Characteristics of the application and its use
Mobile phones operate in the high frequency (HF) range of the electromagnetic spectrum, from several hundred MHz to several GHz, to enable wireless phone calls and data transfer, including communication through the internet. The exact frequency band used differs between technologies (GSM, UMTS, 4G, etc.) and between countries.
HF fields allow the transport of large amount of data at a very fast rate (up to the speed of light) over large distances. The signals must be relayed by a communications network comprising base stations and antennas and often supported by a wired network. To save energy, a mobile phone automatically regulates the signal strength and hence the emitted field to the lowest power level possible to enable a connection to be made. A poor transmission environment, for example caused by the base station being very distant or by the presence of obstacles such as hills, buildings, trees and so on, between the base station and the mobile phone, will result in a higher output power and emission from the mobile phone in order to make a connection. The better the connection, the lower the power output.
HF effects on the body and health implications
HF fields have the ability to penetrate into the body (the higher the frequency, the lower the depth of penetration), with the effect of this being a temperature rise in body tissue. The body can accommodate a small increase in heat, in a similar way that excess body heat is dissipated when performing sporting activity. This is because the human body has a strong ability to regulate its internal temperature. However, above a certain level (referred to as the threshold) depending on the duration of exposure, HF exposure and the accompanying temperature rise can provoke serious health effects, such as heatstroke and tissue damage (burns).
Acute and long-term effects of HF exposure from the use of mobile phones have been studied extensively without showing any conclusive evidence of adverse health effects.
Among all of this research, the risk of tumors in close proximity to the ear where the phone is held, e.g. brain tumors, has been the focus of numerous epidemiological studies. A few of these epidemiological studies have reported a slight increase in risk of some brain tumors for the small group of long-term and heavy mobile phone users (read more). These findings may be explained by reporting biases and weaknesses identified in the studies. Several studies have not reported any increase in brain tumors with mobile phone use. Also, experimental studies on animals and cells have failed to confirm the findings of the epidemiological studies, and there is no biophysical mechanism that could explain carcinogenicity at such low exposure levels. In addition, the increased risk observed in some of the epidemiological studies is inconsistent with the stable frequency of occurrence of these tumors in the population. That is an important consideration, given the widespread and significant increase in the use of mobile phones in the general population during the last few decades.
A considerable amount of research has also been conducted on the relationship between HF fields and other outcomes such as headaches, concentration difficulty, sleep quality, cognitive function, cardiovascular effects, etc. To date, this research has not shown any such health effects. The only consistently observed finding is a small effect on brain activity measured by electroencephalography (EEG). The biological implication of these small changes is, however, unclear. For example, they have not been shown to affect sleep quality or be associated with any other adverse effects.
The overall evaluation of all the research on HF fields as emitted by mobile phones leads to the conclusion that HF exposure below the thermal threshold is unlikely to be associated with adverse health effects.
To avoid health hazards from HF exposure emitted by mobile phones, the temperature rise in the body must be restricted. This can be achieved by limiting the absorption of HF energy, expressed in terms of the Specific Absorption Rate (SAR). In its guidelines ICNIRP recommends distinct SAR values applying to whole-body exposure, which is typical from base stations and for the head, and other locations in the body that are relevant for exposures from mobile phones.
ICNIRP follows up the HF related scientific research and any new information relevant to health. A revision of the current ICNIRP guidelines on HF used in conjunction with a mobile phone is underway.