Bioaccumulation and bioaccessibility of Pb in popular wild mushrooms from regional high geochemical background areas: an over-estimated risk assessed by total Pb

Wild mushrooms are important in human diet, which are also metal(loid)s accumulators. Yunnan is the major producer with geochemically high levels of metal(loid)s like lead (Pb). However, whether and how much Pb can be accumulated and enter human gastrointestinal tracts to induce risk are still elusive. Therefore, the transfer, bioaccessibility and health risk of Pb in soil-mushroom-human continuum were examined. Soil pH and organic matter (OM) content were 4.59–5.71 and 16.5–64.3 g kg –1 , indicating wild mushrooms grow on acidic and humic soils. Soil total and available Pb were 24.9–65.9 and 1.75–6.11 mg kg –1 , with 3.23% of total Pb failed national standard. Though soil Pb content and availability (3.92–11.2%) were relatively low, its accumulation in mushrooms reached 0.29–15.1 mg kg –1 , with 59.1% being standard exceeded and 14.5% being heavily polluted (P i >3). Termitornyces albuminosus showed the highest Pb content, which was 4.36–6.20 folds of the lowest Boletus granulatus . Pb accumulation in mushrooms was due to soil acidification-induced Pb mobilization, which was supported by negatively correlated pH and available Pb (R=-0.36; P <0.05). Although T . albuminosus was efficient in accumulating Pb, its gastric (GP) and gastrointestinal phase (GI) bioaccessibility was lower (55.6% and 116% vs. 74.9–95.3% and 110–167%). So bioaccessibility should be incorporated to avoid risk over-estimation. Though 59.1% of mushrooms failed food safety standard, margin of exposure (MOE) and carcinogenic risk (CR) suggested negligible to low concern risk and no carcinogenic risk. Still, bioaccessibility >100% is counterintuitive. This highlighted the necessity to develop bioaccessibility standard reference materials to achieve more reliable risk predications.