Heavy metal contamination in food crops in Lebanon and health risk analysis

In Lebanon, agricultural soils and crops are exposed to multiple sources of heavy metals; however, only a limited number of studies have assessed contamination in food crops, and these have been restricted to specific regions. This study evaluated heavy metal contamination in leafy vegetables across major agricultural areas of Lebanon. A total of 48 vegetable samples, representing 16 species, were collected from 36 agricultural fields nationwide. Concentrations of zinc (Zn), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), and lead (Pb) were determined using atomic absorption spectrophotometry (ASS). More than 75% of the analyzed samples exhibited elevated concentrations of Cr (15 ± 10 mg kg^-1), Cd (0.38 ± 0.3 mg kg^-1), and Pb (0.72 ± 0.5 mg kg^-1), exceeding WHO/FAO permissible limits. Moderate Zn contamination was observed, with 37% of samples exceeding allowable limits. Copper concentrations were below guideline values in all vegetables except okra, which showed slightly elevated levels. Nickel concentrations were generally low across governorates, with a minor increase in southern Lebanon. Health risk index (HRI) values were below one for Cu, Zn, Cd, and Ni. For Cr, the average HRI was 0.592, while the maximum HRI reached 1.398 under the conservative assumption that all measured Cr was Cr(VI). Because AAS did not distinguish Cr(VI) from the less toxic Cr(III), these Cr-related estimates represent conservative upper bounds, where all measured chromium was assumed to occur as Cr(VI). Upper-bound total carcinogenic risk (TCR) values ranged from 2.72 × 10^-5 to 8.30 × 10^-4 and were dominated by Cr. Excluding Cr-related cancer risk under the Cr(III) assumption reduced TCR values to 2.55 × 10^-6-3.94 × 10^-5, with Cd becoming the predominant contributor. The findings support continued crop monitoring and targeted studies integrating paired soil, crop, and irrigation-water analyses to clarify contamination pathways and guide risk-management measures.