Chromium exposure and occupational health risks among industrial and artisanal tannery workers: a systematic review

Occupational exposure in industrial and artisanal tanneries has been reported in several studies. Tannery workers are exposed to chemical, biological, ergonomic and work-related hazards that may lead to adverse health disorders. The aim of this study was to evaluate systematically the available data on Chromium (Cr) exposure among workers in industrial and artisanal tanneries, as well as the associated clinical manifestations and risk factors in in both settings. A systematic literature search was conducted across major databases, including PubMed, Scopus, Web of Science and Google Scholar, covering studies published between 2010 and 2025. Eligible studies included human observational investigations among workers reporting biomonitoring data on Cr exposure (total Cr, Cr(III)—trivalent, and/or Cr(VI)—hexavalent and evaluating at least one health effect. Studies from all geographical regions were considered. Of 1040 records, 34 studies from eight countries (n = 6565; predominantly male) met the inclusion criteria. Elevated Cr concentrations were detected in the blood of TWs (3.84 ± 0.21–269.7 ± 211.1 µg/L), with substantially higher levels observed in toenails (124.0–298.8 µg/g). Urinary Cr concentrations (8.39–19.1 µg/L) were also elevated but remained below the ACGIH BEI (25 µg/L). Dermatological and respiratory disorders were the most frequently reported occupational health outcomes in industrial tanneries, with comparable effects reported in artisanal settings despite limited Cr exposure. While occupational exposure to Cr(VI) has been consistently associated with oxidative stress (increased MDA levels and decreased GSH and SOD activities) and cytogenetic damage (Increased micronuclei frequency, chromosomal aberrations, and DNA strand breaks), the findings regarding hematological and biochemical changes remained inconsistent across both settings. However, co-exposure to multiple chemical and biological hazards further complicates the specific attribution of observed health effects to Cr(VI). The findings highlight a strong association between occupational Cr exposure and adverse health effects affecting multiple biological systems. Despite existing urinary Cr biomonitoring guidelines, an officially recognized occupational biological limit value for blood Cr in TWs remains lacking. These results underscore the need for improved occupational safety measures, stricter regulatory policies and region-specific biomonitoring studies to establish appropriate reference values, particularly for blood Cr, and improve the interpretation of exposure data.