Blood, Hair, and Nail as Biomarkers of Arsenic Exposure among Leather Industry Workers in Sialkot

Abstract

Background: Arsenic exposure is a major occupational health concern, particularly in industries such as leather tanning where workers are routinely exposed to chemical contaminants. Although blood arsenic reflects recent exposure, hair and nails may provide more reliable indicators of long-term accumulation, yet comparative biomarker studies in Pakistan remain scarce. Objective: This study aimed to quantify arsenic concentrations in blood, hair, and nails of leather industry workers in Sialkot and evaluate their diagnostic accuracy for chronic occupational exposure. Methods: A cross-sectional observational study was conducted between January and October 2023, enrolling 40 leather industry workers and 40 age- and sex-matched non-exposed controls. Biological samples were collected using standardized procedures, and arsenic concentrations were measured with graphite furnace atomic absorption spectrophotometry. Group comparisons, correlations, regression analyses, and receiver operating characteristic (ROC) curves were performed using SPSS version 25, with p < 0.05 considered significant. Results: Workers exhibited markedly higher arsenic concentrations across all biomarkers compared with controls (blood: 35.6 ± 10.4 vs. 12.2 ± 5.1 µg/L; hair: 7.9 ± 2.6 vs. 2.1 ± 1.0 µg/g; nails: 8.5 ± 3.2 vs. 2.5 ± 1.2 µg/g; all p < 0.001). Hair and nail arsenic correlated strongly (r = 0.71, p < 0.001), and ROC analysis identified nails as the most accurate biomarker (AUC = 0.92). Longer employment duration was significantly associated with higher arsenic levels. Conclusion: Hair and nail arsenic provide robust, non-invasive biomarkers for long-term occupational exposure and are superior to blood in detecting cumulative arsenic burden among leather workers. Incorporation of keratinized tissue biomarkers into surveillance programs could enhance occupational health monitoring in high-risk industries.