I sometimes have to grin when someone talks about the signal strength being too low or the frequency being too high to cause damage as if there were some distinct numerical cutoff for any biological effects, like "327.4 mega Herz" or "82.27 picowatts per square cm."
But there are cutoff points? Ionizing vs non-Ionizing radiation. You don't want high frequency, those are the higher energy photons that can actually ionize things and therefore mess up DNA.
However, 2.4 and 5 GHz are both non-ionizing, so the most they do is warm stuff up. They are on the wrong side of the optical band, they can't ionize anything.
You're getting into the Petahertz, x-rays, about six orders of magnitude higher frequency, before you get direct damage.
Without direct damage, you're basically looking at having to cook things to cause damage, which is where total energy levels come in. Until you start pushing kilowatts or more, this type of damage is unlikely unless you can somehow focus it as good as a laser.