parts of the human body to radiation injury are the cells in the stomach and the hematopoietic cells in the bone marrow. The damage of radiation to human body depends on your exposure time and radiation intensity. Long-term effects of radiation on human health The most serious aspect of long-term effects of radiation on human health is that it can cause cancer. Generally speaking, once a normal cell reaches its life, it will "commit suicide" and die to make way for new cells. When cells lose this "suicide" function, cancer occurs. This kind of cell becomes "immortal" and continues to divide and proliferate, out of control. However, the human body has various mechanisms to prevent the occurrence of normal cell canceration, and also has a perfect mechanism for replacing old and new cells. However, the influence of radiation will completely break the human body's own control system and greatly increase the incidence of cancer. It is not advisable to take iodine tablets without authorization. The Chinese Center for Disease Control and Prevention of the Ministry of Health recently issued the essentials of nuclear and radiation accident protection knowledge. The public should avoid panic, act according to the instructions of the government, and stay indoors when there may be radioactive pollution. China CDC said that exposure to ionizing radiation may increase the risk of cancer. It is difficult to predict how far the smoke cloud can float after a nuclear accident, which depends on wind speed and other meteorological conditions. In the early and middle stages of emergencies, concealment is one of the main protective measures. Most buildings can reduce the inhalation dose of people in buildings by about half, and it is generally believed that the concealment time should not exceed 2 days. A person's body surface can be protected by all kinds of daily clothes, and people who have been or are suspected of being contaminated by radiation on the body surface can be decontaminated. The method is simple, and the contaminated clothes, shoes, hats, etc. can be taken off and stored until there is time for testing or treatment later. People should avoid panic, listen to the radio or watch TV in time and act according to the instructions of the government. Stay indoors if there may be radioactive pollution. Iodine tablets should be taken according to the instructions of the government, and only after the government evaluates the accident state can it decide whether to take iodine tablets. You can't take it without personal judgment or out of fear. "After a nuclear accident, even if you are not exposed to radiation, you will feel scared. What is the reason?" China CDC explained that there will be mental anxiety whether it is actually irradiated or not. This situation is attributed to people's self-perception of health risks, which partly depends on whether people believe that the competent authorities are capable and trustworthy, and whether they have taken prompt and effective actions to control the radiation dose. Medical workers should give people necessary psychological counseling to relieve psychological panic. How to deal with nuclear and radiation emergencies According to the introduction of the Chinese Center for Disease Control, once nuclear and radiation emergencies occur, the first thing the public must do is to obtain credible information about the emergencies as much as possible and understand the decisions and notices of government departments. We should maintain information communication with local governments through various means, and remember not to trust rumors or gossip. The second thing is to take necessary protective measures to protect yourself quickly. For example, you can choose the nearest building for concealment, and you should close the doors and windows and close the ventilation equipment. Carry out organized and orderly evacuation according to the arrangement of local government. When it is judged that there is a radioactive dispersion event, you should never face the wind or run with it. You should try to hide to the side of the wind direction and quickly enter the building for concealment. Take respiratory protection, including covering your nose and mouth with wet towels and cloth pieces to filter out radioactive particles. If radioactive pollution is suspected on the body surface, take a bath and change clothes to reduce radioactive pollution. Prevent eating contaminated food or water. In the event of nuclear and radiation terrorism, the public should pay special attention to maintaining a stable mentality and never be alarmed. Can the diseases caused by radiation be cured? When there is nuclear radiation, the first thing you should do is to take off the contaminated clothes to prevent further radiation pollution, and then you should gently wipe your skin with soapy water and clean it. It has been developed that can increase the number of white blood cells in blood, so as to offset the possible effects of radiation on human bone marrow and reduce the risk of infection that may be caused by the damage of human immune system. At present, there are drugs specially used to reduce the damage caused by radiation particles to human internal organs. Radiation will pose greater risks to children. In a sense, children will face greater risks from radiation pollution. This is because children grow faster, cells divide more frequently, and there is a greater chance that cells will make mistakes when they repair the damage automatically, which will lead to serious consequences. Protective measures to be taken at different stages According to the introduction of the Chinese Center for Disease Control, after nuclear and radiation emergencies, different protective measures can be taken at different stages. Within 0/2 days after the incident/kloc-0, the protective measures that can be taken for personnel include: concealment, respiratory protection, taking stable iodine, evacuation, control of import and export channels, etc. Among them, respiratory protection is the action of covering your nose with a dry or wet towel, which can prevent or reduce the inhalation of radionuclides. Taking stable iodine can prevent or reduce radioactive iodine in smoke plume from depositing in thyroid after entering the body. In the middle stage of the incident, a considerable amount of radioactive materials have been deposited on the ground. At this time, for individuals, in addition to suspending respiratory protection, other early protective measures can continue to be taken. In order to avoid excessive accumulated dose due to long-term stay, the competent department can take a controlled and planned way to relocate people from the polluted area. Consideration should also be given to restricting the sale and consumption of locally produced or stored food and drinking water. According to the characteristics of the irradiation route of personnel in this period, the protective measures can also be taken: using stored feed in animal husbandry, decontaminating the body surface of personnel, treating the wounded and sick, etc. Food and water, the use of stored feed and regional decontamination.