Memorandum submitted by the National Radiological Protection Board
1. The National Radiological Protection Board (NRPB) was established by the Radiological Protection Act 1970. Its purpose is to provide advice to protect the health of the public, workers who are occupationally exposed, and patients undergoing medical treatment, from radiation hazards. Advice covers ionising radiations (for example, x-rays and gamma rays) and non-ionising radiations (including ultraviolet radiation and electric and magnetic fields). NRPB also carries out research to underpin its advice and provides technical services.
ADVICE ON HEALTH CONCERNS
2. To support the advice given by the Board and its staff on health-related issues, Advisory Groups on Ionising Radiations (AGIR) and Non-ionising Radiations (AGNIR) have been set up. The AGNIR was established in 1990 under the chairmanship of Sir Richard Doll and has as members leading researchers from the UK in epidemiology and experimental biology. The membership has been changed at intervals to reflect the issues under review. The Group has produced a series of influential reports (See references, below) on health effects of electromagnetic fields (EMFs) 1,2, on exposures from visual display units 3 and on ultraviolet radiation (UVR) 4. A further substantive report on EMFs is being prepared for publication at the end of this year.
3. Advice from NRPB draws on research and assessments by its staff and advice from its Advisory Groups as well as taking input from its active involvement in the work of national and international bodies. The Board aims to ensure that its advice reflects current understanding and evaluation of the scientific evidence. If and when further relevant information becomes available, the Board would review its advice.
MOBILE PHONES AND BASE STATIONS
4. The Science and Technology Committee is specifically concerned about the extent to which there are grounds for health concerns from mobile phones and transmitter base stations. The following summarises NRPB's position on this topic:
5. 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 radiowaves. 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.
6. Cellular radio systems involve communication between mobile telephones and fixed base stations. Each base station provides coverage of a given area, termed a cell. 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 around 14 million users in the UK with about 20,000 base stations.
7. There is a consensus amongst international bodies that exposure guidelines for radiowaves should be set to prevent adverse health effects caused by either whole or partial body heating. Some of the energy in the radiowaves 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. At positions where the public are normally exposed to fields from base station antennas, exposure is likely to be more uniform over the whole body. Restrictions are then based on whole body exposure.
8. The limit for exposure to the head, recommended by NRPB 5 and adopted by the Government for use in the UK, is 0.1 watt of power (time averaged) absorbed in any 10 grams of tissue. Calculations suggest this could result in a maximum rise in temperature of less than a degree centigrade in the eye and about half a degree centigrade elsewhere 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 can cause a rise in temperature of only a fraction of a degree. This is similar to the normal daily fluctuations in body temperature. Such small changes in heat load are thought to be too low to cause adverse effects.
9. For whole body exposure the limit recommended 5 is 0.4 watts per kg (time averaged). The radiowaves 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 would be detected. NRPB staff have made many measurements to confirm this conclusion.
10. 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. NRPB has been active in researching this latter area.
11. Radiowaves do not have sufficient energy to damage genetic material (DNA) in cells directly and cannot therefore initiate cancer. There have been suggestions that they may be able to increase the rate of cancer development (ie influence cancer promotion or progression). NRPB's Advisory Group on Non-ionising Radiation concluded, however, at a meeting in May, 1999 6 "that there was 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 tumour promotion 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.
12. 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.
13. In view of the limited amount of high quality experimental and epidemiological studies published to date, the NRPB has supported the need for further research, as outlined by an Expert Group, which reported to the European Commission in 1996 7. 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 now being developed within the Fifth Framework Programme of the EC.
14. There are aspects of the developing technology of mobile phones that are resulting in progressive reductions in exposure. The change from analogue to digital systems has resulted in an overall reduction in exposures. Additionally, there are power variations during use that can change exposures. Thus both analogue and digital handsets change their output power during a conversation to the minimum necessary to maintain efficient communication with the base station. Calls are initiated at full power and then reduce to the appropriate power level, which is up to a factor of 100 lower in most cases. Power reverts to the maximum immediately after hand-over to an adjacent base station. Some mobile phones use discontinuous transmission and only transmit when the user is actually speaking. This should reduce average output power by more than 50 per cent. During standby mode, when the cellular handset is switched on and ready to receive incoming calls, its output level is much lower than during a call, although some communication has to be maintained so the network is able to keep track of the handset. Typical output powers are likely to be at least 100 times below those used during a call.
15. These power adaptions are designed to make efficient use of the network and will also conserve battery power.
16. NRPB is involved in relevant research on possible health effects resulting from exposure to radiowaves from mobile phones and base stations. The work of its own staff, contacts with other organisations, and the support of its Advisory Group on Non-ionising Radiation ensures relevant advice is given to Government. While the present evidence suggests that provided exposures from mobile phones and base stations are within NRPB guideline levels, they should not have any adverse effect on health, further specific research is needed to underpin this advice. The Public Health Minister, Tessa Jowell, has recently asked the Chairman of NRPB to set up an "Independent Expert Group on Mobile Phones" to conduct a rigorous assessment of existing research and to identify where further research is needed so that the public can receive clear advice about any risks from the use of mobile phones.
1. NRPB. Electromagnetic fields and the risk of cancer. Report of an Advisory Group on Non-ionising radiation. Doc. NRPB, 3, No. 1, 1138 (1992).
2. NRPB. Electromagnetic fields and the risk of cancer. Supplementary report by the Advisory Group on Non-ionising Radiation (12 April 1994). Doc. NRPB, 5, No. 2, 7781 (1994).
3. NRPB. Health effects related to the use of visual display units. Report of an Advisory Group on Non-ionising Radiation. Doc. NRPB, 5, No. 2, 175 (1994).
4. NRPB. Health effects from ultraviolet radiation. Report of an Advisory Group on Non-ionising Radiation. Doc. NRPB, 6, No. 2, 7190 (1995).
5. NRPB. Board Statement on Restrictions on Human Exposure to Static and Time Varying Electromagnetic Fields and Radiation. Doc. NRPB, 4, No. 5, 163 (1993).
6. Minutes of the twenty-second meeting of AGNIR. 11 May 1999.
7. European Commission. Possible health effects related to the use of radiotelephones. Proposals for a research programme by a European Commission Expert Group. (A F McKinlay, Ed). Brussels, European Commission (1996).