I'm surprised.

Consulting an exposure limit calculator (https://www.arrl.org/rf-exposure-calculator) suggests a safe distance (FCC controlled exposure limit) for continuous (30 min) exposure from a 100w FM transmitter antenna at 100 MHz with, say, 5 dB gain is around 5 ft. For a brief exposure it's much less.

Amateur radio operators need to know this, since 100w is quite a typical power level, and they have bands (50 MHz and 144 MHz) not far from commercial FM.

How far away from the antenna were you? The antenna is usually far away from the transmitter that you were replacing.