Lead concentrations in human plasma, urine and whole blood

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 mu g/l, and the imprecision was 5%. Results The lead concentration ranges were 0.20-37 mu g/l for P-Pb, 0.9-176 mu g/l (density adjusted) for U-Pb, and 9-930 mu g/l 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. Conclusions 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 al high lead levels. This development is of importance for studies of exposure, possibly also for studies of risks.