World over the mobile phone use is increasing with each passing day. According to the ITU there are over 6 billion mobile phone connections all over the world and the number of users is more than 3 billion. There is little doubt that in coming years these numbers are going to increase. As newer technologies like 4G are introduced and as the world prepares itself for 5G even more mobile sites and devices will be introduced since the IoT (Internet of Things) will require more connections with each device talking to another. More devices, more coverage, more services and this will ultimately mean more radio signals in the air. A much misunderstood issue related to the growth of mobile phones is that of radio signals and their effects on human health.
With various broadcast and telecommunication services like TV, Radio and Cellular phones simultaneously operating all around us there is a lot of electromagnetic radiation in the environment. Here lies the problem because some people confuse the term “radiation” with atomic energy or any other form of radiation. The important thing to understand is that there are some frequencies which lie in the highest bands and and which have sufficient energy to disrupt the body’s chemical composition such as X-rays or Gamma rays and hence can be a cause for cancer. The lower frequencies are non-ionizing and cannot cause genetic disorders to human body. Please see the figure below for comparison, red area is ionizing spectrum whereas the green is non-ionizing.
Then there’s microwave frequencies which can cause heating to body tissue and Infra red which causes surface heating. It is for this reason that standards have been developed by leading health organizations fro providing protection to the public as well as workers who actually work in or near the sites that radiate electromagnetic energy. The Surface Absorption Rate or the SAR measured in Watts/Kg is a measure of the absorbed RF energy. So the important question to ask is whether, “electromagnetic energy is harmful to human body or not”. According to the World Health Organization more research has been carried out on this subject than has been carried out on many chemicals. The various detailed studies carried out so far conclude that there are no established health issues to the human body because of RF exposure below the recommended standards. However, uncertainties so exist and more studies or research has been recommended on the subject. Which means no single study is conclusive of ill or no effects to the human body. The EMF portal for example has over 19,000 studies on the subject which can be accessed for reference. Also that there are some established facts about effects of EMF like heating etc but cancer or fertility issues have not been established because of exposure to the RF. In any case it is established that exposure to RF energy or Electromagnetic Field (EMF) causes heating of body at surface or even deeper level. Therefore the public exposure limits have been set with large safety margins in order to prevent the known hazards.
IARC which works under the WHO has been actively involved in the classification and review of agents, chemicals or environmental hazards which can be termed as carcinogenic. According to the 2013 IARC Monograph the RF and EMF have been classified as possible carcinogenic agents. The report summarizes that there could be some risk from cell phones so more studies should be carried out in future. It also says that users should resort to hands-free devices and texting as a precaution. Based on this report the WHO published a fact sheet further clarifying that no credible evidence exists of adverse health effects of cell phone use had been found. It further stated that in addition to using hands-free and texting, users should limit call duration and frequency, as a precaution. A brief summary of the IARC Monograph has been prepared by the GSMA which can be accessed here.
SAR Limits. WHO and ITU recommend the ICNIRP limits and these are widely adopted world over. ICNIRP is an independent body that develops safety standards specially for RF range. ICNIRP has set the SAR threshold at 4 W/kg but recommends 10% of this value for site workers i.e. 0.4 W/kg (whole body average SAR) and 2% for general public i.e. 0.08W/kg (whole body average SAR). By all accounts these limits are very strict. Since its not always possible or easy to measure SAR levels so ICNIRP also recommends external exposure limits in the form of Power density, Electric field strength or the Magnetic field strength as all three are related. Based on these recommendations the compliance zones can be set using specialized monitoring equipment. So for near zones where both E and H field are measured as these are not related by the 377 Ohms free space impedance but for far fields only one measurement is good as the other can be derived from it. It is therefore important to have properly calibrated equipment for making the broadband measurements. It is also very important to us proper probes, know the frequencies in advance, check the equipment, look out for hazards like working at height etc.
For complex or congested sites narrow-band (frequency selective) equipment should be used as signals from different antenna will be present there. Besides this Power density (field strength) can also be calculated based on formulae by taking in to account data of transmitted power, antenna gain and the distance. So its also possible to mark safe zones without making measurements, quickly. But for compliance purposes its better to make measurements and tell this it the public or organizations/Government bodies that are watching the environment.
So to summarize this topic, the effects of EMF or RF (as it is sometimes called) on human body is a much misunderstood phenomena. This has been a subject of debate world over as people tend to carry the impression of its being harmful, or carcinogenic. Since the scientific evidence is inconclusive regarding the issue therefore, WHO and other bodies recommend use of hands-free devices or texting for safety of users. But at the same time they also recommend that more studies need to be carried out to gain more insight in to the issue. So it is important to communicate the results to the public. It is also very important for the various Telecom regulators to adopt international safety standards regarding health hazards from RF.
GSMA runs very useful online courses on various subjects. You can follow the link to register yourself for training on Radio Signals and Health here.