The maximum permissible exposure (MPE) levels are not uniform throughout the radio spectrum because the human body absorbs energy differently at various frequencies.
The term "specific absorption rate" or SAR is used to mean the rate at which RF energy is absorbed into the human body.
The maximum permissible exposure (MPE) limits are based on the whole-body specific absorption rate (SAR).
The FCC Regulations most stringent for RF radiation exposure for the frequencies between 30 MHz and 300 MHz.
One biological effect to the eye that can result from RF exposure is the formation of cataracts (because it can cause heating).
You should never look into the open end of a microwave feed horn antenna while the transmitter is operating because you may be exposing your eyes to more than the maximum permissible exposure of RF radiation.
In the near field, the variation of the field strength with distance from the source depends on the type of antenna being used.