Accumulated Body Burden and Endogenous Release of Lead in Employees of a Lead Smelter

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The National Institute of Environmental Health Sciences (NIEHS) and Brogan & Partners are collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives.Bone lead levels for 367 active and 14 retired lead smelter workers were measured in vivo by X-ray fluorescence in May-June 1994. The bone sites of study were the tibia and calcaneus; magnitudes of concentration were used to gauge lead body burden. Whole blood lead readings from the workers generated a cumulative blood lead index (CBLI) that approximated the level of lead exposure over time. Blood lead values for 204 of the 381 workers were gathered from workers returning from a 10-month work interruption that ended in 1991; their blood level values were compared to their tibia and calcaneus lead levels. The resulting relations allowed constraints to be placed on the endogenous release of lead from bone in smelter workers. Calcaneus lead levels were found to correlate strongly with those for tibia lead, and in a manner consistent with observations from other lead industry workers. Relations between bone lead concentration and CBLI demonstrated a distinctly nonlinear appearance. When the active population was divided by date of hire, a significant difference in the bone lead-CBLI slope emerged. After a correction to include the component of CBLI existing before the workers' employment at the smelter was made, this difference persisted. This implies that the transfer of lead from blood to bone in the workers has changed over time, possibly as a consequence of varying exposure conditions. Key words: blood lead indices, bone lead, occupational lead exposure, smelter workers, X-ray fluorescence.

Bone lead as a biological marker in epidemiologic studies of chronic toxicity: conceptual paradigms.

“…Chelatable lead was found to correlate with lead in biopsies of the vertebrae (a mosdy trabecular bone), but not KXRF-measured lead in finger bone (which is mostly cortical bone) (65). Fleming et al (66) on the other hand, found that the relationship of KX.RFmeasured bone lead to blood among lead smelter workers who had not worked for 10 months, as well as retired lead smelter workers, was stronger for the tibia (cortical bone) than the calcaneus (trabecular bone). One potential explanation is that although bone mineral density of the calcaneus has been reported to be a good indicator of overall trabecular bone density (62'), the error for calcaneal measurements is generally larger than that of tibia measurements, which may have resulted in a more attentuated bone lead-blood lead relationship.…”

The ICRP age-specific biokinetic model for lead: validations, empirical comparisons, and explorations.

“…Chelation efficiency, defined in the model as the fraction of the total outflow of Pb from plasma that is assigned to the urinary bladder contents, was empirically set to 0.85 to provide the best fit to the PbB measurements during the chelation period. Table 4 (21)(22)(23)(24).…”

In vivo applications of X-ray fluorescence in human subjects

“…In the study by Gerhardsson et al conducted [33] 367 0.83 0.056 ± 0.002 in 1988, they were able to measure tibia and calcaneus lead in both active and retired workers. In both groups, there were very extensive records of blood lead measurements, because such monitoring had begun at that lead smelting facility in 1950.…”

“…The different slope between blood lead on the one hand and tibia lead or calcaneus lead on the other is presumed to reflect the fact that these are different types of bones, with tibia being predominantly cortical and calcaneus being predominantly trabecular. [35] B = 0.17T + 13 Fleming et al [33] B = 0.136T + 13.0 Erkkilä et al [30] B = 0.072C + 4.0 Gerhardsson et al [31] B = 0.062C + 6.9 Fleming et al [33] B = 0.078C + 13.0…”