Occupational exposure to hexavalent chromium: a systematic review of environmental monitoring methods and analytical advances

Background Hexavalent chromium (Cr(VI)) is a well-established occupational carcinogen, widely utilized in industrial processes such as electroplating, surface treatment, and ferrochromium production. It is also generated as a by-product of welding activities. Accurate monitoring of occupational exposure to Cr(VI) is essential for protecting workers' health. This review aims to critically assess the main challenges associated with existing environmental monitoring techniques for Cr(VI) in welding operations and to propose practical strategies to address these limitations. Methods A systematic literature review was conducted by consulting 3 scientific databases (Scopus, Web of Science, and PubMed). Studies assessing occupational exposure to Cr(VI) published since 2014, were included and analyzed in terms of methods, dosimetric parameters measures, and possible alternative approaches for Cr(VI) characterization. Results The reviewed studies employed diverse environmental monitoring strategies for occupational Cr(VI) exposure assessment, with substantial heterogeneity in sampling conventions, analytical workflows, and speciation capability. Some studies additionally reported biological measurements and/or used exposure modeling as supportive approaches; however, these were not systematically reviewed as primary endpoints. Findings confirm that occupational exposure to Cr(VI) remains a concern in multiple industries, with exposure levels varying according to tasks, process characteristics, and preventive measures. However, major challenges persist. Key issues include the difficulty of distinguishing Cr species, the instability of Cr(VI) during sampling and analysis, and the scarcity of reliable speciation data. Furthermore, particle size distribution—especially the role of ultrafine particles—remains poorly characterized despite its toxicological importance. Innovative tools, including advanced analytical methods and modeling approaches, show promise but require further validation. Conclusions To fill research gaps and improve risk assessment, future studies should (i) accurately differentiate between chemical species of metals; (ii) adopt methods capable of measuring particle size distribution, with focus on ultrafine fractions; and (iii) systematically collect contextual data on Personal Protective Equipment use and work activities.