1. Description of the section
This section gives the frequently asked questions on mobile telephony and electromagnetic fields.
The enormous popularity of mobile telephony in recent years has not only generated a major technological revolution, but has also produced a highly significant transformation from a social, economic and environmental point of view. Never before in the history of humanity has the appearance of a new technology been so widely accepted by society in such a short space of time.
The enormous growth in mobile telephony and the appearance of mobile telephony antennae in cities (required for the system to work) has, in some cases, produced concern among the public as to whether the electromagnetic fields generated by the antennae and the phones themselves might have a harmful effect on health and, in other cases, on the appearance of the landscape.
This concern, in some cases, has meant that deployment of the antennae needed to guarantee good service has not been sufficient. Consequently, both the public's social and economic activity involving mobiles has not been provided with the best service.
In many cases, this concern is increased due to the lack of information and knowledge among the public on how mobile telephony works and what radiofrequency electromagnetic fields (generated by mobile telephony base stations and the phones themselves) are.
2. What is a radio communication system?
Radio communication systems use electromagnetic waves to transmit voice, images or data between two or more points through space.
A radio communication system consists of:
- A transmitter, which has two functions:
- Firstly, it generates the signal which carries the information (voice, images, data).
- Secondly, it transmits this signal over a distance via an antenna, at a specific frequency and strength.
- One or more receivers, which detect the signal sent by the transmitter, can extract the transmitted information.
The best known radio communication systems are radio, television, mobile communications (such as mobile telephony and Wi-Fi) and satellite communications. Such systems also include wireless telephony, communications systems used by emergency services (ambulance, police, fire brigade), remote controls, radars and systems used in aeronautics.
Radio communication systems can be one-way or two-way:
- One-way systems
A radio communication system, such as television, consists of:
- A transmitter (commonly known as a repeater), which sends the signal.
- Various receivers (in this case, each of the aerials installed on the roofs of buildings), which receive the signal.
Thus, there is a transmitter that sends the signal, and the rest of the devices are the receivers of this signal. These radio communication systems are one-way, i.e. the signal is transmitted in one direction only, so the distance between the transmitter and receivers can be several kilometres.
- Two-way systems
A radio communication system such as mobile telephony is two-way and consists of:
- A base station, which sends the signal to mobile phones and which also receives the signal from the phones.
- The mobile phones, which send and receive the signal from the base stations.
In these systems, the distance between the base station and the phones cannot be very great, as the maximum strength of mobile phones is regulated.
3. What is mobile telephony and how does it work?
Mobile telephony is a system that enables conversation, sending and receiving data and access to the Internet wherever the user is, as long as it is within the coverage of a base station (commonly known as mobile phone antennae) of the contracted operator.
Thus, when we say mobile phones have coverage, we mean they are within the area of influence of a base station.
4. What is a mobile telephone base station?
A mobile telephone base transceiver station (BTS) consists of a tower or mast, on which the antennae (the visible part of the base station) are installed, and a hut, which is not usually visible. The hut houses the equipment needed to manage transmission and reception, the cooling equipment that keeps the facility at the right temperature and the batteries that guarantee operation in case of a power cut.
The visible part of the base station, i.e. the tower (or mast) and the antennae, is located on high ground, to provide coverage for its assigned area. This is why, in urban environments, base stations are generally installed on roofs.
A mobile telephone network consists of a group of base stations. The coverage areas of the different base stations must be continuous, to avoid users losing coverage when moving from one area to the next.
When establishing communication over a mobile phone, the network detects the base station (in the area of coverage where the phone is located) and sends the communication to the mobile phone.
Generally, the coverage area of a base station is divided into three zones, known as sectors, and an antenna is used to cover each sector.
5. What are the electromagnetic field exposure levels near to a base station?
The signals transmitted by the antennae are electromagnetic waves that travel through the atmosphere in a straight line at the speed of light.
The signal is strongest near the antenna and in the direction of maximum transmission, while it rapidly decreases the further away one is from the antenna.
The signal is further weakened as it passes through walls. This is why the strength is much lower inside buildings than outside.
Outdoor measurement immediately in front of the antenna
This is where the strongest signals are. This area is not accessible to people, as it is part of the protection zone associated with the antenna. It is generally 3 or 4 metres from the antenna in the direction of maximum transmission.
Outdoor measurement around the antenna
An area normally from 4 to 10 metres around the antenna. This area is outside the protection zone and the levels are thus lower than those indicated in CURRENT regulations.
Indoor measurement in the dwelling of the building on which the base station is located
Very low levels in rooms in the same building as the base station. No antenna in the base station points directly towards it and also the walls and ceiling greatly weaken the signal.
Outdoor measurement at neighbouring buildings
Low levels, as the antennae are more than 10-15 metres away.
Indoor measurement in neighbouring buildings
Very low levels in the rooms of buildings next to the base station, because the walls greatly weaken the signal even if the antenna is pointing roughly in their direction
6. Why are there mobile phone antennae in cities?
The base station and mobile phone always transmit at the lowest strength needed to establish communication between them. This strength is continuously regulated, both by the base station and the mobile phone. Furthermore, mobile phones have a maximum permitted strength.
When the phone is far from the base station, both the phone and base station have to transmit at a higher strength in order to communicate.
The size of the coverage area of a base station generally depends on the number of users to which it provides service and the obstacles around the base station.
Thus an environment with few users and few obstacles has few base stations, and the coverage areas of each station will be larger.
However, a more densely populated urban environment with more users and more obstacles (mainly buildings) has more base stations, and the coverage areas of each station will be smaller.
Urban environments have two characteristics that mean more base stations are required:
- There are more mobile phone users who ‘saturate' the number of simultaneous communications a base station can manage.
- There are a large number of buildings that weaken the base station signal.
Therefore, in cities there have to be more base stations to provide service to users and to provide coverage for the inside and basements of buildings.
7. What are electromagnetic fields?
An electromagnetic field is the combination of an electrical field and a magnetic field. Both electric and magnetic fields are physical phenomena that have always been in existence. For example, the existence of large electric fields produce lightning during storms, while the rotation of the Earth's iron core produces its magnetic field.
We are constantly exposed to electromagnetic emissions of all kinds, which are invisible to the human eye.
Electromagnetic emissions can be natural or artificial in origin. Natural emissions include sun radiation, without which life on earth would not be possible. Artificial emissions include those generated by radios, televisions, mobile phones, WiFi devices and microwave ovens.
Without artificial electromagnetic emissions, today's society would not be possible.
Electromagnetic fields propagate in the form of electromagnetic waves. The most important characteristics of a wave are frequency and length. The higher the wave frequency, the more energy the wave transports.
8. What is ionising and non-ionising radiation?
To operate, mobile telephony uses radiofrequency electromagnetic fields, which are non-ionising emissions (or radiation).
Electromagnetic emissions or radiation can be ionising or non-ionising, depending on the frequency of the electromagnetic wave. The higher the wave frequency, the more energy the wave transports.
Ionising radiation carries enough energy (very high energy) to pull electrons from the atoms of the material it comes into contact with. It can therefore cause harm. Ionising radiation includes X-rays and gamma rays.
Non-ionising radiation does NOT carry enough energy (not too high energy) to pull electrons from the atoms of material it comes into contact with.
Non-ionising radiation includes very low frequency radiation (such as that generated by high-voltage lines), radiofrequency emissions (used by different radio communication systems: radio, television, mobile telephony, Wi-Fi and microwave ovens) and visible light.
Only if it is very strong and the body in question very close can non-ionising radiation increase body temperature. This is the technique used by microwave ovens to heat and/or defrost food.
10. What is the SAR?
The SAR or specific absorption rate is a measure of the rate at which energy is absorbed by the body when exposed to a radiofrequency electromagnetic field. Given the frequency band used by radiofrequency electromagnetic fields, the biological effect produced in an exposed body is the so-called thermal effect, that is, an increase in the temperature of the exposed part of the body. It is determined that an increase in temperature of the exposed part of the body 1ºC can produce adverse biological effects. In the case of human beings, it is determined that this 1ºC increase in temperature results from radiofrequency electromagnetic field exposure of individuals under moderate environmental conditions to a whole-body SAR of 4 W/kg for 30 minutes.
This SAR of 4 W/kg determines the level of radiofrequency electromagnetic field exposure and, once established, a safety factor is applied, which, in the case of the general public, is 50 (4 W/kg: 50 = 0.08 W/kg). Therefore, it is considered that the limit of 0.08 W/kg is sufficient to guarantee the safety of the general public. Applying this reduction increases safety and guarantees the protection of the exposed population.
These radiofrequency electromagnetic field levels resulting from the application of the safety factor are those indicated in the ICNIRP recommendations (table 4), the EU Council Recommendation and Royal Decree 1066/2001 (chart 2 of Annex II). The levels are generally indicated as power density (expressed in W/m2 or in mW/cm2) or as an electric field (expressed V/m).
The measured electric field or power density values must be averaged for a period of 6 minutes.
11. What is the current regulation in Catalonia regarding exposure to electromagnetic fields?
The current regulation in Catalonia regarding maximum exposure levels to electromagnetic fields for the general public is Royal Decree 1066/2001. The levels indicated in this regulation are the same as those indicated in the European Union Council Recommendation in 1999 (1999/519/CE), which are the same as those given by the ICNIRP 1998 guidelines.
In order to prepare Recommendation 1999/519/EC, the European Commission consulted the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) to determine the recommended limits in accordance with the state of scientific knowledge and in compliance with its monitoring and surveillance obligations.
The majority of the Member States of the European Union apply the levels of Council Recommendation 1999/519/EC, with the same levels as in the ICNIRP recommendations.
Countries outside the European Union, such as Japan, Brazil and New Zealand, apply the same levels indicated in the ICNIRP's recommendations. USA and Canada have higher limits.
Measured levels can be given in different, related, units. The most common units are power density (expressed as W/m2 or µW/cm2) and the electric field intensity (expressed as V/m).
The measured levels are expressed in V/m on the radio-electric governance website.
In Catalonia, as can be verified on the radio-electric governance website, the electromagnetic field levels to which the general public is exposed are much lower than the limits established in the applicable regulations.
12. What do the exposure limits expressed in Royal Decree 1066/2001 indicate?
They indicate the level of the sum of all the electromagnetic field emission sources in the zone measured, not just one source of emission.
Moreover, specifically, the limits established by Royal Decree 1066/2001 must be complied with 'in the zones where people are usually present and in the exposure of the emissions of terminal equipment, without prejudice to other specific provisions related to the work environment'.
In relation to mobile phone frequencies, the reference levels set by Royal Decree 1066/2001 are:
900 MHz – Electric field: 41 V/m (power density: 4.5 W/m2)
1800 MHz – Electric field: 58 V/m (power density: 9 W/m2)
2100 MHz – Electric field: 61 V/m (power density: 10 W/m2)
13. How is respect for the limits of Royal Decree 1066/2001 guaranteed?
The installation of each mobile telephone base station must be previously authorised by the Secretariat of State for Telecommunications and the Information Society of the Ministry of Industry, Energy and Tourism which, moreover, regularly inspects the base stations to check that the maximum levels are not exceeded. Mobile phone service providers must send, prior to its commissioning of the base station, the technical project of each base station for approval. Moreover, annually, these service must present a certificate for each base station stating that the limits have not been exceeded. The levels measured at each base station can be consulted on the website of the Ministry of Industry, Energy and Tourism.
14. Are there any additional restrictions on the maximum levels established by Royal Decree 1066/2001?
There are no additional restrictions, but Order 23/2002 indicates that when a base station is installed less than 100 metres from sites catalogued as 'sensitive' (nurseries, pre-schools and primary schools, compulsory secondary education centres, primary care centres, hospitals, nursing and care homes and public parks), mobile phone service providers must minimise the levels of exposure at these sites and must also take measurements there and include them in the technical project sent to the Ministry of Industry, Energy and Tourism, so it can verify that the levels established by applicable regulations are not exceeded. These measurements must be taken each year and forwarded to the said Ministry.
15. What emission limits must mobile phones comply with?
16. What is the output power of a mobile phone?
17. How are levels of exposure to the radiofrequency electromagnetic fields of mobile telephony minimised?
Both the mobile phone and the base station always emit with the minimum power necessary to be able to establish communication with each other. So, when the base station and the mobile phone are relatively close, both the base station and the mobile phone emit with the least amount of power and, therefore, the levels of exposure to radiofrequency electromagnetic fields are reduced.
This is achieved with an additional dimensioning of the mobile phone networks, which guarantees the presence of a sufficient number of base stations and optimal location of the stations in order to provide the necessary service to each zone, taking into account the number of users to whom service is to be provided and the obstacles around the base station.
Therefore, criteria such as generally distancing the base stations from the users are not an effective measure in reducing the levels of exposure to radiofrequency electromagnetic fields, as, in this scenario, both the antennae of the base stations and the mobile phones of the users must emit with more power to communicate with each other, and this increases the level of exposure to radiofrequency electromagnetic fields, above all for the users, who are exposed to the fields of their mobile phones.
18. What security is there around a mobile phone antenna?
Around each base station antenna a protection zone is established to which access is prohibited, thus guaranteeing that outside this protection zone exposure levels are below the maximum levels indicated in current regulations. This protection zone is right in front of each antenna and depends on the strength of the antenna; it generally covers 3 to 4 metres in the direction of maximum emission.
Royal Decree 1066/2001 and Order CTE/23/2002 establish control mechanisms that assure compliance with the levels and restrictions and also demand a detailed study of the levels of exposure before authorising each base station. This study must provide the electromagnetic field level of all the emission sources in the zone as a whole (other base stations, radio, television, etc.), and not just that of the base station to be commissioned.