I'm very glad for this topic!
I recently acquired a Pagasari, and have been happily drinking matcha out of it.
Then, I received a note from an artisan I'm acquainted with that Raku aren't safe for using!!
The horror, the disappointment!
Well, I've been in contact with Pagasari and here is what he says (it's pretty choppy, but he's french and has to use the google translator):
>>To answer your questions, I never used to plom in glazes that I make myself. I use my bowls every day and I am very careful to my health. You can use all kinds of liquids except the vinegar (sometimes there are people who put in the salad bowls tea is weird I know ...) which destroys the structure of the glaze. For everything else there is no problem.
In the raku sometimes the earth is sometimes seeming to leave the apparent carbone but it's something that I do not use in my pieces. I realize thermal shock without plunging the room but the smoke just in water or snow, then I fill the cracks oxides for cracking black. I sometimes put to fire 10 to remove the earth and between each layer of color.
Then you should know that glazes that are fired at 1000 degrees are much more fragile than cooking at high temperatures because the earth is like a sponge that is not closed.
This is part of the charm of Rakus changing with time. Often it takes several months of use so that the true character of the piece appear, the whole magic of this type of object.
ps: sorry for my english I use google translator ^^<<
I think in that first sentence "plom" must be lead; I've sent him another note to clarify; also to make sure he only uses his own self-made glazes (which he doesn't use "plom" in, ever, he says);
I also, though, want to find out what other substances might leach (apparently, if it's Raku, it's gonna leach - holes/bubbles, cracks) - how about barium carbonate (Rob Fornell says that's nasty stuff).
I'll keep us all posted.
I continue to explore this potential problem.
I hope it turns out okay - I'd hate to never be able to safely use mine.