Estimating carcinogenic and non-carcinogenic health risk indices of lead in vegetables fertilized with sewage sludge

<h2>Abstract</h2><h3>Introduction</h3> Sewage sludge is widely applied to enhance soil fertility in arid regions, providing essential nutrients to organic matter-deficient soils. However, its high lead (Pb) content poses health risks, particularly in edible crops, necessitating a balanced assessment of its benefits and potential toxicity. <h3>Methods</h3> This study evaluated five sewage sludge levels (0–6 %) on Pb bioaccumulation, plant growth, and health risk indices in six vegetable species—scallion (<i>Allium fistulosum</i>), radish (<i>Raphanus sativus</i>), cress (<i>Lepidium sativum</i>), basil (<i>Ocimum basilicum</i>), purslane (<i>Portulaca oleracea</i>), and savory (<i>Satureja hortensis</i>)— grown under greenhouse conditions in calcareous soil. Pb concentrations in soil and plant tissues were measured, and health risk indicators, including Hazard Quotient (HQ) and Cancer Risk (CR), were calculated for children and adults. Transfer Factor (TF) and Bioaccumulation Factor (BAF) were assessed to examine Pb dynamics. <h3>Results</h3> Moderate sludge levels improved growth, with aerial and root dry weights increasing by 59.7 % and 46.9 %, respectively. However, soil Pb concentrations increased by 7.9 % and root Pb by up to 88.5 % at higher sludge levels. Health indicators exceeded safety thresholds, with children's HQ peaking at 6.839—significantly higher than adults, suggesting heightened susceptibility. Among species, radish exhibited the highest TF of 1.14, indicating substantial Pb translocation to shoots, while cress had the highest BAF at 1.33, demonstrating greater Pb accumulation. <h3>Conclusion</h3> The findings emphasized the need for selective crop management and careful sludge application in agriculture, especially for high Pb-accumulating crops. Adding amendments like biochar could reduce metal mobility, supporting safer and more sustainable soil fertility practices in nutrient-poor, arid soils.