Evaluation of Chromium in Red Blood Cells as an Indicator of Exposure to Hexavalent Chromium: an In Vitro Study.

Although workers may be exposed to chromium metal, Cr(III) compounds and Cr(VI) compounds in the workplace, only Cr(VI) compounds are of particular concern in terms of possible health hazards. After uptake via ingestion, inhalation and/or percutaneous diffusion, Cr(VI) ions are transported in the blood and penetrate red blood cells (RBC). Due to intracellular reduction of Cr(VI) to Cr(III) and concurrent intracellular protein-binding, RBC represent an easily-accessible target organ for quantitative determination of chromium following exposure to Cr(VI) compounds. Whereas chromium measurements in urine and whole blood (i.e., including plasma) are indicative of recent exposure, chromium in RBC is attributable specifically to Cr(VI) exposure and records the complete RBC lifespan – a much longer period of exposure.
Before RBC-Cr content can be used as a biological exposure indicator (BEI) for Cr(VI), its reliability must be assessed in in-vitro studies. We examine the relationship between chromium added to a blood sample and that subsequently measured in RBC. The influence of the Cr oxidation state, Cr speciation, incubation parameters, ascorbic acid concentration and blood donor were investigated. Though in-vivo studies are still needed to better understand Cr(VI) toxicokinetics, our results suggest that Cr in RBC should seriously be considered as a BEI for Cr(VI).