How do I know whether I am exposed to invisible high-frequency electromagnetic waves? My body cannot sense them. One option I have is to check whether my mobile phone has good reception. However, phones operate on specific frequencies. So rather than finding out on which frequency my phone operates, I could move on to my second option and use a measuring device that is made for detecting high-frequency electromagnetic waves.
Some of my interview partners who are mobilising against 5G – the fifth generation of mobile communication technology – carry EMF meters with them. When I met one activist in a café in Brussels, Belgium, he demonstratively put his device on the table. The apparatus detects frequencies between 200 megahertz (Mhz) and 8 Ghz. However, we did not know – and I still don’t know – how the apparatus aggregates different overlaying electromagnetic wave frequencies and field intensities into one value. It also remained opaque, how the apparatus switches between different measurement units – from Volts per metre (V/m) which relates to the electric field strength to Watts per square metre (W/m2), the unit for the power flux density.
I do not blame us for our ignorance of what is going on inside the apparatus. After several conversations with measuring experts, I have understood that knowing one’s exposure based on EMF measurements is even difficult for experts. One difficulty is that antennas do not radiate symmetrically in all directions, like the sun. With 5G technology, signal transmission has become more targeted – it’s called beam forming – making exposure even less predictable and measurements on a coffee table even more contingent. Moreover, the power of electromagnetic signals and strength of EMF is fluid and pulsating. Limit values for EMF exposure therefore use the average of six-minute-long measurement intervals. Activists who worry about EMF exposure argue that these average values render invisible the peaks and pulsations of electromagnetic signals in our surroundings which they consider as particularly problematic. Finally, I have learned that even if I know how many Volts per metre penetrate the urban air around me, I still don’t know how that impacts my body as exposure effects also depend on the size of a body relative to the wave.