Comparative Analysis of Zinc Concentrations in Blood, Hair, and Nails of Leather Industry Workers and Unexposed Controls: An Analytical Cross-Sectional Study

Abstract

Background: Occupational exposure to heavy metals in the leather industry poses significant health risks, yet zinc—an essential trace element with potential toxic effects in excess—remains under-investigated compared with chromium and lead. Biomonitoring of zinc in multiple biological matrices provides an opportunity to assess both recent and cumulative exposure. Objective: To quantify zinc concentrations in blood, hair, and nails of leather industry workers and compare them with unexposed controls, thereby evaluating occupational exposure risks relative to established reference ranges. Methods: An analytical cross-sectional study was conducted among 40 male tannery workers and 40 age- and socioeconomic-matched controls. Venous blood, scalp hair, and fingernail samples were collected and analyzed using atomic absorption spectrophotometry under standardized laboratory protocols. Descriptive statistics, independent-samples t-tests, and 95% confidence intervals were used to compare groups with significance set at p < 0.05. Results: Workers exhibited significantly higher zinc concentrations in blood (191.8 ± 30.0 µg/dl vs. 86.8 ± 18.4 µg/dl, p = 0.0028), hair (338.5 ± 32.9 µg/g vs. 191.8 ± 32.9 µg/g, p = 0.0042), and nails (296.1 ± 34.2 µg/g vs. 195.3 ± 33.2 µg/g, p = 0.0014) compared with controls. All worker mean values exceeded normal reference ranges, and the highest levels were observed in the oldest, longest-serving worker, suggesting cumulative exposure. Conclusion: Leather industry workers demonstrate substantial zinc overexposure across multiple biomarkers, underscoring occupational health risks and the need for routine biomonitoring, protective measures, and further longitudinal research.