Carol:
> > I'm surprised there was no mention of URPs in your post.  Did you
> > find their existence to be unsubstantiated?

Jean-Louis:
> It's just that I am not familiar with URPs. What does that acronym
> stand for? Unidentified Reaction Products? Utah Republican Party?
> United Record Pressing?

It stands for Unique Radiolytic Products.  They are often mentioned
in discussions of food irradiation, not as much in those of microwave
ovens, but the connection has been made by some.  I'm not very
educated about them myself, but what I have read I've found
interesting.
I don't have references for the non-internet articles I've read about
them, but there is a little overview of some of the objections to
microwave ovens at http://www.icom.net/~nexus/microwave.html , and in
that article, the term "radiolytic compounds" is used.  That term may
be used interchangeably with "URPs" by some people; I don't know.

Carol

PS:  I am well aware that the above-referenced article is not a
     scientific study.