No idea. The claim came from the World health Organisation
http://www.iarc.fr/en/media-centre/iarcnews/pdf/Q&A_Glyphosate.pdf
The EFSA said its not dangerous but their conclusions were based on tests carried out by the manufacturers of Glyphosate's. So make of that what you will.
I personaly have no in depth knowledge on this as its a product we use rarely for treatment of plant growth in masonry.
We now use Benzokonium Chloride and Boron (B10RH) as a masonory biocide but its 10X the cost. That said we find it far more effective on lichens than Glyphosate
The big one for us is Permethrin. Which was on World Health Organisation list of the sefest and most effective treatments???? Then it was banned Permethrin - Wikipedia
I still cant find the official details on why but I found data linking it to Thyroyd cancer and Hormonal defects.
Which makes me think the WHO talk a lot of bol@cks?
In March 2015, IARC classified glyphosate as “probably carcinogenic to humans” (Group 2A). This was based on “limited” evidence of cancer in humans (from real-world exposures that actually occurred) and “sufficient” evidence of cancer in experimental animals (from studies of “pure” glyphosate).
So no evidance at all.
Also the earlier drafts said there was no evidance at all.