In vitro digestion/Caco-2 cell model to estimate cadmium and lead bioaccessibility/bioavailability in two vegetables: the influence of cooking and additives

Bioaccessibility in daily diet and bioavailability in vitro of aflatoxins from maize after cooking

Bioavailability is not a constant percentage of a contaminant in food but is affected by many factors, such as food type, treatment, diet structure and interaction with other compounds. To evaluate these influences, we measured the bioaccessibility of aflatoxins from nine naturally polluted maize samples, collected from southeast China, using an in vitro digestion model, and analysed the intestinal transport of aflatoxins by a Caco-2 cell model. Steam cooking treatment could reduce the aflatoxin levels in maize bread. The degradation rates of aflatoxin B1, aflatoxin B2, aflatoxin G1, and aflatoxin G2 ranged from 24.9±3.2 to 33.9±3.5%, 27.0±2.0 to 39.0±1.8%, 27.9±7.9 to 34.4±8.2% and 25.6±3.6 to 37.2±6.5%, respectively. As a result, the bioaccessibility of aflatoxins determined by an in vitro digestion model (41.5-63.3%) was much lower than the previously reported 80%. Edible oil could increase the bioaccessibility of aflatoxin, whereas lettuce would decrease the exposure amount from maize. With a Caco-2 cell model, the apparent permeability coefficient exceeding 10-5 cm/s indicated that there is high absorption of aflatoxins in the human body, while the intestinal transport can be effectively restrained in the presence of chlorophyll.

In Vitro and In Vivo Testing to Determine Cd Bioaccessibility and Bioavailability in Contaminated Rice in Relation to Mouse Chow

A combination of an in vitro physiologically based extraction test (PBET) and an in vivo mouse model was used to determine Cd oral bioaccessibility and estimate bioavailability in Cd-contaminated rice. The PBET found lower Cd bioaccessibility in the intestinal stage (40–50%) than in the gastric stage (93–98%) for both rice and mouse chow. No significant difference was found in Cd bioaccessibility between contaminated rice and Cd-amended mouse chow in the gastric or gastrointestinal phase (except for rice 1). The result of the in vivo bioassay revealed that Cd absorption in the kidney or liver of mice fed with contaminated rice were significantly higher than in the mouse chow group containing an equal Cd concentration. Correlation analysis between concentrations of different elements in mouse chow or rice and Cd concentrations in mice kidney or liver showed that Fe, Ca, Cu, and Zn had significant negative correlation (r² > 0.7, p < 0.01). These results suggest that nutritional elements in the diet could affect Cd absorption and distribution in organs and that different food matrices may result in unequal Cd health risks at an equal Cd concentration due to the specific mineral content of food.

Lead, Cadmium, and Arsenic Bioaccessibility of 24 h Duplicate Diet Ingested by Preschool Children Attending Day Care Centers in Brazil

Lead, known as a metal with high neurotoxicity to children, cadmium, which is a carcinogenic and bioaccumulative contaminant, and arsenic, a class 1 carcinogenic according to the International Agency for Research on Cancer, are toxic elements (TEs) whose relevant route of exposure may be diet. We determined the bio-accessible fraction of lead, cadmium, and arsenic from the diet of preschool children from two day care centers (DCC). A cross-sectional study was conducted with 64 one–four-year-old children from two DCCs where the 24-h duplicate diet samples were collected. The diet samples were analyzed by ICP-MS for lead, cadmium, and arsenic total concentrations (n = 64) and their bio-accessibility were analyzed for a subsample (n = 10). The dietary intake (DI) mean for lead, cadmium, and arsenic were 0.18 ± 0.11 µg kg⁻¹ bw, 0.08 ± 0.04 µg kg⁻¹ bw, and 0.61 ± 0.41 µg kg⁻¹ bw, respectively. All DI calculated for TEs, considering total intake, were found lower than the tolerable limits (TL) (European Union, or World Health Organization, WHO, when applicable) except for one child’s Pb intake. Bio-accessibilities ranged between 0% to 93%, 0% to 103%, and 0% to 69%, for lead, cadmium, and arsenic, respectively. Although DI for TEs has been found lower than TL, these reference values have been recently decreased or withdrawn since it was for lead and arsenic whose TL were withdrawn by WHO.

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.

Oral Bioaccessibility and Exposure Risk of Metal(loid)s in Local Residents Near a Mining-Impacted Area, Hunan, China

Metal(loid) contamination of food crops and soils resulting from mining activities has been a major concern due to the potential risk to humans. In this study, a total of 36 rice (home-grown and market rice), 38 vegetable, 10 drinking water, 4 river water, 18 soils and 30 urine samples were collected from an abandoned mining area or the local residents in China. Results showed that metal(loid) levels in some of the soil and drinking water samples exceeded the Chinese standard. Rice Cd concentration, rice Pb levels, and vegetable Pb levels exceeded the maximum permissible concentrations in 49%, 68%, and 42% of the samples, respectively. In gastric phases, the average Cd, Pb and As bioaccessibilities in rice were 72%, 70%, and 82%. In gastrointestinal phases, the average Cd, Pb and As bioaccessibilities in rice were 49%, 39%, and 94%. Vegetables (pak choi was selected) showed lower metal(loid) bioaccessibility than rice. The median concentrations of Cd, Pb and As in urine were 3.99, 4.82 and 64.8 µg L⁻¹, respectivley. Rice had the highest contribution rates of Cd and Pb for daily intake, accounting for 114% and 210%, respectively. Vegetables contributed less, and very little contribution came from drinking water. Based on the bioaccessibility data, metal(loid) contamination around the mining area poses a great exposure risk to the local residents through consumption of food crops.

Effect of food matrices on the in vitro bioavailability and oxidative damage in PC12 cells of lead

The bioavailability and oxidative damage toxicity of lead (Pb) in seven food matrices, including rice, milk, tomato, garlic, apple, kelp and pork, were determined using an in vitro digestion/Caco-2 cell model and a rat pheochromocytoma (PC12) oxidative damage model. Results showed that Pb bioaccessibility and bioavailability in the apple and kelp groups were significantly lower than other food matrix groups, with corresponding values of 11.05-28.31% and 1.57-8.81%, respectively. Oxidative damage assays showed that digestion products of apple polyphenol extract, which was selected from seven food matrices, could increase the oxidation resistance and the levels of glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and acetyl cholinesterase (AChE) by 32.23%, 39.02%, 27.14% and 30.90%, respectively. Additionally, malondialdehyde (MDA) and reactive oxygen species (ROS) levels could be decreased by 59.66% and 40.21%, respectively. In conclusion, phenolics were an important food matrix that could decrease the bioavailability and oxidative damage of Pb.

Estimation of the bioaccessibility and bioavailability of Fe, Mn, Cu, and Zn in Chinese vegetables using the in vitro digestion/Caco-2 cell model: the influence of gut microbiota

The influence of the human gut microbiota on the bioaccessibility and bioavailability of trace elements in vegetables has barely been studied. An in vitro digestion model combining the physiologically based extraction test (PBET) and the Simulator of Human Intestinal Microbial Ecosystem (SHIME) was applied. Results showed that the gut microbiota increased the bioaccessibility of iron (Fe) in ten test vegetables by 1.3-1.8 times, but reduced the bioaccessibility of manganese (Mn), copper (Cu), and zinc (Zn) in vegetables in the colon phase by 3.7% to 89.6%, 24.8% to 100.0%, and 59.9% to 100.0%, respectively. Using the Caco-2 cell model to simulate the human absorption process, the bioavailable contents and the bioavailability of the trace elements were further determined. Swamp cabbage was the best source of Fe and Cu; spinach and lettuce provided the highest amounts of bioavailable Mn and Zn, respectively. Referring to the daily reference intakes of trace elements, the obtained data provide a scientific basis for both reasonable ingestion of vegetables in diets and diversification of diets.

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.

Investigation of bioaccessibility of Cu, Fe, Mn, and Zn in market vegetables in the colon using PBET combined with SHIME

The in vitro bioaccessibility of trace metals associated with oral ingestion of market vegetables (lettuce, pak choi, cole, and leaf lettuce) of Beijing, China was studied. The physiologically based extraction test (PBET) combined with the Simulator of Human Intestinal Microbial Ecosystem (SHIME) was applied to simulate stomach, small intestine, and colon of human. In the gastro-intestinal phases, the bioaccessibility of Cu, Fe, Mn, and Zn varied within 5.7–75.5%, 17.3–50.4%, 13.3–49.1%, and 19.9–63.7%, respectively. There was no significant difference in the metal bioaccessibility between the gastric and small intestinal phases, except for higher Cu bioaccessibility in the small intestine. Besides, the bioaccessibility of the four trace metals in the colon phase was first ever reported. A significant decline in Cu bioaccessibility (1.8–63.7%) and slight increases in the bioaccessibility of Fe (16.7–56.4%), Mn (21.2–71.6%), and Zn (15.7–69.7%) were revealed, which could mainly be attributed to the effect of colon microbiota. In addition, the estimated daily intakes (EDIs) of Cu, Fe, Mn, and Zn were worked out to be 0.7, 8.8, 2.7, and 4.5 μg kg⁻¹ body weight d⁻¹, based on which the potential influences of these trace metals in vegetables on the health of the local consumers was demonstrated.

Assessment of the effect of cooking on speciation and bioaccessibility/cellular uptake of arsenic in rice, using in vitro digestion and Caco-2 and PSI cells as model

In vitro digestion/Caco-2 or pig small intestinal epithelium cell line (PSI) uptake models were used to study the bioaccessibility and cellular uptake of arsenic (As) in cooked white rice and brown rice. The arsenite(AsIII), was the predominant species in cooked rice and in its bioaccessible fractions. The percentage of total As bioaccessibility in white rice (75%) was slightly higher (p=0.061) than that in brown rice(66%). However, there was no difference in the inorganic As (iAs) bioaccessibility between white rice (95%) and brown rice (96%). In Caco-2 cell monolayer, total As retention was 7-31%, transport was 4-25%, and uptake (sum of retention and transport) was 16-38%. In PSI cell model, the retention, transport, and uptake of tAs were 10-28%, 14-31%, and 29-50%, respectively. In both cells, the cellular uptake of tAs in brown rice was 1.4-1.5 folds lower (p<0.05) than that of white rice. These results indicate that the cellular uptake of As can be affected by nutritional compositions. These in vitro screening methods can serve as preliminary screens to predict the relative impact in rice matrix having different As species and processing conditions, although more research efforts should be applied to validating the existing in vitro methods.

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.

Biomimetic Gastrointestinal Tract Functions for Metal Absorption Assessment in Edible Plants: Comparison to In Vivo Absorption

A biomimetic gastrointestinal tract, including in vitro digestion and biomimetic biomembrane extraction, has been proposed for absorption assessment of metals from edible plants. However, its validity is still unknown. Herein, two species of edible plants, Anoectochilus roxburghii and Radix astragali, were selected and digested in a bionic mouth, stomach, and intestine, and then trace metals (Cr, Mn, Fe, Ni, Cu, Zn, Se, Sr, As, and Pb) were transformed to their final metal species. To check model predictability, in vitro and in vivo metal absorption were imitated and tested by monolayer liposome extraction and rat stomach or single-pass duodenal intestine, respectively. A strong correlation was established between in vivo and in vitro metal absorption ratios, with 0.89 > R² > 0.66, and a significant relationship (p < 0.05) was exhibited for stomach, intestine, two plant species, and 10 metal species. Our biomimetic system could be used as low-cost alternatives to animal and clinical studies for multi-metal absorption.

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.

The transepithelial transport mechanism of polybrominated diphenyl ethers in human intestine determined using a Caco-2 cell monolayer

Oral ingestion plays an important role in human exposure to polybrominated diphenyl ethers (PBDEs). The uptake of PBDEs primarily occurs in the small intestine. The aim of the present study is to investigate the transepithelial transport characteristics and mechanisms of PBDEs in the small intestine using a Caco-2 cell monolayer model. The apparent permeability coefficients of PBDEs indicated that tri- to hepta-BDEs were poorly absorbed compounds. A linear increase in transepithelial transport was observed with various concentrations of PBDEs, which suggested that passive diffusion dominated their transport at the concentration range tested. In addition, the pseudo-first-order kinetics equation can be applied to the transepithelial transport of PBDEs. The rate-determining step in transepithelial transport of PBDEs was trans-cell transport including the trans-pore process. The significantly lower transepithelial transport rates at low temperature for bidirectional transepithelial transport suggested that an energy-dependent transport mechanism was involved. The efflux transporters (P-glycoprotein, multidrug resistance-associated protein, and breast cancer resistance protein) and influx transporters (organic cation transporters) participated in the transepithelial transport of PBDEs. In addition, the transepithelial transport of PBDEs was pH sensitive; however, more information is required to understand the influence of pH.

In vitro study of soil arsenic release by human gut microbiota and its intestinal absorption by Caco-2 cells

Arsenic (As) speciation is essential in assessing health risks from As-contaminated soil. Release of soil-bound arsenic, As transformation by human gut microbiota, and the subsequent intestinal absorption of soil As metabolites were evaluated. A colon microbial community in a dynamic human gut model and the intestinal epithelial cell line Caco-2 were cultured. Arsenic speciation analysis and absorption of different As species were undertaken. In this study, soil As release (3.7-581.2 mg kg^-1) was observed in the colon. Arsenic in the colon digests was transformed more quickly than that in the soil solid phase. X-ray absorption near-edge spectroscopy (XANES) analysis showed that 44.2-97.6% of arsenite [As(III)] generated due to arsenate [As(V)] reduction was in the soil solid phase after the colon phase. We observed a high degree of cellular absorption of soil As metabolites, exhibiting that the intestinal absorption of monomethylarsonic acid and As(III) (33.6% and 30.2% resp.) was slightly higher than that of dimethylarsinic acid and As(V) (25.1% and 21.7% resp.). Our findings demonstrate that human gut microbiota can directly release soil-bound arsenic, particularly As-bearing amorphous Fe/Al-oxides. Determining As transformation and intestinal absorption simultaneously will result in an accurate risk assessment of human health with soil As exposures.

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.

Comparison of in vitro digestion model with in vivo relative bioavailability of BDE-209 in indoor dust and combination of in vitro digestion/Caco-2 cell model to estimate the daily intake of BDE-209 via indoor dust

There is limited information on the BDE-209 relative bioavailability (RBA) of indoor dust and the absorption of BDE-209 after in vitro digestion was seldom studied. In the present study, BDE-209 RBA in 6 household dust samples measured using an in vivo mouse model was compared to BDE-209 bioaccessibility determined using physiologically based extraction test (PBET) and solubility bioaccessibility research consortium method (SBRC) assays. BDE-209 RBA obtained ranged from 45.9 ± 16.1 to 96.0 ± 17.4% and exhibited a significant relationship with PBET gastric phase (r² = 0.578, p = 0.080), small intestinal phase (r² = 0.728, p = 0.031) and total BDE-209 bioaccessibility (r² = 0.728, p = 0.031), which indicated PBET assay can serve as a surrogate to predict BDE-209 RBA to refine human health exposure. In addition, the absorption of BDE-209 by Caco-2 cell line was assessed. With the consideration of the corresponding bioaccessibility and absorption of BDE-209 by Caco-2 cell line, the human daily intake of BDE-209 via dust ingestion for adults and children was much lower than that estimated by total concentration.

The bioaccessibility of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in cooked plant and animal origin foods

In this study, we compared the effect of boiling and frying food preparation methods in determining the bioaccessibility of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in rice, cabbage, milk powder, eggs, beef, and fresh water fish. We then used these data to calculate a toxic equivalent (TEQ) for risk assessment and compared it to published values that did not account for bioaccessibility. When the foods were prepared by boiling, the mean bioaccessibility (%) in rice (PCBs: 16.5±1.0, PCDD/Fs: 4.9±0.3) and cabbage (PCBs: 4.2±0.9, PCDD/Fs: 1.9±0.7) were lower than in animal origin foods (beef, PCBs: 49.0±3.3, PCDD/Fs: 7.8±0.9; egg, PCBs: 29.7±3.1, PCDD/Fs: 8.6±1.3; fish, PCBs: 26.9±2.5, PCDD/Fs: 7.9±1.3; milk powder, PCBs: 72.3±1.6, PCDD/Fs: 28.4±1.2). When fried in cooking oil, the bioaccessibilities of all analytes in all foods increased, but the increase in plant based foods (rice, PCBs: 3.4×, PCDD/Fs: 3.6×; cabbage, PCBs: 10.3×, PCDD/Fs: 7.9×) was greater than that of animal origin foods (beef, PCBs: 1.6×, PCDD/Fs: 3.4×; egg, PCBs: 2.1×, PCDD/Fs: 1.8×; fish, PCBs: 2.8, PCDD/Fs: 3.2×). Comparison of PCBs/PCDD/Fs bioaccessibility in rice and cabbage showed that bioaccessibility was greater in the low fat, high carbohydrate/protein content food (rice) than in the low carbohydrate/protein, low fat content food (cabbage), regardless of the method used to prepare the food. Adjusting for bioaccessibility reduced the gross estimated daily intake (EDI) of 112pgWHO-TEQ/day, by 88% and 63% respectively for foods prepared by boiling and frying. Our results indicate that: 1) The method used for cooking is an important determinant of PCBs/PCDD/Fs bioaccessibility, especially for plant origin foods, 2) there might be a joint fat, carbohydrate and protein effect that influences the bioaccessibilities of PCBs/PCDD/Fs in foods, and 3) use of bioaccessibility estimates would reduce the uncertainty in TEQ calculations.

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.

Bioaccessibility of heavy metals in vegetables and its association with the physicochemical characteristics

The bioaccessibilites of heavy metals in vegetables grown around a waste-incinerator site were estimated using the physiologically based extraction test (PBET) method, to assess potential health risk to the local consumers. The average gastric and intestinal bioaccessibilities of Cd, Cr, Cu, Ni, and Pb in vegetables varied within 3.2-9.4 and 0.8-5.3 %, 1.4-2.3 and 1.1-1.9 %, 25-46 and 13-26 %, 6.6-30 and 2.6-5.3 %, 11-29 and 7.1-23 %, respectively. Strong negative correlations were found between electrochemical potential (ΔE 0) and bioaccessibility for leaf mustard samples (r (2) = 0.857) and leaf lettuce samples (r (2) = 0.696). In addition, softness index (σp) and electrochemical potential (ΔE 0) exhibited a moderate but not significant relationship with bioaccessibilities on the basis of the multiple regression analysis (0.05 < p < 0.1). The total bioaccessible target hazard quotient (TBTHQ) of the five heavy metals was 2.5, with Pb being the major risk contributor. According to the TBTHQs of each group of vegetables, local consumers are experiencing adverse health effects by consuming most of the vegetables around waste-incinerator site.

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

Metal contamination of urban soils and homegrown vegetables has caused major concern. Some studies showed that cadmium (Cd) was among the most significant hazards in kitchen garden soils and prolonged exposure to this metal could cause deleterious health effects in humans. In general, most risk assessment procedures are based on total concentrations of metals in vegetables. The present study assesses human bioaccessibility of Cd in vegetables cultivated in smelter-impacted kitchen garden soils. Seven vegetables (radish, lettuce, French bean, carrot, leek, tomato, and potato) were considered. Using the UBM protocol (unified BARGE bioaccessibility method), the bioaccessibility of Cd was measured in raw/cooked vegetables. A considerable amount of Cd was mobilized from raw vegetables during the digestion process (on average 85% in the gastric phase and 69% in the gastrointestinal phase), which could be attributed to a high uptake of Cd during the growth of the vegetables. Most Cd is accumulated in the vacuoles of plant cells, except what is absorbed by the cell wall, allowing Cd to be released from plant tissues under moderate conditions. Cooking by the steaming process generally increased the bioaccessibility of Cd in French bean, carrot, and leek. For potato, few or no significant differences of Cd bioaccessibility were observed after the steaming process, while the frying process strongly decreased bioaccessibility in both phases. The estimation of metal bioaccessibility in vegetables is helpful for human health risk assessment.

In Vitro Assessment of Cadmium Bioavailability in Chinese Cabbage Grown on Different Soils and Its Toxic Effects on Human Health

The minimum concentration of cadmium (Cd), by Chinese cabbage grown on Cd contaminated soils that can initiate toxicity in human liver cells using in vitro digestion coupled with Caco-2/HL-7702 cell models was studied. Cadmium bioaccessibility in the gastric phase for yellow soil (YS) cabbage (40.84%) and calcareous soil (CS) cabbage (21.54%) was significantly higher than small intestinal phase with the corresponding values of 21.2% and 11.11%, respectively. Cadmium bioavailability was higher in YS cabbage (5.27%–14.66%) than in CS cabbage (1.12%–9.64%). Cadmium concentrations (>0.74 μg) transported from YS and CS cabbage were able to induce oxidative (MDA, H₂O₂) stress by inhibiting antioxidant (SOD, GPx) enzyme activities in human liver cells (HL-7702). Additionally the study revealed that the ingestion of Cd contaminated Chinese cabbage grown in acidic soil (yellow soil) weakened the antioxidant defense system under all levels of contamination (2, 6, and 9 mg·kg⁻¹) which ultimately escalated the oxidative stress in liver cells; however, in case of CS cabbage, a marked oxidative stress was observed only at 9 mg kg⁻¹ Cd level of soil. Therefore, it is necessary to monitor Cd concentrations in leafy vegetables grown on acidic soils to minimize human health risk.

Childhood lead exposure in an industrial town in China: coupling stable isotope ratios with bioaccessible lead

Fingerprinting based on stable isotopes of lead (Pb) in blood and environmental media helps to identify Pb exposure pathways in children. However, previous studies used stable isotopes of total Pb in media. In this study, a wire rope production town in China (Zhuhang) was selected for investigating the effectiveness of using isotope ratios in bioaccessible Pb to identify childhood Pb exposure pathways. Blood Pb levels of 115 children in Zhuhang were 1.7-20.4 μg dL(-1), averaging 6.1 ± 3.2 μg dL(-1) (mean ± standard deviation), and were ∼1.6 times the national average in China (3.9 ± 1.8 μg dL(-1)). Among different environmental media (housedust, soil, PM10, vegetables, rice, and drinking water), housedust (695 ± 495 mg kg(-1)) and vegetables [0.36 ± 0.40 mg (kg of fresh weight)(-1)] contained elevated Pb concentrations. The isotope ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) of total Pb were the highest in housedust (0.8587 ± 0.0039 and 2.1049 ± 0.0087) but lower than blood Pb ratios (0.8634 ± 0.0027 and 2.1244 ± 0.0061). When using bioaccessible Pb in housedust (0.8639 ± 0.0018 and 2.1171 ± 0.0036), the isotope ratios overlapped with blood Pb ratios, suggesting that incidental ingestion of housedust was the predominant contributor to children's blood Pb. Coupling the stable isotope technique with bioaccessible Pb is more reliable for identifying Pb exposure pathways than total Pb determinations.

Uptake of cadmium by rice grown on contaminated soils and its bioavailability/toxicity in human cell lines (Caco-2/HL-7702)

Cadmium (Cd) enters the food chain from polluted soils via contaminated cereals and vegetables; therefore, an understanding of Cd bioaccessibility, bioavailability, and toxicity in humans through rice grain is needed. This study assessed the Cd bioaccessibility, bioavailability, and toxicity to humans from rice grown on Cd-contaminated soils using an in vitro digestion method combined with a Caco-2/HL-7702 cell model. Cadmium bioaccessibility (18.45-30.41%) and bioavailability (4.04-8.62%) were found to be significantly higher in yellow soil (YS) rice than calcareous soil (CS) rice with the corresponding values of 6.89-11.43 and 1.77-2.25%, respectively. Toxicity assays showed an initial toxicity in YS rice at 6 mg kg(-1) Cd, whereas CS rice did not show any significant change due to low Cd concentrations. The acidic soils of Cd-contaminated areas can contribute to a higher dietary intake of Cd. Therefore, it is imperative to monitor Cd concentration in rice to minimize human health risk.