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Bioaccessibility and bioavailability of potentially toxic elements in healing mud

Healing muds (peloides) and treatments with them are known for centuries. Origin of muds can be various as well as their geochemical characteristics and from that prospective they are rarely well documented (Williams and Haydel, 2010). In treatments individuals are covered with the mud and exposed to it for different periods. Oftentimes it ends in a mouth and gets swallowed. With this in mind, knowledge about concentration of potentially toxic elements is a important and necessary. Sequential extraction chemical analysis proposed by Tessier or BCR protocol are well documented and traditionally used methods (Bacon and Davidson, 2008 ; Rauret et al., 1999 ; Tessier et al., 1979), which gives valuable information about elements fractionation. Moreover, gastric and gastrointestinal protocol generates additional informations, in particular valuable when oral ingestion of soil (mud) is present. Sequential extraction procedures and gastric/gastrointestinal extractions can be seen as the same (similar) procedure but with the different central subject where informations should be addressed to ; environment (in the broader sense) for sequential extraction procedures and Man for gastric/gastrointestinal extraction. Detailed geochemical investigation was obtained on the sediments from Segal Bay, island of Pag, Croatia. This sediment is known as natural healing mud and is used broadly. Analysis providing information on bioavailability and bioaccessibility were performed on air-dried samples. Results of easily leachable elements (step 1 of BCR and Tessier procedure) were compared with the one gathered from gastric/gastrointestinal protocol (Intawongse and Dean, 2006 ; Jantratid et al., 2008), with the main objective to make a conclusion on safety due to exposure to the mud through skin and/or by swallowing it. Term bioaccessibility presents the fraction of a compound that is released from its matrix in the gastrointestinal tract, and it becomes available for intestinal absorption while term bioavailability presents the fraction that can reach the system, but it doesn’t need to be released from the matrix and have an influence on an individual (Carbonell-Capella et al., 2014 ; Intawongse and Dean, 2006). In this abstract results obtained from Tessier and BCR procedure gave informations about bioavailability while the one obtained from gastric and gastrointestinal protocol gave informations about bioaccessibility. Soil organic matter (SOM) and soil inorganic carbon (SIC) were determined by the loss-on- ignition procedure according to (Wang et al., 2012). SOM and SIC were calculated according to the equations described in the paper and all needed input informations are obtained from three step procedure consisting of combustion at 105°C for 12 hours (to remove the soil moisture), followed by combustion at 375°C for 17 hours and at 800°C for 12 hours To gather information’s what happens in gastric and gastrointestinal process, SIF Powder (Biorelevant) was used. This protocol brings informations about Fasted-State Simulated Intestinal Fluid (FaSSIF) , Fed-State Simulated Intestinal Fluid (FeSSIF), and Fasted-State Simulated Gastric Fluid (FaSSGF). Step 1 of BCR and Tessier procedure are focused on similar phase connected with the exchangeable, water and acid-soluble fraction, although nominal target phases of first step of BCR protocol has a wider range. Inductively coupled plasma atomic emission spectrometry, ICP-AES, was used for concentration determination in all fractions.. Analyzed samples has a high amount of organic matter with the average value of 116.34 g kg-1 ±0.356. Results of performed extractions are presented in Fig. 1. Concentrations of analyzed elements obtained from pseudototal chemical analysis extracted by Aqua Regia digestion have, as expected, higher values than from other procedures ( FaSSGF, FaSSIF, FeSSIF, step 1 of Tessier and BCR). Concentration of elements presenting bioavailability and bioaccessibility procedures are similar, slightly higher for procedure presenting bioaccessibility. All analyzed element are in a range of maximum allowed concentration proclaimed by national legislation. Whenever there is a chance that soil and/or sediment will end in digestive system, presented combination of analysis would be a beneficial due to possibility to expend conclusion taking into account bioaccessibility and bioavailability.

healing mud ; BCR and Tessier sequential extraction procedure ; bioaccessibility and bioavailability ; gastric and gastrointestinal extraction

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