Investigation of lead concentrations in whole blood, plasma and urine as biomarkers for biological monitoring of lead exposure.

Lead in blood is a major concept in biomonitoring of exposure but investigations of its alternatives are scarce. The aim of the study was to describe different lead biomarkers' variances, day-to-day and between individuals, estimating their fraction of the total variance. Repeated sampling of whole blood, plasma and urine were conducted for 48 lead-exposed men and 20 individuals under normal environmental lead exposure, in total 603 measurements. For lead workers, the fraction of the total variance attributed to differences between individuals was 91% for whole-blood lead (geometric mean 227 μg/l; geometric standard deviation (GSD): 1.55 μg/l); plasma 78% (0.57 μg/l; GSD: 1.84 μg/l); density-adjusted urine 82%; and unadjusted urine 75% (23.7 μg/l; GSD: 2.48 μg/l). For the individuals under normal lead exposure, the corresponding fractions were 95% of the total variance for whole blood (20.7 μg/l; GSD: 8.6 μg/l), 15% for plasma (0.09 μg/l; GSD: 0.04 μg/l), 87% for creatinine-adjusted urine and 34% for unadjusted (10.8 μg/l; GSD: 6.7 μg/l). Lead concentration in whole blood is the biomarker with the best ability to discriminate between individuals with different mean concentration. Urinary and plasma lead also performed acceptably in lead workers, but at low exposures plasma lead was too imprecise. Urinary adjustments appear not to increase the between-individual fraction of the total variance among lead workers but among those with normal lead exposure.