Characterisation of secondary metal-bearing phases in used dental amalgam and assessment of gastric solubility

Detailed SEM/EDS investigation of used dental amalgams was carried out in order to characterise morphology and chemical composition of secondary metal-bearing phases resulting from long-term exposure of dental amalgam to oral environment, and assess their solubility in gastric environment. The investigation revealed numerous secondary phases, represented by compositionally and morphologically complex Hg-, Cu-, Sn-, Ag-, Zn-bearing sulphides and oxides/hydroxides, while sulphates and phosphates are scarce. Secondary metal-bearing phases mostly occur at the amalgam/tooth interface; however, some phases were found only on the occlusal surfaces of amalgam. Secondary phases mostly form porous aggregates of minute crystallites and micro- or nanocrystalline crusts. In oral environment, these phases are mostly stable and represent trapping media for dissolved potentially toxic metals released during amalgam corrosion. Simplified PHREEQC calculations of solubility of secondary metal-bearing phases in aqueous environment under conditions similar to those in gastric environment showed that secondary phases are more soluble in gastric environment than in oral solutions, which is mostly due to their forms of occurrence. Secondary phases in gastric environment thus act as secondary sources of potentially toxic metals, particularly Sn, Zn and also Cu, which are released both under reducing and oxidising conditions especially in acidic environment. Only very small amounts of Hg are potentially released and should not represent serious threat. Secondary phases that contribute the most to bioaccessibility of these metals are Sn hydroxychlorides, Sn oxides/hydroxides, Sn sulphates/hydroxysulphates, Sn oxides, Zn sulphides and Cu sulphides (Cu₂S).

     

Polychlorinated dibenzo-p-dioxins/furans and dioxin-like polychlorinated biphenyls in food and feed in the Lithuanian market

Foods and feeds were analyzed during the period of 2007–2014 employing validated and accredited methods based on gas chromatography–high-resolution mass spectrometry. Sampling has been carried out in-line with national monitoring programs as well as during import controls into Lithuania. Food samples such as eggs, milk, beef, pork, poultry, fats of plant and animal origin, fish, cod liver, and feed samples such as premixes, feeds of plant origin, compound feed, mineral feed, vegetable oil, and fish meals were analyzed. Most of the samples exhibited concentrations below maximum limits, except cod liver. Health impacts were assessed in respect to human daily intakes. Data between groups are compared.     

Effect of ferrate on green algae removal

Green algae Cladophora aegagropila, present in cooling water of thermal power plants, causes many problems and complications, especially during summer. However, algae and its metabolites are rarely eliminated by common removal methods. In this work, the elimination efficiency of electrochemically prepared potassium ferrate(VI) on algae from cooling water was investigated. The influence of experimental parameters, such as Fe(VI) dosage, application time, pH of the system, temperature and hydrodynamics of the solution on removal efficiency, was optimized. This study demonstrates that algae C. aegagropila can be effectively removed from cooling water by ferrate. Application of ferrate(VI) at the optimized dosage and under the suitable conditions (temperature, pH) leads to 100% removal of green algae Cladophora from the system. Environmentally friendly reduction products (Fe(III)) and coagulation properties favour the application of ferrate for the treatment of water contaminated with studied microorganisms compared to other methods such as chlorination and use of permanganate, where harmful products are produced.

     

Evaluation and validation of two different chromatographic methods (HPLC and LC-MS/MS) for the determination and confirmation of ochratoxin A in pig tissues

This study was undertaken to compare two different analytical methods for the determination and confirmation of ochratoxin A (OTA) in blood serum, kidney and liver of pigs. Sample clean-up was based on liquid-liquid phase extraction. The detection of OTA was accomplished with high-performance liquid chromatography (HPLC) combined either with fluorescence detection (FL) or electro spray ionization (ESI+) tandem mass spectrometry (MS–MS). Comparative method evaluation was based on the investigation of 90 samples of blood serum, kidney and liver per animal originating from different regions of Serbia. The analytical results are discussed in view of the respective method validation data and the corresponding experimental protocols. In general, analytical data obtained with (LC–MS–MS) liquid chromatography electro spray tandem mass spectro metry detection offered comparable good results at the sub-ppb concentration level. The results indicate that the liquid chromatography electro spray tandem mass spectrometric (LC-MS/MS) method was more specific and sensitive for the analysis and confirmation of ochratoxin A in pig tissues then high pressure liquid chromatography (HPLC) method after methylation of OTA.     

Alterations in the rabbit lymphoid tissue after bendiocarb administration

Various pesticides have immuno-suppressive effects, and thus the organisms become responsive to viral, bacterial and parasitic diseases and neoplasm. The aim of the study was to observe the structure of the small intestine (height of enterocytes and crypts), mucosal lymphoid tissue (Payer's patches, lymphocytes in lamina propria) and a lymph node after administration of bendiocarb (2,2-dimethyl-1,3-benzodioxol-4-yl-methylcarbamate) on days 3, 10, 20, 30 and 60 of the experiment. The height of the observed enterocytes showed an increasing tendency. On days 20, 30 and 60 we also observed an increase in diameter of crypts located in intestinal epithelium. The number of cells in lamina propria mucosae was significantly reduced on days 20 and 30 after administration of bendiocarb. Observations of the lymph node showed that on days 10 and 20 there was a significant increase in relative volume of medulla at the expense of the relative volume of the cortex and a decrease in the number of lymphocytes. However, we recorded an increase in diameter of lymphocytes. The intracellular parasite Toxoplasma gondii (T. gondii) belongs to the most common pathogenic parasites in the world and it can cause serious health complications in pregnant and immunodeficient individuals. DNA isolation, standard polymerase chain reaction (PCR) and visualization in a 2.5 % agarose gel, the presence of DNA T. gondii was detected in no examined rabbit brain samples. Using real time PCR T. gondii DNA was detected and quantified in the three rabbit brain samples (10 %).     

Toxicity of metalaxyl, azoxystrobin, dimethomorph, cymoxanil, zoxamide and mancozeb to Phytophthora infestans isolates from Serbia

A study of the in vitro sensitivity of 12 isolates of Phytophthora infestans to metalaxyl, azoxystrobin, dimethomorph, cymoxanil, zoxamide and mancozeb, was conducted. The isolates derived from infected potato leaves collected at eight different localities in Serbia during 2005-2007. The widest range of EC(50) values for mycelial growth of the isolates was recorded for metalaxyl. They varied from 0.3 to 3.9 μg mL(-1) and were higher than those expected in a susceptible population of P. infestans. The EC(50) values of the isolates were 0.16-0.30 μg mL(-1) for dimethomorph, 0.27-0.57 μg mL(-1) for cymoxanil, 0.0026-0.0049 μg mL(-1) for zoxamide and 2.9-5.0 μg mL(-1) for mancozeb. The results indicated that according to effective concentration (EC(50)) the 12 isolates of P. infestans were sensitive to azoxystrobin (0.019-0.074 μg mL(-1)), and intermediate resistant to metalaxyl, dimethomorph and cymoxanil. According to resistance factor, all P. infestans isolates were sensitive to dimethomorph, cymoxanil, mancozeb and zoxamide, 58.3% of isolates were sensitive to azoxystrobin and 50% to metalaxyl. Gout's scale indicated that 41.7% isolates were moderately sensitive to azoxystrobin and 50% to metalaxyl.     

Effects of temperature on sorption-desorption processes of imidacloprid in soils of Croatian coastal regions

Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equations, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were non-linear and may be classified as L-type, suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the K( sor ) ( F ) values decreased for all the tested soils as the temperature increased, indicating that the temperature strongly influences the sorption. Values of ΔG° were negative (-4.65 to -2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous processes. The negative and small ΔH° values (-19.79 to -8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and partitioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of -57.12 to -14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature-dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature treatments existed, and it was more pronounced at 20°C in the soils with higher OC content. The study results emphasize the importance of thermodynamic parameters in controlling soil pesticide mobility in different geographical locations, seasons and greenhouse conditions.     

Antibacterial activity against Clostridium genus and antiradical activity of the essential oils from different origin

In the present study, the antimicrobial and antiradical activities of 15 essential oils were investigated. The antimicrobial activities were determined by using agar disc diffusion and broth microdilution methods against Clostridium genus and antioxidant properties of essential oils by testing their scavenging effect on DPPH radicals activities. We determined the antibacterial activity of Clostridium butyricum, Clostridium hystoliticum, Clostridium intestinale, Clostridium perfringens and Clostridium ramosum. We obtained the original commercial essential oils samples of Lavandula angustifolia, Carum carvi, Pinus montana, Mentha piperita, Foeniculum vulgare Mill., Pinus sylvestris, Satureia montana, Origanum vulgare L. (2 samples), Pimpinella anisum, Rosmarinus officinalis L., Salvia officinalis L., Abies alba Mill., Chamomilla recutita L. Rausch and Thymus vulgaris L. produced in Slovakia (Calendula a.s., Nova Lubovna, Slovakia). The results of the disk diffusion method showed very high essential oils activity against all tested strains of microorganisms. The best antimicrobial activity against C. butyricum was found at Pimpinella anisum, against C. hystoliticum was found at Pinus sylvestris, against C. intestinale was found at Satureia hortensis L., against C. perfringens was found at Origanum vulgare L. and against C. ramosum was found at Pinus sylvestris. The results of broth microdilution assay showed that none of the essential oils was active against C. hystoliticum. The best antimicrobial activity against C. butyricum was found at Abies alba Mill., against C. intestinale was found at Abies alba Mill., against C. perfringens was found at Satureia montana and against C. ramosum was found at Abius alba and Carum carvi. Antioxidant DPPH radical scavenging activity was determined at several solutions of oil samples (50 μL.mL^?1–0.39 μL.mL^?1) and the best scavenging effect for the highest concentration (50 μL.mL^?1) was observed. The antioxidant properties were different in particular plant species. The highest% of inhibition after 30 min. of reaction was observed at Origanum vulgare (93%), Satureia montana (90.66%) and Lavandula augustifolia (90.22%).     

Mineralogy and characterization of deposited particles of the aero sediments collected in the vicinity of power plants and the open pit coal mine: Kolubara (Serbia)

In this paper, particular attention was paid to the presence of aerosol solid particles, which occurred mainly as a result of exploitation and coal combustion in the thermal power plants of the Kolubara basin. Not all of the particles created by this type of anthropogenic pollution have an equal impact on human health, but it largely depends on their size and shape. The mineralogical composition and particle size distribution in the samples of aero sediments were defined. The samples were collected close to the power plant and open pit coal mine, in the winter and summer period during the year 2007. The sampling was performed by using precipitators placed in eight locations within the territory of the Lazarevac municipality. In order to characterize the sedimentary particles, several methods were applied: microscopy, SEM-EDX and X-ray powder diffraction. The concentration of aero sediments was also determined during the test period. Variety in the mineralogical composition and particle size depends on the position of the measuring sites, geology of the locations, the annual period of collecting as well as possible interactions. By applying the mentioned methods, the presence of inhalational and respiratory particles variously distributed in the winter and in the summer period was established. The most common minerals are quartz and feldspar. The presence of gypsum, clay minerals, calcite and dolomite as secondary minerals was determined, as well as the participation of organic and inorganic amorphic matter. The presence of quartz as a toxic mineral has a particular impact on human health.     

Toxicological characterization of the landfill leachate prior/after chemical and electrochemical treatment: A study on human and plant cells

In this research, toxicological safety of two newly developed methods for the treatment of landfill leachate from the Piškornica (Croatia) sanitary landfill was investigated. Chemical treatment procedure combined chemical precipitation with CaO followed by coagulation with ferric chloride and final adsorption by clinoptilolite. Electrochemical treatment approach included pretreatment with ozone followed by electrooxidation/electrocoagulation and final polishing by microwave irradiation. Cell viability of untreated/treated landfill leachate was examined using fluorescence microscopy. Cytotoxic effect of the original leachate was obtained for both exposure periods (4 and 24 h) while treated samples showed no cytotoxic effect even after prolonged exposure time. The potential DNA damage of the untreated/treated landfill leachate was evaluated by the comet assay and cytokinesis-block micronucleus (CBMN) assay using either human or plant cells. The original leachate exhibited significantly higher comet assay parameters compared to negative control after 24 h exposure. On the contrary, there was no significant difference between negative control and chemically/electrochemically treated leachate for any of the parameters tested. There was also no significant increase in either CBMN assay parameter compared to the negative control following the exposure of the lymphocytes to the chemically or electrochemically treated landfill leachate for both exposure periods while the original sample showed significantly higher number of micronuclei, nucleoplasmic bridges and nuclear buds for both exposure times. Results suggest that both methods are suitable for the treatment of such complex waste effluent due to high removal efficiency of all measured parameters and toxicological safety of the treated effluent.