Geeze, that sounds a bit nasty. I wonder where they're getting that information from though?
Nothing that I've ever read about it has ever mentioned Arsenic.
Looking at the chemical formula/structure, which from what I can find is C6H6Na6O21P6, I just can't see where it is/can be represented as a component there either?
Maybe Arsenic, the chemical formula/ structure of which is H3AsO4, is produced/passed from the horse's system as a metabolite of the ITPP, although at this point I can't see how?
Thanks for the story Phil. Interesting stuff.