Unified Bioaccessibility Method Research Articles

Dispersive Solid-phase Microextraction of Lead in Waters and Edible Lettuce and Dill Extracts in the Unified Bioaccessibility Method (UBM) Saliva Solution.

A new thiosemicarbazide-modified, sulfonamide-based poly (styrene) adsorbent (T-CSPS) was prepared starting from the reaction of chlorosulfonated polystyrene and thiosemicarbazide. It was characterized by SEM-EDX, FT-IR, and zeta potential. The T-CSPS was used as an adsorbent for the first time for the dispersive solid-phase microextraction (d-SPµE) and preconcentration of Pb(II) ions from waters and dill and lettuce extracts in the unified bioaccessibility method (UBM) saliva. Lead was then determined using the FAAS. In the first step of optimization, the solution pH was changed from 2 to 8, and pH 4 with a recovery value of 103% ± 5 was selected. Two milliliters of 2mol L-1 HCl was chosen as eluent. Contact times were found to be only 2min. Effects of coexisting ions and sample volume were tested. Under optimal conditions, the preconcentration factor (PF) and the adsorption capacity were 15and 40mgg-1. The RSD% was 2.2% and 3.1% for intra-day and inter-day precision, respectively. The LOD and LOQ were found to be 5.1µg L-1 and 16.9µg L-1, respectively. The accuracy of the d-SPµE was checked by TMDA-70.2 Lake water and BCR-482 Lichen-certified reference materials and also applying d-SPµE to spiked waters and lettuce and dill extracts in UBM saliva.

Bioaccessibility of Fifteen Elements from Dried Fruits by the BARGE (Bioaccessibility Research Group of Europe) Unified Bioaccessibility Method (UBM) and Multivariate Statistical Analysis

The BARGE (Bioaccessibility Research Group of Europe) unified bioaccessibility method (UBM) was applied to assess the bioaccessibility of essential and toxic elements (B, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, and Cd) in 11 dried fruit samples, two certified reference materials, and British Geological Survey guidance material (BGS) 102. The total, UBM gastric, and gastro-intestinal (GI) phase concentrations of elements were determined by inductively coupled plasma—mass spectrometry. The accuracy of the methods was verified using BGS 102 for the BARGE UBM and SRM 1573a for total concentrations. The order for mean bioaccessible fractions (BF %) in gastric phase for the dried fruit was Rb (101) > Sr (79) > Mn (59) > Cr (46) > Ni (37) > Fe (36) = Zn (36) > Cu (33) > Co (32) > Al (24) > V (22) > B (19) > Cd (18) > Mo (8) > As (6). Total and bioaccessible concentrations for Mn, Rb, and Sr are significantly and positively correlated with each other. Multivariate statistical analysis was used to classify bioaccessible elements and samples in gastric and GI phases.

Speciation of chromium in water samples and lettuce extracts in the unified bioaccessibility method (UBM) saliva solution by vortex assisted-dispersive solid phase microextraction

In this study, a new sulfonamide based polymeric adsorbent (5ATT-CSPS) was prepared with reaction between 5-Amino-1,3,4-thiadiazole-2-thiol and chlorosulfonated polystyrene resin and characterized by FT-IR, FESEM-EDX, zeta potential. It was used for the first time as an adsorbent for speciation of chromium in various water samples and lettuce extracts in UBM saliva by dispersive solid phase micro extraction (d-SPµE). The total chromium concentration was determined by F AAS. The parameters affecting the recovery of Cr(III) such as pH, contact times, elution conditions, sample volume, co-existing ions and adsorption capacity were optimized. The adsorbent demonstrated a good performance for adsorption of Cr(III) (R%≥95). It was quantitatively adsorbed in the range of pH 2.0–4.0 whereas Cr(VI) was not adsorbed in the pH range of 2.0-8.0. Therefore Cr(VI) concentration was calculated indirectly. The elution was achieved by 5 mL of 2 mol L-1 HNO3. Adsorption and elution contact times of the adsorbent were 3 min and 2 min, respectively. The preconcentration factor of the method was found to be 8. Considering optimal conditions, limit of detection was found to be 2.9 µg L-1, and precision of the method (as RSD%) was found to be ≤4.3%. The adsorption capacity of the 5ATT-CSPS for Cr(III) was 25 mg g−1.The accuracy of this method was verified by analyzing TMDA-70 certified reference material and by recovery studies in spiked water samples and lettuce extracts in the unified bioaccessibility method (UBM) saliva.

Assessment of the bioaccessibility of PAHs and other hazardous compounds present in recycled tire rubber employed in synthetic football fields.

Recycled tire crumb rubber (RTCR) surfaces contain harmful and carcinogenic substances, which can be ingested by the users of these facilities, mainly athletes and children. In this work, the potential in-vitro oral bioaccessibility of eighteen polycyclic aromatic hydrocarbons (PAHs) from RTCR employed as infill in synthetic football fields was studied in human synthetic body fluids (saliva, gastric, duodenal and bile), prepared according the Unified Bioaccessibility Method. Solid-phase extraction (SPE) using commercial sorbents and a new green material based on cork (cork industry by-product) were used to isolate the bioaccessible PAHs before gas chromatography-tandem mass spectrometry analysis. The method was optimized and validated attending the analytical figures of merit. The feasibility of cork biosorbent for the extraction of the compounds was demonstrated, as well as the suitability of the UBM method to perform the digestion with good precision. The application to real samples collected from football fields demonstrated the presence of 17 of the 18 target PAHs in the biofluids. Most volatile PAHs such as NAP, ACY, ACE, FLU, PHN and ANC, achieved the highest bioaccessibility percentage levels. The carcinogenic B[a]P was detected in 75 % of the samples at concentrations up to 2.5 ng g-1 (bioaccessible fraction). Children exposure assessment was carried out to identify potential risk. Other hazardous and environmentally problematic compounds such as N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone), recently related with the dead of coho salmon, and hexamethoxymethylmelamine (HMMM), among others, were also detected. This is the first study in which the bioaccesibility from real crumb rubber samples of 15 out of the 16 PAHs considered as priority pollutants by the United States Environmental Protection Agency (EPA) and the presence of 6PPD-quinone and HMMM in the bioaccessible fractions is reported.

Mineral and Trace Elements in Nutritious Flours: Total Contents, In Vitro Bioaccessibility and Contribution to Dietary Intake.

The consumption of fruits, vegetables, and cereals in the form of flour has been an alternative for the intake of nutrients, currently seen in a society that seeks a healthier diet. Thus, the assessment of total contents and bioaccessibility is important to better understand the actual intake of nutrients or contaminants present in foods. The objective of this study was to determine the total content and estimate the bioaccessible fraction of Cu, Fe, and Zn in nutritious flours by inductively coupled plasma optical emission spectrometry (ICP OES) after microwave acid digestion. Bioaccessibility was assessed using the in vitro method, taking into account the entire gastrointestinal tract (Unified Bioaccessibility Method (UBM)). The following concentration ranges, in μg g-1, were found: Ca (341-6275), K (2984-13,953), P (476-6110), Na (< 0.39-2995), Fe (1.4-167), Cu (< 0.01-59.6), and Zn (< 0.07-30.3). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed a tendency towards the formation of three groups. The bioaccessible fractions for Cu, Fe, and Zn were considered low, ranging from 0.96 to 40% in the gastrointestinal phase and from 4.1 to 100% in the gastric phase.

Effect of losartan potassium, metformin hydrochloride, and simvastatin on in vitro bioaccessibility of Cu, Fe, Mn, and Zn in oat flour from Brazil

BackgroundThe simultaneous administration of drugs with food can compromise the bioaccessibility and absorption of nutrients. The objective of this study was to evaluate the influence of the use of losartan potassium (LP), metformin hydrochloride (MH), and simvastatin (S) on the in vitro bioaccessibility of micronutrients (Cu, Fe, Mn, and Zn) in oat flour from Bahia, Brazil. MethodsThe experimental procedure consisted of the in vitro extraction of the bioaccessible fraction of Cu, Fe, Mn, and Zn in oat flour—with and without LP (50 mg), MH (500 mg), and S (20 mg)—using the unified bioaccessibility method (UBM), simulating the conditions of the gastrointestinal tract. For decomposition of the samples (oat flour and residue), a digester block with a closed system was used. To determine the total content (flour and residual fraction) and bioaccessible micronutrients, inductively coupled plasma optical emission spectrometry (ICP OES) was used. ResultsThe bioaccessible contents (µg g-1) without the addition of drugs were: Cu 5.86 ± 0.21, Fe 32.80 ± 1.32, Mn 87.90 ± 1.90, and Zn 30.33 ± 2.05, with bioaccessibility ranging from 31.5 % for Fe to 99 % for Mn. The in vitro extraction method was validated by mass balance with recovery values from 89.78 % for Cu to 101.94 % for Mn. The range of bioaccessible contents (µg g-1) were: Cu (<4.14), Fe (32.10 ± 0.20–54.10 ± 2.03), Mn (81.40 ± 0.93–93.22 ± 0.80), and Zn (<10.80–29.11 ± 2.20). The estimation of the bioaccessibility of Cu, Mn, and Zn in oat flour were compromised in the presence of LP, MH, and S (p < 0.05). ConclusionChemical interactions can occur between drugs and micronutrients. Taken together, our results highlight that LP, MH, and S can interfere with the bioaccessibility of Cu, Fe, Mn, and Zn in oat flour in patients who use these drugs, suggesting its rational use in further investigations.

Calcined Oyster Shell-Humic Complex as Soil Amendment to Remediate Cd- and As-Contaminated Soil

Soil acidification in the subtropical region reduces soil productivity and increases the bioavailability of heavy metal(loid)s in soil. Here 800 °C-calcined oyster shell and leonardite-derived humic substance were combined to form a Ca-humic complex to remediate an acidic soil contaminated by cadmium (Cd) and arsenic (As) for safe vegetable production. In the pot experiment, the complex was added to soil as a soil amendment at 0%, 0.5%, 1.0%, 2.0%, and 5.0%. A 2.0% dose reduced Cd and As contents of the vegetable bok choy by 98% and 71%, respectively, alleviating the human health risk of Cd and As from the food chain. The unified bio-accessibility method (UBM) was followed to estimate the bio-accessibility of Cd and As. The complex at a 2.0% dose lowered soil Cd and As bio-accessibility in simulated gastric (BioG) and intestine (BioGI) compartments by 15.5% for BioG-Cd, 39.2% for BioGI-Cd, 28.8% for BioG-As, and 45.0% for BioGI-As, thus reducing the human health risk of Cd and As from soil ingestion. The use of oyster shell waste to produce Ca-humic complex as a soil amendment is a practical means of achieving dual agronomic and environmental benefits, from the remediation of soil contamination to the safe disposal of shell waste.

Mercury bioaccessibility in fish and seafood: Effect of method, cooking and trophic level on consumption risk assessment

The bioaccessible Hg fraction in fish and seafood commonly present in the Mediterranean diet was assessed through three distinct in vitro extraction schemes. Each extraction method provided different results, highlighting the lack of a universal methodology to estimate mercury (Hg) bioaccessibility in those matrices. Bioaccessible Hg fractions ranged from 10 to nearly 90% of total mercury (T-Hg) and increased in predator species (Swordfish - Xiphias gladius, Blue Shark - Prionace glauca and Tuna - Thunnus sp.). Among the three extractions tested, the Unified Bioaccessibility Method (UBM) provided the highest estimation of Hg bioaccessibility for consumers. The tested cooking procedures (frying, grilling and steaming) considerably reduced the bioaccessible fraction. Results indicate that bioaccessible Hg found in ingested fish and seafood is far below the levels set by the current safety risk assessment legislation. These findings highlight the importance of integrating bioaccessibility measurements in food safety legislation.

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.

Assessment of DDT and its Metabolites Bioaccessibility in Historically Contaminated Soils Using Unfed and Fed in Vitro Methods.

Bioaccessibility of hydrophobic organic contaminants (HOCs) from unintentional ingestion of soil is increasingly assessed with in vitro gastrointestinal models incorporating a sorption sink. In this study, the bioaccessibility of DDTs in contaminated soils (n = 11) was determined using "unfed" unified bioaccessibility method (UBM) and fed organic estimation human simulation test (FOREhST) with/without Tenax as an absorbent. By adding Tenax, the bioaccessibility of DDTs determined using UBM was significantly increased from 4.9-30.6% to 31.6-86.0%. In contrast, the bioaccessibility of DDTs determined using FOREhST without/with Tenax were similar with values of 20.0-60.9% vs 31.5-47.6%, implying that the influence of food components on the absorption efficiency of the sink should not be overlooked. Much high fraction of DDTs (bioaccessibility: 11.7-24.8%) remained in FOREhST supernatant after Tenax collection, suggesting that prediction of bioavailability through bioaccessibility obtained by absorbent needs to be treated with caution when bioaccessibility is determined using a "fed state" in vitro method.

Child risk assessment of selected metal(loid)s from urban soils using in vitro UBM procedure

In city agglomerations significant pollution results from fossil fuel combustion from heat and power plants, transportation, and boilers in households. In this context, pollution from recalcitrant, environmentally accumulative metal(loid)s can be a critical human health risk. In day-care centers, playgrounds, kindergartens, schools, and sport facility areas children may ingest significant quantities of potentially polluted soil and dust, increasing incidence of health disorders or diseases. The objective of this study was to assess the oral bioaccessibility and human health risk of As, Cd, Pb, Cr, Ni, Cu, and Zn from potentially polluted urban topsoils by applying gastrointestinal Unified Bioaccessibility Method (UBM) protocol. Total content of studied elements was relatively low and none of studied elements exceeded Polish legal limits for urban soils. According to the Enrichment Factor (EF), studied sites were characterized from minimal to significant degrees of soil pollution by analyzed metal(loid)s in the order: Pb > Zn > Cu > Cd > As > Ni > Cr. Concentrations of the metal(loid)s in bioaccessible phases were varied, and higher for gastric than gastrointestinal bioaccessibility. Metal(loid) bioaccessibility in soils of Bydgoszcz was highly correlated with total concentration. Almost no correlation was found between concentration of these phases and parameters like soil pH, texture, CaCO3, TOC, or CEC. A relationship did exist with landform where the lower positions had greater concentrations. These locations are those with the highest traffic density and operation of old coal heating systems leading to the highest deposition of airborne contaminants. Higher landscape positions are favored for new facilities in newer residential districts. Exposure and health risk from soil ingestion given normal ingestion scenario at any site investigated was very low. Non-carcinogenic and carcinogenic risk was identified only for soil pica behavior. Soil pica ingestion scenario might be considered for children with lapses of adult.

Oral and inhalation bioaccessibility of potentially toxic elements in household dust from former Hg mining district, Idrija, Slovenia.

One of the main sources of potential chronic exposure to potentially toxic elements is household dust, especially in an environment with known point sources of PTE pollution. The literature review clearly shows that the total concentrations of an element in the environment do not provide information to predict its bioavailability. The aim of the present study was to evaluate the oral and inhalation bioaccessibility of PTE present in household dust in the small town of Idrija, the site of the former mercury mine. Unified bioaccessibility method was used to assess oral bioaccessibility of PTE in the stomach and intestine, while inhalation bioaccessibility was assessed by extraction of household dust samples with two synthetic extraction solutions-Gamble's solution (GS) and artificial lysosomal fluid (ALF). A low bioaccessibility of mercury was observed in all synthetic solutions (less than 3%). The highest bioaccessibility of PTE was observed in ALF solution, especially for Zn, Pb and Cd. Only a slightly lower bioaccessibility of these three elements was also observed in the stomach, while the bioaccessibility of other elements in the gastric phase was less than 40%. In general, the bioaccessibility of all elements decreased in the intestine. With the exception of Cr, the lowest bioaccessibility of the elements was observed in GS. Daily ingestion and inhalation doses of PTE from household dust were calculated and their values were below the available recommended or tolerable daily intakes of PTE from food according to the European Food Safety Authority.

An automatic flow-through system for exploration of the human bioaccessibility of endocrine disrupting compounds from microplastics.

This article reports on the first attempt towards investigating the leaching rates in the human gastrointestinal (GI) tract of plastic-borne contaminants that can be ingested accidentally using physiologically relevant body fluids. Oral bioaccessibility under fasted and fed states was determined in dynamic mode exploiting an automatic flow setup. The flow system is able to mimic the fast uptake of the released species from the polymeric matrix by absorption in the human digestive system by the in-line removal of the leached species. Complex GI extractants based on the Unified Bioaccessibility Method (UBM, fasted state) and Versantvoort test (fed-state) were brought through a microplastic-loaded metal microcolumn for semi-continuous leaching of plasticizers (phthalic acid ester congeners) and monomer/antioxidant species (bisphenol A, BPA) followed by in-line solid-phase extraction and clean-up of GI extracts prior to liquid chromatography analysis. The temporal extraction profiles were fitted to a first-order kinetic model for the estimation of maximum bioaccessibility pools and apparent leaching rates. Among all studied contaminants, only BPA, dimethylphthalate and diethylphthalate were appreciably released under dynamic GI conditions from high-density polyethylene pellets (average size of 110 μm), with average bioaccessibility values spanning from 51 to 84% and 48 to 87% for UBM and Versantvoort methods, respectively. No statistically significant differences in oral bioaccessibility pools were found under fed- and fasted-state dynamic extractions. The apparent kinetic constants under the fed state were greater by ≥30% as a consequence of the effect of the larger amounts of bile salts and digestive enzymes in the Versantvoort test on the leaching rates. The estimated average daily intake, in which bioaccessibility data are contemplated, indicated that plastic materials exceeding 0.3% (w/w) BPA might pose real risks to human health.

Microscale extraction versus conventional approaches for handling gastrointestinal extracts in oral bioaccessibility assays of endocrine disrupting compounds from microplastic contaminated beach sand.

The unified bioaccessibility method (UBM) was harnessed to assess invitro oral bioaccessibility pools of dialkyl phthalate congeners (with methyl, -ethyl, -butylbenzyl, -n-butyl, -2-ethylhexyl, and -n-octyl moieties) and bisphenol A at the 17μgg-1 level in beach sand contaminated with polyethylene microplastics. A variety of sample preparation approaches prior to the analysis of the UBM gastrointestinal extracts, including traditional methods (protein precipitation, liquid-liquid extraction, and solid-phase extraction) and dispersive liquid-liquid microextraction (DLLME) were comprehensively evaluated for clean-up and analyte enrichment. DLLME was chosen among all tested approaches on account of the high extraction efficiency (73-95%, excluding bis(2-ethylhexyl)phthalate and di-n-octyl phthalate), high sample throughput (∼7min per set of samples), and environmental friendliness as demonstrated by the analytical eco-scale score of 83, and the green analytical procedure index pictogram with green/yellow labeling. The release of the less hydrophobic plastic-laden compounds (dimethyl phthalate, diethyl phthalate and bisphenol A) from the contaminated sample into the body fluids was significant, with bioaccessibility values ranging from 30 to 70%, and from 43 to 74% in gastric and gastrointestinal fluids, respectively, and with relative standard deviation<17% in all cases. The majority of the compounds were leached during gastric digestion, likely as the combined action of the low pH and the gastric enzymes. The risk exposure analysis revealed that accumulation/concentration in the body fluids is potentially relevant for dimethyl phthalate, diethyl phthalate and bisphenol A, with relative accumulation ratios ranging from 1.1±0.1 to 2.6±0.4. The average daily intake values for the suite of compounds, corrected with the bioaccessibility fraction, ranged from 60 to 430ngkg of body weight-1·day-1, in all cases, far below the tolerable daily intakes, thus indicating the lack of children health risk by ingestion of microplastic-laden sand with elevated concentrations of plasticizers.

Selenium bioaccessibility in native seleniferous soil and associated plants: Comparison between in vitro assays and chemical extraction methods

Selenium (Se) bioaccessibility in soil and crops from seleniferous areas is closely relevant to Se intake risks of local residents. The current in vitro digestion methods used for Se bioaccessibility evaluation are single and inconsistent, and most of them are only for food and neglect soil. In this study, 14 Se-contaminated soils and their corresponding crops in Naore Village (seleniferous area) were used as the research objects. Four in vitro digestion assays, including Solubility Bioaccessibility Research Consortium method (SBRC), physiologically-based extraction test (PBET), in vitro gastrointestinal method (IVG), and Unified Bioaccessibility Method (UBM) were used to determine the bioaccessible Se concentration in soil and edible parts of crops. Results showed that the Se in natural seleniferous soil mainly existed in relatively stable forms, i.e., residual and Fe-Mn oxide-bound Se (average of 80%). Only 10.6% of the total Se was distributed in water-soluble and exchangeable Se fractions. The Se content in crops was significantly positively correlated with the organic-bound and phosphate-extractable Se contents in the corresponding soil (p < 0.05). The organic-bound Se was clearly a potentially bioavailable Se source in soil. The Se bioaccessibility in soil and crops measured using the four in vitro methods in gastric/intestinal digestions were in the same order, which was PBET > UBM > SBRC > IVG. Similar to the absorption and utilization of soil Se fractions by crops, the water-soluble, organic-bound and exchangeable Se in soil were the main contributors of bioaccessible Se in the digestive juices in various in vitro methods. Furthermore, the bioaccessible Se in crops and soil measured via PBET method demonstrated the most significant correlation between the total Se in crops and the phosphate-extractable Se in soil. Therefore, the PBET method was the optimum in vitro method for the evaluation of Se bioaccessibility in crops and soil.

In vitro bioaccessibility of metals from tape tea – A low-cost emerging drug

BackgroundAn in vitro physiologically relevant test based on the standard Unified Bioaccessibility Method (UBM) combined with inductively coupled plasma mass spectrometry was performed in this study to ascertain the elemental bioaccessibility pools of tape tea as emerging low-cost abuse drug under fasted conditions. MethodsElemental quantification in tape tea and body fluid extracts was performed by an inductively coupled plasma quadrupole mass spectrometer - ICP-MS, and for sample preparation of the bioaccessibility extracts prior to ICP-MS analysis, a microwave-assisted acid decomposition was applied by using a microwave oven. The Unified Bioaccessibility Method (UBM) was considered for investigation of elemental bioaccessibility in tape tea, required a full set of organic compounds, salts, and enzymes. ResultsConsidering total element evaluation through ICP-MS, Co, Ni, Mn, and Zn are found at the highest concentrations in the sample, namely 415 ± 36, 202 ± 55, 1389 ± 225 and 2397 ± 197 μg L−1, respectively. Regarding the oral bioaccessibility test, after both gastric and gastrointestinal extractions Co, Ni, and Mn are fully bioaccessible while for Zn the bioaccessibility is ca. 66 %. ConclusionAccording to the first results in the literature proposed for these samples, the bioaccessibility results indicate an increment in day-to-day total element concentration and depending on the concentration of each element that an individual consumes in its usual diet, the total concentration can exceed the TDI. There are several possible toxic effects caused by the excess of Co, Ni and Mn, which might be expected by their high total concentrations.

A critical evaluation of the use and ‘misuse’ of As and Pb bioaccessibility data in human health risk assessments

With the now widescale reporting of oral bioaccessibility data at contaminated sites, following our investigation of three sites (one public open space and two residential) for As and Pb contamination, a critical evaluation of the application and utility of such bioaccessibility testing was undertaken to better inform future use. Mean As and Pb soil levels across the sites varied between 12.5 and 24,900 mg/kg and 149–5930 mg/kg, respectively. Using the Unified Bioaccessibility Method (UBM) for in vitro bioaccessibility testing the highest bioaccessible concentrations were identified in the gastric phase. At site 1, a residential urban garden site the maximum bioaccessible As was 50.2% while the maximum bioaccessible Pb was 64.8%; similarly in site 2, also a residential urban garden site the maximum bioaccessible As was 38.72% while the maximum bioaccessible Pb was 66.0%. However, at site 3, a public open space site, the maximum bioaccessible As was 29.7% while the maximum bioaccessible Pb was 38.4%. Using the appropriate soil screening values and recommended statistical testing, we highlight that the use of bioaccessibility testing was unnecessary at sites 1 and 2 (residential urban garden sites), while at site 3 the value of oral bioaccessibility testing is highlighted as part of a ‘lines of evidence approach’ to support the site's specific risk assessment. We need to move away from the uncritical, blanket application of oral bioacessibility testing and strategically target where the results of these data add real value to site determination.

Evaluation of single-extraction methods to estimate the oral bioaccessibility of metal(loid)s in soils

Incidental ingestion of polluted soil particles exposes the population to toxic metal(loid)s. To refine the methods of exposure and risk assessment, it is relevant to use bioaccessible concentrations of metal(loid)s determined via in vitro digestion methods. However, some validated methods are complex and costly, involving high technical skills and numerous reagents. The objective of the present study was to evaluate the suitability of four simple chemical extractions to mimic the bioaccessible fraction of As, Cd, and Pb in the gastric (G) and gastrointestinal (GI) phases obtained using the validated UBM (unified bioaccessibility method) test. Acetic acid (0.11 M), citric acid (0.11 M), EDTA (0.16 M), and hydrochloric acid (HCl, 0.65%) were separately tested in 201 soil samples with a wide range of physicochemical parameters and metal(loid)s concentrations. Significant linear relationships were observed with HCl, EDTA, and to a lesser extent with citric acid. For the cheaper HCl method, correlations with the UBM ranged from 0.91 to 0.99 for the G phase and from 0.72 to 0.97 for the GI phase. This test can be used at least as a first-tier screening to assess the oral bioaccessibility of As, Cd, and Pb.

Stability of Arsenic Species During Bioaccessibility Assessment Using the In Vitro UBM and HPLC-ICP-MS Detection

The stability of four major arsenic (As) species during application of the BARGE (Bioaccessibility Research Group of Europe) unified bioaccessibility method (UBM) has been assessed. The concentrations of As species in the UBM gastric and gastro-intestinal (gastric + intestinal) phases were determined using HPLC-ICP-MS whilst the total As content in the samples was determined using ICP-MS alone. The arsenic species studied were arsenite As(III), arsenate As(V), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA). These species were separated in 10min using an anion exchange column (Hamilton PRP-X100) with a mobile phase containing 20mmolL-1 NH4H2PO4/1% methanol (pH 6.0). The recoveries of arsenic species spiked into the gastric and gastro-intestinal fluids were in the range 90-108%. No interconversion between As species was observed as a result of applying the BARGE UBM, which is a particularly important finding for the reliability of As(III) measurements. The accuracy of the BARGE UBM for in vitro extractable As(V) was verified using British Geological Survey (BGS) guidance material 102 (an ironstone soil). For a commercial rice sample, the bioaccessibility sequence of As was DMA > As(III) > As(V) for the gastric phase and As(III) > DMA > As(V) for the gastro-intestinal phase.

In vitro assessment of oral and respiratory bioaccesibility of trace elements of environmental concern in Greek fly ashes: Assessing health risk via ingestion and inhalation

Fly ash engender significant environmental and human health problems due to enhanced contents of potentially harmful trace elements (TrElems). This study aims to evaluate human exposure to TrElems via a combined ingestion (i.e., oral bioaccessibility) and inhalation (i.e., respiratory bioaccessibility) pathway. Five fly ash samples were collected from power plants operating in the main lignite basins of Greece, while the ingestible (<250 μm) and inhalable (<10 μm) particle size fractions were utilized. The Unified Bioaccessibility Method (UBM) was utilized to assess the oral bioaccessibility, while the respiratory bioaccessible fractions were extracted using the Artificial Lysosomal Fluid (ALF). All studied FAs exhibited significantly higher contents in Ba, Cr, Ni, V and Zn. Cadmium was presented relative enriched in the finer size fraction (<10 μm), while Ba, Co, Cr, Cu, Mn, Ni and V were depleted. The UBM-extractable concentrations fluctuated greatly among the studied FAs, while notably lower bioaccessible contents were recorded in the gastrointestinal phase. On the other hand, ALF-extractable concentrations were surprisingly higher than the corresponding UBM-extractable ones in the gastric phase. The oral bioaccessibility of the studied TrElems ranged from 12.5 to 100%, while respiratory bioaccessibility presented high values exceeding 45% on average. A significant effect of fly ash type on human bioaccessibility was revealed. Thus, high-Ca FAs exhibited significantly higher bioaccessibility of the studied TrElems via ingestion, while a relatively higher bioaccessibility via inhalation was observed for high-Si FAs. Regarding non-carcinogenic health risk via ingestion and inhalation, Cr and Co exhibited the highest HQing and HQinh values, however there were significantly lower than safe level (HQ < 1). On the contrary, Cr was the dominant contributor to carcinogenic risk with CR values being well above threshold or even tolerable risk levels.