Q) What is the maximum power level that an amateur radio station may use at VHF frequencies before an RF exposure evaluation is required?
A) 50 watts PEP at the antenna
NJ2X Notes:
FCC Part 97.3 Definitions
PEP (peak envelope power). The average power supplied to the  antenna transmission line by a transmitter during one RF cycle at the crest of  the modulation envelope taken under normal operating conditions.