Oral bioaccessibility trends for As, Cd, Cr, Ni, and Pb in vegetables grown in contaminated soils: A systematic review

Urban and peri-urban agriculture has the potential to address social, economic, and environmental issues by bringing communities together, producing low-cost food, and greening derelict locations. However, many urban and peri-urban brownfield sites have a legacy of soil metal and metalloid contamination, and so crops grown on these sites may pose risks to human health. This review uses orally bioaccessible fractions (BAFs) of common urban and peri-urban soil contaminants observed in vegetables across literature to produce hierarchies of relative ingestion risks according to potentially toxic element (PTE), in vitro test, and vegetable type. This will inform human health risk assessment linked to consuming vegetable crops grown on PTE-contaminated land and identify areas where further research is required. BAF values were obtained from relevant literature collected from multiple online databases, for a range of PTEs, in vitro test methods, and vegetable types. Overall, median PTE BAFs were ranked as: Cd > Ni > Cr > As > Pb. Across in vitro tests, the unified BARGE method (UBM) reported the highest median vegetable BAFs when assessing all PTEs and vegetables (median 63.0% G and 59.6% GI). Median crop BAFs were ranked as follows: non-vegetables, for example, rice/fungi > legumes > root > bulb > leaf. These results will inform the site design of urban and peri-urban agroecosystems to mitigate PTE ingestion risks.