The level of biologic lead (expressed as the ratio of atomic lead to atomic calcium) in bones of Peruvians buried 1600 years ago was found to be 3 x 10(-8), as compared to 2100 to 3500 x 10(-8) in the bones of present-day residents of England and the United States. The ratio of barium to calcium was 2 to 3 x 10(-6) in bones of ancient Peruvians and present-day Americans. Barium and lead have similar morphologic distributions in organisms, so this discrepancy for lead must result from overexposure of present-day people to industrial lead and not from natural variations. The magnitude of this discrepancy has been confirmed by two different lines of investigation not reported in this article. This new evidence suggests that natural interactions of lead in human cells have not yet been determined because reagents, nutrients and controls used in laboratory and field studies have been contaminated with lead far in excess of naturally occurring levels.
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