Lead concentrations in human plasma, urine and whole blood

Abstract

Objectives Blood-lead levels (B-Pb), and to some extent urinary lead (U-Pb), are the most employed measures of lead exposure and risk. However, the small fraction of lead present in plasma (usually below 1 % of that in blood) is probably more relevant to lead exposure and toxicity. Nevertheless, the lead content of plasma lead (P-Pb) has only seldom been used, mainly due to analytical limitations, which have now been overcome. We examined P-Pb in occupationally exposed subjects, as well as its relationship with B-Pb and U-Pb. Methods Blood samples were obtained from 145 male workers, 110 of whom were employed in lead work. After a simple dilution of plasma, P-Pb was determined by inductively coupled plasma mass spectrometry. The detection limit was 0.04 kgll, and the imprecision was 5%. Results The lead concentration ranges were 0.20-37 kg11 for P-Pb, 0.9-176 kg11 (density adjusted) for U-Pb, and 9-930 kg11 for B-Pb. A close exponential relation was obtained between B-Pb and P-Pb. When B-Pb was plotted versus log P-Pb, a straight line (log P-Pb = 0.00225 . B-Pb -0.58; r = 0.97) was obtained. Both the relation between U-Pb and P-Pb and that between U-Pb and B-Pb showed a large scattering (r = 0.78 in both cases). The relation to B-Pb appeared to be exponential, while that to P-Pb appeared to be linear. C O~C~U S~O~S The low detection limit and good precision of P-Pb determinations make it possible to use P-Pb in assessments of lead exposure and risk. Furthermore, in relative terms, P-Pb is a more sensitive measure than B-Pb, especially at high lead levels. This development is of importance for studies of exposure, possibly also for studies of risks.

Uso do chumbo em urina como indicador de exposição e sua relação com chumbo no sangue

“…Os resultados encontrados nesta pesquisa para as correlações entre Pb-U e Pb-S estão de acordo com aqueles relatados em outros estudos realizados com crianças e adultos expostos ambiental e ocupacionalmente ao chumbo 16,17,18,19,20,21,22,23,24 . Um estudo sobre mulheres e crianças expostas ambientalmente encontrou uma relação linear pobre entre os dois indicadores pesquisados, particularmente nas faixas mais baixas de exposição 17 .…”

“…Pb-S Pb-U r Valor de p n Média ± DP Média ± DP Contudo, esta relação mostrou grande dispersão, parecendo ser exponencial 23 .…”

“…Embora existam inúmeros estudos sobre a contaminação por chumbo 11,12,13,14,15,16,17,18,19,20,21,22,23,24 , poucos são aqueles que descrevem as relações entre o metal no sangue e na urina 8,16,17,18,19,20,21,22,23,24 . Uma revisão sobre biomarcadores de exposição ao chumbo relata a existência de correlação não linear entre esses dois indicadores biológicos 8 .…”

Lead-binding proteins - a way to understand lead toxicity?

“…The pro p o rtion of lead in plasma increases with i n c reasing lead concentrat i o n , so that a curved re l at i o n appears between the concentration in whole blood and that in plasma [4,5]. The large difference between the lead conc e n t rations in cells and plasma may be explained by the presence of a protein with high affinity for lead, inside the red blood cells.…”

Lead concentrations in tibial and calcaneal bone in relation to the history of lead exposure

“…Therefore, Borjesson et a1 (8) calculated an adjusted cumB-Pb with respect to the turnover rate of lead in the skeleton. It gave a somewhat better prediction of bone-Pb than the unadjusted cumB-Pb.The assumption of a rectilinear relationship between bone-Pb and cumB-Pb or adjusted cumB-Pb is, however, hard to justify, since there is recent, strong evidence of a markedly nonlinear, close association between B-Pb and the lead concentration in plasma (P-Pb), the magnitude of which is only 11100 of B-Pb levels (22,23). The nonlinear relation between B-Pb and P-Pb is probably an effect of gradual saturation of the strongest binding sites for lead in the red cells, localized on the enzyme 6-aminolevulinic acid dehydratase (24,25).…”