Chromium in Biological Samples in Association with Cancer Risk by Site: A Systematic Literature Review

Purpose of Review Chromium (Cr) is widely used in industrial activities and ubiquitous in the environment. Hexavalent Cr is classified as a human carcinogen (Group 1) by the International Agency for Research on Cancer (IARC), based on evidence mostly from occupational studies. We systematically reviewed the existing evidence on the association between Cr measured in biological samples and cancer risk and mortality (overall or site-specific). Recent Findings We included articles published in PubMed and EMBASE from database inception until 3rd February, 2025, that quantified Cr concentrations in biological samples (blood, urine, finger-/toenails) and examined its relationship with cancer risk or mortality. A total of 32 (published between 1993 and 2024) articles met the eligibility criteria and were included in the review: most (n = 25) had a retrospective case-control design, four were nested case-control studies, and three were cohort studies. The highest number of articles were for cancer of the breast (n = 8), lung (n = 5), head and neck (n = 4), urinary tract (n = 4), and thyroid (n = 4). The association between Cr levels and cancer risk varied according to cancer site and biological matrix, with no clear patterns emerging for any cancer site. Cumulative cancer risk was assessed in a single prospective study, which detected an inverse association with blood Cr levels. No study exists examining Cr in relation to cancer mortality. Summary The current evidence on the association between Cr in biological samples and cancer risk is still limited and reveals no clear pattern for any cancer type. This picture contrasts with that provided by studies conducted in occupational settings, highlighting the need for further research to clarify the true impact of Cr exposure on cancer burden.