Use of an in vitro digestion method to estimate human bioaccessibility of Cd in vegetables grown in smelter-impacted soils: the influence of cooking

The association between toxic metals (As, Pb and Cd) exposure and rice cooking methods: A systematic review and meta-analysis

Heavy metal exposure through rice consumption (Oryza sativa L.) is a human health concern. This systematic review and meta-analysis investigated the association between toxic metals exposure and rice cooking methods. Based on the inclusion and exclusion criteria, fifteen studies were selected as eligible for the meta-analysis. Our results showed a significant decrease in the content of arsenic, lead, and cadmium following the cooking rice (WMD= -0.04 mg/kg, 95% CI: -0.05, -0.03, P = 0.000), (WMD = -0.01 mg/kg, 95% CI: -0.01, -0.01, P = 0.000), and (WMD = -0.01 mg/kg, 95% CI: -0.01, -0.00, P = 0.000), respectively. Furthermore, based on the subgroup analysis the overall rank order of cooking methods in the rice was rinsed > parboiling > Kateh > high-pressure, microwave, and steaming. The findings of this meta-analysis indicate the beneficial effects of cooking on reducing arsenic, lead, and cadmium exposure via rice consumption.

Are high-risk heavy metal(loid)s contaminated vegetables detrimental to human health? A study of incorporating bioaccessibility and toxicity into accurate health risk assessment

Heavy metal(loid)s in the environment threaten food safety and human health. Health risk assessment of vegetables based on total or bioaccessible heavy metal(loid)s was widely used but can overestimate their risks, so exploring accurate methods is urgent for food safety evaluation and management. In this study, a total of 224 frequently consumed vegetables and their corresponding grown soils were collected from Yunnan, Southwest China. The total contents and bioaccessibilities of heavy metal(loid)s in vegetables were measured, their health risks were evaluated using the non-carcinogenic and carcinogenic risk models provided by USEPA. Besides, the gastrotoxicity of high-risk vegetables was also evaluated using a human cell model. Results showed that 6.25-43.8 % of Cr, Cd, and Pb contents in Zea mays L., Coriandrum sativum L., or Allium sativum L. exceeded the maximum permissible level of China, which were not consistent with those in corresponding soils. The bioaccessibility of Cr, Cd, As, Pb, Cu, Zn, Ni, and Mn in vegetables in the gastric phase was 0.41-93.8 %. Health risks based on bioaccessibility were remarkably decreased compared with total heavy metal(loid)s, but the unacceptable carcinogenic risk (CR > 10-4) was found even considering the bioaccessibility. Interestingly, gastric digesta of high-risk vegetables did not trigger adverse effects on human gastric mucosa epithelial cells, indicating existing health risk assessment model should be adjusted by toxic data to accurately reflect its hazards. Taken together, both bioaccessibility and toxicity of heavy metal(loid)s in vegetables should be considered in accurate health risk assessment and food safety-related policy-making and management.

In Vitro Assessment of the Physiologically Relevant Oral Bioaccessibility of Metallic Elements in Edible Herbs Using the Unified Bioaccessibility Protocol

In this work, the total content of seven metallic elements (Fe, Cu, Zn, Mg, Pb, Ni, and Co) in common edible herbs was determined and related to their bioaccessibility by an in vitro human digestion model. Specifically, the unified bioaccessibility protocol developed by the BioAccessibility Research Group of Europe (BARGE) was used to determine the release of each element during gastric and gastrointestinal digestion. The results show that Fe, Zn, and Mg are released during gastric digestion (34-57% Fe, 28-80% Zn, 79-95% Mg), but their overall bioaccessibility is reduced in the gastrointestinal tract (<30%). On the contrary, Cu is more bioaccessible during gastrointestinal digestion (38-60%). Pb, Ni, and Co exhibited similar bioaccessibility in both gastric and gastrointestinal fluids. Principle component analysis of the data shows that the classification of the nutritional value of herbs differs between the total and the gastrointestinal concentration, suggesting that the total concentration alone is not an adequate indicator for drawing secure conclusions concerning the nutritional benefits of edible plant species.

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.

Bioaccessibility of Cu, Mn, Fe, and Zn in Fruit and Vegetables by the In Vitro UBM and Statistical Evaluation of the Results

The total, gastric, and gastro-intestinal Cu, Mn, Fe, and Zn concentrations in eight fruit and vegetable samples were investigated. The unified bioaccessibility method (UBM) developed by BARGE (Bioaccessibility Research Group of Europe) was performed for in vitro bioaccessibility experiments. Total and bioaccessible concentrations of Cu, Mn, Fe, and Zn were determined by ICP-OES and ICP-MS, respectively. The accuracy of the methods was verified using BGS 102 for the BARGE UBM and SRM 1573a for total analysis. The mean BF (%) order for Cu, Mn, Fe, and Zn was Mn (101) > Zn (88) > Fe (60) > Cu (30) in gastric phase and Mn (78) > Zn (69) > Fe (46) > Cu (29) in gastro-intestinal phase. The results show that Mn and Zn in all the samples have the greatest bioaccessible values, while the values for Cu are much lower. The relationships among total, gastric, and gastro-intestinal element concentrations were investigated using statistical analysis such as correlation analysis, principal component analysis (PCA), and cluster analysis (CA). Total and bioaccessible Cu, Mn, and Zn concentrations were significantly correlated with each other.

Anthropogenic activities affecting metal transfer and health risk in plastic-shed soil-vegetable-human system via changing soil pH and metal contents

Accumulation and concomitant risk of metals in plastic-shed soil (PSS)-vegetable system around industrial areas have attracted growing public concern recently, while limited studies have focused on human bioaccessible metals in various plastic-shed vegetables and health risk calculated using bioaccessible metals. Previous studies showed that intensive farming and industrial activities could prominently affect metal migration from PSS to vegetables via altering PSS pH, total and bioavailable metal contents. In contrast, whether changes in PSS pH and metal contents control bioaccessible metals in vegetables and health risk is still unknown. For PSS management and sustainable plastic-shed vegetable production in the areas with rapid industrialization, 41 PSS and 32 plastic-shed vegetable samples were sampled from the industrial areas of Yangtze River Delta, China to systematically clarify the specific connections among anthropogenic activities, soil pH and metal contents, and metal transfer and health risk in PSS-vegetable-human system. The results indicated that Cr and Cd contents in 15.6% and 9.38% of vegetable samples exceeded the allowable limits in China. Tolerable cancer risk existed and was mainly induced by bioaccessible Cr in vegetables. Decreased PSS pH mainly caused by heavy use of nitrogen fertilizers increased bioavailable Ni, Cd, Zn, Pb, and Cu in PSS and subsequently enhanced their total and bioaccessible contents in vegetables. Prominent Cr accumulation in PSS induced by industrial wastewater irrigation exacerbated Cr uptake by vegetables, which increased bioaccessible Cr in vegetables and contributed greatly to cancer risk. To reduce transfer and health risk especially of Cd and Cr in the food chain, some appropriate measures related to source control and remediation should be proposed for preventing and mitigating PSS acidification and Cr accumulation.

Metal(loid) concentrations, bioaccessibility and stable lead isotopes in soils and vegetables from urban community gardens

Community gardens are "green oases" of recent cities with many benefits for human society. From a human health perspective, these benefits can be damaged by chemical contamination of soil and cultivated vegetables. Using geochemical approaches, this study characterised (i) total metal(loid) concentrations in soils and two commonly grown vegetables in urban community gardens (Bratislava, Slovakia), (ii) gastrointestinal bioaccessibility using a modified physiologically based extraction test (PBET), and (iii) stable lead (Pb) isotopes in order to identify sources of metal(loid)s, solubilisation in the human body and migration of Pb from soil to vegetables. While some soils could be considered contaminated when compared to the Slovak legislation for agricultural soil, the bioaccessibility of metal(loid)s did not exceed 20% in the intestinal phase, with the exception of cadmium (Cd). Tomatoes and lettuce contained low total and bioaccessible concentrations of metal(loid)s, being safe for people who consume their own grown vegetables. There were differences in Pb isotope composition among bulk soils, vegetables and bioaccessible Pb, with less radiogenic Pb being preferentially mobilised. Statistical methods considering the compositional nature of the geochemical data and the enrichment factor (EF) distinguished well metal(loid)s of natural origin (As, Co, Cr, Fe, Mn, Ni, V) from those with anthropogenic contributions. This research has shown the usefulness of integrating different methodologies to better understand the geochemistry of metal(loid)s in urban soils with their highly diversified sources.

Bioaccessibility of Cd and its Correlation with Divalent Mineral Nutrients in Locally Grown Rice from Two Provinces in China

Rice and rice products are the main sources of Cd contamination in humans. The total and bioaccessible concentrations of Cd and three divalent nutrients, Mn, Cu, and Zn, in locally grown rice grains from Hunan and Guangdong Provinces in China were investigated. An in vitro physiologically based extraction test method was introduced to evaluate the bioaccessibility of the target metals in the rice grains. The mean concentrations of Cd in the rice grains were 0.245 mg/kg and 0.235 mg/kg from Hunan and Guangdong Provinces, respectively. Large variations were observed in the Cd concentrations, indicating a heterogeneous distribution of Cd contamination throughout the study areas. The bioaccessibility of Cd, Mn, and Zn in the gastrointestinal fractions was significantly lower than that in the gastric fractions. In contrast, the bioaccessibility of Cu at the intestinal phase was detected in the rice grains from both provinces. The correlation analysis showed significant relationships between total Cd concentrations and bioaccessible Cd fractions, indicating that higher total Cd in rice grains always resulted in higher bioaccessible Cd. Consistent correlations in the rice grains were observed between Zn and Mn. However, a lack of correlation was found between Cd and Zn in the current study. Risk assessment according to bioaccessible Cd would significantly reduce the exposure risk to Cd from rice consumption.

In Vivo-In Vitro Correlations for the Assessment of Cadmium Bioavailability in Vegetables

The correlation of in vitro and in vivo assays for determining bioavailable Cd amounts in vegetables is limited. Herein, the correlations between Cd relative bioavailability (Cd-RBA) in rat models and Cd bioaccessibility in four in vitro assays were examined in vegetables. Results showed that the combined liver plus kidney data provided the appropriate endpoint and was used as a biomarker to estimate Cd-RBA. The Cd-RBA was negatively correlated with the mole ratio of Ca/Cd and Fe/Cd in vegetables. Strong in vivo-in vitro correlations were found from physiologically based extraction test (PBET) and in vitro gastrointestinal (IVG) (R² = 0.66-0.69). We concluded that PBET and IVG were optimal models for Cd-RBA determination in vegetables. The nutritional elements in the vegetables could affect Cd absorption. Furthermore, the Cd bioavailability in vegetables should be considered because risk estimates solely based on the total Cd concentration in vegetables would overestimate Cd intake.

Bioaccessibility and bioavailability adjusted dietary exposure of cadmium for local residents from a high-level environmental cadmium region

The critical health risks caused by cadmium (Cd) via dietary exposure are commonly assessed by detecting Cd concentrations in foods. Differently, in this study, the bioaccessibility and bioavailability of Cd in major local harvests were introduced to assess the dietary exposure of local residents from a high-level environmental Cd region. The results indicated that certain Cd was released into the digestive juice after in vitro digestion with a bioaccessibility of 20-63% for rice and 3-32% for leafy vegetables, and the released portion was partially absorbed by Caco-2 cells with a bioavailability of 2-21% for rice and 0.2-13% for leafy vegetables. The results obtained from the toxicokinetic model revealed that the predicted urinary Cd values from the estimated daily intake (EDI) of Cd, which accounted for bioaccessibility and bioavailability, were consistent with the actual measured values, and the EDIs were considerably lower than the acceptable daily intake. This suggests that the bioaccessibility and bioavailability adjusted dietary Cd exposure should be more precise. The key issues addressed in our study implores that a potential health risk cannot be neglected in people with high consumption of rice from high-level zone.

Evaluation of Cadmium Transfer from Soil to the Human Body Through Maize Consumption in a Cadmium Anomaly Area of Southwestern China

Evaluating the bioavailability, bioaccessibility, and transferability of cadmium (Cd) in soil-grain-human systems is essential in areas with a Cd anomaly in the karst region of southwestern China. In the present study, the main controlling factors and prediction models for Cd transfer in a soil-grain-human system were investigated in a typical area where natural processes and anthropogenic activities interact in the karst region of southwestern China. The environmental availability of Cd (diethylenetriaminepentaacetic acid- and CaCl₂ -extractable Cd [ CdCaCl2 ]) in the soil varies significantly because of the diversity of soil properties. However, Cd concentrations in the maize grain were significantly related only to the CdCaCl2 concentrations in the soil (r = 0.595, p < 0.01), indicating that soil CdCaCl2 is a good indicator for evaluating Cd uptake by maize grain. Of all the measured soil properties, the soil cation exchange capacity (CEC) and the soil calcium (Ca_soil ) were the most important factors influencing Cd accumulation in the soil-maize grain system. A transfer model combining CdCaCl2 , soil CEC, and Ca_soil was sufficiently reliable for predicting Cd accumulation in the maize grain (R²  = 0.505). Although there is room for improvement regarding the prediction performance of the chain model combining soil CdCaCl2 with Ca_soil to predict the bioaccessible Cd concentration in maize grain (R²  = 0.344 for the gastric phase and R²  = 0.356 for the gastrointestinal phase), our findings provide a useful reference to further explore a model that can be used for a relatively rapid and reliable estimation of dietary Cd exposure for specific regions prior to crop harvest. Environ Toxicol Chem 2021;40:2923-2934. © 2021 SETAC.

Aging and phytoavailability of newly introduced and legacy cadmium in paddy soil and their bioaccessibility in rice grain distinguished by enriched isotope tracing

Phytoavailability of Cadmium (Cd) plays a critical role in its accumulation in soil-rice systems. However, differential aging and phytoavailability of newly introduced Cd (Cd_N) and legacy Cd (Cd_L) in the soil-rice system remains unknown. Moreover, distinguishing their aging and phytoavailability is challenging. Enriched ¹¹²Cd isotope was introduced into a series of pot experiments, combined with sequential extraction and isotope dilution (¹¹⁰Cd isotopic spike), to investigate the aging and distribution of Cd_N and Cd_L under different treatments. The treatments included simulated acid rain, slaked lime, and biochar. Cd_N aged quickly than Cd_L in flooded soil and its availability was similar to that of Cd_L after tillering stage. The grain Cd contents were positively correlated to Cd concentrations in the overlying water. Acid rain reduced the soil pH, increasing the grain Cd, while slaked lime reduced grain Cd content. The acidic biochar used in this study increased grain Cd, possibly through soil acidification-induced Cd release. The differences in bioaccumulation and translocation factors between Cd_N and Cd_L in rice plants under slaked lime and biochar treatments suggested their different in vivo complexations and translocations. Analysis of bioaccessibility of Cd_N and Cd_L in rice grains provided valuable insights regarding human Cd exposure.

Benefit-risk assessment of metal bioavailability in edible fungi by biomimetic whole digestive tracts with digestion, metabolism, and absorption functions

As worldwide edible fungi, Lentinula edodes and Agaricus bisporus accumulate both essential and harmful metals. Metal bioavailability is important for metal benefit-risk assessment. A full functional model of digestive tracts (including digestion, metabolism, and absorption) is established. Under the digestive tract functions, the bioaccessible and bioavailable metals are released from edible fungi and absorbed by intestinal tract, respectively. Based on bioavailable metal contents in the intestine, safe dosage and maximum consumption are 43.52 g/d and 248.7 g/d for Agaricus bisporu, 20.59/328.9 g/d (for males/ female) and 132.9 g/d for Lentinus edodes; V, Co, Ni, Cu, Zn, Se, Cr, Cd and Pb in Agaricus bisporus and Lentinula edodes are absorbed mainly in the large intestine; Fe is mainly absorbed in small intestine; edible fungi species-specificity in metal bioavailability is observed for As and Mn, which are mainly absorbed by small and large intestine for Agaricus bisporus and Lentinus edodes, respectively; and then metal toxicity on small and large intestine is disclosed. Metal benefit-risk is assessed by the content of monolayer liposome-extracted metal in the chyme from small and large intestine, which is controlled by the gastrointestinal functions, metal and edible fungi species.

Study on the bioaccessibility and bioavailability of Cd in contaminated rice in vitro and in vivo

Cadmium (Cd) is a widespread heavy metal pollutant in the environment that damages human health. In this study, the bioaccessibility and bioavailability of Cd in different Cd-contaminated rice (low pollution level cadmium rice (Rice-L, 0.111 mg/kg), medium pollution level cadmium rice (Rice-M, 0.400 mg/kg), and high pollution level cadmium rice (Rice-H, 0.655 mg/kg)) were estimated and determined by an in vitro digestion model Rijksinstituut voor volksgezondheiden milieu (RIVM), Caco-2 cell model, and mouse model. The results indicated that Cd in the oral cavity (15.65-28.28%) displayed the lowest bioaccessibility comparing with small intestine (90.04-94.73%) and the stomach (99.30-100.70%) in vitro after cooking. In addition, the results showed that the bioaccessibility of Cd in CdCl₂ , CdCl₂ +normal rice (Rice-N), Rice-H, Rice-M, Rice-L group were 99.29%, 92.57%, 90.04%, 94.73%, and 91.11%, respectively; the in vitro bioavailability of Cd in CdCl₂ , CdCl₂ +Rice-N, Rice-H, Rice-M, and Rice-L group were 27.50%, 20.78%, 21.90%, 26.90%, 36.46%, respectively, we found that the group of CdCl₂ is significantly higher than CdCl₂ +Rice-N and Rice-H (p < 0.05), while the targets hazard quotient (THQ) value of rice ingested without considering the in vitro bioavailability is 2.7-4.6 times than the THQ value with considered and the relative bioavailability (RBA) of Cd in Rice-L, Rice-M, Rice-H are 80.25%, 64.32%, and 60.91%, respectively. These results indicate that the rice substrate has impact on the bioaccessibility and bioavailability of Cd, and might overestimate the health risks of Cd if bioavailability was not considered. PRACTICAL APPLICATION: Studying the bioaccessibility and bioavailability of cadmium in rice is a promising strategy to obtain a more accurate human health risk assessment of cadmium exposure in rice, as well as provide a theoretical basis for the formulation of cadmium limit standard in grain, which was also conducive to the rational and full utilization of rice resources in China.

Bayesian toxicokinetic modeling of cadmium exposure in Chinese population

Cadmium (Cd) is a toxic heavy metal widely present in the environment. Estimating its internal levels for a given external exposure using toxicokinetic (TK) models is key to the human health risk assessment of Cd. In this study, existing Cd TK models were adapted to develop a one-compartment TK model and a multi-compartment physiologically based toxicokinetic (PBTK) model by estimating the characteristics of Cd kinetics based on Cd exposure data from 814 Chinese residents. Both models not only considered the effect of gender difference on Cd kinetics, but also described the model parameters in terms of distributions to reflect individual variability. For both models, the posterior distributions of sensitive parameters were estimated using the Markov chain-Monte Carlo method (MCMC) and the approximate Bayesian computation-MCMC algorithm (ABC-MCMC). Validation with the test dataset showed 1.4-22.5% improvement in the root mean square error (RMSE) over the original models. After a systematic literature search, the optimized models showed acceptable prediction on other Chinese datasets. The study provides a method for parameter optimization of TK models under different exposure environment, and the validated models can serve as new quantitative assessment tools for the risk assessment of Cd in the Chinese population.

Risk Assessment for Oral Bioaccessibility of Lead and Cadmium in the Potato Growing in Smelter-Impacted Soil

Smelting activities are an important source of heavy metals in soil. More seriously, oral ingestion of crops growing in contaminated soil potentially cause harmful effects on human health. The main purpose of this study is to apply the in vitro model (PBET) and Monte Carlo Simulation (MSC) to the health risk assessment process in order to more accurately and realistically evaluate health risks of residents eating contaminated potato. Results indicated in the raw and cooked potato, the bioaccessibility of Pb was 65.9% and 74.5%, and that of Cd was 79.6% and 61.7%, respectively. Additionally, the bioaccessible hazard quotient (BHQ) was less than the permitted level except for the BHQ of Pb for children. This indicated there wasn't potential non-carcinogenic risk for most potato-consumers but the dietary exposure risk for local children cannot be neglected. Sensitivity analysis showed that the bioaccessibility and ingestion rate appeared decisive with respect to potentially deleterious health effects.

Selenium and cadmium in bioaccessible fraction of organic weaning food: Risk assessment and influence of dietary components

BACKGROUND

The tendency of some sectors of the population to consume organic food has also come to include baby food. Nevertheless, it is necessary to develop studies to support the true nutritional and toxicological value of these products, making special emphasis in several trace elements. To our knowledge, no studies have been conducted on this type of organic food.

METHODS

Weaning foods with different formulations categorized as organic were analyzed to determine Se and Cd contents as well as its bioaccesibility. The analyses were conducted by electro thermal atomic absorption spectroscopy (ET - AAS) after the treatment of the samples with acid mineralization. Besides, macronutrient analyses (protein, fat and dietary fiber) were also developed. Finally, a novelty statistic approach such as @Risk was used to evaluate contributions to DRI or PTWI of Se and Cd derived for consumption of these weaning foods.

RESULTS

Se content ranged between 2.44-15.4 μg Kg ¹. Samples with meat ingredients showed the highest Se contents, while weaning foods consisting of fruits or vegetables presented the lowest concentrations. Se bioccessible concentration ranged between 1.90-4.35 μg Kg^-1 with a greater uniformity amongst analyzed samples. Regarding Cd, concentrations of this heavy metal ranged between 1.23 and 3.64 μg Kg^-1. Furthermore, Cd bioaccessibility of organic weaning foods ranged between 0.17 and 1.38 μg Kg^-1. The solubility of all samples studied was around 20% from the initial Cd concentration. A negative statistical correlation between fat content - Cd bioaccesible (p < 0.05; r = - 0.756) and Cd content - Se bioaccesible (p < 0.05; r = - 0.777) were also found.

CONCLUSIONS

Cd concentrations are considerably lower than those reported in weaning formulas which were not categorized as organic. On the other hand, the analysed organic jars did not represent a significant source of Se. The probabilistic assessment developed, showed that contributions to DRI of Se for infants 1-3 years old by consumption of these weaning foods, are excessively low (15% at best).

Chemical Forms and Health Risk of Cadmium in Water Spinach Grown in Contaminated Soil with an Increased Level of Phosphorus

(1) Background: Even in croplands with a low concentration of cadmium (Cd), there is still a risk for planting crops because of the high accumulation capacity of some leafy vegetables. (2) Methods: In this study, water spinach was planted in four main soil series (Wa, Eh, Tk, and Yu) in central Taiwan, which were spiked with Cd. The soil available phosphorous content was increased to 10–17 mg/kg, and the accumulation and developed chemical forms of Cd were analyzed. (3) Results: The experimental results showed that addition of phosphorous to Wa and Eh promoted the growth of water spinach. Accumulation and upward translocation of Cd were also increased in the phosphorus treatment compared with the control. The addition of phosphorus increased the percentage of Cd compartmentalized in undissolved Cd phosphate, which revealed that the mobility and toxicity of Cd were reduced in the phosphorus treatment. However, most of the water spinach was not edible because the vegetable-induced hazard quotient, which was calculated using three methods, showed hazardous potential in general.

An apple a day? Assessing gardeners' lead exposure in urban agriculture sites to improve the derivation of soil assessment criteria

Globally, many of our urban agriculture sites (UAS) contain high levels of lead (Pb), a contaminant of toxicological concern to humans. To improve the derivation of soil assessment criteria at UAS, and avoid inappropriate closure of these valuable community spaces, we sampled nearly 280 paired soil and crop samples across 31 UAS gardens. This sampling was coupled with an exposure and food frequency questionnaire and participants blood Pb levels (BLL), (43 gardeners and 29 non-gardening neighbours). In 98% of the sampled soils, Pb concentrations were above the current UK soil guideline for UAS (80 mg/kg), however despite the high soil Pb (geometric mean: 324 mg/kg), and high soil bioaccessible Pb (geometric mean: 58.7%), all participants BLL were <4.1 μg/dL (range: 0.6-4.1 μg/dL). Indeed, there was no statistically significant difference between the BLL of the UAS gardeners and those of their non-gardening neighbours (p = 0.569). Pb uptake, however, varied with crop type and our study highlights the suitability of certain crops for growing at UAS with elevated Pb (e.g. tubers, shrub and tree fruit), whilst limiting the consumption of others (selected root vegetables, such as rhubarb, beetroot, parsnips and carrots, with observed Pb concentrations > 0.1 mg/kg FW). The importance of defining the exposure scenario of a specific sub-population (i.e. UAS gardeners) is highlighted. Our preferred models predict site specific assessment criteria (SSAC) of 722-1634 mg/kg. We found fruit and vegetable consumption rates by all participants, and not just the UAS gardeners, to be considerably higher than those currently used to derive the UK's category 4 screening levels (C4SLs). Furthermore, the soil to plant concentration factors (SPCFs) used to derive the UAS C4SL significantly over predict Pb uptake. Our study indicates it may be appropriate to develop a distinct exposure dataset for UAS. In particular we recommend the derivation of SPCFs that are reflective of urban soils, both in terms of the range of soil Pb concentrations typically observed, but also the sources (and hence human oral bioaccessibility and plant-availability) of this Pb.

Effect of inoculation with arbuscular mycorrhizal fungi and blanching on the bioaccessibility of heavy metals in water spinach (Ipomoea aquatica Forsk.)

A plant's tolerance to heavy metals (HMs) and its detoxification mechanisms are associated with the subcellular distribution of HMs and their chemical forms. In this study, water spinach (Ipomoea aquatica Forsk.) was grown in two soils contaminated with a single HM (cadmium, Cd) or combined HMs (Cd and nickel, Ni). Inoculation of arbuscular mycorrizal fungi (AMF) was conducted to increase the accumulation of phosphorus (P) in plants. One major exception was to decrease the migration and accumulation of HMs in edible parts by the formation of P-HM complexes. The effects of blanching and simulated digestion on bioaccessibility were also assessed. The experimental results showed that the water spinach species used in this study had a high capacity to accumulate HMs. AMF treatment improved water spinach growth and decreased the accumulation of Ni but not that of Cd. Soluble and inorganic Cd and Ni were the major subcellular fractions and chemical forms in water spinach; these two HMs also exhibited higher migration capacities in comparison to chromium (Cr). Relative to raw tissues, 45-84% of Cd, Cr, and Ni were leached after blanching. Approximately 32-55%, 16-50%, and 27-40% of Cd, Cr, and Ni, respectively, were bioaccessible and could be metabolized by in vitro digestive fluids.

Effects of washing, soaking and domestic cooking on cadmium, arsenic and lead bioaccessibilities in rice

BACKGROUND

The health risk of heavy metals such as cadmium (Cd), arsenic (As) and lead (Pb) in rice can be assessed by their concentration and bioaccessibility. In this work, japonica cultivar Xinfeng 2 and indica cultivar T-You 15 were washed, soaked and cooked using three common domestic cooking methods. The present study investigated the effects of washing, soaking, normal cooking, high-pressure cooking and microwave cooking on the concentration, bioaccessibility and health risk of Cd, As and Pb in rice.

RESULTS

Washing significantly reduced concentrations of Cd, As and Pb, and all three types of cooking reduced bioaccessibilities of these elements. No significant differences in bioaccessibility were observed among rice prepared with different cooking methods. Concentrations and bioaccessibilities of Cd, As and Pb highly affected the values of average daily dose, hazard quotient and lifetime cancer risk. High concentration and bioaccessibility cause As to pose non-carcinogenic and carcinogenic health risks to adults and children. Moreover, compared with adults, children have a high chance of exposure to non-carcinogenic and carcinogenic health risks.

CONCLUSION

Washing and cooking of rice lowered the health risk by reducing Cd, As and Pb concentrations and bioaccessibilities respectively. © 2018 Society of Chemical Industry.

Assessment of the bioavailability, bioaccessibility and transfer of heavy metals in the soil-grain-human systems near a mining and smelting area in NW China

Elucidating the transfer behaviour of heavy metals from soils to grains and ultimately to humans is of great significance for both human health risk assessment and pollution control. In this study, the bioavailability of heavy metals (Cd, Cu, Pb, Zn, Cr and Ni) in farmland soils and bioaccessibility in grains (spring wheat, maize and rice) were determined to elaborate transfer dynamics in the soil-grain-human systems near a mining and smelting area in the Dongdagou watershed, Baiyin district, Gansu province, NW China. The results showed that Cd, Cu, Pb and Zn concentrations in soils were elevated compared to background levels, while Cr and Ni concentrations were relatively low throughout the region. High levels of bioavailable soil Cd were found using both EDTA and CH₃COOH extraction methods. Mean concentrations of Cd, Pb and Zn in spring wheat grains and the Cd and Cr concentrations in maize grains exceeded the relevant maximum levels for pollutants according to the Chinese national standards for food safety. Except for Ni (41.90%) and Pb (31.39%), heavy metal bioaccessibility was relatively low in grains, ranging from 10.80% (Cd) to 17.18% (Zn). CH₃COOH-extracted Cd, Pb and Ni, EDTA-extracted Zn, and total Cu in soils were the best indices for evaluation of uptake in grains (R²=0.54-0.91, p<0.001). Internal exposure doses of Cd and Ni in humans from spring wheat grain consumption was predicted by the linear correlations between bioaccessible and total metal concentrations (R²=0.61 and 0.67; p<0.001). The results from this study provide sufficient data and theoretical support for the use of these methods for local pollution prevention and control.

Cadmium bioaccumulation and gastric bioaccessibility in cacao: A field study in areas impacted by oil activities in Ecuador

Cacao from South America is especially used to produce premium quality chocolate. Although the European Food Safety Authority has not established a limit for cadmium (Cd) in chocolate raw material, recent studies demonstrate that Cd concentrations in cacao beans can reach levels higher than the legal limits for dark chocolate (0.8 mg kg^-1, effective January 1st, 2019). Despite the fact that the presence of Cd in agricultural soils is related to contamination by fertilizers, other potential sources must be considered in Ecuador. This field study was conducted to investigate Cd content in soils and cacao cultivated on Ecuadorian farms in areas impacted by oil activities. Soils, cacao leaves, and pod husks were collected from 31 farms in the northern Amazon and Pacific coastal regions exposed to oil production and refining and compared to two control areas. Human gastric bioaccessibility was determined in raw cacao beans and cacao liquor samples in order to assess potential health risks involved. Our results show that topsoils (0-20 cm) have higher Cd concentrations than deeper layers, exceeding the Ecuadorian legislation limit in 39% of the sampling sites. Cacao leaves accumulate more Cd than pod husks or beans but, nevertheless, 50% of the sampled beans have Cd contents above 0.8 mg kg^-1. Root-to-cacao transfer seems to be the main pathway of Cd uptake, which is not only regulated by physico-chemical soil properties but also agricultural practices. Additionally, natural Cd enrichment by volcanic inputs must not be neglected. Finally, Cd in cacao trees cannot be considered as a tracer of oil activities. Assuming that total Cd content and its bioaccessible fraction (up to 90%) in cacao beans and liquor is directly linked to those in chocolate, the health risk associated with Cd exposure varies from low to moderate.

Bioaccessibility and Human Exposure Assessment of Cadmium and Arsenic in Pakchoi Genotypes Grown in Co-Contaminated Soils

In many countries cadmium (Cd) and arsenic (As) commonly coexist in soils contaminated by mining activities, and can easily enter the human body via consumption of leafy vegetables, like the popularly consumed pakchoi (Brassica chinensis L.), causing major health concerns. In the present study, bioaccessibility and human exposure of Cd and As were assessed in twenty genotypes of pakchoi cultured at two different levels of co-contamination to identify low health risk genotypes. The bioaccessibilities of Cd and As represent a fraction of the total metals content could be bioaccessible for human, in the present study, significant differences in pakchoi Cd and As bioaccessibility were observed among all tested genotypes and co-contaminated levels. Cd and As bioaccessibility of pakchoi were in the ranges of 24.0-87.6% and 20.1-82.5%, respectively, for in the high level co-contaminated soils, which was significantly higher than for low level co-contaminated soils with 7.9-71.8% for Cd bioaccessibility and 16.1-59.0% for As bioaccessibility. The values of bioaccessible established daily intakes (BEDI) and the total bioaccessible target hazard quotients (TBTHQ) of Cd and As were also considerably higher in high level co-contaminated soils than in low level co-contaminated soils. Two genotypes (Meiguanqinggengcai and Zhenqing60F1) contained relatively low concentrations and bioaccessible Cd and As and, their BEDI and TBTHQ for Cd and As ranged below the tolerable limits set by the FAO/WHO (BEDI of Cd < 0.83 μg kg^-1 bw day^-1, BEDI of As < 3 μg kg^-1 bw day^-1) and United States Environmental Protection Agency (TBTHQ for Cd and As < 1), this applied for both levels of co-contaminated soils for adults and children. Consequently, these findings suggest identification of safe genotypes in leafy vegetable with low health risk via genotypic screening and breeding methods could be a useful strategy to ensure the safety of food crops grown in those Cd and As co-contaminated fields due to mining activities.

Health risk assessment of potentially harmful elements and dietary minerals from vegetables irrigated with untreated wastewater, Pakistan

In the developing world, vegetables are commonly grown in suburban areas irrigated with untreated wastewater containing potentially harmful elements (PHEs). In Pakistan, there is no published work on the bioaccessibility aspect of PHEs and dietary minerals (DMs) in sewage-irrigated soil or the vegetables grown on such soils in Pakistan. Several industrial districts of Pakistan were selected for assessment of the risk associated with the ingestion of vegetables grown over sewage-irrigated soils. Both the total and bioaccessible fraction of PHEs (Cd, Co, Cr, Ni, and Pb) and DMs (Fe, Cu, Mn, Zn, Ca, Mg, and I) in soils and vegetable samples were measured. The concentrations of these PHEs and DMs in sewage-irrigated and control soils were below published upper threshold limits. However, compared to control soils, sewage irrigation over the years decreased soil pH (7.7 vs 8.1) and enhanced dissolved organic carbon (1.8 vs 0.8 %), which could enhance the phyto-availability of PHEs and DMs to crops. Of the PHEs and DMs, the highest transfer factor (soil to plant) was noted for Cd and Ca, respectively. Concentrations of PHEs in most of the sewage-irrigated vegetables were below the published upper threshold limits, except for Cd in the fruiting portion of eggplant and bell pepper (0.06-0.08 mg/kg Cd, dry weight) at three locations in Gujarat and Kasur districts. The bioaccessible fraction of PHEs can reduce the context of dietary intake measurements compared to total concentrations, but differences between both measurements were not significant for Cd. Since the soils of the sampled districts are not overly contaminated compared to control sites, vegetables grown over sewage-irrigated soils would provide an opportunity to harvest mineral-rich vegetables potentially providing consumers 62, 60, 12, 104, and 63 % higher dietary intake of Cu, Mn, Zn, Ca, and Mg, respectively. Based on Fe and vanadium correlations in vegetables, it is inferred that a significant proportion of total dietary Fe intake could be contributed by soil particles adhered to the consumable portion of vegetables. Faecal sterol ratios were used to identify and distinguish the source of faecal contamination in soils from Gujranwala, Gujarat, and Lahore districts, confirming the presence of human-derived sewage biomarkers at different stages of environmental alteration. A strong correlation of some metals with soil organic matter concentration was observed, but none with sewage biomarkers.

Oral bioaccessibility and human exposure assessment of cadmium and lead in market vegetables in the Pearl River Delta, South China

A systematic investigation into cadmium (Cd) and lead (Pb) concentrations and their oral bioaccessibility in market vegetables in the Pearl River Delta region were carried out to assess their potential health risks to local residents. The average concentrations of Cd and Pb in six species of fresh vegetables varied within 0.09-37.7 and 2.3-43.4 μg kg^-1, respectively. Cadmium and Pb bioaccessibility were 35-66 % and 20-51 % in the raw vegetables, respectively, and found to be significantly higher than the cooked vegetables with 34-64 % for Cd and 11-48 % for Pb. The results indicated that Cd bioaccessibility was higher in the gastric phase and Pb bioaccessibility was higher in the small intestinal phase (except for fruit vegetables). Cooking slightly reduced the total concentrations and bioaccessibility of Cd and Pb in all vegetables. The bioaccessible estimated daily intakes of Cd and Pb from vegetables were far below the tolerable limits.

Measurement of metal bioaccessibility in vegetables to improve human exposure assessments: field study of soil-plant-atmosphere transfers in urban areas, South China

The quality of cultivated consumed vegetables in relation to environmental pollution is a crucial issue for urban and peri-urban areas, which host the majority of people at the global scale. In order to evaluate the fate of metals in urban soil-plant-atmosphere systems and their consequences on human exposure, a field study was conducted at two different sites near a waste incinerator (site A) and a highway (site B). Metal concentrations were measured in the soil, settled atmospheric particulate matter (PM) and vegetables. A risk assessment was performed using both total and bioaccessible metal concentrations in vegetables. Total metal concentrations in PM were (mg kg^-1): (site A) 417 Cr, 354 Cu, 931 Zn, 6.3 Cd and 168 Pb; (site B) 145 Cr, 444 Cu, 3289 Zn, 2.9 Cd and 396 Pb. Several total soil Cd and Pb concentrations exceeded China's Environmental Quality Standards. At both sites, there was significant metal enrichment from the atmosphere to the leafy vegetables (correlation between Pb concentrations in PM and leaves: r = 0.52, p < 0.05) which depended on the plant species. Total Cr, Cd and Pb concentrations in vegetables were therefore above or just under the maximum limit levels for foodstuffs according to Chinese and European Commission regulations. High metal bioaccessibility in the vegetables (60-79 %, with maximum value for Cd) was also observed. The bioaccessible hazard index was only above 1 for site B, due to moderate Pb and Cd pollution from the highway. In contrast, site A was considered as relatively safe for urban agriculture.

Assessment of influences of cooking on cadmium and arsenic bioaccessibility in rice, using an in vitro physiologically-based extraction test

The health risks associated with rice consumption may decrease if consumers use cooking practices which can reduce the bioaccessibility of metal(loid)s. The effects of cooking on the Cd and As bioaccessibility, at three contamination levels of rice, were studied. Results indicated that cooking reduced bioaccessibility of Cd and As in rice. Cooking resulted in a significant increase (p<0.01) of Cd and As concentrations in the residual fraction. Low volume water-cooking of rice to dryness reduced total Cd by about 10% for rices A and B, while medium or high volume water-cooking had no effect on Cd bioaccessibility in all rice types. In contrast, low volume cooking did not remove As, but a significant decrease (p<0.05) was observed when cooking with higher volumes of water. This study provides information for a better understanding of more realistic estimation of metal(loid)s exposure from rice and the possible health risks.