Systematic literature study on possible effects of exposure to radiofrequency electromagnetic fields on the risk of cancer in humans

Background

The World Health Organisation (WHO) has been studying the potential health effects of exposure to electromagnetic fields (EMFs) for decades. The Environmental Health Criteria (EHC) monographs are the WHO’s risk assessments for chemical, biological and physical health factors. They are drawn up by independent scientists and are the result of a thorough and critical review of the entire body of research on a specific chemical or physical factor such as electromagnetic fields¹.

To date, the WHO has published three such EHC monographs on these fields, including static², extremely low-frequency (ELF)³ and radiofrequency (RF) fields. The last EHC monograph on radiofrequency electromagnetic fields was published in 1993⁴. In view of a large number of new publications in this field, this monograph is currently being comprehensively updated, which will lead to a new EHC monograph on the subject.

To ensure that the EHC monograph is based on the most up-to-date knowledge and includes all available scientific evidence on particularly relevant diseases or symptoms (endpoints), the WHO commissioned a series of systematic reviews in autumn 2019 to address specific questions (see Spotlight on EMF Research from 24 April 2024⁵). One such question is whether the available epidemiological studies – i.e. observational studies on humans – can be used to deduce possible influences of exposure to radiofrequency electromagnetic fields on the risk of cancer. The use of technology that emits these fields has increased steadily since the 1950s and includes applications in medicine, industry, the home, the military and, in particular, telecommunications.

Since the late 1990s and early 2000s, when the use of mobile phones became widespread among the general public, concerns have been raised about the potential health effects of mobile phone technology. Without a hands-free system, phone use was associated with comparatively high exposure of the head in those days. Scientific interest therefore focused primarily on a possible connection with tumours of the head (including gliomas, meningiomas and acoustic neuromas). As a result, a series of epidemiological studies have been initiated to investigate the possible long-term effects of mobile phones on the risk of brain tumours.

Objective

Specialist scientists from the BfS and other institutions have been commissioned by the WHO to conduct a systematic review of the scientific literature on the possible effects of exposure to radiofrequency electromagnetic fields and the occurrence of cancer in humans. The evidence currently available from human observational studies was to be summarised, analysed and evaluated.

Methods and implementation

In 2021, the authors published the protocol for conducting the systematic review in a peer-reviewed scientific journal⁶. For example, this protocol transparently set out the inclusion and exclusion criteria, the criteria for assessing possible risks of bias in the studies, and details of the methodology and assessment criteria. Literature research was carried out by searching for studies in the Medline and Embase databases and the EMF-Portal, which specialises in scientific literature on the health effects of exposure to electromagnetic fields.

A distinction was made between three scenarios of how people can be exposed to fields: near-field exposure of the head from mobile phones (mobile phones and cordless phones), far-field exposure of the whole body from mobile phone masts and radio transmitters, and occupational exposure from radiofrequency fields. The review focused on cancers of the head – specifically, gliomas in the brain and tumours of the meninges, the auditory nerve and the salivary glands. In the case of whole-body exposure, leukaemia was also considered.

Potential risks of bias were assessed by adapting the Risk of Bias (RoB) tool from the Office of Health Assessment and Translation (OHAT) and assigning each so-called exposure-endpoint combination from the included studies to one of three quality levels (low, moderate or high) according to its bias potential. Various types of meta-analyses and sensitivity analyses were carried out in order to synthesise the data. Confidence in the evidence for or against possible associations was assessed specifically for the investigated exposure-endpoint combinations using the OHAT method (high, moderate, low or very low confidence in the evidence), which is based on the approach known as Grading of Recommendations, Assessment, Development and Evaluations (GRADE).

The results were published in the special issue "WHO assessment of health effects of exposure to radiofrequency electromagnetic fields: systematic reviews" of the journal Environment International, which specialises in systematic reviews⁷.

Results

In total, the researchers reviewed over 5,000 studies. Of these, the analysis ultimately included 63 epidemiological studies from 22 countries, dating from 1994 to 2022. These were mainly case-control studies, but also included cohort studies.

According to the results of the meta-analyses, near-field exposure of the head due to mobile phone use is not associated with an increased risk of gliomas, meningiomas, acoustic neuromas, pituitary tumours or salivary gland tumours in adults, nor is the risk of brain tumours increased in children. There is also no evidence of an increased risk of gliomas, meningiomas or acoustic neuromas when using cordless phones. No evidence was found that children have an increased risk of leukaemia or brain tumours in the case of whole-body exposure to fixed transmitters (radio antennas or mobile phone base stations). Likewise, there is no evidence of an increased risk of brain tumours due to occupational exposure to radiofrequency electromagnetic fields. However, due to risks of bias that are typical of epidemiological studies, there is only moderate or low confidence in the available evidence that underpins the results of the systematic review.

In addition, 50 articles were included as “complementary evidence”. These provided additional insights into topic-relevant biases, radiofrequency dose modelling, incidence trend simulations and time series analyses. The incidence trend simulation studies and time series analyses were used to assess the external validity of the epidemiological studies and consistently showed that the increased risks observed in some case-control studies do not correspond to the actual incidence rates of the respective cancers observed in several countries and over long periods of time.

Literature

1) World Health Organization. Radiation and health - Health risk assessment 2024.

2) World Health Organization. Static fields: World Health Organization; 2006.

3) World Health Organization. Extremely low frequency fields: World Health Organization; 2007.

4) World Health Organization. Electromagnetic fields (300 Hz to 300 GHz): World Health Organization; 1993.

5) Spotlight on “WHO assessment of health effects of exposure to radiofrequency electromagnetic fields: systematic reviews”, a special series in Environment International.

6) Lagorio, Susanna, et al. "The effect of exposure to radiofrequency fields on cancer risk in the general and working population: A protocol for a systematic review of human observational studies." Environment international 157 (2021): 106828.

7) Karipidis, Ken, et al. "The effect of exposure to radiofrequency fields on cancer risk in the general and working population: A systematic review of human observational studies – Part I: Most researched outcomes." Environment international 191 (2024): 108983.