Mobile phones are low power radio devices that transmit and receive microwave radiation at frequencies of about 900 Megahertz (MHz) and 1800 MHz. There are many other sources of radio waves. Television broadcasts in the UK operate at frequencies between 400 MHz and 860 MHz and microwave communication links (dishes) operate at frequencies above 1000 MHz.
Cellular radio systems involve communication between mobile telephones and fixed base stations. Each base station provides coverage of a given area, termed a cell. While cells are generally thought of as regular hexagons, making up a 'honeycomb' structure, in practice they are irregular due to site availability and topography. Depending on the base station location and mobile phone traffic to be handled, base stations may be from only a few hundred metres apart in major cities, to several kilometres apart in rural areas. If a person with a mobile phone moves out of one cell and into another, the controlling network hands over communications to the adjacent base station. The use of mobile phones is developing rapidly and at present there are about 14 million users in the UK with about 20,000 base stations.
There is a consensus amongst international bodies that exposure guidelines for radio waves should be set to prevent adverse health effects caused by either whole or partial body heating. Some of the energy in the radio waves emitted by mobile phones is absorbed in the head of the user, mostly in superficial tissues. Exposure guidelines relevant to mobile phones are therefore expressed in terms of absorbed energy in a small mass of tissue in the head. The limit for exposure of the head, recommended by NRPB and adopted by the Government for use in the UK, is 0.1 watt of power absorbed in any 10 g of tissue (time averaged over 6 minutes). Calculations suggest this could result in a maximum rise in temperature of less than one degree centigrade in the head, even after prolonged exposure.
In practice, the output from mobile phones used in the UK results in only a fraction of this amount of energy being deposited in the tissues of the head, and therefore the rise in temperature would only be a fraction of a degree. This is similar to the normal daily fluctuations in body temperature and such small changes in heat load are considered to be too low to cause adverse effects.
At positions where the public are normally exposed to fields from base stations antennas, exposure is likely to be more uniform over the whole body. The restriction averaged over the whole body mass is 0.4 watts per kilogram (time averaged over 15 minutes). The radio waves produced by transmitters used for mobile phones are sufficiently weak that the guidelines can only be exceeded if a person is able to approach to within a few metres directly in front of the antennas.
Radio wave strengths at ground level and in regions normally accessible to the public are many times below hazard levels and no heating effect could possibly be detected. NRPB staff have made many measurements to support this view.
Concerns about other possible, so-called athermal, effects arising from exposure to mobile phone frequencies have also been raised. These include suggestions of subtle effects on cells that could have an effect on cancer development or influences on electrically excitable tissue that could influence the function of the brain and nervous tissue.
Radio waves do not have sufficient energy to damage genetic material (DNA) in cells directly and cannot therefore cause cancer. There have been suggestions that they may be able to increase the rate of cancer development (ie influence cancer promotion or progression). The NRPB Advisory Group on Non-ionising Radiation concluded, however, at a meeting in May 1999 '... that there was no human evidence of a risk of cancer resulting from exposure to radiations that arise from mobile phones'.
Furthermore, the evidence from biological studies on possible effects on tumour promotion or progression, including work with experimental animals, is not convincing. The lack of evidence does not, however, prove the absence of a risk and more specific research is warranted.
There has also been concern about whether there could be effects on brain function, with particular emphasis on headaches and memory loss. Few studies have yet investigated these possibilities, but the evidence does not suggest the existence of an obvious health hazard.
In view of the limited amount of high quality experimental and epidemiological studies published to date, NRPB has supported the need for further research as outlined by an Expert Group, which reported to the European Commission (EC) in 1996. This recommended a comprehensive programme covering cellular studies, experimental investigations in animals together with human volunteer studies and epidemiology. The Group stressed the need to replicate studies suggesting the possibility of effects. This programme is being developed within the Fifth Framework Programme of EC.
Summary: Despite the rather limited epidemiological and experimental data available, NRPB concludes that the totality of the evidence available does not suggest that the use of mobile phones have any detrimental effect on human health. Nevertheless, there does remain a need for further research.
June 1999
The following summarises the NRPB position on the issue of the safety of mobile phones. NRPB advice is based on critical appraisal of epidemiological (human health) evidence, biological studies and an examination of the physical interaction of electromagnetic fields with the human body.
There is a consensus among national and international expert bodies concerned with radiation protection that standards for the protection of people should be based on sound scientific evidence relating to established effects on human health. Recommended limits of exposure for radiofrequency radiation (which includes microwave radiation) in the United Kingdom and elsewhere are based on restricting whole and partial body heating. NRPB has published guidelines1 advising restrictions on the rate at which energy is absorbed in the body. Compliance with the guidelines will ensure that temperature rises are sufficiently small not to be harmful.
Mobile telephones are low power radio devices that transmit and receive microwave radiation. Exposure limits relevant to mobile phones are expressed in terms of absorbed energy in small masses of tissue in the head. In the UK, the limit recommended by NRPB is 0.1 watt of power absorbed in any 10 g of tissue in the head. The responsibility for complying with the recommended exposure limit lies with manufacturers. Calculations using an anatomically realistic mathematical model of the human head indicate that mobile phones currently used in the UK comply with the exposure limit.
Concerns about possible adverse health effects of exposure to electromagnetic fields, including cancer, have been raised. NRPB takes such concerns seriously and has committed considerable resources to addressing this general scientific issue. The NRPB Advisory Group on Non-ionising Radiation (AGNIR), chaired by the eminent epidemiologist Professor Sir Richard Doll, has reviewed the scientific evidence on exposure to electromagnetic fields and the risk of cancer. The conclusion of the Group was that there is no firm evidence that electromagnetic fields cause cancer but that there is a need for further good quality research to be carried out. The AGNIR continues to review the published literature.
Scientific data relating to other possible effects arising from exposure to electromagnetic radiation at frequencies similar to those of mobile phones are few and inconsistent. Some studies in rodents have suggested that extended exposure to high levels of microwave radiation can influence the function of the brain. The studies are not however, representative of human exposure conditions arising from the use of mobile phones. Effects on memory and other brain functions in people using mobile phones under normal conditions of use are not expected. There is a need, however, for further research, including replication of those studies where effects have been reported.
In 1996 the European Commission (EC) set up an Expert Group mandated to draw up a 'blueprint for research' into possible health effects relating to the use of mobile telephony. The Expert Group comprised experts in the fields of biology, medicine, epidemiology, dosimetry, telecommunications and radiation protection drawn from eight of the member states of the European Communities. The Head of the NRPB Non-ionising Radiation Department, Dr Alastair McKinlay, chaired the Expert Group, which reported to EC at the end of September 1996. The Group reviewed the published scientific literature, examined research needs and identified appropriate studies to be carried out. It recommended a comprehensive research programme covering cellular studies, experimental investigations in animals, human volunteer studies and epidemiology. The proposed work programme includes studies on any mechanisms of interaction of microwave radiation with cells and tissues, an examination of possible effects on DNA, brain cells, physiology, behaviour and cancer-related processes, as well as epidemiological studies on the risk of brain and other cancers. The Group also provided an overview of a research management infrastructure to ensure the independence and quality of the research work.
NRPB endorses the call for research in this area and fully supports the EC initiative.
Information Sheet No 2/98
12 February 1998
The use of radio waves to carry information is an integral part of modern life and there are many different types of radio transmitter in the environment. These include the broadcast transmitters used for radio and television, the radio equipment used by the emergency services, mobile telephones and their associated base stations.
Mobile telephone base stations are low power radio transmitters with antennas mounted on either free-standing towers or on buildings. Radio signals are fed through cables to the antennas and then launched as radio waves into the area, or cell, around the base station. Two types of antennas are used for the transmissions; pole-shaped antennas are used to communicate with mobile telephones and dish antennas communicate to other base stations and link the network together.
There is a consensus among national and international expert bodies concerned with radiation protection that exposure guidelines for the protection of people should be based on sound scientific evidence relating to established effects on human health. Recommended limits on exposure to radiowaves (including radiofrequency and microwave radiation) in the United Kingdom and elsewhere are based on restricting whole and partial body heating. NRPB has published guidelines1-3 advising restrictions on the rate at which energy is absorbed in the body. Compliance with the guidelines will ensure that temperature rises are sufficiently small not to be harmful.
The transmissions from any particular base station are variable and dependent upon the number of calls and the number of transmitters in operation. In general, the following points are relevant to the exposure of people to radio waves emitted by base stations.
When measurements are made of radio wave signal strengths at a given location, it is possible to detect the signals from many different radio transmitters, and all will contribute to a person’s total exposure. NRPB measurements have shown that signals from less obvious, or more distant, transmitters can sometimes exceed exposures produced by a visually more prominent transmitter such as a mobile telephone base station. Nevertheless, at locations to which the public normally has access around base stations, the exposure from all radio sources combined is usually very many times below exposure guideline levels.
Concerns about possible adverse health effects of exposure to electromagnetic fields, including cancer, have been raised. NRPB takes such concerns seriously and has committed considerable resources to addressing this general scientific issue. The NRPB Advisory Group on Non-ionising Radiation (AGNIR), chaired by the eminent epidemiologist Professor Sir Richard Doll, has reviewed the scientific evidence on exposure to electromagnetic fields and the risk of cancer. AGNIR continues to review the published literature.
In May 1999 the Group concluded that 'there is no human evidence of a risk of cancer resulting from exposure to radiations that arise from mobile phones'. Furthermore, biological studies on possible effects on human prevention or progression, including work with experimental animals does not provide clear evidence of a risk. The lack of evidence does not, however, prove the absence of a risk and more specific research is warranted, although the Advisory Group agreed that on the basis of present evidence there was no cause for concern.
In 1996 the European Commission (EC) set up an Expert Group mandated to draw up a 'blueprint for research' into possible health effects relating to the use of mobile telephony. The Head of the then Non-ionising Radiation Department at NRPB, Dr Alastair McKinlay, chaired the Expert Group, which reported to EC at the end of September 1996. The Group reviewed the published scientific literature, examined research needs and identified appropriate studies to be carried out. It recommended a comprehensive research programme covering cellular studies, experimental investigations in animals, human volunteer studies and epidemiology. The proposed work programme includes studies on possible mechanisms of interaction of microwave radiation with cells and tissues, an examination of possible effects on DNA, brain cells, physiology, behaviour and cancer-related processes, as well as epidemiological studies on the risk of brain and other cancers. The EC Fifth Framework Programme of Research includes the major aspects of these recommendations.
NRPB endorses the need for research in this area and fully supports the EC initiative.
December 1999
Last updated 20th December 1999