Total and bioaccessible heavy metals in cabbage from major producing cities in Southwest China: health risk assessment and cytotoxicity

Abstract

Green leafy vegetables are economical and nutritious, but they may be contaminated with heavy metals. In this study, we assessed the total and bioaccessible concentrations of As, Cd, Pb and Cr in a popular vegetable cabbage (Brassica oleracea) from four major producing cities in Yunnan, Southwest China. With the mean concentrations of As, Cd, Pb and Cr being 0.24, 0.20, 0.32 and 1.28 mg kg⁻¹, the As, Cd and Pb concentrations were within the limits of 0.2–0.5 mg kg⁻¹ based on Chinese National Standards and the WHO/FAO, but Cr concentration was 2.6-times greater than the limit of 0.5 mg kg⁻¹. Based on an in vitro bioaccessibility assay of the Solubility Bioaccessibility Research Consortium (SBRC), As bioaccessibility was the lowest at 11% while those of Cd, Pb and Cr were much greater at 68–87%. The estimated daily intake (EDI) of metals through cabbage ingestion was similar for children and adults. Among the four metals, only Cr's EDI at 2.29–1.87 exceeded 1 based on total and bioaccessible concentrations. The high Cr concentration at 1.28 mg kg⁻¹ coupled with its high bioaccessibility at 67.5% makes Cr of concern in cabbage. However, human gastrointestinal cells exposed to the gastric digesta with high bioaccessible heavy metals and risky EDI, showed no obvious cytotoxicity, indicating that existing models based on total or bioaccessible heavy metals may overestimate their human health risk. Taken together, to accurately assess the human health risk of heavy metals in cabbage, both total/bioaccessible concentrations and the gastrointestinal cell responses should be considered.