Science - Introduction
There has been a considerable amount of research into the effects of radio frequency emissions, including the frequencies used by TETRA, over a number of years. The balance of scientific evidence does not demonstrate any link between radio frequency emissions at levels below the safety standards and adverse effects on health. In this science section you can:
- look at what has happened so far in terms of reports, statements and expert reviews about RF in general and TETRA in particular (click on "The Story So Far" below)
- find out who the recognised experts are and why, and look at what they have to say (click on "Who are the experts and what do they say?" below)
- get information about the research studies into TETRA that have been completed and those that are in progress (click on "Research Studies on TETRA" below).
On our ‘Useful links’ page (click here) we list a number of other web sites from which you can obtain further information.
You might, for example, like to visit the Sense About Science website. This is an independent charitable trust that responds to the misrepresentation of science and scientific evidence on issues that matter to society, from scares about plastic bottles, fluoride and the MMR (Measles, Mumps, Rubella) vaccine to controversies about genetic modification, stem cell research and radiation. The trust works with scientists and civic groups to promote evidence and scientific reasoning in public discussion.
The Story So Far
Science cannot prove categorically that something is safe; the only certainty in science is that there is no certainty. It is not possible to prove a negative, so no-one can prove conclusively that a product or technology is not harmful. Scientific methodology is empirical. Knowledge develops from observation and measurement, producing theories that can be used to predict what might happen under certain conditions, testing those theories through experiments and studies, peer-reviewing the findings, methodology, and conclusions, and attempting to replicate the results. In this way a body of robust scientific evidence builds up. If, after many years, a number of studies find no harmful effects, scientists can say with growing confidence that a product is probably safe.
There have been more than 60 years of research on RF energy exposure and health. The online database maintained by the Institute of Electrical and Electronics Engineers (IEEE) lists more than 2,700 peer-reviewed publications on possible RF bioeffects, including some at the frequencies used by the TETRA standard. Expert groups and health authorities around the world have regularly reviewed the research results and consistently agree that there is no proven evidence of adverse health effects at exposure levels below the internationally accepted limits. Advisory bodies like the World Health Organisation advocate a precautionary approach given remaining uncertainties about the impact of long-term use of RF, but this does not mean that radio technologies should not be used and it reaffirms the importance of science-based standards.
The Independent Experts Group on Mobile Phones (the "Stewart Inquiry") published a report in 2001 which considered the potential health impact of review the radio frequencies at which the mobile phone networks operated. The committee did not examine TETRA in detail and so did not make any specific recommendations about TETRA technology.
However it did mention scientific work, dating back to the 1970s, that implied that radio signals with modulations around 16Hz might have an impact on release of cellular calcium. The report acknowledged that this evidence was inconclusive but suggested that “as a precautionary measure, amplitude modulation around 16Hz should be avoided if possible in future development of signal coding”. Professor Lawrie Challis, who was the vice chairman of the Stewart Inquiry, has explained publicly that this recommendation was made not because of any worries about health, but merely to acknowledge the existence of unreplicated research dating back to the 1970s.
During the years since then both industry and Government have responded to the recommendations made by the Stewart Report, for example:
- The Government adopted the ICNIRP safety guidelines which were already being used for TETRA systems. (Click here to find out more about ICNIRP.)
- The Mobile Telecommunications and Health Research (MTHR) programme was set up, co-funded by industry and Government and independently managed under the Chairmanship of Professor Lawrie Challis until 2008 and then Professor David Coggon. This programme has included a number of TETRA studies which can be found in the "Research Studies on TETRA" section of this page (below).
- Studies have been commissioned by the Home Office, including a study on the effect of the TETRA signal on cellular calcium conducted by DSTL.
The Stewart team conducted an update inquiry in 2004 and published a further report (Mobile Phones and Health, 2004), known as “Stewart 2”. This included a section on TETRA which reaffirmed the conclusions of the 2001 report by the Advisory Group on Non-Ionising Radiation. AGNIR had said “it is notable that the signals from TETRA base stations are not pulsed, whereas those from mobile terminals and repeaters are. Although areas of uncertainty remain about the biological effects of low level RF radiation in general, including modulated signals, current evidence suggests that it is unlikely that the special features of the signals from TETRA terminals and repeaters pose a hazard to health."
Mobile Telecommunications and Health Research Programme (MTHR)
In 2007 MTHR published a report on progress with the research programme describing it as a "substantial report from a large research programme" with the reported work all published in peer-reviewed journals. To download a copy of the complete report click here.
The MTHR press release accompanying that report included:
“Mobile phones have not been found to be associated with any biological or adverse health effects according to the UK’s largest investigation into the possible health risks from mobile telephone technology."
"The six year research programme has found no association between short term mobile phone use and brain cancer. Studies on volunteers also showed no evidence that brain function was affected by mobile phone signals or the signals used by the emergency services (TETRA)."
"the largest and most robust studies of electrical hypersensitivity undertaken anywhere in the world. These studies have found no evidence that the unpleasant symptoms experienced by sufferers are the result of exposure to signals from mobile phones or base stations."
"The MTHR programme also investigated whether mobile phones might affect cells and tissue beyond simply heating them. The results so far show no evidence for this and the committee believes there is no need to support further work in this area."
"The situation for longer term exposure is less clear as studies have so far only included a limited number of participants who have used their phones for 10 years or more. The committee recommends more research be conducted in this area."
The main references to TETRA in the body of the MTHR 2007 report are listed here for ease of reference. More details may be found on Research Studies on TETRA (click here).
Standard Exposure System
Dr Phil Chadwick of MCL was commissioned to design a system to produce RF exposures representative of those to real phone and TETRA radio users. (Report page 7.)
The roll-out of the TETRA-based network for the emergency services prompted concern about the possible effects of exposure to pulse-modulated fields from the handsets.
- Work by Dr Peter Dimbylow, HPA, characterised the way energy is absorbed in the head from a TETRA handset (published in Phys Med Biol, 48, 3911-26 - click here to view an abstract or here to read the entire report).
- Work by Dr Stuart Butler at the Burden Neurological Institute in Bristol assessed cognitive and electro-physiological effects TETRA signals in healthy volunteers (click here to read the report).
- Work by Dr Sarah Bowditch at DSTL examined the effects of TETRA signal exposure on cognitive function and the results of a self assessment of mood, workload and anxiety (submitted for publication).
- Prof Tony Barker at Sheffield assessed impact of RF exposure (including a TETRA signal) on blood pressure and heart rate (published in Bioelectromagnetics, 26(2), 102 – 8).
- Work by Prof Elaine Fox at the University of Essex concluded that self-reported hypersensitivity is between around 1% and 4% of the population.
- Previous provocation studies (using an electromagnetic source and sham signal to see if symptoms can be provoked) were reviewed by Dr James Rubin at King’s College London, who reported that the great majority of studies failed to find any evidence that symptoms of hypersensitivity are caused by exposure to electromagnetic fields (published in Psychosom Med, 67, 224-32).
- A team at King’s College, London carried out a double-blind provocation study to investigate whether the TETRA radios used by the emergency services can cause unpleasant symptoms such as headaches, dizziness and tingling. To see the report click here.
- Prof Adrian Burgess at Imperial College London and University of Swansea studied a group of police officers, including both those who report symptoms when using TETRA radios and those who do not, using a battery of cognitive tests, recording measures of brain activity and completion of a well-being questionnaire.
- Prof Simon Wellesley at King’s College is working on an MTHR2-supported study with groups of police officers, some who report symptoms and some who do not, using sham, continuous, and modulated RF signal exposures.
- Prof Elaine Fox at the University of Essex studied exposure to base station signals with a group that attributes symptoms to base station exposure and one that does not. Users were exposed to sham or TETRA base station signals and asked to self-assess severity of symptoms. For the results of the study, click here.
A study by Dr Sienkiewicz at the HPA, with colleagues at the University of Bristol and DSTL, searched for evidence that RF fields could cause changes in brain function, using TETRA, GSM, and UMTS signals.
In June 2008, MTHR announced a new cohort study to investigate whether the use of mobile phones is linked to long term health affects such as brain cancer and neurodegenerative diseases. The study will be carried out by a team at Imperial College London and will monitor the health of 200,000 mobile phone users over a number of years. Imperial College is already conducting a long term health monitoring cohort study with police users of TETRA.
Report by the HPA's independent Advisory Group on Non-ionising Radiation (AGNIR) - April 2012
A report by the Health Protection Agency’s independent Advisory Group on Non-ionising Radiation (AGNIR), updating its previous 2003 review, concluded that there is still no convincing evidence that RF field exposure below internationally agreed guideline levels (which are applied in the UK) causes health effects in adults or children. The press release relating to the report may be found here, whilst the report itself may be seen here (both open in a new window).
Key conclusions are:
- The evidence suggests that RF field exposure below guideline levels does not cause symptoms in humans and that the presence of RF fields cannot be detected by people, including those who report being sensitive to RF fields.
- A large number of studies have now been published on cancer risks in relation to mobile phone use. Overall, the results of studies have not demonstrated that the use of mobile phones causes brain tumours or any other type of cancer.
- As mobile phone technology has only been in widespread public use relatively recently, there is little information on risks beyond 15 years from first exposure. It is therefore important to continue to monitor the evidence, including that from national brain tumour trends. These have so far given no indication of any risk.
- Studies of other RF field exposures, such as those at work and from RF transmitters, have been more limited but have not given evidence that cancer is caused by these exposures.
- Research on other potential long-term effects of RF field exposures has been very limited, but the results provide no substantial evidence of adverse health effects; in particular for cardiovascular morbidity and reproductive function.
Who are the experts and what do they say?
Science can never guarantee that anything is absolutely safe. But it can offer strong reassurance that any risk from a technology is small, particularly when set against the many risks we accept in our daily lives. Reputable scientists do not make unsubstantiated claims, but formulate hypotheses which they test rigorously through experiments and studies.
For a study to have scientific weight it must be peer-reviewed and replicated in an independent laboratory. In this way the body of scientific evidence on any issue is built up over a period of time.
Those who are already acknowledged by their peers to be experts in the field of RF naturally tend to be the scientists who are asked to undertake reviews of the whole body of scientific evidence and to sit on Government advisory bodies. In so doing they are careful to weigh both positive and negative evidence, and quality of the study on any issue, and produce a balanced report. These scientists rightly remain absolutely independent of both Government and industry.
A number of experts and expert bodies have been involved in reviews of the potential health impact of RF during the past decade and below are some examples of what they say:
Institute of Engineering and Technology position statement 2012
The Institution of Engineering and Technology (IET) published an updated Position Statement that aims to provide an accessible guide to the findings of the IET’s "Biological Effects Policy Advisory Group" (BEPAG). This position statement encapsulates the IET’s position on the possible harmful biological effects of low-level electromagnetic fields of frequencies up to 300 GHz. BEPAG has concluded that the balance of scientific evidence to date still does not indicate that harmful effects occur in humans due to low-level exposure to EMFs.
The executive summary stated:
- “...that the balance of scientific evidence to date does not indicate that harmful effects occur in humans due to low-level exposure to EMFs.”
- “In summary, the absence of robust new evidence of harmful effects of EMFs in the past two years is reassuring and is consistent with our findings over the past two decades. The widespread use of electricity and telecommunications has demonstrable value to society, including health benefits. BEPAG is of the opinion that these factors, along with the overall scientific evidence, should be taken into account by policy makers when considering the costs and benefits.”
MTHR Programme Management Committee
“The MTHR programme was set up to resolve uncertainties identified by previous evaluations of the possible health risks associated with the widespread use of mobile phone technology. None of the research supported by the programme and published so far demonstrates that biological or adverse health effects are produced by radiofrequency exposure from mobile phones…………
………………………reassuringly no epidemiological association was found between short term mobile phone use (less than 10 years) and cancers of the brain and nervous system. Studies on volunteers provided no evidence that brain function is effected by exposure to the signals emitted by mobile phones or TETRA radios………………………
…………………the committee has recognised that while many of the concerns raised by the Stewart Committee have been reduced by the programme and work done elsewhere some still remain…………priorities will include work to assess whether longer term exposure (greater than 10 years) increases the risk of developing cancers of the brain and nervous system” - MTHR report, September 2007
World Health Organisation
“To date, no adverse health effects have been established as being caused by mobile phone use.” see WHO Fact Sheet No. 193 (June 2011)
“Despite extensive research, to date there is no evidence to conclude that exposure to low level electromagnetic fields is harmful to human health.” (See Key Point #6 at http://www.who.int/peh-emf/about/WhatisEMF/en/index1.html).
“To date, all expert reviews on the health effects of exposure to RF fields have reached the same conclusion: There have been no adverse health consequences established from exposure to RF fields at levels below the international guidelines on exposure limits published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP, 1998).” Children and Mobile Phones: Clarification statement (second paragraph) at http://www.who.int/peh-emf/meetings/ottawa_june05/en/index4.html.
Advisory Group on Non-Ionising Radiation (advises NRPB, now part of HPA)
“Overall AGNIR concluded that in aggregate the research published since the IEGMP report does not give cause for concern and that the weight of evidence now available does not suggest that there are adverse health effects from exposure to RF fields below guideline levels” - AGNIR 2004
“although areas of uncertainty remain about the biological effects of low level radiation in general, and about modulated signals in particular, current evidence suggests that it is unlikely that the unique features of the TETRA system pose a hazard to health” - National Radiological Protection Board - NRPB 2001
European Commission Scientific Committee on Emerging and Newly-Identified Health Risks (2007)
“RF field exposure has not convincingly been shown to have an effect on self-reported symptoms or well-being.”
“In conclusion, no health effect has been consistently demonstrated at exposure levels below the limits of ICNIRP (International Commission on Non-Ionizing Radiation Protection) established in 1998.”
Members of Stewart Inquiry and AGNIR
“nobody has established a medical risk and on balance there is no real reason to worry about TETRA. It is certainly no greater risk than a mobile phone…….the large body of scientific evidence to date indicates that non-ionising radiation does not have any biological effect.” - Prof Colin Blakemore, Head of the Medical Research Council, member of the Stewart Inquiry and member of the National Radiological Protection Board’s Advisory Group on Non-Ionising Radiation (AGNIR), 2002
“heating effects from base stations are utterly negligible” - Prof Lawrie Challis, University of Nottingham, Vice Chairman of Stewart Inquiry, Chairman of the MTHR research programme and member of the NRPB Advisory Group on Non-Ionising Radiation (AGNIR), 2003
“the RF emission from a TETRA base station is continuous and not pulsed. Measurements show no pulse modulation at 17.6 Hz and its harmonics to within experimental error. The changes in RF emission at these frequencies are 1% or less and can all be attributed to limits in the measurement procedure. There are regular interruptions in the streams of digital signals but the average level of RF emission is unchanged” - Prof Lawrie Challis 2003
“there is a common misconception that heat from TETRA handsets can negatively affect the brain or body when used due to a warming effect. These claims are unrealistic as TETRA handsets emits less than one tenth of the energy needed to raise body temperature by one degree centigrade, and therefore operate many times below the international guidelines on exposure to non-ionising radiation” - Prof Colin Blakemore, 2002.
International Agency for Research on Cancer (IARC)
Extracts from IARC's World Cancer Report 2008:
“Radiofrequency radiation emitted by mobile telephones has been investigated in a number of studies. There is some evidence that long-term and heavy use of mobile/cellular phones may be associated with moderate increased risks of gliomas, parotid gland tumours, and acoustic neuromas; however, evidence is conflicting and a role of bias in these studies cannot be ruled out.” (p. 170)
“With reference to radio frequency, available data do not show any excess risk of brain cancer and other neoplasms associated with the use of mobile phones.” (p. 170)
Concerning brain tumours: “After 1983 and more recently during the period of increasing prevalence of mobile phone users, the incidence has remained relatively stable for both men and women.”(p. 461)
Click here to see the full report (NB. Large file - 119MB)
Health Protection Agency
In a Press Release published in May 2011, in response to the IARC classification of radio waves in Group 2B "possibly carcinogenic", the HPA stated:
“HPA advice is that there is no clear scientific evidence of a cancer risk from exposure to radiofrequencies at levels below international guidelines but the possibility remains.”
Click here to see the full Press Release.
Funding for studies which look specifically at TETRA signals has come from both the MTHR programme which is funded jointly by Government and industry, and directly from the Home Office.
Below you can find brief summaries of studies that are specifically TETRA-related:
Studies Currently in Progress
Long term health monitoring study - Imperial College London
In 2003, to address concerns raised by the publication of the Stewart Report, the Home Office commissioned two studies – a long-term health monitoring study (see subsequent paragraphs) and an investigation of possible acute effects of TETRA. The latter study has now published its findings – see “Possible Acute Effects of TETRA” in the Recently Completed Studies section below.
Professor Paul Elliott’s team at Imperial College London is carrying out a long-term health monitoring study on police users of TETRA radios. Conducted with a cohort of up to 80,000 users over 15 to 20 years, this will look at the incidence of and mortality for diseases such as cancer and Parkinson’s, sick absence levels and trends for retirements on health grounds. Health screening is offered to participants, partly to collect data and partly as an incentive to participate in the study.
A summary of a presentation about the Long Term Health Monitoring study made by Imperial College team members at a THG event in September 2006 can be found here (opens in a new window).
The most recent update on the Long Term Health Monitoring Study, published in Environmental Research in October 2014, may be found here. To visit the relevant Environmental Research web page click here.
Recently Completed Studies
Possible Acute Effects of TETRA
In 2003, to address concerns raised by the publication of the Stewart Report, the Home Office commissioned two studies – a long-term health monitoring study (see Studies Currently in Progress above) and an investigation of possible acute effects of TETRA.
A presentation on the latter study was given at a THG seminar in 2009 by Adrian Burgess, Professor of Psychology at Aston University, Birmingham – a summary of the presentation may be viewed here – and its findings were published in July 2016. The paper describing the findings may be found here, whilst a set of related FAQs may be found here. To visit the relevant Environmental Research web page, click here.
BDBOS studies on the impact of the TETRA radio on the health of the user
BDBOS = Bundesanstalt für den Digitalfunk der Behörden und Organisationen mit Sicherheitsaufgaben (Federal Agency for Public Safety in Digital Radio in Germany).
The BDBOS commissioned a study entitled “Investigation of the effects of the TETRA radio signal on cognitive functions of volunteers”. This study was w been published in September 2014 and concluded: “Overall, the study does not provide any evidence of an impairment of health due to TETRA exposure.” A summary of the study, its methods, results and conclusions may be seen here.
Hand-held Devices in Vehicles
In February 2014 the BDBOS announced the results of a study held by the Federal Office for Radiation Protection about the impact of the BOS digital TETRA radio on the human body. The study shows that the impact of the BOS TETRA radio with regards to the head and body temperature is in line with the regulations.
The studies and measurements show that the statutory limits are complied with. This is particularly true for the use of handheld radios (HRT) in vehicles.
The study, related to the TETRA standard, held by the Federal Office for Radiation Protection, demonstrates that the statutory limits are respected at all realistic uses of the BOS digital radio.
The so-called SAR study examined the extent to which the BOS digital radio temperature increases in the body and in the head region occur in the use of walkie-talkies. The study considered different realistic uses. This included the use of hand-held radio equipment in vehicles.
During the measurements, scenarios of police practice were highlighted. Simultaneously several different mobile devices (GSM, HRT, MRI) in very close proximity within vehicles or rooms and be worn without the external antenna or to the person where used.
As a result, the investigation of the BOS digital radio Baden-Württemberg project group, showed that the measurement results are well below the applicable limits.
The report of the study (in German) may be viewed here.
Hypersensitivity and exposure to TETRA radio signals - Kings College London
A team at King’s College, London has carried out a double-blind provocation study to investigate whether the TETRA radios used by the emergency services can cause unpleasant symptoms such as headaches, dizziness and tingling.
The results of the study, titled "Can Exposure to a terrestrial trunked radio (TETRA-like) signal cause symptoms? A randomised double-blind provocation study", were published on 23 September 2010 in Occupational Environmental Medicine. A pdf of the article can be seen by clicking here (opens in a new window).
A presentation by Dr James Rubin about the methodology of this study, made at a THG event in 2008 can be found here (opens in a new window).
Hypersensitivity and exposure from TETRA base stations – University of Essex
Professor Elaine Fox and her team from the University of Essex conducted a two-year study to establish if there are any short-term health effects from exposure to TETRA mobile radio masts, and in particular to look at people who appear to be particularly sensitive to the technology. For the results of the study, click here.
Defence Science and Technology Laboratory (DSTL) - Work on cellular calcium
The biomedical sciences department of the Defence Science and Technology Laboratory conducted an investigation into the effect of TETRA signals on cellular calcium. The study simulated the maximum exposure that can arise from TETRA handsets, as well as looking at several lower power levels to see if there could be ‘power windows’ where TETRA signals could cause a reaction.
No effects on calcium response were found at any of the TETRA power levels. The results were published in the International Journal of Radiation Biology in December 2006 (click here to view, please note that this is not a free document).
A summary of a presentation made by Dr John Tattersall of DSTL at a THG seminar in 2007 can be found here (opens in a new window).
Defence Science and Technology Laboratory (DSTL) - Cognitive Study
The Home Office funded work by Dr Sarah Bowditch and her team at DSTL to examine the effects of TETRA signal exposure on cognitive function and to assess the results of a self assessment of mood, workload and anxiety. No effects on mood or anxiety measures or reported symptoms were observed, and no impact of signal exposure was observed on 21 of 22 cognitive tasks. The work has been submitted for publication to Bioelectromagnetics Journal.
A summary of a presentation given by Sarah Smith at a THG seminar in 2007 can be found here (opens in a new window).
Heart Rate and Blood Pressure Study - University of Sheffield
A double blind provocation study, using both GSM and TETRA signals, was undertaken by a team led by Professor Tony Barker. The study investigated whether exposure to the signals caused changes in heart rate or blood pressure and also measured levels of adrenaline in the bloodstream, Neither changes in heart rate and blood pressure nor in blood chemistry were observed as a result of exposure. The work was published in Bioelectromagnetics 2007 28(6):433-438).
A summary of a presentation given by Professor Barker at a THG seminar in 2008 can be found here (opens in a new window).
In-vehicle Exposure - Dr Phil Chadwick
Dr Phil Chadwick investigated exposure to TETRA signals in vehicles and on motor-cycles. He measured SARs (Specific Absorption Rates) in situations where TETRA radios were used in cars or on motor-cycles and where there were combinations of hand held and vehicle-mounted radios, to see whether there was additivity or whether the vehicle structure had an effect. The work found that the impact of vehicle antennae was negligible and found no additive effect in a vehicle containing more than one police officer with a radio. The full report can be found here (opens in new window).
A presentation given by Dr Phil Chadwick at a THG seminar in 2007 can be found here (opens in a new window).