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Scientifically discussed biological and health effects of high frequency fields
The existence of health effects below the limit values was neither confirmed by the results of the DMF, nor by other up-to-date studies conducted on national or international levels.
- Long-term effects for periods of use exceeding a decade remain an open issue. Therefore, further research is conducted into this question.
Studies on biological effects of high-frequency electromagnetic fields were an essential part of the German Mobile Telecommunication Research Programme (Deutsches Mobilfunk Forschungsprogramm, DMF). Research was conducted into both mechanisms of action mainly based on cell experiments and the effects on humans and animals with the emphasis placed on potential risks to human health.
The possible health effects of high-frequency electromagnetic fields were also considered in the epidemiological studies performed within the scope of the German Mobile Telecommunication Research Programme in order to establish statistical correlations between exposure and morbidity within the population.
No evidence of non-thermal effects below the limits
The existence of potential non-thermal effects below the limit values was neither confirmed by the results of the DMF, nor by other up-to-date studies conducted on national or international levels. Thermally induced biological effects as a result of temperature changes smaller than 1 °C below or close to the limits are possible, but not health relevant. Overall, the results give no reason to question the protective effect of the current limit values:
- Studies on immunologically relevant cells revealed no biologically significant effects of high-frequency electromagnetic fields.
- The nervous system as well as sensory organs were not found to be impaired in functionality.
- No correlation was established between electromagnetic fields from mobile phones and tinnitus induction.
- The so-called "melatonin hypothesis", assuming decreased melatonin levels to be induced by exposure to high-frequency fields, could not be confirmed.
- Blood-brain barrier damage caused by high frequency electromagnetic fields below the limits could not be substantiated, neither in a cell culture model nor in animal experiments.
- Concerning electrohypersensitivity, the evidence that there is no causal link between exposure to electromagnetic fields and nonspecific symptoms has been improved.
No impairment of general health and cognitive performance
Neither experimental studies on volunteers nor epidemiological studies were able to demonstrate a relationship between high-frequency electromagnetic fields from mobile phones or base stations and sleep disorders, headache, or other general health impairments. Memory, ability to respond, and further aspects of cognitive performance were not impaired either. Exposure to mobile phones may slightly affect sleep and waking brain activity (EEG), but the values remain within the normal physiological range. This effect is not recognized subjectively and is not reflected in behavior, cognitive performance, or sleep quality.
The presence of a base station can, however, induce sleep disorders in connection with concern on possible health effects even if the base station is not operating. Shielding of electromagnetic fields in the bedrooms of the persons concerned did not improve sleep quality.
Regarding the question of electromagnetic hypersensitivity, increasing evidence has suggested that there is no causal connection between exposure to electromagnetic fields and unspecific symptoms.
The phenomenon of "electrohypersensitivity" has been investigated in several scientific studies. About one percent of the German population consider themselves to be electrosensitive, that means, they attribute various health complaints like headache, sleep disturbances, fatigue or difficulty to concentrate to the presence of electromagnetic fields in their environment. For a long time the complaints concerned predominantly low frequency electric and magnetic fields. Since the fast spread of mobile communications, predominantly high frequency electromagnetic fields are considered to be the reason.
International studies show consistently that persons considering themselves to be electrosensitive are not able to perceive electromagnetic fields and that their existing health complaints are not causally related to the fields. By contrast, knowledge about the existence of fields combined with possible health concerns may cause complaints.
As a result of the numerous studies carried out so far, it can be concluded that a causal relationship between electromagnetic fields and the complaints of electrosensitive persons can be excluded with high probability. The WHO also shares this assessment. In fact sheet No. 296 from December 2005 WHO notes that there is no scientific basis for a causal relationship between the symptoms of electrosensitive persons and the action of electromagnetic fields. The Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) presents a similar conclusion in the latest comprehensive risk assessment of electromagnetic fields from 2015.
No increased cancer risk
Epidemiological studies on adult mobile phone users have not found an increased risk for brain cancer, acoustic neuroma (benign tumour of the hearing nerve) or uveal melanoma for a period of use of less than ten years. The use of cordless phones or the presence of a DECT base station in the bedroom close to the bed was not associated with an increased brain tumour risk either.
For very long periods, the existing data are not sufficient to exclude a possible cancer risk as a result of the use of terminals (mobile phones, DECT phones). Some epidemiological studies, especially from Sweden, suggest an increased risk; other studies and long-term trends suggest that there is no risk for up to 15 years. This uncertain data basis has led the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) to classify high-frequency electromagnetic fields as "possibly carcinogenic" in 2011. This assessment is attributed exclusively to tumours of the head and neck region and the use of terminals. An increased risk for other types of cancer or cancer in the vicinity of base stations can largely be excluded.
No acute effects in children and adolescents
No correlation between exposure to high-frequency fields and acute health problems in children has been scientifically established. Studies on behavior and brain activity from Australia and Switzerland indicate that children and adolescents are not more vulnerable to acute mobile phone exposure than adults. Frequent use of mobile phones can lead to changes in behavior and cognitive abilities of children and adolescents, which may be negative or positive, and predominantly more closely related to the kind of use of the devices than to the exposure to electromagnetic fields. For example, an intensive late-night and night use causes sleep problems and daytime sleepiness.
Further research conducted into long-term effects including children
The results of long term studies considering mobile communications and WLAN conducted within the scope of DMF on mice and rats as well as long term studies from Italy and France do not corroborate the hypothesis of a special sensitivity of early stages of development. Embryonic and postembryonic development, cognitive performance, immune system and fertility have been investigated.
There are no indications for a relationship between childhood leukemia and the fields from high power radio and television transmitters.
Long-term effects for periods of use exceeding fifteen years remain an open issue because the latency periods for cancer development are long and the period of time elapsed since mobile communication technology has been used by the general public is comparatively short. Therefore, further research is conducted into this question. The international cohort study COSMOS follows since 2007 the health status of 290.000 mobile phone users from six european countries over the range of 20 – 30 years.
Equally, the question of whether health risks from long-term exposure are higher for children than for adults, whether due to age-related differences or due to a longer life-time exposure, cannot be answered conclusively by the results available up to now. This question is further pursued as well, particularly since dosimetric studies using various models of children’s heads revealed that certain tissues and brain areas can be comparatively higher exposed especially in younger children than in adults.
The international case-control study CEFALO from four European countries did not find an increased risk for brain tumors in children and adolescents aged 7 – 19 years and using mobile phones. A further epidemiological study on brain tumors and mobile phone use in children and adolescents below 25 years of age – MOBI-KIDS – is currently performed worldwide in 14 countries.
The remaining open questions as to biological and health effects of high-frequency electromagnetic fields are subject to further research, as well as possible effects in frequency bands that have not been used for wireless digital communication technology up to now.
The scope of the German Mobile Telecommunication Research Programme did not involve specific investigation of the transfer method used for new communications. However, the DMF and further scientific studies have identified no effects of high-frequency electromagnetic fields that would be specific for particular frequency ranges or associated with specific modulation types only. Although such mechanisms of action cannot be excluded for frequency ranges not studied in detail as a matter of principle from the scientific point of view, they are very unlikely considering the numerous results available from research on national and international levels. A recent literature study performed by the BfS on the transferability of results between different frequency ranges concludes that all scientifically proven effects of high-frequency electromagnetic fields are of thermal origin and well comparable among each other.
Viewing the results obtained within the scope of the DMF as well as the current state of knowledge on the international level, there is no reason to doubt the protective effect of the current limit values.
However, attention should still be paid to minimising exposure of the users and the general public when operating existing, or developing new wireless communications to be on the safe side in the BfS' view.
Fundamentally, the BfS requires that basic parameters of new technologies are announced in sufficient time to enable science and radiation protection to test new technologies for compatibility with health.
State of 2017.04.25