[Telepathic Intruder]

"Did he use a cell phone as a telemarketer?
Yes, as I said, all day for years. But the funny thing about radiation is that there is no way to tell if it's the culprit or just a bystander. You can receive 10 times the lethal dose and be fine or a tiny dose and be not so fine.

[marktwain]

Radiation damage is somewhat random. But there are strong indications that small doses do no harm.

It is all about the dose. You see the same thing with chemical poisons. A “fatal” dose is determined by the effects. When half the population dies from a dose, that is the LD50 level (lethal dose, 50%) terminology.

There are many items that are essential for life that are lethal in sufficient quantities.