Mike:
Time to pay you back for all your valuable color management advice. There are a bunch of printers in California that print for Sony, and they have very stringent heavy metal requirements for Japanese printing. They require testing for Cadmium, Mercury, Lead, and I think Silver. While at the deceased printing organization called GATF, we did a lot of that in Bassemir Kronenberg ink and paper lab. It was sent out to have tests by atomic absorption spectroscopy or inductively couple plasma analysis. The costs were $30 or $50 per ink per element. The results were always in the parts per billion, or below detectable limits by any chemical method. That's the deal though, you have to have proof that it isn't there. Now, if you are using a yellow ink that is made with lead chromate, like in the 1940's, well, you got a problem, but none of the modern yellow organic pigments contain lead. Lead chromate is still used to color plastics, and thus the issues with toys from China. We also had to test staples used for saddle stitching, to prove that the above metals were not present, or below the allowed limits.
If you are really concerned about this, you can buy ink from a place called ColorCon, where all the inks are made for food contact. Might be pricey, but factor in the cost of testing.
John Lind
Cranberry Township, PA
724-776-4718