Lead Exceedance in Vegetables Grown on Guideline-compliant Soils: Heavy Metal Contamination and Human Health Risk in Cumilla, Bangladesh

Cumilla district combines intensive year-round vegetable production with an export processing zone, dense brick-kiln clusters and heavily trafficked national highways, yet no systematic soil-vegetable survey of toxic metals has been reported for the district. This study quantified copper (Cu), chromium (Cr) and lead (Pb) in five widely grown vegetables (potato, tomato, chili pepper, cauliflower and cabbage) and their matched surface field soils (0-15 cm) across six upazilas spanning an industrial-to-rural gradient, and tested the hypothesis that crop contamination tracks soil contamination closely enough for soil monitoring to serve as a proxy for food safety screening. Thirty matched crop-soil pairs (60 composites) were digested in HNO 3 : HClO 4 (2: 1) and analysed by flame atomic absorption spectrophotometry; the method returned recoveries of 94.7-102.3%, relative standard deviations of 1.7-2.9% and determination coefficients above 0.999. Concentrations in vegetables (dry weight) ranged from 3.92 to 15.98 mg/kg for Cu, 0.50 to 2.96 mg/kg for Cr and 7.27 to 21.90 mg/kg for Pb; matched soils ranged from 9.78 to 24.93, 20.23 to 88.00 and 10.84 to 31.59 mg/kg, respectively. Every field soil complied with FAO/WHO agricultural soil guidelines for all three metals, yet every vegetable composite exceeded the 0.3 mg/kg maximum allowable limit for Pb. Pollution load indices exceeded unity in all 30 vegetables (1.10-2.55) and remained below unity in all 30 soils (0.20-0.46), while potential ecological risk indices indicated uniformly low ecological risk. Hazard indices exceeded unity and cumulative cancer risks exceeded 10 -4 in every sample, with Pb contributing 78-90% of the non-carcinogenic hazard. A fresh-weight sensitivity analysis reduced these magnitudes roughly nine-fold but did not alter the exceedance conclusions. Soil compliance therefore coexists with crop non-compliance, and regulatory screening in Bangladesh must be based on direct analysis of the edible crop rather than on soil.