It is all nonsense. Amateur Radio operators log thousands of hours each year willingly sitting inside EM fields that are up to thousands of times stronger than what comes out of a cellular phone, with no ill effects. They also are exposed to wavelengths that much more greatly affect living tissue, than the ones cell phones use.
IIRC average output power from a cellphone is less than 1.8W of RF. Industry standard HT (handheld) Ham radio is 5W.
If you want REALLY strong EM fields, look at those of us with multi-kilowatt tesla coils. We're doing just fine*.
*Never touch the output of a TC, and never be the lowest imepdance path for the RF current. Exposure to the EM field is harmless, but exposure to the RF current is NOT!