In this link over, 200 years ago Dr B. Franklin seemed to suspect that lead was the culprit in a few ailments. Of all the safety issues we deal with I have always been most concerned about what we breathe/absorb and the long term affects. There is no safe level of lead exposure. The Franklin Expidition would attest to that if any had survived their canned goods.

http://books.google.ca/books?id=YB0bPpCC...p;q&f=false