Microwave ovens use a frequency of around 2.45 GHz, much higher than the 800
MHz cellphones, however close to the 2.5 GHz cordless phones. It's not
necessarily the frequency that one should be concerned about, but rather the
relative RF power density levels produced by each device and its proximity to
biological systems. Because cell phones/cordless phones emit such a small
power density levels, there is no observable biological effect, i.e. heating
tissue. Microwave ovens on the other hand are purposefully designed to heat
media in via HUGH amounts of RF deposition in the oven chamber via more than
1000 watts.

The distinction between a cordless phone/cellular phone and a microwave
oven can not be more clear. It like a match stick burning at a distance of
several feet and a roaring fireplace fire at the same distance...one will not
have any effect on you, the other will certainly warm your skin. Its as simple
as that.

Bruce.