Natural skeletal levels of lead in Homo sapiens sapiens uncontaminated by technological lead

Lead, Ba and Ca concentrations were determined in tooth enamel, femur and rib from buried skeletons of PreColumbian Southwest American Indians, 10 subjects who lived 1000 years ago on the Pacific coast at 34°N, and 13 subjects who lived 700 years ago in a desert valley tributary of the Colorado River at 37°N 111°W, both groups living in environments uncontaminated by technological Pb. For the coastal tribe, average Pb/Ca ratios were 1.1 × 10 −7 in enamel, 2.3 × 10 −7 in femur and 4.7 × 10 −7 in rib, while Ba/Ca ratios were 1.2 × 10 −5 in enamel, 32 × 10 −5 in femur and 38 × 10 −5 in rib (wt ratios). For the desert tribe, average Pb/Ca ratios were 4 × 10 −7 in enamel, 11 × 10 −7 in femur and 37 × 10 −7 in rib, while Ba/Ca ratios were 1.1 × 10 −5 in enamel, 7.5 × 10 −5 in femur and 6.2 × 10 −5 in rib. It is shown that biologic levels of Pb and Ba in buried femur and rib at both burial sites and in buried enamel at the Arizona site are obscured by excessive diagenetic additions of Pb and Ba from soil moisture. It is shown that one-third of the Pb in enamel at the Malibu site is biologic, yielding a skeletal Pb/Ca (wt) ratio of 4 × 10 −8. This is equivalent to a mean skeletal concentration of 13 ng Pb g −1 bone ash, and a mean natural body burden of 40 μg Pb/70 kg adult Homo sapiens sapiens, uncontaminated by technological Pb. This value is about one-thousandth of the mean body burden of 40 mg industrial Pb/70 kg adult American today, which indicates the probable existence within most Americans of dysfunctions caused by poisoning from chronic, excessive overexposures to industrial Pb.