Here’s what the US Government has to say about microwaving
But when you dig deeper into this issue you find that beginning in 1957, and continuing to the present, the Russians have done the most diligent research into the biological effects of microwave ovens. In 1976 they outlawed their use and issued an international warning about the biological and environmental damage that can result from the use of microwave ovens (from "The Effects of Microwave Apparatus on Food & Humans" by William P. Kopp).
Interestingly enough, much of the microwave
oven research originates outside of the US
There’s even more good stuff out there if you can read German or Russian.
My favorite quote from all of these articles: “Microwave safe means safe for the plastic, not the food it holds.”