Electromagnetic fields have been around in different forms since the birth of the universe. They differ from each other by frequency and visible light is its most familiar form.
Electric and magnetic fields are part of the electromagnetic spectrum which extends from static electric and magnetic fields, through radio frequency (RF), infrared radiation, and visible light to X and gamma-rays.
An electromagnetic field consists of waves of electric and magnetic energy moving together through space. Often the term "electromagnetic field" or EMF is used to indicate the presence of electromagnetic radiation.
Part of the electromagnetic spectrum extending from 3 kHz frequency to 300 GHz is referred as radio frequency (RF). Television and radio transmitters (including base stations) and microwaves, mobile telephones, and radars produce radio frequency fields. These fields are used to transmit information and form the basis of telecommunications as well as radio and television broadcasting all over the world. Many home devices also transmit EMF at radio frequencies such as cordless phones, baby monitors and radio-controlled toys.
Electromagnetic radiation at frequencies above the UV band are classified as "ionizing radiation", because they have enough energy to effect changes in the atoms, by liberating electrons (ionizing) and thus altering their chemical bonds. X-rays and gamma rays are common forms of ionizing radiation.
Ionizing radiation occurs at frequencies above 2900 THz (2900×1012 Hz). This corresponds to a wavelength of about 103.4 nm, which lies near the lower wavelength-edge of the Ultraviolet (UV) spectrum.
Electromagnetic radiation at frequencies below the UV band are classified as "non-ionizing radiation" because they lack the energy to liberate electrons, i.e. ionize or effect changes in atomic structure. Radio frequency fields are non-ionizing radiation.
Wireless communication technology has become indispensable part of the modern society. The use of mobile phones, tablets and wireless devices have become basic communication tools of everyday life for billions of people around the world, and also common for medical applications. Base stations and telecommunications towers are continuously being erected to provide good quality wireless communications.
Together with the introduction of wireless communication technologies, there has been some public concern about the potential health risks associated with wireless communications including the use of mobile phones and living near base stations.
Electromagnetic fields (EMFs) of all frequencies represent one of the most common and fastest growing environmental influences. As part of its charter to protect public health and in response to public concern, the WHO established the International EMF Project in 1996. The purpose of the EMF Project is to assess the scientific evidence of possible health effects of EMF in the frequency range from 0 to 300 GHz.
Further information on the WHO EMF project is available at http://www.who.int/peh-emf/about/en/.
In terms of EMF and health the WHO notes that:
In regards to mobile phones and health, the WHO notes that:
"While an increased risk of brain tumours from the use of mobile phones is not established, the increasing use of mobile phones and the lack of data for mobile phone use over time periods longer than 15 years warrant further research of mobile phone use and brain cancer risk. In particular, with the recent popularity of mobile phone use among younger people, and therefore a potentially longer lifetime of exposure, WHO has promoted further research on this group and is currently assessing the health impact of RF fields on all studied endpoints."
With respect to base stations and health, the WHO notes that:
"Studies to date provide no indication that environmental exposure to RF fields, such as from base stations, increases the risk of cancer or any other disease."
In terms of human exposure guidelines, the WHO notes that:
Extensive research has been conducted into possible health effects of exposure to many parts of the electromagnetic spectrum.
As noted by the WHO, in the area of biological effects and medical applications of non-ionizing radiation approximately 25,000 articles have been published over the past 30 years. Despite the feeling of some people that more research needs to be done, scientific knowledge in this area is now more extensive than for most chemicals.
At frequencies above 10 MHz, the first scientifically-established effect to occur is heating. At frequencies below 10 MHz, the first effect to be experienced is non-thermal nerve stimulation (a tingling sensation).
Summary of the IARC classification of RF EMF
IARC World Cancer Report 2014
A mobile phone or wireless device is a low-power two way radio operating at a maximum of 2 watts (peak). It contains both a transmitter and a receiver and uses radio frequency fields to send and receive calls, text messages, emails, pictures and data.
When you make a call on a mobile phone, send or receive text messages or data, you are connected to a nearby base station through a radio frequency signal. The base station then communicates with the core of the network to a central exchange to determine where the call is to be forwarded to, then either your call is forwarded to the fixed line network and to an individual fixed land line phone, or if you are calling another mobile phone, your call will be forwarded to another base station and on to the mobile phone you are calling.
When you access data via your mobile device, the central exchange connects you to the internet.
Mobile phone base stations are low-power, multi-channel two-way radios located inside an equipment hut or cabinet. The base station antennas, which transmit and receive the radio signal, can be mounted on transmission towers, poles, roof-mounted structures or in small microcell boxes providing localized coverage. Mobile phone base station radio transmitters typically operate at between 2-50 watts. In rural areas base stations may use additional power amplifiers for the transmitter and receiver to extend the coverage.
The location and positioning of the base station antennas are carefully chosen to match the required coverage area. Small base station antennas are often located inside buildings to provide dedicated indoor coverage.
It's important to know the difference between antennas and towers. Towers are the structures to support the antennas. Like a street light where the brightness depends on distance from the light and not on its support pole. You need to keep your distance from the antennas that transmit the radio signal and not the towers that hold the antennas.
You also need to be aware of the many different designs of mobile phone base stations that vary widely in their power and characteristics, affecting their potential for exposing people to RF signals. Research has shown that at the ground level, the intensity of radio frequency signal from base stations are typically less than one thousandth of those from mobile phones.
Overall mobile phone base stations operate at low power. The power from a mobile phone base station will vary depending on the number of mobile phone calls and amount of data traffic being carried. In addition to the data and mobile phone calls, a pilot signal is continuously transmitted from the base station so that nearby mobile phones can detect the network.
Mobile phones use low power transmitters that are less than two watts peak. Mobile phones are designed to automatically transmit at the lowest possible power to maintain a quality connection. This is a feature known as adaptive power control.
Refer to the Mobile Phones Q&A section for more information.
Specific absorption rate (SAR) is a measure of the amount of RF energy that is absorbed by the tissues in the human body and expressed in watts per kg (W/kg). This measurement is used to determine whether or not a mobile phone complies with the safety standards or guidelines.
The SAR from a mobile phone varies considerably during use due to adaptive power control and the connection back to the mobile network. A maximum SAR value does not provide sufficient information about the amount of RF exposure under typical usage conditions to reliably compare individual cell phone models. The level of exposure depends on the distance between the person and the mobile and the amount of RF power the mobile transmits.
Mobile devices will attempt to use the minimum amount of energy to provide a reliable service quality while at the same time preserve battery life, actual exposure varies continually depending on a range of factors:
Mobile phone manufacturers must ensure that their products comply with the maximum SAR levels specified in the human exposure guidelines.
Mobile phones are tested for compliance at their highest possible power level through rigorous tests and multiple SAR measurements, therefore SAR values reported for each model of mobile phone tend to significantly overstate real-life exposure levels, as they rarely operate at maximum power levels during everyday use.
Each model of mobile phone or wireless device is tested using internationally agreed standards.
The SAR in the head is tested using a 'phantom' head and the SAR in the body is tested using a 'phantom' torso. The phantoms are filled with liquids that simulate the electrical properties of human tissue.
The SAR values are measured with the phone or device
A probe inside the liquid measures the electric field strength inside the phantom and uses this to determine the maximum SAR value for the model of phone or device in each particular configuration.
As a result, the testing is both complex and time consuming. For full compliance testing, the process can take up to several weeks depending on the model in question.
A video showing the SAR testing procedure is available at EMF Explained.
SAR data from actual measurements of seven different devices is shown in the following attachment tested to the ICNIRP SAR limit of 2W/kg averaged over a 10 gram mass.SAR Test Results
Yes. The SAR can vary due to the different operating frequencies, usage positions and power.
The SAR can also vary depending on the mobile technology. Newer mobile technologies are more efficient and use less RF power; therefore, the EMF exposure from newer technology devices is lower for similar voice or data services.
No. The maximum SAR varies for a number of reasons including the type and location of the antenna, the operating frequency, and test position. However these variations do not mean that there are variations in safety.
Variations in the maximum reported SAR reflect that they were recorded under different conditions but are also influenced by technical parameters such as the antenna used and its placement within the device.
SAR is designed to demonstrate compliance with the relevant national or international limits, and in doing so, can be derived from a wide variety of testing configurations that are rarely directly comparable or even reflective of everyday usage conditions.
The declared maximum SAR value of a phone does not for example reflect that once a call is established the mobile phone will power down to the minimum power level required to reach the base station and maintain a quality call.
The SAR information for a mobile phone should be available from the manufacturer's web site. This information and any other instructions on use should also be printed in the user manual that accompanies each mobile phone. Certain regulatory agencies provide the SAR values of mobile phones on their website.
For SAR values got to the SARTICK website.
A number of national and international organizations have formulated guidelines establishing limits for occupational and general public RF EMF exposure up to 300GHz.
|ICNIRP Guidelines||The exposure limits for EMF fields developed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) - a non-governmental organization in official relations with the WHO, were developed following reviews of all the peer-reviewed scientific literature, including thermal and non-thermal effects.
The guidelines are based on evaluations of biological effects that have been established to have health consequences. The main conclusion from the WHO reviews is that EMF exposures below the limits recommended in the ICNIRP International Guidelines do not appear to have any known consequence on health.
ICNIRP has an ongoing program to monitor scientific research and ensure the human exposure guidelines are up to date.
Visit the ICNIRP web site at http://www.icnirp.org
|ICES/IEEE Safety Standards||The Institute of Electrical and Electronics Engineers (IEEE) is a professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence, and includes the International Committee on Electromagnetic Safety (ICES) focused on development and maintenance of EMF Safety Standards. IEEE C95.1-2005 - Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz.|
The ICNIRP and IEEE guidelines are similar, science based and accepted in many countries around the world.
The basic SAR restrictions recommended by ICNIRP for the general public have been set 50 times below the levels at which adverse health effects have been established. The wide safety margin ensures that any increase in body tissue temperature is negligible.
For workers, the limits are five times higher than those of the general public. The rationale for having lower limits for the general public is that this group includes children, pregnant women, the elderly and other persons of varying health status or susceptibility, and exposure might be continuous (24 hours a day) and people may be totally unaware of an exposure. The SAR values are to be averaged over any six-minute period of exposure. This averaging period reflects the fact that it takes time for body temperature to rise during exposure to RF fields.
Recommendation ITU-T K.61 - "Guidance on measurement and numerical prediction of electromagnetic fields for compliance with human exposure limits for telecommunication installations"
EMF Estimator is a software application that implements the methodology described in ITU-T K.70 to calculate the cumulative radio frequency exposure levels in the vicinity of transmitting antennas.
Recommendation ITU-T K.90 "Evaluation techniques and working procedures for compliance with exposure limits of network operator personnel to power-frequency electromagnetic fields"
Find supporting software here.
Recommendation ITU-R BS.1698 "Evaluating fields from terrestrial broadcasting transmitting systems operating in any frequency band for assessing exposure to non-ionizing radiation"
Report ITU-D Question 23/1 "Strategies and policies concerning human exposure to Electromagnetic fields"
ITU-R Handbook "Spectrum Monitoring"
IEC Standards are developed by the International Electrotechnical Commission. The IEC is a not-for-profit, non-governmental organization, founded in 1906. The IEC's members are National Committees, and they appoint experts and delegates coming from industry, government bodies, associations and academia to participate in the technical and conformity assessment work of the IEC.
IEC Technical Committee 106 is responsible for preparing international standards on measurement and calculation methods to assess human exposure to electric, magnetic and electromagnetic fields.
A list of the relevant IEC standards is available from the IEC TC106 web site.
Note: The IEC and ICNIRP have agreed on the sharing of responsibilities for EMF standards. EMF exposure limits guidelines are developed by ICNIRP and EMF exposure assessment standards developed by IEC.
The IEEE also prepares compliance assessment standards for electromagnetic fields in the frequency range 3 kHz to 300 GHz. The relevant IEEE standards for EMF are available from the IEEE web site using "EMF" in the search box on the web site.
The IEC and IEEE also have a formal sharing arrangement. Based on the dual-logo agreement between IEC and IEEE, in the future the EMF compliance assessment standards developed by the IEC will also carry the IEEE logo, i.e. will become IEEE standards.
Do mobile phones emit radiation?
How much power does a mobile phone transmit?
How does Adaptive Power Control Work?
Does the EMF from my mobile vary?
What are the exposure levels from mobile phones?
What is the typical power of a mobile?
How can I reduce exposure from my mobile?
Do mobile phone shields reduce exposure?
Do mobiles radiate less EMF when close to a base station?
Do mobiles emit less EMF when the signal display has full bars?
Does texting emit less EMF compared to a voice call?
Are we at a high risk of EMF exposure when using mobile phones inside high speed transportation?
Is using a mobile phone in the car or at home safer because these constitute a barrier to radiation?
Are children more vulnerable to the EMF from mobile phones than adults?
What are the EMF levels around base stations?
Is it safe to live near a base station or locate base stations near schools or hospitals?
Do more base stations reduce EMF?
Is it safe to locate base stations on hospitals?
Are there restricted areas in front of base station antennas?
Who sets the EMF human exposure standards?
Is there a safety margin built into the standards?
Are children and pregnant women protected by the safety standard?
Are people with electronic implants protected by the safety standard?
Is it possible to cook an egg or grains of corn using a mobile phone?
Is the power output of a mobile phone enough to make the brain boil?
Does use of a mobile phone attract lightning?
Can a mobile phone cause a gas station to catch fire?
As part of its mandate, ITU carries out a series of activities on human exposure to electromagnetic fields.ITU-T Activities on EMF
The ITU (International Telecommunication Union) is the United Nations specialized agency for information and communication technologies (ICTs).
This Guide has been developed by ITU with the contribution of its membership which comprises governments, private sector entities and academic institutions.
This application will be regularly updated based on new information or research made available by ITU and WHO.
International Telecommunications Union http://www.itu.int
World Health Organization http://www.who.int
EMF Explained Series http://www.emfexplained.info
Mobile Manufacturers Forum http://www.sartick.com/
GSM Association http://www.gsma.com/health
Australian Mobile Telecommunications Association http://www.amta.org.au/