It continues to amaze me that supposedly learned folks will vilify comparatively safe modern conveniences when others which have a far greater potential for impacting health are ignored. For instance, the power meter or water meter that transmit a very short distance (very low power) only occasionally when compared with your cell phone which is in continuous contact with a tower 1-5 miles away (higher transmit power).
Dating back to the 1930’s and 1940’s the Navy was doing research on exposure to high-frequency signals. They were concerned that putting radar on ships and smaller craft would put crew members in danger or that perhaps RADAR could be used as a weapon against enemies. Fortunately, they were unable to develop an efficient weapon; but, they also determined that exposure to radiation in the mid bands (700mhz to 1ghz) had little to no impact on skin, internal organs, or brain tissue. One of their findings (since repeated) was that high power transmissions at close range could warm the skin and, if continued, the internal organs as well.
In order to protect us, the FCC has restricted the amount of power that handheld devices and household devices (cellphones, wifi routers, IOT devices) may transmit with an eye to preventing the type of exposure that could warm the skin even in contact. The potential for trouble begins when you start to expose living tissue to higher frequency signals like the 2.4ghz, 5ghz (high-performance routers), and the 100ghz and higher used in the newest 5G devices. Sadly, the further above 1ghz (1000mhz) the signal gets, the more energy it carries, and the less we know about the long-term effects of exposure to it.
The higher energy in the signal (5G wideband for instance) greatly enhances its ability to carry data (speed and reliability) making its use a highly sought-after practice as demands for ever faster and more reliable internet dramatically increase.