Exposure to hexavalent chromium [Cr(VI)] may occur in several occupational activities, e.g., welding, Cr(VI) electroplating and other surface treatment processes. The aim of this study was to provide EU relevant data on occupational Cr(VI) exposure to support the regulatory risk assessment and decision-making. In addition, the capability and validity of different biomarkers for the assessment of Cr(VI) exposure were evaluated. The study involved nine European countries and involved 399 workers in different industry sectors with exposures to Cr(VI) such as welding, bath plating, applying or removing paint and other tasks. We also studied 203 controls to establish a background in workers with no direct exposure to Cr(VI). We applied a cross-sectional study design and used chromium in urine as the primary biomonitoring method for Cr(VI) exposure. Additionally, we studied the use of red blood cells (RBC) and exhaled breath condensate (EBC) for biomonitoring of exposure to Cr(VI). Personal measurements were used to study exposure to inhalable and respirable Cr(VI) by personal air sampling. Dermal exposure was studied by taking hand wipe samples. The highest internal exposures were observed in the use of Cr(VI) in electrolytic bath plating. In stainless steel welding the internal Cr exposure was clearly lower when compared to plating activities. We observed a high correlation between chromium urinary levels and air Cr(VI) or dermal total Cr exposure. Urinary chromium showed its value as a first approach for the assessment of total, internal exposure. Correlations between urinary chromium and Cr(VI) in EBC and Cr in RBC were low, probably due to differences in kinetics and indicating that these biomonitoring approaches may not be interchangeable but rather complementary. This study showed that occupational biomonitoring studies can be conducted successfully by multi-national collaboration and provide relevant information to support policy actions aiming to reduce occupational exposure to chemicals.

The EU human biomonitoring initiative, HBM4EU, aims to co-ordinate and advance human biomonitoring (HBM) across Europe. As part of HBM4EU, we presented a protocol for a multicentre study to characterize occupational exposure to hexavalent chromium (Cr(VI)) in nine European countries (HBM4EU chromates study). This study intended to collect data on current occupational exposure and to test new indicators for chromium (Cr) biomonitoring (Cr(VI) in exhaled breath condensate and Cr in red blood cells), in addition to traditional urinary total Cr analyses. Also, data from occupational hygiene samples and biomarkers of early biological effects, including genetic and epigenetic effects, was obtained, complementing the biomonitoring information. Data collection and analysis was completed, with the project findings being made separately available. As HBM4EU prepares to embark on further European wide biomonitoring studies, we considered it important to reflect on the experiences gained through our harmonised approach. Several practical aspects are highlighted for improvement in future studies, e.g., more thorough/earlier training on the implementation of standard operating procedures for field researchers, training on the use of the data entry template, as well as improved company communications. The HBM4EU chromates study team considered that the study had successfully demonstrated the feasibility of conducting a harmonised multicentre investigation able to achieve the research aims and objectives. This was largely attributable to the engaged multidisciplinary network, committed to deliver clearly understood goals. Such networks take time and investment to develop, but are priceless in terms of their ability to deliver and facilitate knowledge sharing and collaboration.