Wi Fi Safety

Is Wi Fi as used in a home environment, broadcasting at 2.4Ghz, safe. Does anyone know the long term biological effect of exposure to this type of radio frequency.
What power levels are used by Wi Fi equipment in a typical home setup and what’s the relationship between power/frequency/distance. For example, Radiation obeys the Inverse Square Law, I’m led to believe. Finally, what’s the dividing line between Radiation and Radio Frequencies.
Thanks in anticipation.