Kinetics of Lead in Bone and Blood after End of Occupational Exposure

Abstract

In 14 retired lead workers, followed for over 18 years after end of exposure, repeated analyses of lead levels in finger bone by an in vivo X-ray fluorescence method revealed a decrease of lead concentration. The data were analysed using an exponential retention model. For the whole group the biological half-time was 16 (asymptotic 95% confidence interval, CI 12,23) years. The median of the estimated bone lead levels at the end of exposure was 85 micrograms.g-1 above the "background" (3 micrograms.g-1). A simultaneous follow-up of blood lead levels displayed a decrease, which could be described by a tri-exponential retention model with group half-times of 34 (CI 29,41) days, 1.2 (CI 0.9,1.8) years, and 13 (CI 10,18) years, respectively. The median of the estimated blood lead levels at the end of exposure for the three components were 0.49, 0.61, and 1.1 mumol.l-1 above the "background" (0.38-0.56 mumol.l-1), respectively. The well-documented decrease of lead exposure in the general population over the years, urged the use of a decreasing "background" of blood lead during the time of the study. The slowest of the three components represented the skeleton (probably mainly cortical bone), as did mainly probably also the intermediate one (trabecular bone). The data show the rather slow turnover of lead in the skeleton, the usefulnes of in vivo skeletal lead measurements as a long-term exposure index, and the importance of bone as a source of "endogenous" lead exposure.

Lead concentrations in cortical and trabecular bones in deceased smelter workers

“…Thereafter, the technique has gradually been developed and used for studies of lead exposed workers (5)(6)8). The last three decades, in vivo measurements with XRF have been used to estimate the previous lead exposure in lead exposed populations (4-5, 8-10, 13, 21).…”

Characterizing Golden Eagle Risk to Lead and Anticoagulant Rodenticide Exposure: A Review

“…Lead in blood has a much shorter retention half-time than lead in bone (days compared to years); therefore, PbB concentration provides a marker for more recent exposure, while lead in bone appears to reflect longer-term cumulative exposures (Borjesson et al 1997;Nilsson et al 1991;Schutz et al 1987). Lead in tooth enamel is thought to reflect exposures in utero and during early infancy, during which development of tooth enamel and coronal dentine is completed.…”

“…A portion of lead in bone readily exchanges with the plasma lead pool and, as a result, bone lead is a reservoir for replenishment of lead eliminated from blood by excretion (Alessio 1988;Chettle et al 1991;Hryhirczuk et al 1985;Nilsson et al 1991;). Lead forms highly stable complexes with phosphate and can replace calcium in the calcium-phosphate salt, hydroxyapatite, which comprises the primary crystalline matrix of bone (Lloyd et al 1975).…”

Heavy metals investigation in bovine tissues in Brazil

“…The elimination of lead is incomplete and slow, resulting in bioaccumulation in target tissues, especially after long term exposure. Its half-life is approximately 250 days in ewes, between 95 and 760 days in cattle (Mehennaoui et al, 1988;Rumbeiha et al, 2001), and 2 to18 years in humans (Nilsson et al, 1991;Rabinowitz, 1991).…”