I think what you must have heard is that water does a good job of
absorbing radiation whose frequency is 2.4 GHz. The main way it absorbs
the radiation is by the wiggling of the water molecules' electrical
dipoles by the electrical field of the radiation. Magnetic effects
really don't have anything to do with it.
Since we're mostly made of water, we must absorb some energy from
devices emitting microwaves. Obviously, that can make serious problems
if some part of you gets too hot. So far as I know, there's no good
evidence of dangers from various devices like the ones you mention, and
no known likely mechanism for such danger. Of course, biology can have
some tricky surprises.
For a while, there was much talk of danger from low-frequency
fields from power lines. The power line question has been investigated
very thoroughly now, and it's clear that any danger is either extremely
small or zero.
Mike W.
(published on 10/22/2007)
