We should be able to get our paws on that mandate if it's government related.
I was thinking the changeover to bromate would be in the trade publications which are obscure. Which is why my eyes popped when I saw your research. A public health PhD/MD told me that information was probably in some old basement somewhere.
But regarding the FDA, there has to be a paper trail. Have you called the FDA and told them you're doing a research project? If you have any trouble you can call your congressperson.