From: John Allain <John.Allain(a)Donnelley.InfoUSA.Com> Microwaves run around 900mhz. That is the majik freq for really shaking water ions till they warm up. The key concern is the power/area* time With the threshold around 900mhz being about 10milliwatts/square inch. The effect is frequency sensitive where very low frequencies are less impact then say microwave. the primary damaging effect is heating either localized or generalized. I've been burnt by a 20watt UHF (474mhz) twoway radio when a bozo keyed up while I was working on the antenna. It punched a nice hole in my finger that took a long time to heal. cell phones FYI are in the 850mhz range and relatively low power in the sub .5W range with a low energy density. FYI the average HAM VHF or UHF portable is usually 2-10 times higher power output {1 to 5W}. There is some risk, I would consider it low by any standard I've seen. Oh, people who drive while talking on cell phones are 4 times more likely to be involved in an accident. That has been verified. Allison