Frequently Asked Questions
- What is radiofrequency (RF) energy?
- What are typical sources of RF exposure?
- Are there other types of electromagnetic radiation?
- What is the difference between RF and other forms of electromagnetic radiation?
Electromagnetic energy and Health
Radiofrequency (RF) energy is a type of electromagnetic radiation. Electromagnetic radiation consists of waves of electrical and magnetic energy which 'radiate' (that is, travel) through space. The number of waves occurring per second is known as the frequency of the electromagnetic radiation and is measured in Hertz (Hz). Radiofrequency electric and magnetic waves occur at a rate of 3 kilohertz (kHz) - 300 Gigahertz (GHz).
Typical sources of radiowaves include television and radio transmitters, mobile phone signals, mobile phone towers, magnetic resonance imaging (MRI), microwave ovens, and smart meters. The sun also emits radiowaves.
Radiowaves are only one portion of the electromagnetic spectrum. Other forms of electromagnetic radiation includes ultraviolet light, visible light, and x-rays. Each of these types of radiation are defined by their frequency.
The frequency of an electromagnetic wave has very important consequences for the way in which it interacts with the human body. Very high frequency electromagnetic waves, such as x-rays, gamma rays, and radiation emitted from radioactive substances are classified as ionising forms of radiation. This means that they carry sufficient quantum energy to strip electrons away from atoms creating free radicals which can be damaging to cells in the human body, subsequently high doses of ionising radiation is damaging to the human body and human DNA and can cause cancer.
Radiowaves, visible light and microwaves are all considered non-ionising forms of radiation. This is because, no matter how intense, non-ionising radiation is incapable of breaking electrical bonds within atoms. However, non-ionising radiation does cause a heating effect which is proportional to its intensity and if present in sufficient quantity may be harmful.
Electromagnetic Energy and Health
It is widely accepted that emissions from mobile phones cause minute heating of the brain. This is due to two factors. First, the electric field generated by mobile phone causes electrically charged particles in brain tissue to move. The electrical properties of the brain tissue provide some resistance to this movement, and this produces heat. Second, the electric field causes water molecules, which are positively charged at one end and negatively charged at the other, to rotate such that they are electrically aligned with the electrical field. Due to the cohesive properties of water, there is again some resistance to this process, thus producing heat.
The power output of mobile phones are limited by international standards to protect users from excessive heating. These standards dictate that the average specific energy absorption rate (SAR) in any 10g region of biological tissue produced by radiofrequency emission must be less than 2 W/kg for the public and 10 W/kg for those who are occupationally exposed. At these levels, the degree of heating within the brain at the point closest to a mobile phone antenna is thought to be less than 1°C. This heat is thought to dissipate quickly to surrounding tissue and is thought to pose no health risk. Based on current evidence, RF-induced heating of brain tissue is the only widely accepted explanation for possible RF-induced changes in cognition (memory and attention).
Nevertheless, there have been several theories about how mobile phone emissions may interact with biological tissue through mechanisms which do not involve heat (non-thermal mechanisms). For example, it has been suggested mobile phone emission could also exert magnetic forces on the ferrimagnetic compound magnetite (Fe3O4) which occurs naturally within the body. Because this compound is often mechanically linked to cellular ion channels (the gates to the inside of cells) within the brain, these forces may open ion channels leading to altered nerve cell activity. However, this and many other non-thermal theories are doubtful, as almost all supporting evidence has been obtained using electromagnetic radiation outside of the radiofrequency range or of far greater intensity than is emitted by mobile phones. Based on present evidence and currently accepted laws of biophysics, it has been argued in several recent scientific reviews that it is very unlikely that mobile phones are able to interact with biological matter through non-thermal mechanisms. Nevertheless, a select number of proposed non-thermal interaction mechanisms have some experimental support which requires further research.
There has been numerous studies of the relationship between radiowave exposure and cancer, ranging from animal and biological tissue sample studies to human studies in which the health of human volunteers is monitored in relation to their exposure to radiowaves (e.g. through mobile phone use). This literature has been reviewed by numerous national and international committees, expert working groups and agencies. In 2011 the World Health Organsiation/International Agency for Research on Cancer (IARC) classified radiofrequency electromagnetic fields as being possibly carcinogenic to humans (classification group 2B) based on an increased risk for glioma associated with wireless phone use. The evidence was evaluated as being limited, and this classification reflects this, indicating that there could be some risk and additional research is therefore required.
The antennas used by base stations are placed up high and emit radiowaves in a horizontal direction. Radiowaves spread out as they travel and hit the ground at some distance from the antenna, like water from a water sprinkler. This means that the point of maximum radiowave exposure is located at some distance from the antenna. Typically peak exposure may occur at 100 metres from the antenna, but even here the amount of radiowave exposure received is considered very low and is considerably less than one would receive when using a mobile telephone. However distances to peak radiowave strength vary considerably based on the antenna height, tilt and orientation (e.g. distance of 14 to 480 metres from the antenna have recently been reported in Australia). The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) conducted a study in which radiowaves were measured in the vicinity of 60 mobile phone base stations in five Australian state capitals. In all cases the measured levels were found to be far below the applicable exposure limits.