Factors affecting the bioaccessibility of fluoride from seafood products

Effects of calcium supplements on oral bioavailability of fluoride in soil based on In Vivo and In Vitro methods

Dietary calcium (Ca) intake can alleviate fluoride (F) induced fluorosis to maintain bone health. However, it is unclear whether calcium supplements can reduce the oral bioavailability of F present in contaminated soils. Here we evaluated the effects of Ca supplements on F bioavailability in three soils using an in vitro method (Physiologically Based Extraction Test) and an in vivo mouse model. Seven Ca salts, commonly used in calcium supplements, significantly reduced the F bioaccessibility in the gastric and small intestinal phases. Particularly for Ca phosphate at 150 mg Ca supplementation, F bioaccessibility in the small intestinal phase was reduced from 35.1-38.8% to 0.7-1.9% where soluble F concentrations were less than 1 mg/L. Overall, the eight Ca tablets tested in this study showed greater efficiency at decreasing F solubility. The in vitro bioaccessibility after Ca supplementation was consistent with the relative bioavailability of F. As supported by X-ray photoelectron spectroscopy, a possible mechanism is that freed F can be bound by Ca to form insoluble CaF2 and exchanged with OH groups from Al/Fe hydroxide to strongly adsorb F. These findings provide evidence of Ca supplementation in reducing health risks associated soil F exposure.

Human health risk assessment in aluminium smelting site: Soil fluoride bioaccessibility and relevant mechanism in simulated gastrointestinal tract

Incidental oral ingestion is considered to be an important exposure route for humans to soil contaminants, such as fluoride (F). For 25 soil samples containing 4000 mg F/kg from aluminium smelting site in southwestern China, this study investigated F bioaccessibility in the human gastrointestinal tract in vitro. Fluoride bioaccessibility (2.4-48.8%) in the gastric phase was primarily caused by the dissolution of F-Ca and F-Al compounds (assigned to residual phase), identified by X-ray photoelectron spectroscopy and sequential extraction. Following modification to the small intestinal phase, the variation in F bioaccessibility (2.5-38.8%) should be the result of concurrent processes, including the formation of F complexes and competitive adsorption, and inversely the precipitation of fluorite and surface adsorption of formed F-Al complexes. The colon incubation with human gut microbiota yielded a 1.3-fold increase in F bioaccessibility (3.9-45.7%), probably due to the dissolution of F bound to Fe (hydr)oxides. Bioaccessibility adjustment can reduce hazard quotient of fluoride, and non-carcinogenic risk for children should be noted that soil F intake contributed 21.7% on average, up to 76.6% of oral reference dose. This will result in better understanding of human health risk assessment associated with F exposures.

Fluoride absorption, transportation and tolerance mechanism in Camellia sinensis, and its bioavailability and health risk assessment: a systematic review

Tea is the one of the most popular non-alcoholic caffeinated beverages in the world. Tea is produced from the tea plant (Camellia sinensis (L.) O. Kuntze), which is known to accumulate fluoride. This article systematically analyzes the literature concerning fluoride absorption, transportation and fluoride tolerance mechanisms in tea plants. Fluoride bioavailability and exposure levels in tea infusions are also reviewed. The circulation of fluoride within the tea plantation ecosystems is in a positive equilibrium, with greater amounts of fluoride introduced to tea orchards than removed. Water extractable fluoride and magnesium chloride (MgCl₂ ) extractable fluoride in plantation soil are the main sources of absorption by tea plant root via active trans-membrane transport and anion channels. Most fluoride is readily transported through the xylem as F^- /F-Al complexes to leaf cell walls and vacuole. The findings indicate that tea plants employ cell wall accumulation, vacuole compartmentalization, and F-Al complexes to co-detoxify fluoride and aluminum, a possible tolerance mechanism through which tea tolerates higher levels of fluoride than most plants. Furthermore, dietary and endogenous factors influence fluoride bioavailability and should be considered when exposure levels of fluoride in commercially available dried tea leaves are interpreted. The relevant current challenges and future perspectives are also discussed. © 2020 Society of Chemical Industry.

Human Health Implication of Major and Trace Elements Present in Commercial Crustaceans of a Traditional Seafood Marketing Region, Egypt

The present study focused on the distribution of some major and trace elements (S (as SO₄^2-), Na, K, B, Ca, Mg, F, Li, Al, Fe, Zn, Cu, Mn, Ni, Co, Cd, and Pb) in both flesh (Fl) and total cephalon/exoskeleton (C/E) tissues of selected crustacean species obtained from an Egyptian traditional seafood marketing region. The sequence of studied elements in (Fl) and (C/E) tissues in descending orders was S (as SO₄^2-) > Na > K > B > Mg > Ca > Li > F > Al > Zn > Fe > Cu > Pb > Ni > Mn > Co > Cd, and S (as SO₄^2-) > Na > B > K > Mg > Ca > F > Li > Al > Fe > Cu > Zn > Mn > Pb > Ni > Co > Cd, respectively. Both length-weight relationship and Fulton's condition factor showed the physical and biological statuses of the crustaceans. Ion quotient calculations of the studied tissues pointed to their importance in decreasing hypertension, preeclampsia, and heart disease. Human health risk due to the consumption of the crustacean species was determined using some guideline limits, metal pollution index (MPI), estimated daily intake (EDI), health comparison values (CVs), dietary intake (DRI-ULs), target hazard quotient (THQ), total target hazard quotient (TTHQ), and provisional tolerable weekly intake (%PTWI). MPI values of cephalon/exoskeleton tissues were greater than those of the flesh with ranges between 11.4-24.0 and 4.6-14.3, respectively. Interestingly, the calculations of TTHQ of toddler and adult were lesser than one and not expected to pose any risk concern to human from crustaceans' consumption.

Interactions of food matrix and dietary components on neonicotinoid bioaccessibility in raw fruit and vegetables

Humans are frequently exposed to the residues of various neonicotinoids, highlighting the need to understand human exposure through oral ingestion of contaminated foods. In this study, the effects of different food matrices (tomato, cucumber, and carrot) and their interaction with dietary component additives, including proteins and dietary fiber, was investigated. The results showed that the presence of a food matrix had a significant effect on the bioaccessibility of neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, and thiacloprid) in both the gastric and intestinal environments. Neonicotinoids in tomato presented relatively low bioaccessibility, indicating that the daily intake of the tomato can be regarded as being relatively safer. Moreover, the addition of protein or dietary fiber to fruit and vegetables had a marked influence on neonicotinoid bioaccessibility and the effects varied between the different matrices. In particular, the addition of 2.0% dietary fiber significantly reduced the bioaccessibility (18.38-67.91%). Therefore, we recommend that consuming an increased intake of dietary fiber could improve the safety of fruit and vegetables in daily life. The present results can support the identification of suitable food intake conditions for the significant reduction of pesticide residue levels.

Factors Affecting the Bioaccessibility and Intestinal Transport of Difenoconazole, Hexaconazole, and Spirodiclofen in Human Caco-2 Cells Following in Vitro Digestion

This study examined how gastrointestinal conditions affect pesticide bioaccessibility and intestinal transepithelial transport of pesticides (difenoconazole, hexaconazole, and spirodiclofen) in humans. We used an in vitro model combining human gastric and intestinal digestion, followed with Caco-2 cell model for human intestinal absorption. Bioaccessibility of three tested pesticides ranged from 25.2 to 76.3% and 10.6 to 79.63% in the gastric and intestinal phases, respectively. A marked trend similar to the normal distribution was observed between bioaccessibility and pH, with highest values observed at pH 2.12 in gastric juice. No significant differences were observed with increasing digestion time; however, a significant negative correlation was observed with the solid-liquid (S/L) ratio, following a logarithmic equation. R² ranged from 0.9198 to 0.9848 and 0.9526 to 0.9951 in the simulated gastric and intestinal juices, respectively, suggesting that the S/L ratio is also a major factor affecting bioaccessibility. Moreover, significant dose- and time-response effects were subsequently observed for intestinal membrane permeability of difenoconazole, but not for hexaconazole or spirodiclofen. This is the first study to demonstrate the uptake of pesticides by human intestinal cells, aiding quantification of the likely effects on human health and highlighting the importance of considering bioaccessibility in studies of dietary exposure to pesticide residues.

In-vitro bioaccessibility of five pyrethroids after human ingestion and the corresponding gastrointestinal digestion parameters: A contribution for human exposure assessments

Bioaccessibility is a crucial parameter in assessing the absorption of contaminants during the human digestive process, but few studies have involved the differences in the bioaccessibilities of pesticides. To investigate the mode of using the in vitro bioaccessibility to refine estimates of dietary exposure to pesticide residues, this study measured the bioaccessibilities of five pyrethroids in apples, and then, it modelled physicochemical predictors (gastrointestinal pH, digestive times, and the solid-liquid (S/L) ratio) of the bioaccessibilities of pyrethroids. Apple samples of gastric and intestinal phase digestive juices were obtained from an in vitro simulated digestion model. Our survey of in vitro digestion models found that the bioaccessibilities ranged from 4.42% to 31.22% and 10.58%-35.63% in the gastric and intestinal phases, respectively. A sharp trend similar to a normal distribution was observed between the bioaccessibilities and pH values. The bioaccessibility reached its highest value at a pH of 1.91 in the simulated gastric juice and did not significantly change with an increase of the digestive time. A significant negative correlation occurred between the bioaccessibility and S/L ratio, which followed a logarithmic equation. The correlation coefficients (R²) ranged from 0.9259 to 0.9831 and 0.9077 to 0.9960 in the simulated gastric and intestinal juice, respectively, suggested that both the pH value and S/L ratio were the main factors affecting the bioaccessibility. Furthermore, a combination of the acceptable daily intake (ADI) and bioaccessibility for human exposure assessments indicated the implication that traditional risk assessment using ADI may seriously overestimate the actual risk.

Integrated multi-ISE arrays with improved sensitivity, accuracy and precision

Increasing use of ion-selective electrodes (ISEs) in the biological and environmental fields has generated demand for high-sensitivity ISEs. However, improving the sensitivities of ISEs remains a challenge because of the limit of the Nernstian slope (59.2/n mV). Here, we present a universal ion detection method using an electronic integrated multi-electrode system (EIMES) that bypasses the Nernstian slope limit of 59.2/n mV, thereby enabling substantial enhancement of the sensitivity of ISEs. The results reveal that the response slope is greatly increased from 57.2 to 1711.3 mV, 57.3 to 564.7 mV and 57.7 to 576.2 mV by electronic integrated 30 Cl⁻ electrodes, 10 F⁻ electrodes and 10 glass pH electrodes, respectively. Thus, a tiny change in the ion concentration can be monitored, and correspondingly, the accuracy and precision are substantially improved. The EIMES is suited for all types of potentiometric sensors and may pave the way for monitoring of various ions with high accuracy and precision because of its high sensitivity.

Influence of Physiological Gastrointestinal Parameters on the Bioaccessibility of Mercury and Selenium from Swordfish

Swordfish tend to accumulate mercury (Hg), but they are rich in selenium (Se), an element that can counteract the toxic effects of Hg. The aim of the present study was to evaluate the concentrations and bioaccessibility of Hg and Se in cooked swordfish and to identify the digestion parameters (pH, residence time, and enzyme concentrations) that may influence their bioaccessibility. The Hg concentrations ranged between 0.17 and 2.82 mg/kg wet weight (ww) and the bioaccessibility between 14 and 92%. The range for Se concentrations was narrower (0.29-1.17 mg/kg ww), with a bioaccessibility that was generally greater than that of Hg (59-103%). Most of the solubilization took place in the gastric step, where acidic pH and the increase in the pepsin concentration led to greater bioaccessibility, especially for Hg. In the intestinal stage, the most notable effect was the decrease in the bioaccessibility of Hg in the presence of bile salts.

Ce-Fe-modified zeolite-rich tuff to remove Ba(2+)-like (226)Ra(2+) in presence of As(V) and F(-) from aqueous media as pollutants of drinking water

The sorption behavior of the Ba(2+)-like (226)Ra(2+) in the presence of H2AsO4(-)/HAsO4(2-) and F(-) from aqueous media using Ce-Fe-modified zeolite-rich tuff was investigated in this work. The Na-modified zeolite-rich tuff was also considered for comparison purposes. The zeolite-rich tuff collected from Wyoming (US) was in contact with NaCl and CeCl3-FeCl3 solutions to obtain the Na- and Ce-Fe-modified zeolite-rich tuffs (ZUSNa and ZUSCeFe). These zeolites were characterized by scanning electron microscopy and X-ray diffraction. The BET-specific surface and the points of zero charge were determined as well as the content of Na, Ce and Fe by neutron activation analysis. The textural characteristics and the point of zero charge were changed by the presence of Ce and Fe species in the zeolitic network. A linear model described the Ba(2+)-like (226)Ra(2+) sorption isotherms and the distribution coefficients (Kd) varied with respect to the metallic species present in the zeolitic material. The As(V) oxianionic chemical species and F(-) affected this parameter when the Ba(2+)-like (226)Ra(2+)-As(V)-F(-) solutions were in contact with ZUSCeFe. The H2AsO4(-)/HAsO4(2-) and F(-) were adsorbed by ZUSCeFe in the same amount, independent of the concentration of Ba(2+)-like (226)Ra(2+) in the initial solution.