Lead Exposure Assessment in Sialkot Leather Workers: ICP-OES Biomonitoring Protocol Across Blood, Hair, and Nails

Abstract

Background: Lead (Pb) exposure remains a major occupational and environmental health concern in low- and middle-income countries where industrial hygiene controls are limited. Leather manufacturing involves the use of Pb-containing pigments, solders, and dyes, predisposing workers to chronic exposure. However, validated, field-ready biomonitoring protocols suitable for resource-constrained laboratories remain scarce. Objective: To develop and validate an ICP-OES–based biomonitoring protocol for Pb determination across blood, hair, and nail matrices and to assess Pb exposure levels in Sialkot leather workers compared with unexposed controls. Methods: A cross-sectional study was conducted among 120 leather industry workers and 60 matched controls. Biological samples were digested with matrix-optimized acid ratios and analyzed at 340.458 nm using ICP-OES. Method validation included calibration linearity, recovery, precision, limit of detection (LOD), and limit of quantitation (LOQ). Statistical analysis compared Pb levels across groups and assessed matrix concordance. Results: The method demonstrated excellent linearity (R² ≥ 0.999) and recovery (95–104%) across matrices. Mean Pb concentrations were significantly higher in workers than controls in blood (0.312 vs 0.141 mg/L), hair (2.47 vs 1.33 mg/kg), and nails (1.91 vs 0.96 mg/kg; all p < 0.001). Strong cross-matrix correlations (ρ = 0.57–0.68) indicated consistent exposure patterns. Conclusion: The validated ICP-OES protocol provides a reproducible, low-cost approach for multi-matrix Pb biomonitoring and demonstrates clinically relevant Pb accumulation among leather workers in Sialkot.