Browsing by Author "Dang, Fei"
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- Are Chinese consumers at risk due to exposure to metals in crayfish? A bioaccessibility-adjusted probabilistic risk assessmentPublication . Peng, Qian; Nunes, Luís; Greenfield, Ben K.; Dang, Fei; Zhong, HuanFreshwater crayfish, the world's third largest crustacean species, has been reported to accumulate high levels of metals, while the current knowledge of potential risk associated with crayfish consumption lags behind that of finfish. We provide the first estimate of human health risk associated with crayfish (Procambarus clarkii) consumption in China, the world's largest producer and consumer of crayfish. We performed Monte Carlo Simulation on a standard risk model parameterized with local data on metal concentrations, bioaccessibility (phi), crayfish consumption rate, and consumer body mass. Bioaccessibility of metals in crayfish was found to be variable (68-95%) and metal-specific, suggesting a potential influence of metal bioaccessibility on effective metal intake. However, sensitivity analysis suggested risk of metals via crayfish consumption was predominantly explained by consumption rate (explaining >92% of total risk estimate variability), rather than metals concentration, bioaccessibility, or body mass. Mean metal concentrations (As, Cd, Cu, Ni, Pb, Se and Zn) in surveyed crayfish samples from 12 provinces in China conformed to national safety standards. However, risk calculation of phi-modified hazard quotient (HQ) and hazard index (HI) suggested that crayfish metals may pose a health risk for very high rate consumers, with a HI of over 24 for the highest rate consumers. Additionally, the phi-modified increased lifetime risk (ILTR) for carcinogenic effects due to the presence of As was above the acceptable level (10(-5)) for both the median (ILTR = 2.5 x 10(-5)) and 90th percentile (ILTR = 1.8 x 10(-4)), highlighting the relatively high risk of As in crayfish. Our results suggest a need to consider crayfish when assessing human dietary exposure to metals and associated health risks, especially for high crayfish-consuming populations, such as in China, USA and Sweden.
- High retention of silver sulfide nanoparticles in natural soilsPublication . Li, Min; Greenfield, Ben K.; Nunes, Luís; Dang, Fei; Liu, Hai-long; Zhou, Dong-mei; Yin, BinSilver, either in ionic or nanoparticulate form, is widely used in consumer products. However, silver sulfide (Ag2S) are more likely to be the form that Ag enters the environment. The retention of silver sulfide nanoparticles (Ag2S-NPs) in natural soils is critical for bioavailability and toxicity but remains unclear. Here, we examined the retention of Ag2S-NPs in 11 natural soils with varying properties using batch assays. More than 99% of Ag2S-NPs were retained in soil solids, irrespective of soil properties. Such high retention of Ag2S-NPs, at least partially, explained the distinct differences in phytoavailability performed in soil vs. liquid media in the literature. Nanoparticles containing Ag and S were identified in representative soil solids by high resolution transmission electron microscopy equipped with an energy dispersive X-ray spectrometer. Iron-rich acidic soil had a high dissolution of Ag2S-NPs ranging from 47.1% to 61.7% in porewater. In contrast to Ag2S-NPs, silver nanoparticles (AgNPs) and Ag+ in these soils were less retained (as described by Freundlich model) and the retention was closely associated with soil properties. These findings highlight the unique behaviors of Ag2S-NPs in natural soils.