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. Â 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.