Bioaccessibility Of Heavy Metals Research Articles

Human health risk assessment and toxic effect of heavy metal(loid)s in Bamboo shoot products

Bamboo shoots and their products are an important part of the human diet. However, the accumulation and accurate human health risk of heavy metal(loid)s in bamboo shoots are largely unknown. In this study, we determined the total and bioaccessible concentrations of As, Cd, Pb, and Cr in natural and processed bamboo shoot products from markets in southwest China. The health risk assessment and enterotoxicity after consumption of heavy metal(loid)s contaminated samples were further studied using a human colonic epithelial cell (Caco-2 cell) model. The results showed that the average concentrations of As, Pb, Cd, and Cr in the collected samples were 0.036, 0.056, 0.008, and 0.049 mg/kg, while Pb contents in 21 collected fresh bamboo shoot samples exceeded the allowable limit value of 0.1 mg/kg by 1.00–4.60 folds. Besides, As in 2% fresh bamboo shoots exceeded the limit value of 0.50 mg/kg. The average bioaccessibility of heavy metal(loid)s in fresh bamboo shoots was as follows: Cr (47.20%) > Pb (39.56%) > Cd (15.64%)> As (13.29%). Estimated daily intake (EDI) of heavy metal(loid)s after intake of fresh bamboo shoots was higher in children than that in adults, the THQ of As is > 1 based on the total heavy metal(loid)s, indicating a potential non-carcinogenic risk for children. However, health risks assessment based on bioaccessibility were significantly decreased. Furthermore, intestinal digesta of high-risk samples did not trigger detrimental effects on Caco-2 cells, suggesting existing health risk assessment model may overestimate their health risks and should be adjusted by bioaccessibility and cellular toxicity validation to accurately reflect their health risk. Our data may provide a novel and scientific insight into the health risk assessment of bamboo shoots as well as their products and propose a more scientific approach to accurate health risk assessment for heavy metals polluted foods.

Health risk assessment of heavy metal(loid)s in road dust via dermal exposure pathway from a low latitude plateau provincial capital city: The importance of toxicological verification

The human health risk assessment through the dermal exposure of metal (loid)s in dust from low latitude and high geological background plateau cities was largely unknown. In this study, the road dust samples were harvested from a typical low-latitude plateau provincial capital city Kunming, Southwest China. The total concentration and dermal bioaccessibility of heavy metal (loid)s in road dust were determined, and their health risks as well as cytotoxicity on human skin keratinocytes were also assessed. The average concentrations of As (28.5 mg/kg), Cd (2.65 mg/kg), Mn (671 mg/kg), and Zn (511 mg/kg) exceeded the soil background values. Arsenic had the highest bioaccessibility after 2 h (3.79%), 8 h (4.24%), and 24 h (16.6%) extraction. The dermal pathway when bioaccessibility is considered has a higher hazard quotient than the conventional method using total metal(loid)s in the dust. In addition, toxicological verification suggested that the dust extracts suppressed the cell viability, increased the reactive oxygen species (ROS) level and DNA damage, and eventually activated the mitochondria-mediated apoptosis pathway, evidenced by the upregulation of Caspase-3/9, Bax, and Bak-1. Cadmium was positively correlated with the mRNA expression of Bax. Taken together, our data indicated that both dermal bioaccessibility and cytotoxicity should be considered for accurate human skin health risk assessment of heavy metal(loid)s in road dust, which may provide new insight for accurate human health risk assessment and environmental management.

Remediation of Cd(II), Zn(II) and Pb(II) in contaminated soil by KMnO4 modified biochar: Stabilization efficiency and effects of freeze–thaw ageing

Biochar has been widely used in soil remediation because of its porosity and impressive efficiency. Many studies have demonstrated the good affinity of biochar for heavy metals (HMs), but efficient modification methods to increase the stability of multiple HMs are lacking. Moreover, few studies focus on biochar’s potential ability to ageing resistance and changes in its physicochemical properties during freeze–thaw (F/T) cycles. Here, KMnO4-modification biochar (MBC) was prepared and the immobilization and anti-freeze performance of MBC on Cd, Zn and Pb in soil were investigated. The addition of 10 % MBC decreased concentrations of toxicity characteristic leaching procedure (TCLP) by 66.80 %, 25.39 % and 99.68 % for Cd, Zn and Pb, respectively, after 28 days, accompanied by a significant decrease in the phytoavailability and bioaccessibility of HMs in soil. Soil fertility was also improved by MBC application. Furthermore, frequent F/T cycles obviously induced the fragmentation of soil particles and enhanced the activity of HMs. Conversely, MBC particles became finer, accompanied by further oxidation and higher alkalinity but degraded pore structures during F/T cycles. The oxidation of lignocellulose and changes in C-O stretching were greatest among all functional groups in biochar. Therefore, MBC could suppress the migration of HMs through precipitation, cohesion of soil particles, and stronger complexation by oxygen-containing functional groups. Moreover, fractions of HMs were also transferred from exchangeable to potentially labile or nonlabile species. Overall, MBC displayed advantages in the stabilization of HMs and showed higher resistance to F/T cycles and promise for long-term remediation of HM-contaminated soils in cold regions.

Bioaccessibility assessment of arsenic and cadmium in polished and unpolished rice: Comparison of three in vitro methods

INFOGEST is a standardized in vitro digestion method suitable for foods, but rarely used to study the bioaccessibility of heavy metals in food. This study aimed to explore the differences between INFOGEST and the extensively used Physiologically Based Extraction Test (PBET) and Unified Bioaccessibility Research Group of Europe Method (UBM) methods for determining the bioaccessibility of As and Cd in rice. Intestinal As (79.3 ± 8.5 %, 75.8 ± 12.7 %, and 72.3 ± 12.2 % for INFOGEST, PBET, and UBM, respectively) and Cd (47.0 ± 6.4 %, 40.7 ± 13.8 %, and 38.1 ± 15.7 % for INFOGEST, PBET, and UBM, respectively) bioaccessibilities in the rice samples determined by the three methods were generally similar (p > 0.1, except for As bioaccessibility between INFOGEST and UBM). Furthermore, PBET was significantly correlated with INFOGEST for As bioaccessibility (R2 = 0.416) and with UBM for Cd bioaccessibility (R2 = 0.879). Additionally, PBET indicated that the bioaccessibilities of As and Cd in the polished rice were 17.0 % and 19.8 % higher, respectively, than that in the unpolished rice. This study highlights the influence of in vitro methods and rice matrices on heavy metal bioaccessibility values, necessitating a more accurate assessment of health risks associated with rice consumption.

Road dust exposure and human corneal damage in a plateau high geological background provincial capital city: Spatial distribution, sources, bioaccessibility, and cytotoxicity of dust heavy metals

Ocular surface diseases are common in the plateau city, Kunming China, the continued daily exposure to heavy metals in dust may be an important inducement. In this study, the 150 road dust samples from five functional areas in Kunming were collected. The concentrations, distribution, possible sources, and bioaccessibility of heavy metals were analyzed. The adverse effects of dust extracts on human corneal epithelial cells and the underlying mechanisms were also assessed. The concentrations (mg·kg−1) of As (19.1), Cd (2.67), Cr (90.5), Cu (123), Pb (78.4), and Zn (389) in road dust were higher than the soil background, with commercial and residential areas showing the highest pollution. Their bioaccessibility in artificial tears was As (6.59 %) > Cu (5.11 %) > Ni (1.47 %) > Cr (1.17 %) > Mn (0.84 %) > Cd (0.76 %) > Zn (0.50 %) > Pb (0.31 %). The two main sources of heavy metals included tire and mechanical abrasion (24.5 %) and traffic exhaust (21.6 %). All dust extracts induced cytotoxicity, evidenced by stronger inhibition of cell viability, higher production of ROS, and altered mRNA expression of antioxidant enzymes and cell cycle-related genes, with commercial- areas-2 (CA2)-dust extract showing the greatest oxidative damage and cell cycle arrest. Our data may provide new evidence that dust exposure in high geological background cities could trigger human cornea damage.

Total contents, fractionation and bioaccessibility of nine heavy metals in household dust from 14 cities in China

The potential health risk caused by long-term exposure to heavy metals in household dust is not only depended on their total content, but also bioaccessibility. In this study, twenty-one dust samples were collected from residential buildings, schools, and laboratories in 14 provincial-capital/industrial cities of China, aiming to evaluate the total contents, fractionation, bioaccessibility and health risks of nine heavy metals (As, Cd, Cr, Ni, Pb, Mn, Zn, Fe, and Cu). Results showed that the highest levels of Cd, Cr, Ni and Zn were found in laboratory dust, As, Pb and Mn in school dust, and Fe and Cu in residential dust, indicating different source profiles of the heavy metals. The mean bioaccessibility of the heavy metals across all samples as evaluated using SBRC (Solubility Bioavailability Research Consortium), IVG (In Vitro Gastrointestinal), and PBET (Physiologically Based Extraction Test) assays was 58.4%, 32.4% and 17.2% in gastric phase (GP), and 24.9%, 21.9% and 9.39% in intestinal phase (IP), respectively. Cadmium had the highest content in the fractions of E1+C2 (43.7%), as determined by sequential extraction, and Pb, Mn, and Zn had a higher content in E1+C2+F3 (64.2%, 67.2%, 78.8%), resulting in a higher bioaccessibility of these heavy metals than others. Moreover, the bioaccessibility of most heavy metals was inversely related to dust pH (R = −0.18 in GP; −0.18 in IP; P < 0.01) and particle size, while a positive correlation was observed with total organic carbon (R = 0.40 in GP; 0.38 in IP; P < 0.01). The exposure risk calculated by the highest bioaccessibility was generally lower than that calculated by the total content. However, Pb in one school dust sample had an unacceptable carcinogenic risk (adult risk = 1.19 × 10−4; child risk = 1.08 × 10−4). This study suggests that bioaccessibility of heavy metals in household dust is likely related to geochemical fractions and physical/chemical properties. Further research is needed to explore the sources of bioaccessible heavy metals in household dust.

Changes in oral bioaccessibility of heavy metals in non-digestive sucking habits due to the formation of complexes between digestive fluid components and metals/metalloids

Humans, especially infants, are exposed to harmful substances through various means, including non-nutritive sucking behaviors. Here, we compared the “one-compartment model” and the “three-compartment model” within the “suck model” to assess the oral bioaccessibility of heavy metals in various products and evaluated whether these models can be employed to assess 12 heavy metals present in consumer products. Several certified reference materials, including plastic, paint, glass, and metals, were employed to ensure sample homogeneity. By comparing the two models, we validated that a considerable amount of complexes were formed between saliva components and the extracted heavy metals and that some of these complexes dissociated during reactions with the gastric/intestinal fluids. Furthermore, we observed that in the cases of Cu and Pb, additional complexes were formed as a result of reactions with gastric/intestinal fluids. We measured the total concentrations of the extracted heavy metals using artificial saliva through acid digestion and found that up to 99.7% of the heavy metals participated in the formation of complexes, depending on the characteristics of the sample (e.g., composition) and the target element. This result indicates that the current suck model may notably underestimate the oral bioaccessibility of heavy metals in products associated with sucking behaviors. Therefore, we propose a more conservative and simpler test method for assessing oral bioaccessibility of heavy metals that involves measuring the total concentrations of heavy metals extracted from consumer products using artificial saliva. By doing so, we can account for potential variations in the digestive milieu (e.g., due to ingested food) and the inconsistency in complex formation-dissociation characteristics.

Assessment of heavy metal contamination in street dust: concentrations, bioaccessibility, and human health risks in coal mine and thermal power plant complex.

Coal mining has also been associated with adverse environmental and health impacts including cancer and respiratory disorders, with the presence of thermal power plants exacerbating the problem of heavy metal pollution. Minimal studies have been conducted on the environmental impacts, health risks, and bioaccessibility of heavy metals in coal mine areas. Consequently, samples of street dust were collected from different locations in the Singrauli mine complex and analysed. Heavy metals (Cu, Ni, Zn, Cr, Co, As, and Mo) were found to be higher than the background concentration, with the maximum concentration was found in areas close to the Thermal Power Plants, like Near Vindyachal TPP, Near Shakti Nagar TPP, and Anpara. The highest geo-accumulation index value was found for Co, Mo, Zn, and As, indicating moderate to strong pollution levels. Health risk assessment (for both adults and children) revealed that Cr and Fe posed significantly higher Hazard Quotient and Hazard Index (HI) values, indicating significant non-carcinogenic threats. Moreover, Carcinogenic Risk (CR) values for Cd, Cr, and Ni indicated a risk of carcinogenicity to the public exposed to road dust. The study also examined the bioaccessibility of the metals, which showed that the gastric phase accumulated a higher percentage of Ni (42.52%), Pb (34.79%), Co (22.22%), As (20%) and Cu (15%) than the intestinal phase. Strong positive correlation was observed between metal concentration (Cu, Pb, Cr, Fe, Zn, and Mn), HI, and CR of adult and child, while bioaccessibility of intestinal phase was positively correlated with gastric phase of metals (Cu, Ni, Co, As, and Mn).

Assessment of bio-accessibility of heavy metals (Cd, Pb, and As) through consumption of medicinal plants collected from different regions in Nyamira- Kenya

Background: In this study, the total and bio-accessible levels of cadmium (Cd), lead (Pb), and arsenic (As) in 19 Kenyan medicinal plants from two regions (Manga and Borabu) are presented. Methods: Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the total and bio-accessed heavy metals in plants. The NIST 1647 plant reference material was used to study the performance of the method. The method offered excellent quality parameters in terms of detection and quantification limits of 0.08 and 0.24 µg/kg, 0.5 and 1.5 µg/kg, and 3.1 and 9.5 µg /kg, linearity (r2 &gt; 0.997) and recoveries of 95%, 99% and 93% for Cd, Pb, and As, respectively. Results: The dry weights of the plants from Manga and Borabu showed low concentrations of Cd (270 ± 20 and 260 ± 20), As (320 ± 20 and 480 ± 40), and Pb (1230 ± 110 and 1160 ± 100) µg/kg. Significantly higher mean concentrations of Cd, Pb, and As (0.45 ± 0.11, 0.46 ± 0.12 and 0.37 ± 0.10 µg/kg) than (0.32 ± 0.07, 0.34 ± 0.11 and 0.26 ± 0.08 µg/kg) were bioaccessible enzymatically than aquatically from dry weight (p&lt;0.05). The percentage bioaccessibility of the elements from the plants ranged from 0.08 to 10.66% and 0.02 to 2.56% for the enzymatic and aquatic procedures, respectively. Conclusion: The low bioaccessible concentrations of heavy (toxic) elements in plants justify their therapeutic use.

Water-Soluble Ions and Heavy Metal Levels, Source Apportionment, and Health Risk of Indoor Dust in the Mogao Grottoes of Dunhuang, China

The direct ingestion of indoor dust particles at historical heritage sites is a primary exposure pathway for employees to heavy metals. Water-soluble ions (WSIs) and heavy metal levels, sources, bioaccessibility, and health risks associated with indoor dust in the Mogao Grottoes were analyzed using comprehensive methods to determine the differences in the concentrations and distribution characteristics of WSIs and heavy metals between statue dust and floor dust. The concentrations of WSIs and heavy metals and the magnetic values of χ lf and SIRM in indoor dust were higher than those in street dust and topsoil. The mean χ lf and SIRM of statue dust particles were 100.3 × 10 − 8 m 3 k g − 1 and 1686.9 × 1 0 − 5 Am 2 k g − 1 . Specifically, the concentration of Pb was 277 mg k g − 1 , 15-fold higher than the background value, indicating the continual receipt of heavy metals with high magnetic minerals during dust deposition. WSIs mainly originate from the weathering of surrounding rocks and earthen plaster; Pb originates from the shedding of paint of murals and sculptures; and Zn, Cu, and magnetic minerals originate from traffic sources. The bioaccessibility of heavy metals is high in the gastrointestinal phases of indoor dust. Overall, the health risks posed by heavy metals in indoor dust were low, with moderate to high risks in individual caves. Ingestion presents the highest noncarcinogenic and carcinogenic risk to employees. These results provide essential knowledge on indoor dust characteristics in the Mogao Grottoes, facilitating strategies for dust pollution mitigation and employee health risk control.

Bioaccessibility and reliable human health risk assessment of heavy metals in typical abandoned industrial sites of southeastern China

Heavy metal pollution caused by a large number of abandoned industrial sites cannot be underestimated, but its human health risks have not been accurately assessed. This study investigated the pollution of heavy metals in soils of the typical abandoned industrial sites in southeastern China. Based on the bioaccessibility of different heavy metals (Pb, Ni, Cu, Zn, Cd, Cr) in the industrial soils, the human health risks were accurately evaluated, and the controlling factors were quantitatively assessed. The results showed that the heavy metals in each typical abandoned industrial sites had a high degree of spatial heterogeneity. Among them, Cd was the most susceptible to relevant discrete input from external factors such as human activities, followed by Zn, Pb, Cr, Ni and Cu. The bioaccessible concentration of heavy metals by the physiological-based extraction test (PBET) had a good correlation (R2 = 0.58 ∼ 0.86) with its bioavailable concentration by diethylenetriaminepentaacetic acid (DTPA) extraction. The regression model based on soil parameters had great potential to predict the bioaccessibility of heavy metals in abandoned industrial sites (R2 = 0.49 ∼ 0.95). The total concentration of heavy metals, Fe, soil texture and pH were the controlling factors of the metal bioaccessibility. Compared with the total concentration, the hazard index (HI) and carcinogenic risk (CR) values calculated based on gastrointestinal bioaccessibility were decreased by 39.0∼77.9% and 68.2∼79.9% in adults, and 45.3∼88.0% and 73.9∼83.5% in children, respectively. This work provides a feasible theoretical basis for reliable assessment of the human health risks of heavy metals in the abandoned industrial sites in the future.

Fermentation affects heavy metal bioaccessibility in Chinese mantou.

Effect of different fermentation methods on heavy metal bioaccessibilities in wheat flour is undetermined. In this work, gastric and gastrointestinal heavy metal bioaccessibility in wheat flour products (control-wheat dough, T1-mantou made with normally fermented dough, T2-mantou made with over-fermented dough and T3-mantou made with over-fermented dough + Na2CO3) made from two wheat flour samples (NX and QD) was assessed via a modified physiologically-based extraction test. Cadmium, Zn and Mn bioaccessibility in the gastric phase (GP) was greater than in the gastrointestinal phase (GIP), yet the opposite was observed for Cu (p < 0.05). Lead bioaccessibility in the GIP of the QD sample was 1.37-4.08 times greater than that in the GP, while only the control had greater bioaccessibility in the GIP than that in the GP (p < 0.05) for the NX sample. Treatments T2 and T3 had greater Cd, Cu, Zn and Mn bioaccessibilities than the control and T1 in the GP (p < 0.05). In the GIP, however, only T3 had greater Mn bioaccessibility than the control for the NX sample. Enhanced degradation of the heavy metal-phytate following over-fermentation may have led to greater heavy metal bioaccessibility. Results should help food processors reduce human absorption of excessive heavy metals present in wheat flour foods.

Inhalation Bioaccessibility and Risk Assessment of Metals in PM2.5 Based on a Multiple-Path Particle Dosimetry Model in the Smelting District of Northeast China.

PM2.5 can deposit and partially dissolve in the pulmonary region. In order to be consistent with the reality of the pulmonary region and avoid overestimating the inhalation human health risk, the bioaccessibility of PM2.5 heavy metals and the deposition fraction (DF) urgently needs to be considered. This paper simulates the bioaccessibility of PM2.5 heavy metals in acidic intracellular and neutral extracellular deposition environments by simulating lung fluid. The multipath particle dosimetry model was used to simulate DF of PM2.5. According to the exposure assessment method of the U.S. Environmental Protection Agency, the inhalation exposure dose threshold was calculated, and the human health risk with different inhalation exposure doses was compared. The bioaccessibility of heavy metals is 12.1–36.2%. The total DF of PM2.5 in adults was higher than that in children, and children were higher than adults in the pulmonary region, and gradually decreased with age. The inhalation exposure dose threshold is 0.04–14.2 mg·kg−1·day−1 for the non-carcinogenic exposure dose and 0.007–0.043 mg·kg−1·day−1 for the carcinogenic exposure dose. Cd and Pb in PM2.5 in the study area have a non-carcinogenic risk to human health (hazard index < 1), and Cd has no or a potential carcinogenic risk to human health. A revised inhalation health risk assessment may avoid overestimation.

A comparative and modeled approach for three biochar materials in simultaneously preventing the migration and reducing the bioaccessibility of heavy metals in soil: Revealing immobilization mechanisms

The effectiveness and feasibility of the three biochar materials for remediation of arsenic (As) and lead (Pb) contaminated soil were explored in this study. Significant reduction of bioaccessibility and migration risks of both heavy metals have been explained mechanistically by incubation, column experiments and numerical simulation. Langmuir equation fitted As and Pb sorption isotherms better in the control and biochar (BC) amended soils, while Freundlich model was more suitable for iron modified biochar (Fe-BC) and sulfur/iron modified biochar (S/Fe-BC) amended soils, indicating that modified biochar promoted chemical adsorption process for As and Pb. For the three biochar materials, S/Fe-BC showed the best effects on reducing the bioavailability of As and Pb, with a decrease of 40.42%–64.21%. The reduction in bioaccessibility by metal portioning into available and non-available fractions was better for illustrating the mechanisms including adsorption, precipitation/coprecipitation and As(III) oxidation behind S/Fe-BC efficacy. Moreover, S/Fe-BC can effectively inhibit the leaching behavior of As and Pb under acid rain, which increased by 99.89% and 90.18%, respectively, compared with the control. The HYDRUS-1D modeling indicated that S/Fe-BC could continuously treat As (100 mg/L) and Pb (1000 mg/L) contaminated water for 16.22 years and 40.86 years, respectively, and ensure the groundwater quality criteria being met. Based on these insights, we believe that our study will provide meaningful information about the potentials of biochar derived materials for soil heavy metals’ remediation.

Bioaccessibility of microplastic-associated heavy metals using an in vitro digestion model and its implications for human health risk assessment.

Microplastics can act as carriers of heavy metals and may enter humans through ingestion and threaten human health. However, the bioaccessibility of heavy metals associated with microplastics and its implications for human health risk assessments are poorly understood. Therefore, in this study, four typical heavy metals (As(V), Cr(VI), Cd(II), and Pb(II)) and one typical microplastic (polyvinyl chloride, PVC) were chosen to estimate the human health risk of microplastic-associated heavy metals by incorporating bioaccessibility. Significant adsorption of heavy metals was observed with the following order for adsorption capacity: Pb(II) > Cr(VI) > Cd(II) > As(V); the efficiencies for desorption of these four heavy metals from PVC microplastics were all below 10%. The Fourier transform infrared spectroscopy results indicated that the functional groups on the surface of the virgin PVC microplastics did not play an important role in the capture process. Heavy metals in both gastric and small intestinal phases were prone to release from PVC microplastics when bioaccessibility was evaluated with the in vitro SBRC (Soluble Bioavailability Research Consortium) digestion model. In addition, Pb(II) bioaccessibility in the gastric phase was significantly higher than those in the other phases, while As(V), Cr(VI), and Cd(II) bioaccessibilities showed the opposite trend. After incorporating bioaccessibility adjustments, the noncarcinogenic hazards and carcinogenic risks determined were lower than those based on total metal contents. The individual hazard quotients (HQ) and carcinogenic risks (CR) for ingestion of these four heavy metals from PVC microplastics were all lower than the threshold values for adults and children. In summary, this study will provide a new view of the human health risks of heavy metals associated with microplastics.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-20983-8.

Application of magnetic susceptibility and heavy metal bioaccessibility to assessments of urban sandstorm contamination and health risks: Case studies from Dunhuang and Lanzhou, Northwest China

Direct ingestion of sandstorm particles is an important pathway in human exposure to heavy metals. This study investigated the potential health risks of heavy metals transported in sandstorms from Dunhuang to Lanzhou in northwestern China using environmental magnetic parameters and metal bioaccessibilities in simulated gastric and intestinal tracts. The mean magnetic susceptibility of sandstorms in Lanzhou was 366.86 × 10−8 m3/kg, which was more than 5-fold higher than that of sandstorms in Dunhuang, indicating that these sandstorms continuously receive heavy metals with high magnetic mineral content along their pathways. Heavy metal concentrations in sandstorms were higher than background values and those in urban topsoil. Enrichment factors and pollution load indices showed that these heavy metals were derived from both natural and anthropogenic sources, with Cu, Zn, Pb, and Cd being strongly influenced by anthropogenic sources. The bioaccessibilities of Cd, Cu, Zn, and Pb in the sandstorms of Lanzhou were very high, ranging from 22.69% (Cu) to 50.86% (Pb) for gastric phase, and 12.07% (Pb)–22.11% (Cd) for interstinal phase, with the significant reduction in χlf of the physiologically-based extraction testing (PBET) treated sandstorms. The magnetic minerals are significant correlation with the concentrations of heavy metals in sandstorm and effect the release of heavy metals during human digestion process. The overall ecological risk posed by heavy metals contained in sandstorms was relatively low; however, the risk was moderate to high at individual sites. Ingestion posed the highest carcinogenic and non-carcinogenic risks for both adults and children, with the risk for children being higher.

A Comparative and Modeled Approach for Three Biochar Materials in Simultaneously Preventing the Migration and Reducing the Bioaccessibility of Heavy Metals in Soil: Revealing Immobilization Mechanisms

A Comparative and Modeled Approach for Three Biochar Materials in Simultaneously Preventing the Migration and Reducing the Bioaccessibility of Heavy Metals in Soil: Revealing Immobilization Mechanisms

Interactions among heavy metal bioaccessibility, soil properties and microbial community in phyto-remediated soils nearby an abandoned realgar mine

Soil samples were collected from a representative arsenic (As) contaminated region under phytoremediation of hyperaccumulation plants. Relative abundance and diversity of microbial communities in the soil samples were characterized via 16S rRNA genes sequencing. At the phylum level, Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes and Firmicutes shows the highest abundance, accounting for more than 90 % of the classified sequences in the soil samples. Physicochemical parameters including pH, total organic carbon (TOC), cation exchange capacity (CEC), and electrical conductivity (EC), and heavy metal concentrations including total and bioaccessible contents in the soil samples were determined to investigate potential relationships between the microbial communities and the environmental factors. Principal component analysis (PCA) based on the operational taxonomic units (OTUs) matrix revealed distinct separation among the samples. The soil pH was confirmed as the dominant force to discriminate the soil samples with similar land use type and heavy metal contamination. There was little relevance between the total concentrations of heavy metals and the microbial communities. However, the bioaccessible concentrations of heavy metals were associated with the physicochemical parameters and relative abundances of bacterial genera according to correlation analyses. Although the soil samples were considerably contaminated by As, the abundances of bacterial phyla linked with As were lower than 1.0 % in most of the soil samples. The results indicated that the abundances of microbial communities in the soils were the consequence of concerted effects from all the environmental factors.

Bioaccessibility and public health risk of heavy Metal(loid)s in the airborne particulate matter of four cities in northern China

Atmospheric coarse particulate matter (PM10) enriched with heavy metal(loid)s could pose potentially significant health risk to humans, while accurate health risk assessment calls for characterization of their bioaccessibility, besides the total contents. The health risk of major toxic heavy metal(loid)s in the PM10 from four large cities in northern China via inhalation was investigated based on their total contents and bioaccessibility. The annual mean concentrations of PM-bound Zn, As, Pb, and Mn in the atmosphere of the four cities were 650, 305, 227, and 177 ng⋅m−3, respectively. The levels of heavy metal(loid)s in the PM10 were generally higher in winter but lower in summer in all four cities, which resulted primarily from the emissions associated with coal combustion for district and household heating and the unfavorable meteorological conditions in winter. The bioaccessibility of heavy metal(loid)s in the PM10 ranged from 0.9 to 48.7%, following the general order of Mn > Co > Ni > Cd > Cu > As > Cr > Zn > Pb. Based on their total contents in the PM10, most heavy metal(loid)s posed significant public health risk via inhalation exposure in the four cities. However, after accounting for the bioaccessibility of metal(loid)s, the non-carcinogenic risk of most metal(loid)s was negligible, except for As in the PM10 of Jinzhong, while only the carcinogenic risk posed by Cr and As in the PM10 exceeded the acceptable level. These findings demonstrate the importance of characterizing the bioaccessibility of airborne PM-bound heavy metal(loid)s in health risk assessment and could guide the on-going efforts on reducing the public health risk of PM10 in northern China.

Effect of gut microbiota on invitro bioaccessibility of heavy metals and human health risk assessment from ingestion of contaminated soils.

To identify the role of gut microbiota in human health risk assessment, the bioaccessibility of heavy metals in 14 soil samples were determined in simulated gastrointestinal fluids. Compared to the small intestinal phase, the bioaccessibility values of the colon phase varied, either increased by 3.5-fold for As, by 2.2-fold for Cr, and by 1.6-fold for Ni, or reduced by 4.4-fold for Cu, respectively. The colon incubation with adult gut microbiota yielded higher bioaccessibility value of As (1.3 times) and Fe (3.4 times) than that of the child in most soil samples. Colon bioaccessibility was about 60% greater of Cd for the adult and 30% higher of Cr for the child. Congruent data on the bioaccessibility of Cu and Ni was observed. In addition, correlation analysis indicated that invitro bioaccessibility was primarily related to total concentrations of heavy metals in soils, followed by soil pH and active Fe/Mn oxide. Significantly, risk assessment calculated based on colon bioaccessibility indicated that the target hazard quotient (THQ>1) of As was presented in 3 soil samples for the adult (1.05-3.35) and in 9 soil samples for the child (1.06-26.93). The hazard index (HI) of the child was 4.00 on average, greater than that of the adult (0.62), primarily due to the contribution of As and Cd. It suggested non-carcinogenic risks are likely to occur in children through typical hand-to-mouth behavior. The adjustment of colon bioaccessibility will result in more accurate risk assessment of human exposure to heavy metals from oral ingestion of contaminated soils.