Mobile Phone Base Stations
Public Health Considerations

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This factsheet is designed to explain how mobile phone base stations and telecommunications masts work. It also addresses some of the key public concerns about the possible health effects of exposure to radiation from telecom equipment.

How do mobile phone base stations work?

Mobile phone base stations are radio transmitters with antennas mounted on either free-standing masts 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. A typical larger base station installation would consist of a plant room containing the electronic equipment as well as the mast with the antennas.

Several types of antennas are used for the transmissions; panel-shaped sector antennas or pole-shaped omni antennas are used to communicate with mobile phones. Dish antennas form terminals for point to point microwave links that communicate with other base stations and link the network together into cells.

Several types of antennas are used for the transmissions; panel-shaped sector antennas or pole-shaped omni antennas are used to communicate with mobile phones. Dish antennas form terminals for point to point microwave links that communicate with other base stations and link the network together into cells.

What are the different types of antenna?

Macrocellular base stations provide the main infrastructure for a mobile phone network and their antennas tend to be mounted at sufficient height to give them a clear view over the surrounding geographical area. For this reason they tend to be obvious, particularly for the older sites with free-standing steel lattice towers.

Microcell base stations provide additional radio capacity where there are a high number of users such as in cities and towns. They often resemble lamp-posts or may be mounted at street level typically on the external walls of existing buildings. Microcell antennas are a lot smaller than macrocell antennas and emit at lower power outputs.

What are the current emission standards?

The emission standards have been set by the International Commission on Non Ionising Radiation Protection (ICNIRP). They are designed to prevent body heating effects. The Specific Energy Absorption Rate (SAR) is a measure of the rate at which energy is absorbed by body tissue in an electromagnetic field. It is measured in units of watts per kilogram (W/kg). The limits are stricter for the public than telecom workers on the assumption that the public includes children, the elderly and the sick.

What are Safety Zones?

If you stand within 2 metres of the antenna, the radiation will be strong enough to cause a heating effect. The safety zone is therefore anything outside this immediate 2m danger zone. It is impossible to enter this danger zone accidentally because the antenna is usually 10 to 15 metres above the ground for microcells and up to 50 metres for macrocells. The main signal is directed towards the ground at an angle of approximately 6 degrees. The diagram below shows that the area directly under the antenna is safe because the signal is at its weakest. It also shows that by the time the main beam reaches ground level the power is far too weak to cause a heating effect.

Mobile phone base station - safety zones

This drawing is based on a mobile phone base station operating under normal conditions working in isolation from other antenna.
Safety levels based on thermal standards. Danger zone exceeds current thermal safety standards.

The main signal is normally directed towards the ground at an angle of approximately 6 degrees from the horizontal plane.

Key:

1. If power density in the region of two metres from an 1800 MHz antennae is 10 W/Cm²
2. Then the power density noted at a distance of 10 metres would be approx. 0.4 W/Cm²; (4% of the reading at 2 metres)
3. The power density at 100 metres would be approx. 0.004 W/Cm² (0.04% of the reading at 2 metres)
4. The power density at ground level at 150 Metres from the base station would then be approx. 0.002 W/Cm² (0.02% of the reading at 2 metres)

* Danger zone approximately 2 metres from an antennae depending on power rating and the number of calls being made at the time.

Actual measured readings are often much lower. Where higher readings have been noted this is usually due to other sources of radiowaves in the area, such as TV or Radar.

 

What are the possible effects on health?

Scientists have investigated three possible types of effect on health from exposure to radiofrequency (RF) emissions:

1. Heating effects. Similar to microwave heating.
2. Cancer/tumour growth.
3. Brain pattern effects.

Many independent research studies have been carried out. So far, none show that any of the above are cause for concern, provided that the emissions comply with the recognised ICNIRP standards. The two most widely published studies were:

• The Stewart Report, Independent Expert Group on Mobile Phones (IEGMP), “Mobile Phones and Health”, 2000.
• The Swerdlow Report, Advisory Group on Non-Ionising Radiation (AGNIR), “Health effects from radiofrequency electromagnetic fields”, 2003.

Both can be examined on the website of the National Radiological Protection Board (NRPB) at www.nrpb.org

However, there are limitations to the research carried out so far and mobile phones have only been in widespread use for a relatively short time. The Advisory Group concludes that there is still a possibility that there could be health effects from exposure to radiofrequency transmissions below guideline levels so continued research is needed.

Regarding exposures in the vicinity of mobile phone base stations, AGNIR has examined data from a number of surveys and concluded that exposure levels are extremely low and the evidence indicates that they are unlikely to pose a health risk.

Nevertheless, AGNIR points out the limitations of published research and concludes:

“In aggregate the research published since the IEGMP report does not give cause for concern. The weight of evidence now available does not suggest that there are adverse health effects from exposures to RF fields below guideline levels, but the published research on RF exposures and health has limitations, and mobile phones have only been in widespread use for a relatively short time. The possibility therefore remains open that there could be health effects from exposure to RF fields below guideline levels; hence continued research is needed.”

So are mobile phone base stations safe?

The current scientific evidence indicates that they are safe as long as they are set up properly and satisfy the ICNIRP emission standards.

However, since mobile phones have been in use for a relatively short time, further research is needed to totally rule out long-term side effects. It is for this reason that Hampshire County Council continues to adopt a precautionary approach to the siting of mobile phone base stations on its land and buildings.
The precautionary approach is explained in two leaflets from the Department of Health entitled 'Mobile phones and health' and 'Mobile phone base stations and health' available via www.doh.gov.uk

Who Monitors the Emissions from Mobile Phone Base Stations?

 

• Hampshire County Council’s Scientific Service has special equipment for measuring the emissions from mobile phone base stations and antennas. A survey was carried out of six schools on which had been erected mobile telephone base stations and antennas. The equipment used measured a broad spectrum of emissions from 300 KHz to 50 GHz. Four sets of measurements were taken at each of the schools, spread over the school year, and as far as practicable, at different times of the school day. A total of 390 measurements were taken. All results were very satisfactory. (Only 2 exceeded 1% of the ICNIRP standard and none exceeded 2%).

• National audits carried out by the Radiocommunications Agency (RA) used more sophisticated equipment and covered lots more schools. Their results were below 1/400th of the ICNIRP standard. A national database of results can be found at http://www.ofcom.org.uk/static/archive/ra/topics/mpsafety/school-audit/summary2001.htm.The County Council has now arranged for the six schools to be monitored by the RA as part of their national audit.

• A database of all base station locations is available at www.sitefinder.radio.gov.uk. This gives type of transmission, antenna height, frequency range (900MHz, 1800MHz or 2.2GHz), transmitter power and maximum licensed power.

• The national body responsible for controlling the telecommunications industry is OFCOM. Their website www.ofcom.org also contains information on mobile phone base stations.

• Hampshire Scientific Service is able to carry out monitoring in the vicinity of new mobile phone base stations and antennas where they are close to County Council establishments to ensure that emissions comply with the ICNIRP standards.

 

This advice is designed to provide basic guidance to Consumers. It is not a complete or authoritative statement of the law.
We will be pleased to offer this information in larger print or translated into any language on request.

Reference Number

152/001/Mar 04