I'm not the right guy to ask. As stated, I have no indepth knowledge about the topic.
I would however assume that the
International Agency for Research on Cancer would be a credible source.
I do not have a link to the study itself, I just read a few citations. What I read was pretty inconclusive, but some of it suggested there was a close link to developing acoustic neuroma which is a benign form of brain tumor.
(That part of the study was done
at this institute)
Actually here it is, knock yourself out:
http://www.ncbi.nlm.nih.gov/pubmed/16136046?dopt=Citationhttp://www.ncbi.nlm.nih.gov/pubmed/16835295?dopt=Citationhttp://www.ncbi.nlm.nih.gov/pubmed/17636416?dopt=Citation
