BACKGROUND: The pan-European human biomonitoring initiative HBM4EU targets the harmonization of human biomonitoring (HBM) procedures and data for both environmental and occupational exposure, including chromium. The determination of chromium in urine (U-Cr), plasma (P-Cr) and whole blood (WB-Cr) is a common HBM application in employees occupationally exposed to chromium (VI) compounds. METHODS: European laboratories which have registered as candidate laboratories for chromium analysis within HBM4EU were invited to participate in a quality assurance/qualitycontrol (QA/QC) programme comprising interlaboratory comparison investigations (ICI) for the parameters U-Cr, P-Cr and WB-Cr. Participating laboratories received two samples of different concentrations in each of four rounds and were asked to analyse the samples using their standard analytical procedure. The data were evaluated by the Z-score approach and were reported to the participants after each round. RESULTS: The majority of the 29 participating laboratories obtained satisfactory results, although low limits of quantification were required to quantify chromium concentrations in some of the ICI materials. The robust relative standard deviation of the participants' results (study RSDR) obtained from all ICI runs ranged from 6 to 16 % for U-Cr, 7-18 % for P-Cr and 4-47 % for WB-Cr. The application of both inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (EAAS) appeared appropriate for the determination of chromium in urine, plasma and whole blood with regard to occupational exposure levels. CONCLUSION: This QA/QC programme succeeded in establishing a network of laboratories with high analytical comparability and accuracy for the analysis of chromium across Europe.

Aarhus University Department of Environmental Science Frederiksborgvej 399 4000 Roskilde Denmark

Department of Environmental Sciences Jožef Stefan Institute Jamova 39 1000 Ljubljana Slovenia

Environmental Exposure and Epidemiology Norwegian Institute of Public Health Oslo Norway

Institute and Outpatient Clinic of Occupational Social and Environmental Medicine Friedrich Alexander Universität Erlangen Nürnberg Henkestraße 9 11 91054 Erlangen Germany

Institute for Prevention and Occupational Medicine of the German Social Accident Insurance Institute of Ruhr Universität Bochum Bürkle de la Camp Platz 1 44789 Bochum Germany

L'Université Nantes Angers Le Mans F 44307 Nantes France

National Center for Environmental Health Instituto de Salud Carlos 3 Majadahonda Spain

University of Chemistry and Technology Prague Department of Food Analysis and Nutrition Technicka 5 160 00 Prague Czech Republic

Wageningen Food Safety Research part of Wageningen University and Research Akkermaalsbos 2 6708 WB Wageningen the Netherlands

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