Microwaves, from a home appliance, are not powerful enough to harm people. Microwaves have a long wave length that can last a long time, which makes it good for transmitting information, but has trouble penetrating matter, which means its easily shielded. So, even the thin plastic cover on your microwave at home is able to contain the waves transmitted.
Some have argued that outdoor microwaves can be damaging, but no long term studies have shown any significant damage to humans. Birds may be affected, their ability to judge direction seems to be faulty in areas with high microwave emmissions.