It’s a very difficult question when we don’t really know what it is about EM fields that are most bioactive, or even if it’s one factor, or many, or even if any factor is linear (ie, more is worse). My impression, and that is all it is, is that patterns in digital transmissions are the focal issue, since bio-systems are exquisitely good at pattern recognistion,
and we know that some of the patterns are similar to physiological patterns.
Why patterns, not frequency?
Because repetition frequency and waveform frequency get muddled up and are not the same. A carrier frequency may be harmless (may be) whilst its structural repetition frequency or pattern may be harmful. Your foot taps to a musical rhythm, not to the acoustic frequency of a concert “G2) “.