Is the radiation from wireless Internet terrible? From Shell Technology

Rumor: A wireless broadband router is installed on the wall opposite our room. Everyone uses it to surf the Internet. The signal is quite sufficient and convenient. This signal source is so close to us that it will radiate a lot, and it will be on all year round. There are some minor problems. Truth: When it comes to radiation and radiation safety, we must first distinguish what kind of radiation it is. Nuclear radiation, ultraviolet radiation, mobile phone radiation and high-voltage line radiation are all different, and their effects on health are also very different. If you don't know the difference between them, you can learn the basic knowledge of radiation first. A complete introduction to radiation: How much do you know about radiation damage? (1), (2) From the Daya Bay nuclear accident, we can get a general understanding that weak radio frequency signals will not affect human health. Specific to this misunderstanding, first of all, the electromagnetic wave band used by wifi wireless Internet access is generally 2.4GHz to 5GHz, which is close to the RF electromagnetic wave band used by mobile phones (slightly higher than the frequency used by mobile phones). It belongs to non-ionizing radiation, and the heating effect on human tissues may affect health, and it needs high intensity to cause harm. In the past decades, researchers have done a lot of research on the relationship between electromagnetic radiation in this band and the onset of some diseases, and there are many results that they think will have an impact, but most of these studies are just guesses or weak ties, which have not been widely recognized and have not risen to a worrying level. For example, it was recently reported that "laptop wifi will reduce male sperm motility" [1], and the paper thinks that there may be other effects besides thermal effect to reduce male sperm motility [2], but in this experiment, only semen in vitro was continuously irradiated for 4 hours, which is different from the actual situation that sperm in vivo received WiFi radiation; Whether sperm with reduced fluidity and increased DNA fragmentation will have a significant impact on the whole sperm population remains to be determined. In addition, there were only 20 experimental samples, and no repeated experiments were carried out. The setting of the control group is also unreasonable. Therefore, it is too early to simply infer that laptop wifi will reduce male sperm motility, and more research and verification are needed. The basic view of the scientific community on this kind of radiation in daily life is still: "At present, there is no credible evidence to prove that weak radio frequency signals will have an impact on human health". (Friendly recommendation shell user @ Leng Yue Rushuang's interpretation of this article-"Will notebook WiFi reduce male sperm motility? How should non-related professionals correctly understand and interpret the research results of biology and medicine? Discussion. " Secondly, it should be noted that the radiation of wireless Internet access mainly depends on the power of the signal, which is not necessarily related to the bandwidth of the wireless router. Bandwidth is equivalent to the amount of information you express at the same time, and power is equivalent to the sound when you speak. The bandwidth of communication depends on many factors. Just because the bandwidth is large doesn't mean that the radiation must be large. For example, the radiation of the first generation of mobile phones is much larger than that of the current mobile phones, but the bandwidth is very small, and only voice signals can be transmitted, even if there is a short message function; The latest mobile phones can transmit all kinds of multimedia information, but the radiation generated is decreasing. Actual measurement: far less than the safety upper limit. Nowadays, the coverage of wireless Internet service in cities is getting higher and higher, and wifi access points can be seen everywhere. So how much radiation will these wireless access points produce? In 2007, the Hong Kong Telecommunications Authority measured the radiation intensity around 62 wifi wireless routers in restaurants, convenience stores, libraries, houses, offices and other places in the city [3], and found that the measured values were only 0.03% to 0.3% of the safety upper limit of the International Commission on Non-ionizing Radiation, and these radiation values were measured very close to the wireless routers, and in most cases the radiation received by the routers would be much lower than these values. As Hong Kong is densely populated, small in area, with widespread wireless Internet access and dense wifi sites, the radiation situation in other cities should be low and unlikely to be higher than that in Hong Kong. In addition, there is basically no difference in wireless Internet devices used in different cities, so this measurement result is universal. The British Health Protection Agency once estimated that even if the wireless router with a certain distance from the body is turned on all the year round, the radiation it produces in 1 year is only equivalent to the radiation of a mobile phone for dozens of minutes [4]. Of course, the above only considers the radiation at the end of the wireless router. If you often use wireless internet access, you should also consider the radiation at the end of your laptop. The wireless router antenna stands upright outside, which is very conspicuous. mm with radiation phobia will inevitably have doubts when thinking about it. But in fact, for wifi users, the main source of wireless Internet radiation is not those routers that look "very professional and radiant", but laptops in their hands when surfing the Internet. Because when surfing the Internet wirelessly, the antenna in the user's laptop and the antenna on the router send and receive information to each other. The radiation emitted by the antenna in the notebook computer is not much smaller than that of the router, but the power of electromagnetic wave radiation is inversely proportional to the second power of the distance. The general wireless router may be several meters away, and the laptop is in front of you, but it is only a few centimeters. In this way, your laptop is often the real radiation source. So how does the wireless internet access function of notebook computer compare with the radiation size of mobile phone? According to the British Health Protection Agency's research [5], the SAR value of the radiation absorption rate of laptop wireless Internet access is only 1% when answering the phone with a mobile phone, mainly because of the distance mentioned above. Because mobile phones can be close to the brain, and laptops are far from the body. But we surf the internet wirelessly, which takes several hours at a time, and the mobile phone has a chance to talk for several minutes at a time. Considering the length of time, the radiation of laptop wireless internet access and mobile phone radiation should be about an order of magnitude. Whether it is a laptop or a mobile phone, their radiation value is usually at the level of milliwatts per square meter, which is far lower than the safety upper limit stipulated by the International Commission on Non-ionizing Radiation-10 watts per square meter (this upper limit is only a safety limit in case of emergency, which does not mean that you will get sick if you exceed this value, but there will be slight health risks). Conclusion: The rumor is shattered. Just like the radiation of mobile phones, the radiation of routers and laptops with wireless Internet access is within a safe range, so there is no need to panic. [Note] SAR value of radiation absorption rate: the amount of electromagnetic radiation absorbed by human tissues per unit time.