A comparison of concentrations of lead in human tissues.

Abstract

This postmortem study of lead concentrations in the tissues of 129 subjects is an extension to a report by Barry and Mossman (1970). Lead concentrations in bone greatly exceeded the concentrations in soft tissues and were highest in the dense bones. Bone lead concentrations increased with age in both sexes, more especially in male subjects and in dense bone, varying between mean values of 2-16 ppm in the ribs of children to over 50 ppm in the dense petrous temporal bones of elderly male adults. Male adults contained over 30% more lead in their bones than females. Mean concentrations of lead in the soft tissues varied from less than 0-1 ppm in organs such as muscle and heart to over 2 ppm in the aorta. In most tissues with lead values in excess of 0-2 ppm the male concentrations exceeded female values by about 30%. With the exception of the aorta, spleen, lung, and prostate, lead concentrations did not increase with age in the soft tissues of either sex after about the second decade of life. Children showed concentrations of lead in their soft tissues comparable to female adults, but the concentrations in bone were much lower. It is suggested that children do not possess the same capacity as adults to retain lead in bone. In male adults occupationally exposed to lead the concentrations of lead in bone exceeded the concentrations in unexposed male adults within the same age group by two-to three-fold. Soft tissue lead concentrations between the two groups were less divergent. An assessment of the total body burden of lead revealed higher levels in adult male subjects than in females at mean values of 164-8 mg compared to 103-6 mg, respectively. Over 90% of the total body burden of lead in adults was in bone, of which over 70% was in dense bone. Male adults occupationally exposed to lead had mean total body burdens of 566-4 mg Pb, of which 97% was in bone. The release of lead from bone in conjunction with calcium was not considered to be of physiological significance. Lead concentrations of hair and nails were higher than soft tissue lead concentrations and varied widely. Hair lead measurements were not considered to provide a reliable assessment of lead absorption. The concentrations of lead in tissues of a mixed group of subjects with no known occupational exposure to lead have been shown to be comparable to the findings in earlier studies. Present levels of lead in the environment are not considered to be a hazard to the health of the population in general.

Blood lead levels and bone turnover with weight reduction in women

“…Most of the body Pb resides in the skeleton (Barry, 1975), which may offer protection to other tissues, but can also be a long-term source of Pb transfer to other tissues under conditions of bone resorption. For example, demineralization of bone in postmenopausal women can increase blood Pb (BPb) levels by 25% (Silbergeld et al, 1988), whereas the high bone turnover associated with pregnancy and lactation increases Pb levels in blood and breast milk (Gulson et al, 2003;Manton et al, 2003).…”

Indices of potential lead hazard.

“…The total for these two pools is about 3 mg. This is less than the total of 10-30 mg found in soft tissue at autopsy by Schioeder and Tipton (59) and the 9.3 mg mean in nonoccupationally exposed men, the 15.7 mg in men with occupational exposure, and the 6.2 mg in women, found by Barry (35).…”

“…However, its diagnostic value at the borderline of hazardous conditions is quite limited. It has been found that PbB is more a measure of very recent exposure (30)(31)(32)(33) than of total body burden, and most lead in the body is within the hard and soft tissues (33)(34)(35)(36). Below are some of the best data for "normal" concentrations of PbB.…”

“…This pool is in direct communication with ingested lead, PbU, and the second and third pools. Since the mean lifetime in pool one was 35 days and the mean lifetime of erythrocytes is 110-120 days, it is inferred that lead enters and leaves the erythrocytes several times during the erythrocyte lifetime. This study supports the finding of Butt et al (42).…”

“…Analyses of the lead in different bones and in different parts of the same bones (34,35) and the metabolic, compartmental studies of Rabinowitz et al (33,90) show that bone is heterogeneous with regard to the uptake and metabolism of lead. There are both rather mobile and relatively stable compartments.…”