The fact that cell phone technology uses microwave transmission frequencies is largely a byproduct of the fact that, by the time cell phone and handset technology became feasible in the late 1980s, just about all of the lower frequency (and presumably safer) spectrum had already been allocated. The lion's share of this most valuable radio spectrum went to VHF and UHF TV.
Although the new Digital TV channels in the U.S. use the exact same spectrum as the old analog channels, there's a bit difference in the efficiency of spectrum use. Whereas with analog TV an entire 6-MHz channel generally needed to be left blank -- unused -- between each channel that's in use, DTV eliminates this requirement. If and when the old analog channels are ever finally switched off -- the current plan calls for 2009 to be the final date for this, but it's already been pushed back several times -- those VHF and UHF frequencies will most likely be auctioned off, with cell phone carriers picking largely picking them up.
And you know what that will mean? Cell phones that do NOT use microwave frequencies. The industry isn't talking about it, because like the legendary "safe cigarette" any discussion of this would imply that the other stuff isn't safe, but if you're concerned about cell phone safety you actually have good reason to look forward to the reclaiming of the analog TV spectrum sooner rather than later.