The electromagnetic spectrum is roughly divided in two: one side of which comprises ionising radiation, which begins with short-wave ultraviolet light (UV-C) and extends to X-rays and gamma radiation. This radiation can detach electrons from molecules and thus directly alter matter – in other words, ionise it. This damages the DNA in the body, which can lead to cancer.
The majority of the electromagnetic spectrum, however, is non-ionising. A single light particle (photon) does not have enough energy to ionise molecules or atoms. In addition to visible light, this also includes radio waves and millimetre waves, i.e. the frequencies used for mobile communications. Whether these frequencies can also lead to cancer has been investigated for many years. According to the International Commission on Non-Ionizing Radiation Protection (ICNIRP 2020), no evidence of a connection between the use of mobile phones and the development of tumours has been found to date.
Exposure to mobile radio signals occurs mainly from one’s own mobile phone, but also from those belonging to others. This is due to the fact that the strength of electromagnetic fields (EMFs) decreases very quickly as it gets further away from the source. The greatest exposure is thus caused by the closest device, namely the mobile phone, and the head, which is next to the device when making calls, is particularly heavily exposed.
Swiss researcher Milena Foerster has calculated which sources are responsible for the average daily dose in the brains of adolescents. Result: mobile phones (calls 80%, mobile data 5%) and cordless phones (9%) are the main sources. Mobile base stations, on the other hand, only contribute 3.4% of the exposure (Foerster et al. 2018). Reason enough to further investigate the relationship between mobile phones and cancer (brain tumours).
In 2013, the International Agency for Research on Cancer (IARC) published a monograph on high-frequency EMFs and categorised EMFs as “possibly carcinogenic to humans (2b)”. In addition to cell and animal experiments, some inconsistencies in epidemiological studies have prevented the IARC from giving EMFs the all-clear. In the mid-2000s, a Swedish group led by Prof. Hardell asserted a strong correlation between brain tumours and EMFs in smaller studies, but this has not yet been reproduced by other research groups (Hardell 2006). Conversely, the wide-scale international INTERPHONE study actually found that most mobile phone users had a reduced risk of developing brain tumours. Only in the category of the most frequent users was there an increased risk. However, the interpretation of this data is made more difficult by psychological effects (biases), as the authors of the study themselves describe. For example, the duration of use of the mobile phone was not measured, but rather estimated by the participants on the basis of their memory. Therefore, these studies cannot be considered an indication of a link to brain tumours, but they have led the IARC to categorise high-frequency EMFs as potentially carcinogenic. A revision of the IARC monograph is expected in 2024.
Another source of data is the national cancer registries. Since the introduction of mobile communications in the 1990s, the spread of the technology has grown explosively and exposure has therefore also increased sharply. If the risk were as high as Hardell claims, the number of diagnosed brain tumours would certainly be considerably higher today than it was 30 years ago. However, this is not the case. The IARC explains the small increase observed with improved diagnostics.
Various recent reports, such as ICNIRP 2020, the World Cancer Report 2020, the aforementioned Swiss Cancer Report, a study from England (de Vocht 2021) and one from South Korea (Choi et al. 2021), all share the same message: despite great research efforts, no mechanism has yet been found to explain how high-frequency EMFs cause cancer. Epidemiological research largely indicates that EMFs are not carcinogenic. If there is, however, an undiscovered risk, it is likely very small.