The lower wattage for handhelds was usually 5 watts at VHF and 4 watts at UHF and 3 watts for 700/800mhz. It is a RF exposure limit. Many public safety officials use a remote speaker/mic where the handheld/portable is still worn on the side of the body while transmitting. Anything more is considered "harmful exposure". You should stay about 3 feet away from a transmitting mobile radio with a mounted antenna, as most mobiles transmit at 15-50 watts, plus the antenna gain, if any.