Mobile phones and health: an interim report
2001
Introduction
It has been estimated that there are currently 39.9 million users of mobile phones in the UK, and within 5 years an estimated 25% of all calls will be made from mobiles.(1)
Worldwide, there are currently around 700 million users, and by the end of 2002 there could be as many as one billion. Concerns have been raised that use of this technology has increased dramatically without sufficient understanding of the potential adverse health effects of the electromagnetic fields produced by the phones and their base stations.
The aim of this document is to summarise the current knowledge about mobile phones and public health, and to outline the on-going and planned research.
Mobile phones and base stations: the basics
Radiowaves, x-rays and light are all forms of electromagnetic radiation, which are known collectively as the electromagnetic spectrum. They vary in frequency (Hz) and hence the amount of energy they carry – the higher the frequency, the higher the energy (see figure 1).
Figure 1 : the electromagnetic spectrum (2)
Mobile phone systems operate within the radiofrequency (RF) section (30kHz-300GHz) of the electromagnetic spectrum. Analogue phones operate at 450MHz and 900MHz, digital phones (GSM) at 900MHz or 1800MHz, and third generation phones (3G) to be launched in a few years, at approximately 2000MHz (2GHz).
The phone systems depend on RF communication between handsets and fixed base stations. In engineering terms, “base station” describes the electronic equipment contained in the plant room at the base of the mast. However, this term is frequently used to refer to the complete installation comprising base station, mast and antenna (see figure 2).
Figure 2 : base station
Figure 2 also shows the degree of exposure, in terms of power density, at ground level with increasing distance from a typical GSM900 antenna, where the top of the beam is situated 15m from ground level.
The main beam is tilted downwards so that the lower edge of the beam touches the ground at a distance of 100m from the mast. Power density increases from 100m to a maximum of 35 mWm-2 at a distance of 180m from the mast, after which it decreases with greater distance.
There may be a small amount of exposure between 10-100m due to other radiating elements on the antenna, but this is unlikely to exceed 17 mWm-2.(13)
Each base station covers phone use in a specific area or ‘cell’, as great as 10km in rural areas, or as small as 0.2-0.5km in towns where demand is greatest. As the wavelengths at 900MHz are twice as long as those at 1800MHz, they are better at reaching the shielded regions behind obstructions as a result of diffraction (bending).
So in order to obtain identical coverage, fewer base stations are needed at 900MHz than 1800MHz.(3) On receipt of a call, the base station closest to the handset will transmit and receive the RF signal. As the user moves, this signal may be transferred to a nearer base station in order to maintain an optimum user signal at the lowest possible power output.
Other forms of mobile communication that operate using a similar system of a handset and a base station include cordless telephones (analogue, operating at 914-960MHz, and the new digital DECT system, operating at 1.88-1.9GHz), and portable radio systems.
A new cellular radio system, TETRA, is increasing in use across Europe. It operates at either 400MHz or 900MHz, and is designed for use in closed groups, particularly the emergency services.(3) Little research has been conducted into its possible adverse health effects, and therefore this research is necessary.
At high intensities RF radiation has heating properties that can be detrimental to health (thermal effects). For this reason guidelines are in place to limit the intensity of the radiation (see page 4). The use of RF radiation in daily life is not new, however, and figure 1 shows other technologies that operate at this frequency.
Major publications and sources of public information about mobile phones and base stations (1996-2000)
- EC Expert Group on Telecommunication Technology Report, 1996(4)
- The World Health Organization established its International EMF project in 1996
- May 1998 WHO produced a fact sheet for the public, revised in June 2000(5)
- Department of the Environment, Transport and the Regions and The National Assembly for Wales, Code of Best Practice, Telecommunications prior approval procedures as applied to mast/tower development, 1998(6)
- EC Council passed its recommendations about research into electromagnetic fields, July 1999(7)
- The Royal Society of Canada Report, A review of the potential health risks of radiofrequency fields from wireless telecommunication devices(8), March 1999
- COST (Co-operation in the Field of Scientific and Technical Research) report, Possible health effects related to the use of radiotelephones, was published in September 1999, updating the 1996 EC Expert Group report(9)
- The House of Commons Science and Technology Select Committee on the Scientific Advisory System published its report, Mobile phones and health in September 1999(10)
- Scottish Parliament Transport and the Environment Committee, Report into the proposals to introduce new planning procedures for telecommunications development, March 2000(11)
- The UK Consumers’ Association report on protective devices for mobile phones, The Ring of Truth,(12) April 2000
- UK Independent Expert Group on Mobile Phones (IEGMP) commissioned by the Government and chaired by Sir William Stewart, published Mobile phones and health(3) in May 2000. Often referred to as “The Stewart Report”
- NRPB report, Exposure to radio waves near mobile phone base stations (NRPB-R321), June 2000(13)
- Australian Consumers’ Association report, Is hands-free safer?(14) August 2000 Department for Trade and Industry report, SAR test on mobile phones used with and without personal hands-free kits,(15) August 2000
- UK Consumers’ Association published further data on hands-free kits in November 2000(16)
- Department of Health produced two public information leaflets in December 2000(17)