High-frequency electromagnetic fields (HF-EMF) are the basis of digital wireless communication, e.g. between WLAN routers and computers, tablets and, last but not least, mobile phones in all public places and in virtually all private homes. In the coming years, the number of EMF sources of different frequency ranges is expected to increase further. The main reason for this is the rapidly advancing, comprehensive digitalisation of almost all areas of work, life and the economy, with which mobile technologies are also associated. TAB Working Report No. 196 summarises the current state of knowledge on possible health risks of radiofrequency electromagnetic fields, in particular of mobile radio. 
The aim of the report is to present the quality and thus the significance of the current state of scientific knowledge on EMF in a comprehensible way, both for policy makers and for the interested public. 

Key findings

State of research on possible health effects of HF-EMF

Although a large number of scientific publications on a range of health issues have been published in the last 10 years, the progress of knowledge has been slow. Often, even in studies of high scientific quality, the presence or absence of a particular biological or health effect cannot be consistently demonstrated. The state of evidence is therefore often unclear and the need for research to clarify open questions remains high. Overall, the current state of knowledge is as follows: 

There is increasing evidence that HF exposure affects the behaviour of laboratory animals. In addition, there are a number of strong indications that HF-EMF increases the risk of selected tumours (heart, lung, liver, lymph). In particular, the results of two large, high-quality studies from the 20s have led to an intensive discussion of these findings. Animal studies have also found evidence that HF-EMF could have an influence on neurodegenerative diseases. Possibly, an increased number of oxygen radicals in cells under HF-EMF exposure plays a role. The evidence for this effect in cell studies is not yet convincing, but recent animal studies support this finding with limited evidence. With regard to carcinogenesis, recent animal studies may also show increased incidences. According to these studies, mice treated with a carcinogenic substance (here: ethylnitrosourea) show increased liver and lung tumours as well as increased lymphomas when the animals are exposed to HF-EMF. However, no clear dose-response relationship was found.

There is also evidence of some effects of HF in more recent human studies. These relate to a possible effect on sleep, although the overall evidence is insufficient. Limited evidence for an effect on sleep quality has been found only in children. Experimental studies also suggest a negative effect on the growth of neurites (elongated extensions of nerve cells). If these results can be replicated and confirmed, this would be of great importance for the development of neurodegenerative diseases, as neurites are the precursors of dendrites and axons.

Because of the many possible implications for neurodegenerative diseases and cognition, further research is needed to clarify these aspects. 

According to several experts and the WHO, children are generally more sensitive to HF-EMF than adults and should therefore be considered separately. The TAB report therefore also analysed the specific research on the effects of EMF on children and adolescents. The result shows that due to the overall quantitatively and qualitatively insufficient number of studies, the evidence for effects of mobile phone communication on cognition, behaviour and subjective complaints in children and adolescents cannot be conclusively assessed. The insufficient number of studies, especially with regard to possible adverse health effects, also means that effects (especially long-term effects) cannot be excluded at this time. With regard to effects on early childhood development, cancer and physiological parameters, the data are insufficient to draw conclusions on possible effects. It is problematic that it is not yet possible to say with certainty, based on studies, whether children and adolescents in general are more sensitive to mobile phone exposure than adults. This would be of great importance. Therefore, there is still a great need for high-quality studies in children and adolescents, in which the risk of brain tumours in particular should be taken into account.Similarly, the results of epidemiological studies on behavioural problems, cognitive abilities and health complaints should be verified in cohort studies with objective prospective exposure assessment. There is also a need for high quality experimental studies of effects on the nervous system.

Impact of 5G technologies

How the exposure of the population to HF-EMF will change as a result of the widespread deployment of 5G is currently difficult to estimate. At present, it can be assumed that overall exposure to mobile phone waves will increase because 5G will operate in parallel with older infrastructures. It is currently unclear how the characteristics in which 5G differs from older wireless standards will affect exposure. In particular, this relates to a network topology of smaller radio cells and so-called "beam forming", which is intended to concentrate the radiation power in the spatial areas where it is actually used. The argument for increased exposure is that smaller cells allow base stations to be operated closer to people. In addition, beamforming generates a higher EMF intensity in the direction of the beam. However, it is also possible to reduce exposure, as the transmitting power can be lower with smaller cells, and people who are not in the direction of the beam are less exposed. Much will depend on how the networks are ultimately configured and used. And in the absence of significant exposure, epidemiological data cannot be used. There is also a lack of targeted laboratory studies, as these depend on real exposure situations from 5G. In principle, however, there are ways to address the health concerns expressed by some in a responsible and precautionary way, even with limited knowledge:

1. prudent avoidance (precautionary principle), i.e. the setting of limits should be accompanied by the pursuit of the lowest reasonably achievable level of exposure. 
2. the formulation of concrete specifications for the construction of transmitters, the technical design of terminal equipment and the design of the basic supply infrastructure. 
3. targeted information on the technical details of all planned expansion stages, on the areas of application, equipment and installations that can actually be expected, and thus on the exposure situation that can be expected. 
4. the promotion of independent national and international research at the highest level. 
5. new ways and venues for uncertainty and risk information and dialogue, given the great need for exchange between the various stakeholders. 
6. evaluation of the system of risk governance with regard to the usually institutionally separate processing of evidence assessment, recommendations for action and political decisions.

Evidence and context

In interpreting and assessing both the scientifically clarified and the unclarified aspects of the health effects of EMF, there are also very different views and approaches among scientific experts, and these different insights and views have their respective justifications. It also becomes clear that a purely evidence-based view is an indispensable basis, but by no means sufficient to carry out a comprehensive risk assessment, to deal politically or socially with the strong conflicts of interests and values that exist in the problem area of mobile radio, and to decide on possible precautionary measures. It has to be said that there are limits to modelling, investigating, reproducing, validating, explaining and interpreting (without contradiction). It can be assumed that, ultimately, it is not possible to discuss the state of the evidence in this area exclusively in scientific terms, to communicate it meaningfully to the public, or to use it for political decision-making without taking into account the various contextual factors that are considered to be relevant in different ways. This is shown by many years of experience from past debates on mobile radio (and other similarly complex and conflict-prone issues such as green genetic engineering or nuclear energy). 
More promising for goal-oriented discourses are mutual listening and unbiased dialogue between science, the public and politics. It seems essential to build and strengthen trust so that individual concerns, scope for action and values can be heard and taken seriously by policymakers. In this way, it will be easier to classify the current state of knowledge and the associated shortcomings and controversies in a meaningful and purposeful way, and to negotiate options for social decision-making, taking into account all scientifically clarified, controversial and unclarified aspects. A good knowledge of the state of the art is just as important as the recognition and acknowledgement of interests, controversies, knowledge gaps and different risk cultures.

Options for further action - participation and risk governance

Dealing with risks is fundamentally a political task that builds on scientific knowledge and at the same time goes beyond it. The need for action should be identified and individual options for action identified, assessed and compared. It is important to give interested members of the public the opportunity to have their say before political decisions are taken. Public discussion of risks is essential if decisions are to be accepted. Attention should be paid to a good structuring of the debate and a strong focus on content, taking into account the quantitative risk assessment. Clearly selected controversial aspects and the possible consequences of regulation or different options for action should be discussed, and the results of the risk assessment should be prepared and communicated to the public, especially where there are contradictions. It should also be borne in mind that public participation not only has a positive effect on confidence building, but can also allow the discussion of lay assessments, such as subjective intuitive findings, which have some value for risk assessment (e.g. the increase in multiple exposure situations). This in turn could act as a corrective in terms of transparency or balancing (real or perceived) vested interests, while increasing the ability to deal appropriately with potential risks and the expertise on the subject (among those concerned).
When deciding on precautionary measures, the general and recognised principles of risk management should be applied. These include the principle of proportionality and the weighing of the advantages and disadvantages of taking or not taking action. Costs and benefits should be weighed against each other, and non-economic dimensions such as public acceptance of planned measures should be included in the consultation or decision-making process. Only on the basis of a broad knowledge base can it be assessed whether there is a need for action and, if so, whether precautionary measures need to be defined to achieve the desired level of protection. In addition to adjusting limit values, restrictions on use (e.g. the establishment of protection zones where the use of mobile phones or the installation of transmitters is banned or severely restricted), technical standards or increased public information may be considered.

Shortcomings in risk governance (e.g. lack of public participation, ignorance of existing conflicts of interest, failures in risk communication or misinformation in the media) can lead to a loss of mutual trust and a breakdown in the debate, resulting in both scientific and democratic policy deficits. Ultimately, it is a very important task to remove obstacles to open mutual communication between the groups of actors, in particular between science, civil society and politics, in order to enable credibility, relevance and legitimacy of the information flow and thus also legitimate (political) decisions. This is the best way to take into account the social context of both the risks and the decisions to be taken (especially on regulation and precaution).
Against this background, from the point of view of TAB, it would be worth considering evaluating the (previous) process of risk assessment and risk management to determine whether the relevant stakeholders were involved in a timely and comprehensive manner and whether the communication of the individual steps is (or was) appropriate, equal, open and transparent.