Are microwaves dangerous to humans

As long as it hasn't been damaged in any way and is taken care of, a microwave can be used for many years - my own parents are using both a standard microwave and a combination microwave/conventional oven that they've owned since 1982.

The main health hazards with microwaves are to people with pacemakers and similar type medical implants - not all microwaves are taken care of the same.