External quality assessment of human biomonitoring in the range of environmental exposure levels.

The number of human biomonitoring (HBM) applications for identifying and assessing the chemical exposure of the general population from the environment has distinctly increased during the last decade. An appropriate external quality assessment of the applied methods is essential to assure the accuracy and the comparability of HBM results. The international programme of the German External Quality Assessment Scheme (G-EQUAS) provides proficiency testing for most of the HBM parameters, which are commonly used for the assessment of the human exposure to chemicals. Since 1992, G-EQUAS provides intercomparison runs for biological monitoring parameters in the environmental exposure range twice a year, with a successive increase of parameter numbers. In round no. 45 (2010) 18 metals in blood, plasma and urine und 36 organic parameters in urine and plasma were provided. Additionally analyses of 4 haemoglobin adducts were offered. For each parameter, two samples with different concentrations of the biomarker were sent to the participants. The target values as well as the tolerance ranges were estimated on the basis of the results from reference laboratories. The successful participation was certified, if the participant's results were within the tolerance ranges for both samples. The number of participants ranged from 3 to 37 international laboratories according to the individual parameter. The highest interest was observed for the detection of metals in blood, serum and urine, whereas only a few of the participants took part in the analyses of organophosphate metabolites and haemoglobin adducts. The rate of a successful participation ranged from 38 to 100%. Poor success rates were found for organophosphate metabolites, 1-naphthol and cotinine in urine. A training effect was observed for a group of laboratories which participated regularly in the analysis of organochlorinated compounds in serum. Copyright Â