Accumulation of heavy metals in edible tissues of radish and lettuce: implications for food safety and human health

Heavy metals are persistent contaminants that can accumulate in agricultural soils and enter the human food chain through edible crops. This research aimed to evaluate the accumulation of copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), and nickel (Ni) in the edible tissues of radish (Raphanus sativus L.) and lettuce (Lactuca sativa L.) cultivated in agricultural soils from the Sakarya River region, Turkiye. Two contrasting agricultural soils were examined: Soil 1 was collected from a rural area away from factories, industrial facilities, and major roads, whereas Soil 2 was collected from an area near medium-scale industrial facilities and a major highway. Health risks were evaluated for infants, toddlers, children, teenagers, and adults. Vegetables grown in Soil 2 exhibited substantially higher metal concentrations than those grown in Soil 1. In Soil 2, the mean Cd and Ni concentrations were 235 and 172 mg/kg in radish roots, respectively, compared with 85 and 90 mg/kg in lettuce leaves. Estimated daily intake values indicated that radish consumption contributed greater metal exposure risks than lettuce. Infants and toddlers were the most vulnerable groups. Human health risk assessment indicated that plant ingestion is the main exposure pathway. Lifetime carcinogenic risk values ranged from 1.50 × 10−4 to 1.89 × 10−2, beyond the acceptable limit. The hazard index ranged from 0.204 to 38.0, exceeding the safety threshold mainly for vegetables grown in Soil 2. These findings highlight the necessity of soil monitoring, pollution regulation, and safe crop selection to reduce human health risks. Studies previously in Sakarya province have primarily concentrated on the heavy metal pollution in river water, sediments, fish, roadside soils, agricultural soils, and aquatic plants. However, heavy metal contamination in the edible parts of radish and lettuce cultivated in Sakarya agricultural soil, along with associated human health risk assessment, remains inadequately documented, even though these vegetables are commonly used in salads. Therefore, this study provides novel site-specific information on heavy metal soil pollution, edible tissue uptake, and carcinogenic and non-carcinogenic risk assessment across five age groups, thereby contributing to current knowledge of food safety and metal exposure in contaminated agricultural soils.