Investigation of the fate of chromium from industrial and urban sources using chromium stable isotopic tracers and advanced chromatography and mass spectrometry-based techniques: environmental and health concerns

Chromium (Cr) compounds are widely used in different industrial applications. In the environment, the most abundant are trivalent Cr (Cr(III)) compounds, which originate from geogenic sources, and also from anthropogenic activities, while hexavalent Cr (Cr(VI)) is present mostly as an industrial contaminant. The toxicity of Cr depends primarily on its chemical forms. Cr(VI) compounds are known carcinogens, while Cr(III) species are far less toxic. Oxyanion chromate (CrO4)2-) can enter cells via sulfate/phosphate transport system where it is rapidly reduced to Cr(III), while Cr(III) compounds cannot penetrate cell membranes. As Cr(VI) is specifically accumulated in red blood cells (RBC), increased concentrations of Cr in RBC indicate recent or long-term exposure to Cr(VI). Cr content in RBC is a biomarker of Cr(VI) exposure. Humans are exposed to Cr(VI) mainly at workplace. In order to minimize the health risks, it is necessary to understand the pathways of cycling, transformation, fate and toxicity of Cr at the workplace and in the human body. To protect the general population from possible emissions of Cr(VI) from chrome plants and to prevent negative impacts on human health and the environment, it is necessary to monitor the cycling and transformation of Cr species also in the outdoor environment and in the potentially exposed population. In such investigations, analytical chemistry plays a crucial role. Reliable and accurate analytical results of total Cr concentrations and the results of speciation analysis are of great importance in evaluating the impact of Cr on the environment and living organisms. In Slovenia there are numerous galvanization plants. Unior d.d., Zreče is one of the most important Slovenian and global forging industries. The company Unior takes all measures to ensure safe working conditions for its employees in the chrome galvanization. Nevertheless, recently an accidental release of CrO3 into the atmosphere happened from the Unior’s galvanic plant. Although the accident most likely had no adverse effects on human health and the environment, Unior was obliged to perform more frequent (twice per year) monitoring of emissions at the workplace and in exhaust gasses by an accredited contractor. To protect the human health and prevent environmental pollution, Unior wanted to obtain more detailed information about the impact of galvanization on employees, the inhabitants of Zreče and the environment. To answer these questions, we propose extensive research using advanced analytical methods. To trace the pathways of Cr(VI) reduction in RBC and interactions of Cr(III) with the serum proteins, whole blood of both unexposed and occupationally exposed individuals will be spiked with isotopic tracers of 50Cr(VI) and 53Cr(III), and Cr speciation analysis performed in the RBC and serum samples using new and/or optimized chemical speciation (HPLC-ICP-MS) and LA-ICP-MS methods. The reduction process of Cr(VI) in plants and in soil will also be studied by using enriched isotopic tracers of 50Cr(VI). New analytical protocols will be proposed for the determination of total concentrations of Cr and Cr(VI) in inhalable, respirable, ultra-respirable, nanosized, and dissolved air particulate matter fractions at workplace in indoor air and outdoor air at selected locations in the wider area of Zreče. The concentrations of Cr in RBC, serum, urine, and hair samples of both occupationally exposed workers and unexposed residents of Zreče will also be determined. In case of identified negative impacts on human health and the environment, measures for improvement will be proposed. The results will serve not only the workers employed in Unior and the residents of Zreče, but will be important globally, for chrome galvanizing workers around the world and Europe. World science will also benefit from new analytical procedures and protocols used to understand Cr cycling in the human organism and the environment.