Obviously all EM radiation can be harmful in high enough doses; but, generally speaking, the shorter the wavelength of the wave, the more harm is done to biological organisms. Thus the bath of radio, microwave, IF and visible light waves bombarding us do little damage in the doses we generally get. UV light can kill you though, and people do die of sunburn (and skin cancer.) A big burst of x-rays is extremely not healthy. The shortest, and most damaging, waves are gamma waves which are emitted constantly during the process of radioactive decay from unstable nuclei created by the fission process.
Longer waves are much more easily stopped by materiel barriers. Your cellphone em (which is actually harmful) is easily stopped by its holder. X-ray techs wear lead aprons. The amount of beta and gamma radiation coming off those busted Fuku reactors would require you to live in a lead house.
My Aunt's husband is a optical physicist for Corning, and for what it worth, he wont have a microwave oven in his home because they leak so much radiation.