Radiation, invisible and ubiquitous, is a scary thing to think about. Many people will blame some aspect of physical discomfort for radiation, such as headaches, sore eyes, acne on the face, blamed on computer radiation. In order to prevent radiation, and will think of all kinds of prescriptions, put a pot of cactus in front of the computer, the legend is that it can absorb radiation. Eat a certain food, which is said to prevent damage caused by radiation. Pregnancy, of course, more to prevent radiation damage to the fetus, so radiation protection maternity clothes in the country popular, has a history of more than a decade. Is radiation really so harmful to the body? That depends on what kind of radiation. One type of radiation is the rays emitted during the decay of a radioactive isotope or nuclear reaction, called nuclear radiation. Some nuclear radiation rays are so penetrating that they can penetrate the skin and enter the body, causing damage to human tissues and organs. However, if radioactive materials are inhaled into the human body and have zero contact with human tissues, the rays they emit can also cause damage to human tissues and organs. Daily life can be exposed to nuclear radiation is mainly cosmic rays, the more to high altitude cosmic rays are stronger, defensible. High altitude flight per hour by the amount of radiation about 0.01 mS, flying 10 hours equivalent to receive a chest X-ray. There are also studies that a year in New York and Tokyo to fly between the seven round trips by the amount of radiation to reach the maximum value of 50 mS of radiation workers a year. There is no good way to reduce radiation from cosmic rays except to reduce the number of high-altitude flights. Other nuclear radiation comes from radioactive substances, such as radioactive radon gas released from soil or building stone. Radon gas produces rays with poor penetration, but will induce cancer after being inhaled into human body, and is the second most important factor causing lung cancer, second only to smoking. The presence of radon gas can only be measured with special instruments. Another type of radiation is produced by electromagnetic waves. According to the order of frequency from low to high (wavelength from long to short), electromagnetic waves can be divided into: radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays and γ-rays. The highest frequency of gamma rays is actually a kind of nuclear radiation rays, it and X-rays penetration is very strong, can enter the interior of the body, and the body cells ionization (that is, the electrons in the atom run out), called ionizing radiation, can cause damage to human tissue. Daily life γ rays are not easy to encounter, X-rays in the home mainly from the picture tube television and computer monitors. The electrons in the picture tube in the high-speed movement will inevitably emit X-rays, but the intensity is very low, because in the design and manufacturing process of television sets and monitors will have a strict limit on this. They are usually required to X-ray radiation intensity measured at a distance of about 5 cm from the screen can not exceed 0.5 micro-Roentgen per hour, which is equivalent to the intensity of cosmic ray radiation that people are exposed to when flying at high altitude. Of course, people in the use of computers and watching TV can not be so close to the screen, the actual radiation to be much lower. What’s more, it is now common to use LCD monitors and televisions, they do not have a picture tube, there is no problem of X-ray radiation. Although ultraviolet radiation is not ionizing radiation, but can break chemical bonds, the same can damage human tissue. Only the penetrating ability of ultraviolet light is not strong, and it is the skin and eyes on the surface of the human body that will be damaged. UV rays in daily life mainly come from sunlight. As long as you do a good job of shading, such as playing umbrellas, wearing sunglasses and applying sunscreen on exposed parts of the skin, you can prevent damage from UV rays. Visible light and electromagnetic waves with frequencies lower than visible light do not directly damage the body’s molecules. When they hit the body, they are absorbed by the body and their energy is transferred to the body’s tissues, making them locally heated. The stronger the power of electromagnetic waves, the higher the energy carried, the greater the increase in temperature of human tissue after absorption, to a certain extent may burn human tissue. So this type of electromagnetic radiation is harmful to the human body, depending on how high their power. We usually say that the electromagnetic radiation emitted by electrical appliances, refers to the microwave and radio waves, their power is much lower than the power of the human tissue can be burned. So, in addition to burns, there is no possibility of causing other harm to the human body, such as inducing cancer? The World Health Organization summarized nearly three decades of relevant research and concluded that the available evidence does not establish that exposure to low-intensity electromagnetic fields produces any health consequences. That is, a large number of studies have shown that there is no evidence that the kind of low-intensity electromagnetic waves encountered in daily life affect human health. For the greater concern of fetal health, a large body of evidence also shows that exposure to EMFs at normal environmental levels does not increase the risk of spontaneous abortions, malformations, low birth weight babies, congenital diseases, and other harmful effects. The electric waves emitted by cell phones can be absorbed by human tissue close to it, producing a heating effect. Is there a health risk associated with long-term cell phone use? In 2011 the International Agency for Research on Cancer (IARC) released a report concluding that there is no evidence that long-term cell phone use can cause other cancers, but limited evidence of an increased risk of glioma, thus classifying radio frequency electromagnetic fields as “The IARC did not give a quantitative risk, but a 2004 study it cited said that an average of 30 minutes of cell phone use per day for 10 years increased the risk of glioma by 40 percent. Glioma is a brain tumor with an annual incidence of about 5 in 100,000 people and an additional 2 per year at this risk. The U.S. Food and Drug Administration disputes the results, arguing that the current study is insufficient to confirm an association between cell phone use and brain tumors, and that the incidence of brain tumors actually decreased during a period of substantial increase in cell phone use in the United States. Other studies have produced different results. For example, according to an analysis of 358,403 Danish cell phone users between 1990 and 2007, long-term cell phone use was not found to increase the risk of brain tumors (including gliomas and meningiomas). Finally, let’s look at so-called radiation-protective maternity clothing, which is made of woven metal wire. It cannot block the penetrating nuclear radiation and X-rays that are harmful to the human body, but tries to shield the electromagnetic radiation in the daily environment. But daily electromagnetic radiation is longer wavelength microwave and radio waves, they are able to bypass, if the radiation protection clothing is not wrapped all over the body, but worn like maternity clothes, then electromagnetic waves can still enter the body from the collar, cuffs, hem and other openings and cannot be blocked. Moreover, since the results of scientific research show that electromagnetic radiation in the daily environment is harmless to the fetus, why try to shield it? So only in China, and rather credible than the combination of the traditional concept of fetal preservation, the so-called anti-radiation maternity clothes have a market, out of the country, it is rare to see.