this is the way I'm looking at it, someone please correct me if I don't grasp the situation.

definitions:

• "ionising radiation"
broadly refers to particles (alpha/beta particles; cosmic rays) and EM radiation types that are sufficiently energetic to directly or indirectly (respectively) displace electrons in the atomic structure of matter they pass through. there is no single definition of what counts as ionising radiation when it comes to human cells. it's normally said to be around 10eV – 30eV, but we'll come up with a catch-all definition for argument's sake later. we want to avoid ionisation of DNA, white blood cells, that sort of thing.

• f = v / λ (Hz)

• c = 3 × 10⁸ (m/s)

• h = 6.62607015 × 10⁻³⁴ (J⋅s)

• E = hf = hc/λ (eV)

___________

premises:

• EM rays of high frequency have proportionately high photon energy

• ionisation by EM radiation requires higher photon energy

• the lowest threshold for ionisation of an atom of any element is caesium, at 3.9eV (low end ultraviolet)

• the lowest energy EM radiation that can affect, damage or ionise bare DNA in a vaccuum will be greater than 3.9eV (or 3900meV) [1][2][3]

• the highest frequency officially proposed for 5G to date is 86 GHz (λ ≈ 3.5 × 10⁻³m) [4]

• an 86GHz microwave would have photon energy of 3.6×10⁻⁴eV (or 0.36meV)

(8.6 × 10⁻¹⁰) × (6.62607004 × 10⁻³⁴) ≈ 5.7 × 10⁻²³J ≈ 0.00036eV

• 0.36meV is a lot less energy than 3900meV

___________

conclusion:

EM radiation in proposed 5G range is unable to ionise — and very unlikely to cause any damage to — organic molecules like DNA in a vacuum, without even contemplating absorption/attenuation or the fact that the vast majority of 5G is going to be even lower freq than 86 GHz.

this is just ionisation we're talking about here, i.e. the shredding of your cells by penetrative, energetic radiation. 5G will not be used at anywhere near the kind of wattage as your microwave oven puts out. even if you put yourself in a microwave, yes you get cooked but this is because you absorb the EM radiation and it induces kinetic energy in you, as it would a bowl of porridge. similarly, if you sit yourself in front of a radar you'll probably feel pretty damn hot as well.

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I've seen some crazy people yelling about how 5G is almost the same frequency as crowd-dispersal microwave weapons use — but again, this weaponised form is a focused BEAM. if you use enough visible light you can cook yourself as well. incidentally, even with 5G masts all over the place (and they will be because it has a shorter effective range than 4G LTE) you won't be subjected to anywhere near the wattage a microwave oven or a military radar put out.

if low energy EM waves damage DNA, your immune system, or cause anything related to cancer, it is not by any known physical mechanism [5]

interestingly enough, I caught this on wikipedia:

An international appeal to the European Union made on
September 13, 2017 garnered over 180 signatures from
scientists representing 35 countries. They cite unproven
concerns over the 10 to 20 billion connections to the 5G
network and the subsequent increase in RF-EMF exposure
affecting the global populace constantly. The appeal
also references the International Agency for Research on
Cancer's (IARC) conclusion in 2011 that frequencies
30 kHz – 300 GHz are possibly carcinogenic in humans.

this seems like something that will blow up in paranoid people's minds, and will make purveyors of fake news lick their lips, but consider that the entry on the list cited is

"radiofrequency electromagnetic fields such as, but not limited to, those associated with wireless phones"

so not just 5G at all, but also your granddad's radio, your 3G burner phone, your bluetooth headphones, your kid's remote-controlled car, your drone, etc.

the spectacular list of "possibly carcinogenic things" in question [6] includes aloe vera and the occupation of carpentry/joinery. hey, maybe electromagnetic radiation causes cancer — but then again, so does interacting with pretty much everything else on the planet!

also haven't we been using mm-λ waves in radars for ~50 years now? not seen any super mutants yet.

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[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC20415/

[2]: http://users.ox.ac.uk/~atdgroup/publications/Folkard,%20M.,%...

[3]: http://users.ox.ac.uk/~atdgroup/publications/Prise,%20K.M.,%...

[4]: https://www.ofcom.org.uk/__data/assets/pdf_file/0021/97023/5...

[5]: https://www.cancer.gov/about-cancer/causes-prevention/risk/r...

[6]: https://en.wikipedia.org/wiki/List_of_IARC_Group_2B_Agents_-...