Having spent 30 years in the printing industry I cannot say for certain that lead is not in inks but there are heavy metals used in the pigments. So we make sure that the lead is gone but what about the heavy metals left, is it then ok to let your child eat a book?
Don't forget we will have to ban all ebooks because if your child took apart the ebook and ate the inner workings there is lead and heavy metals there also.
