Mechanisms of chromium toxicity, carcinogenicity and allergenicity: review of the literature from 1985 to 2000

Adsorption behavior comparison of trivalent and hexavalent chromium on biochar derived from municipal sludge

In this work, static equilibrium experiments were conducted to distinguish the adsorption performance between the two valence states of chromium on biochar derived from municipal sludge. The removal capacity of Cr(VI) is lower than 7mg/g at the initial chromium concentration range of 50-200mg/L, whereas that of Cr(III) higher than 20mg/g. It indicates that Cr(III) is much easier to be stabilized than Cr(VI). No significant changes in the biochar surface functional groups are observed before and after the adsorption equilibrium, demonstrating the poor contribution of organic matter in chromium adsorption. The main mechanism of heavy metal adsorption by biochar involves (1) surface precipitation through pH increase caused by biochar buffer ability, and (2) exchange between cations in solution (Cd(2+)) and in biochar matrix (e.g. Ca(2+) and Mg(2+)). The reduction of Cr(VI) to Cr(III) is necessary to improve removal efficiency of chromium.

Human exposure to trace elements through the skin by direct contact with clothing: Risk assessment

Metals in textile products and clothing are used for many purposes, such as metal complex dyes, pigments, mordant, catalyst in synthetic fabrics manufacture, synergists of flame retardants, antimicrobials, or as water repellents and odour-preventive agents. When present in textile materials, heavy metals may mean a potential danger to human health. In the present study, the concentrations of a number of elements (Al, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Sc, Se, Sm, Sn, Sr, Tl, V, and Zn) were determined in skin-contact clothes. Analysed clothes were made of different materials, colours, and brands. Interestingly, we found high levels of Cr in polyamide dark clothes (605 mg/kg), high Sb concentrations in polyester clothes (141 mg/kg), and great Cu levels in some green cotton fabrics (around 280 mg/kg). Dermal contact exposure and human health risks for adult males, adult females, and for <1-year-old children were assessed. Non-carcinogenic and carcinogenic risks were below safe (HQ<1) and acceptable (<10(-6)) limits, respectively, according to international standards. However, for Sb, non-carcinogenic risk was above 10% of the safety limit (HQ>0.1) for dermal contact with clothes.

Effective treatment of alkaline Cr(VI) contaminated leachate using a novel Pd-bionanocatalyst: Impact of electron donor and aqueous geochemistry

Palladium catalysts offer the potential for the effective treatment of a variety of priority reducible pollutants in natural waters. In this study, microbially synthesized magnetite nanoparticles were functionalized with Pd(0), creating a highly reactive, magnetically recoverable, nano-scale catalyst (Pd-BnM). This was then investigated for the treatment of model Cr(VI) contaminated solutions at a range of pH values, and also alkaline Cr(VI) contaminated leachates from chromite ore processing residue (COPR); a contaminant issue of global concern. The sample of COPR used in this study was obtained from a site in Glasgow, UK, where extensive Cr(VI) contamination has been reported. In initial experiments Pd-BnM was supplied with H₂ gas or formate as electron donors, and Cr(VI) removal from model synthetic solutions was quantified at various pH values (2-12). Effective removal was noted at neutral to environmentally relevant alkaline (pH 12) pH values, while the use of formate as an electron donor resulted in loss of performance under acidic conditions (pH 2). Reaction kinetics were then assessed with increasing Pd-BnM loading in both model pH 12 Cr(VI) solutions and the COPR leachate. When formate was used as the electron donor for Pd-BnM, to treat COPR leachate, there was significant inhibition of Cr(VI) removal. In contrast, a promotion of reaction rate, was observed when H₂ was employed. Upon sustained reaction with model Cr(VI) solutions, in the presence of excess electron donor (formate or H₂), appreciable quantities of Cr(VI) were removed before eventual inactivation of the catalyst. Faster onset of inactivation was reported in the COPR leachates, removing 4% and 64% of Cr(VI) observed from model Cr(VI) solutions, when formate and H₂ were used as electron donors, respectively. XAS, TEM-EDX and XPS analysis of the catalysts that had been inactivated in the model solution, showed that the surface had an extensive covering of reduced Cr(III), most likely as a CrOOH phase. COPR reacted catalysts recorded a lower abundance of Cr(III) alongside a high abundance of the leachate components Ca and Si, implicating these elements in the faster onset of inactivation.

Treatment of Alkaline Cr(VI)-Contaminated Leachate with an Alkaliphilic Metal-Reducing Bacterium

Chromium in its toxic Cr(VI) valence state is a common contaminant particularly associated with alkaline environments. A well-publicized case of this occurred in Glasgow, United Kingdom, where poorly controlled disposal of a cementitious industrial by-product, chromite ore processing residue (COPR), has resulted in extensive contamination by Cr(VI)-contaminated alkaline leachates. In the search for viable bioremediation treatments for Cr(VI), a variety of bacteria that are capable of reduction of the toxic and highly soluble Cr(VI) to the relatively nontoxic and less mobile Cr(III) oxidation state, predominantly under circumneutral pH conditions, have been isolated. Recently, however, alkaliphilic bacteria that have the potential to reduce Cr(VI) under alkaline conditions have been identified. This study focuses on the application of a metal-reducing bacterium to the remediation of alkaline Cr(VI)-contaminated leachates from COPR. This bacterium, belonging to the Halomonas genus, was found to exhibit growth concomitant to Cr(VI) reduction under alkaline conditions (pH 10). Bacterial cells were able to rapidly remove high concentrations of aqueous Cr(VI) (2.5 mM) under anaerobic conditions, up to a starting pH of 11. Cr(VI) reduction rates were controlled by pH, with slower removal observed at pH 11, compared to pH 10, while no removal was observed at pH 12. The reduction of aqueous Cr(VI) resulted in the precipitation of Cr(III) biominerals, which were characterized using transmission electron microscopy and energy-dispersive X-ray analysis (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The effectiveness of this haloalkaliphilic bacterium for Cr(VI) reduction at high pH suggests potential for its use as an in situ treatment of COPR and other alkaline Cr(VI)-contaminated environments.

Chromate Reductase YieF from Escherichia coli Enhances Hexavalent Chromium Resistance of Human HepG2 Cells

Hexavalent chromium (Cr(VI)) is a serious environmental pollutant and human toxicant. Mammalian cells are very sensitive to chromate as they lack efficient chromate detoxifying strategy, e.g., chromate-reducing genes that are widely present in prokaryotes. To test whether introduction of prokaryotic chromate-reducing gene into mammalian cells could render higher chromate resistance, an Escherichia coli chromate-reducing gene yieF was transfected into human HepG2 cells. The expression of yieF was measured in stably transfected cells HepG2-YieF by quantitative RT-PCR and found up-regulated by 3.89-fold upon Cr(VI) induction. In chromate-reducing ability test, HepG2-YieF cells that harbored the reductase showed significantly higher reducing ability of Cr(VI) than HepG2 control cells. This result was further supported by the evidence of increased Cr(VI)-removing ability of crude cell extract of HepG2-YieF. Moreover, HepG2-YieF demonstrated 10% higher viability and decreased expression of GSH synthesizing enzymes under Cr(VI) stress. Subcellular localization of YieF was determined by tracing GFP-YieF fusion protein that was detected in both nucleus and cytoplasm by laser confocal microscopy. Altogether, this study successfully demonstrated that the expression of a prokaryotic Cr(VI)-reducing gene yieF endowed mammalian cell HepG2 with enhanced chromate resistance, which brought new insight of Cr(VI) detoxification in mammalian cells.

Long-term Coexposure to Hexavalent Chromium and B[a]P Causes Tissue-Specific Differential Biological Effects in Liver and Gastrointestinal Tract of Mice

Complex mixtures of environmental agents often cause mixture-specific health effects that cannot be accounted for by a single mechanism. To study the biological effects of exposure to a mixture of chromium-VI and benzo[a]pyrene (B[a]P), often found together in the environment, we exposed mice for 60 days to 0, 55, 550, or 5500 ppb Cr(VI) in drinking water followed by 90 days of coexposure to B[a]P at 0, 1.25, 12.5, or 125 mg/kg/day and examined liver and gastrointestinal (GI) tract for exposure effects. In the liver, the mixture caused more significant histopathology than expected from the sum of effects of the individual components, while in the GI tract, Cr(VI) alone caused significant enterocyte hypertrophy and increases in cell proliferation and DNA damage that were also observed in mice coexposed to B[a]P. Expression of genes involved in drug metabolism, tumor suppression, oxidative stress, and inflammation was altered in mixed exposures relative to control and to singly exposed mice. Drug metabolism and oxidative stress genes were upregulated and tumor suppressor and inflammation genes downregulated in the proximal GI tract, whereas most markers were upregulated in the distal GI tract and downregulated in the liver. Oral exposure to Cr(VI) and B[a]P mixtures appears to have tissue-specific differential consequences in liver and GI tract that cannot be predicted from the effects of each individual toxicant. Tissue specificity may be particularly critical in cases of extended exposure to mixtures of these agents, as may happen in the occupational setting or in areas where drinking water contains elevated levels of Cr(VI).

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Biogenic nano-magnetite and nano-zero valent iron treatment of alkaline Cr(VI) leachate and chromite ore processing residue

Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, was tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR). The performance of this biomaterial, targeting aqueous Cr(VI) removal, was compared to a synthetic alternative, nano-scale zero valent iron (nZVI). Samples of highly contaminated alkaline groundwater and COPR solid waste were obtained from a contaminated site in Glasgow, UK. During batch reactivity tests, Cr(VI) removal from groundwater was inhibited by ∼25% (BnM) and ∼50% (nZVI) when compared to the treatment of less chemically complex model pH 12 Cr(VI) solutions. In both the model Cr(VI) solutions and contaminated groundwater experiments the surface of the nanoparticles became passivated, preventing complete coupling of their available electrons to Cr(VI) reduction. To investigate this process, the surfaces of the reacted samples were analyzed by TEM-EDX, XAS and XPS, confirming Cr(VI) reduction to the less soluble Cr(III) on the nanoparticle surface. In groundwater reacted samples the presence of Ca, Si and S was also noted on the surface of the nanoparticles, and is likely responsible for earlier onset of passivation. Treatment of the solid COPR material in contact with water, by addition of increasing weight % of the nanoparticles, resulted in a decrease in aqueous Cr(VI) concentrations to below detection limits, via the addition of ⩾5% w/w BnM or ⩾1% w/w nZVI. XANES analysis of the Cr K edge, showed that the % Cr(VI) in the COPR dropped from 26% to a minimum of 4-7% by the addition of 5% w/w BnM or 2% w/w nZVI, with higher additions unable to reduce the remaining Cr(VI). The treated materials exhibited minimal re-mobilization of soluble Cr(VI) by re-equilibration with atmospheric oxygen, with the bulk of the Cr remaining in the solid fraction. Both nanoparticles exhibited a considerable capacity for the remediation of COPR related Cr(VI) contamination, with the synthetic nZVI demonstrating greater reactivity than the BnM. However, the biosynthesized BnM was also capable of significant Cr(VI) reduction and demonstrated a greater efficiency for the coupling of its electrons towards Cr(VI) reduction than the nZVI.

Effects of alternating wetting and drying versus continuous flooding on chromium fate in paddy soils

Anthropogenic chromium (Cr) pollution in soils poses a great threat to human health through the food chain. It is imperative to understand Cr fate under the range of conditions suitable for rice growth. In this study, the effects of irrigation managements on dynamics of porewater Cr(VI) concentrations in rice paddies and Cr distribution in rice were investigated with pot experiments under greenhouse conditions. Soil redox potential in continuous flooding (CF) treatments showed that reducing conditions remained for the whole duration of rice growing period, while soil redox potential in alternating wetting and drying (AWD) treatments showed that soil conditions alternately changed between reducing and oxic. As soil redox potential is an important factor affecting Cr(VI) reduction in paddy soils, dynamics of Cr(VI) concentration were clearly different under different irrigation managements. In CF treatments, porewater Cr(VI) concentrations decreased with time after planting, while in AWD treatments porewater Cr(VI) concentrations were increased and decreased alternately response to the irrigation cycles. Chromium(VI) concentrations in the CF treatments were lower than those in AWD treatments for most part of rice-growing season. Moreover, Cr concentrations in rice tissues were significantly influenced by irrigation with relatively higher values in the AWD treatments, which might be attributed to the higher porewater Cr(VI) concentrations in AWD treatments. Therefore, it would be better to use CF than AWD management in Cr-contaminated paddy soils to reduce Cr accumulation in rice, and thus to reduce the potential risk to human health.

Study on the binding interaction of chromium(VI) with humic acid using UV-vis, fluorescence spectroscopy and molecular modeling

In this report, the binding interaction of chromium(VI), as Cr2O7(2-), with humic acid was studied by using UV-visible absorption, fluorescence spectroscopy, and molecular modeling method. The fluorescence spectral data indicated that the binding interaction existed between Cr2O7(2-) and humic acid and the order of magnitude of binding constants were 10(3). The rise in temperature caused a decrease in the values of the binding constant of humic acid with Cr2O7(2-). Thermodynamic analysis presented that multi-intermolecular forces including hydrogen bonding, hydrophobic, and electrostatic forces were involved in the binding process at pH 6.5. The spectral data also indicated that Cr2O7(2-) affected the aromatic ring structures in humic acid. Furthermore, the molecular modeling analysis indicated that a lot of reactive groups and binding cavities in HA played a key role in its binding with Cr2O7(2-).

Hexavalent chromium induces expression of mesenchymal and stem cell markers in renal epithelial cells

Cr(VI) causes severe kidney damage. The patient's renal function could gradually recover by spontaneous kidney regeneration. The molecular effect of Cr(VI) on recovery of kidney cells, however, has not been clearly elucidated. Here we show that Cr(VI) induces expression of mesenchymal and stem cell markers, cell markers, such as paxillin, vimentin, α-SMA, nanog, and CD133 of HK-2 cells. Moreover, Cr(VI) activates epithelial-to-mesenchymal transition (EMT). By revealing that levels of dihydrodiol dehydrogenase were promptly reduced following Cr(VI) challenge, our data suggested that DDH could be involved in a Cr(VI)-related oxidation to generate massive reactive oxygen species and H2 O2 , and to create intracellular hypoxia, which then increased levels of SUMO-1 activating enzyme subunit 2, and sumoylation of eukaryotic elongation factor-2, to mediate the subsequent molecular and cellular responses, e.g., expression of mesenchymal and stem cell markers. Pretreatment with vitamin C reduced Cr(VI)-related cellular effects. However, no evident effect was observed when vitamin C was added following Cr(VI) challenge.

An in ovo investigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy

Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 μM physiological dosage (PD) and 430 μM (×1000 PD) CdCl2, as well as 0.476 μM (PD) and 746 μM (×1000 PD) K2Cr2O7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light- and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscopy, the PD of both Cd and Cr had no effect on liver tissue or cellular morphology. At ×1000 PD both Cd and Cr caused sinusoid dilation and tissue necrosis. With TEM analysis, Cd exposed hepatocytes presented with irregular chromatin condensation, ruptured cellular membranes and damaged or absent organelles. In contrast Cr caused only slight mitochondrial damage. EELS revealed the bio-accumulation of Cd and Cr along the cristae of the mitochondria and chromatin of the nuclei.

⁵²Mn production for PET/MRI tracking of human stem cells expressing divalent metal transporter 1 (DMT1)

There is a growing demand for long-term in vivo stem cell imaging for assessing cell therapy techniques and guiding therapeutic decisions. This work develops the production of ⁵²Mn and establishes proof of concept for the use of divalent metal transporter 1 (DMT1) as a positron emission tomography (PET) and magnetic resonance imaging (MRI) reporter gene for stem cell tracking in the rat brain. ⁵²Mn was produced via proton irradiation of a natural chromium target. In a comparison of two ⁵²Mn separation methods, solvent-solvent extraction was preferred over ion exchange chromatography because of reduced chromium impurities and higher ⁵²Mn recovery. In vitro uptake of Mn-based PET and MRI contrast agents (⁵²Mn²⁺ and Mn²⁺, respectively) was enhanced in DMT1 over-expressing human neural progenitor cells (hNPC-DMT1) compared to wild-type control cells (hNPC-WT). After cell transplantation in the rat striatum, increased uptake of Mn-based contrast agents in grafted hNPC-DMT1 was detected in in vivo manganese-enhanced MRI (MEMRI) and ex vivo PET and autoradiography. These initial studies indicate that this approach holds promise for dual-modality PET/MR tracking of transplanted stem cells in the central nervous system and prompt further investigation into the clinical applicability of this technique.

Metal-Dependent Root Iron Plaque Effects on Distribution and Translocation of Chromium and Nickel in Yellow Flag (Iris pseudacorus L.)

Iris pseudacorus L. (yellow flag) is a wide-use wetland plant for constructed wetlands for removing metals from wastewater. This study aims to understand effects of root iron plaque on sequestration and translocation of Cr and Ni in yellow flag seedlings using a hydroponic experiment. Yellow flag seedlings (4-week-old seedlings with 4-6 leaves) with or without iron plaque induction (at 50 mg Fe2+ L(-1) for 72 hours) were spiked for 6 days in the Hoagland solution with Cr or Ni at 0.5, 5, and 50 mg L(-1), equivalent to 1, 10, 100 times of thresholds of surface water quality, respectively. Results indicated that root iron plaque significantly reduced translocation of Cr and Ni to root but increased from root to shoot. Root iron plaque formation counteracted Cr toxicity to yellow flag seedlings while the control showed Cr toxicity to root at 5 mg L(-1)and to shoot at 50 mg L(-1) with significant biomass loss. Neither Ni exposures caused significant biomass loss nor root iron plaque formation significantly changed Ni distribution among plant parts. Our study suggests that root iron plaque effects on metal sequestration and translocation in yellow flag seedlings were metal-dependent.

A New Visual Trap for Rhagoletis cerasi (L.) (Diptera: Tephritidae)

The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is the most important pest of sweet cherries in Europe. The aim of our experiments was to develop a new, cost-efficient, lead chromate-free and more eco-friendly trap for monitoring and mass trapping of R. cerasi. Five different-colored yellow panels and three different trap shapes were compared to a standard Rebell^® amarillo trap in three experimental orchards in 2012. Trap color F, with a strong increase in reflectance at 500–550 nm and a secondary peak in the UV-region at 300–400 nm, captured significantly more flies than the standard Rebell^® amarillo trap. Yellow traps with increased reflectance in the blue region (400–500 nm) were least attractive. Trap shape was of minor importance, as long as the object was three-dimensional and visible from all directions. Based on economic and practical considerations, a cylinder-shaped trap “UFA-Samen Kirschenfliegenfalle” was developed for commercial use and is currently under on-farm evaluation.

Induction of the homologous recombination system by hexavalent chromium in Rhizobium etli

Induction of homologous recombination in Rhizobium etli to repair the DNA damage caused by hexavalent chromium (Cr) was evaluated. Mutants in recombination genes such as addA, recF, recA, ruvB, recG, and a double mutant ruvBrecG showed different sensitivity levels to Cr. As expected, the recA mutant showed the highest susceptibility, while complementation restored the Cr-resistant phenotype, similar to the wild-type strain. Small plasmid recombination increased up to 30-fold in the presence of Cr (0.05 mM) in the wild-type strain, while no change was observed in the recA mutant. A 20-fold increase in small plasmid recombination was also observed in the addA mutant in the presence of Cr. In addition, the ruvB mutant showed similar increases with Cr exposure to the wild-type strain, suggesting that other genetic elements may substitute its important role during recombination. Interestingly, continuous Cr exposure (0.05 mM) clearly induced the genetic expression of addA, recA, and ruvB genes. Finally, recombination mutants also showed susceptibility to other DNA-damaging agents such as tellurite and selenite. Together, these results confirm the induction and significance of the R. etli homologous recombination system to repair DNA damage caused by hexavalent Cr.

Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) analysis uncovers broad changes in chromatin structure resulting from hexavalent chromium exposure

The ability of chromatin to switch back and forth from open euchromatin to closed heterochromatin is vital for transcriptional regulation and genomic stability, but its dynamic structure is subject to disruption by exposure to environmental agents such as hexavalent chromium. Cr(VI) exposure disrupts chromatin remodeling mechanisms and causes chromosomal damage through formation of free radicals, Cr-DNA adducts, and DNA-Cr-protein cross-links. In addition, acute, high-concentration, and chronic, low-concentration exposures to Cr(VI) lead to significantly different transcriptional and genomic stability outcomes. We used mouse hepatoma Hepa-1c1c7 cells to investigate how transcriptional responses to chromium treatment might correlate with structural chromatin changes. We used Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) analysis coupled with deep sequencing to identify regions of the genome that may switch between open and closed chromatin in response to exposure to varying Cr(VI) concentrations. At either Cr(VI) concentration, chromatin domains surrounding binding sites for AP-1 transcription factors become significantly open, whereas BACH2 and CTCF binding sites are open solely at the low and high concentrations, respectively. Parallel gene expression profiling using RNA-seq indicates that the structural chromatin changes caused by Cr(VI) affect gene expression levels in the target areas that vary depending on Cr(VI) concentration, but show no correlation between global changes in the overall transcriptional response and Cr(VI) concentration. Our results suggest that FAIRE may be a useful technique to map chromatin elements targeted by DNA damaging agents for which there is no prior knowledge of their specificity, and to identify subsequent transcriptomic changes induced by those agents.

Diatomite releases silica during spirit filtration

The purpose of this study was to ascertain whether diatomite is an inert filter aid during spirit filtration. Surely, any compound with a negative effect on the spirit composition or the consumer's health could be dissolved. In this study different diatomites were treated with 36% vol. ethanol/water mixtures and the amounts and structures of the extracted compounds were determined. Furthermore, Brandy de Jerez was diatomite- and membrane-filtered at different temperatures and the silicon content was analysed. It was found that up to 0.36% by weight of diatomite dissolved in the aqueous ethanol and amorphous silica, in the form of hollow spherical microparticles, was the most abundant component. Silicon concentrations in Brandy de Jerez increased by up to 163.0% after contact with diatomite and these changes were more marked for calcined diatomite. In contrast, reductions of more than 30% in silicon concentrations were achieved after membrane filtration at low temperatures.

Immunotropic effects of hexavalent chromium soluble compounds on the thymus and peripheral blood values in a subacute experiment

Intraperitoneal injections of hexavalent chromium (sodium bichromate) in the concentrations of 0.025 μg/kg (10-fold lower than MAC; group 1) and 2.5 μg/kg (10-fold higher than MAC; group 2) to rats in a subacute experiment caused dose-dependent morphological changes in the thymus: increased the counts of cells in a state of destruction, macrophages, and plasmocytes and impairs interactions between epithelial reticular cells and lymphocytes with formation of cystic cavities. Proliferation of lymphoblasts and large lymphocytes of the glandular cortical matter was detected in groups 1 and 2, of medium-sized and minor lymphocytes in group 1. Lymph node-like zones with Hassall's corpuscles, pigment foci in the cortical matter, and plasmocytes in the medulla were detected throughout the entire study in controls and in group 1 animals and on days 1 and 7 in group 2. Histiocytes, macrophages, cells in a state of destruction, and siderophages were detected in dilated lymph sinuses. Normal tissue of the gland left lobe in group 2 was completely replaced by lymph node-like zones on days 15 and 30, while the right lobe retained the structure characteristic of the gland. A dose-dependent reduction of the peripheral blood erythrocyte and platelet counts and a decrease in hemoglobin level were observed in experimental animals. On day 30 peripheral blood lympho- and leukocytosis developed at the expense of higher counts of B (CD20) and T lymphocytes (CD3) and their subpopulations - T helpers (CD4), T suppressors (CD8), and immature lymphocytes in group 1 and at the expense of higher counts of only B lymphocytes (CD20) and immature lymphocytes in group 2.

Does bearing size influence metal ion levels in large-head metal-on-metal total hip arthroplasty? A comparison of three total hip systems

BACKGROUND

The purpose of the study was twofold: first, to determine whether there is a statistically significant difference in the metal ion levels among three different large-head metal-on-metal (MOM) total hip systems. The second objective was to assess whether position of the implanted prostheses, patient demographics or factors such as activity levels influence overall blood metal ion levels and whether there is a difference in the functional outcomes between the systems.

METHODS

In a cross-sectional cohort study, three different metal-on-metal total hip systems were assessed: two monoblock heads, the Durom socket (Zimmer, Warsaw, IN, USA) and the Birmingham socket (Smith and Nephew, Memphis, TN, USA), and one modular metal-on-metal total hip system (Pinnacle, Depuy Orthopedics, Warsaw, IN, USA). Fifty-four patients were recruited, with a mean age of 59.7 years and a mean follow-up time of 41 months (12 to 60). Patients were evaluated clinically, radiologically and biochemically. Statistical analysis was performed on all collected data to assess any differences between the three groups in terms of overall blood metal ion levels and also to identify whether there was any other factor within the group demographics and outcomes that could influence the mean levels of Co and Cr.

RESULTS

Although the functional outcome scores were similar in all three groups, the blood metal ion levels in the larger monoblock large heads (Durom, Birmingham sockets) were significantly raised compared with those of the Pinnacle group. In addition, the metal ion levels were not found to have a statistically significant relationship to the anteversion or abduction angles as measured on the radiographs.

CONCLUSIONS

When considering a MOM THR, the use of a monoblock large-head system leads to higher elevations in whole blood metal ions and offers no advantage over a smaller head modular system.

The effects of naturally occurring acids on the surface properties of chrysotile asbestos

Chrysotile asbestos is considered an environmental health hazard. It is postulated that the surface of chrysotile, with its inherent positive charge and chemical content of trace transition metals within the mineral is a causative factor of the concern. Weathering may reduce the negative health effects of chrysotile asbestos, by alteration of the outer brucite layer of the chrysotile. To assess the changes in the surface properties of chrysotile asbestos by simulated weathering, chrysotile was treated with oxalic, hydrochloric, and carbonic acids. Naturally occurring chrysotile, from a mine site and serpentinitic stream sediments from the Sumas River were analyzed and compared. Oxalic acid, a chelating acid, was the most effective at extracting the majority of the trace elements present in the chrysotile, reducing their positive surface charge and producing visible changes at the surface of the fibers as shown by Field Emission Scanning Electron Microsopy (FESEM). Carbonic acid had little effect on the surface properties. Stream environments had minor detectable effects on the surface properties on the chrysotile stream sediments.

Long-term exposure to low-concentrations of Cr(VI) induce DNA damage and disrupt the transcriptional response to benzo[a]pyrene

Living organisms are exposed on a daily basis to widespread mixtures of toxic compounds. Mixtures pose a major problem in the assessment of health effects because they often generate substance-specific effects that cannot be attributed to a single mechanism. Two compounds often found together in the environment are the heavy metal chromium and the polycyclic aromatic hydrocarbon benzo[a]pyrene (B[a]P). We have examined how long-term exposure to a low concentration of Cr(VI) affects the transcriptional response to B[a]P, a second toxicant with an unrelated mechanism of action. Growth of mouse hepatoma cells for 20 passages in medium with 0.1 or 0.5 μM Cr(VI) increases DNA damage and apoptosis while decreasing clonogenic ability. Treated cells also show transcriptome changes indicative of increased expression of DNA damage response and repair genes. In them, B[a]P activates cancer progression pathways, unlike in cells never exposed to Cr(VI), where B[a]P activates mostly xenobiotic metabolism pathways. Cells grown in Cr(VI) for 20 passages and then cultured for an additional 5 passages in the absence of Cr(VI) recover from some but not all the chromium effects. They show B[a]P-dependent transcriptome changes strongly weighted toward xenobiotic metabolism, similar to those in B[a]P-treated cells that had no previous Cr(VI) exposure, but retain a high level of Cr(VI)-induced DNA damage and silence the expression of DNA damage and cancer progression genes. We conclude that the combined effect of these two toxicants appears to be neither synergistic nor additive, generating a toxic/adaptive condition that cannot be predicted from the effect of each toxicant alone.

Polymeric nanofibers for the removal of Cr(III) from tannery waste water

We demonstrate the use of cysteine-modified polymer nanofibers for the rapid and efficient removal of Cr(III) from real tannery waste water samples. Various parameters such as pH, load of nanofibers and time of exposure were optimized to achieve maximum removal. The optimum parameters were found to be 0.1 mg of nanofibers per mL of tannery waste water with a pH of 5.5 and an exposure time of 45 min. Almost 99% Cr(III) was removed at these ideal conditions thus demonstrating the efficacy of our material. The maximum removal capacity at these ideal conditions was estimated to be approximately 1.75 g of chromium/gram of polymeric material. This is probably due to a variety of factors including the apparent high surface to volume ratio exhibited by these nanofibers and also due to the availability of numerous cysteine groups that are known to have high binding affinities with heavy metal ions. These nanoscale polymeric materials show great potential towards the removal of heavy metal cations from waste waters.

Elucidating the mechanism of Cr(VI) formation upon the interaction with metal oxides during coal oxy-fuel combustion

The thermodynamics underpinning the interaction of Cr-bearing species with basic metal oxides, i.e. K2O, Fe2O3, MgO and CaO, during the air and oxy-fuel combustion of coal have been examined. The synchrotron-based X-ray adsorption near-edge spectroscopy (XANES) was used for Cr speciation. For the oxides tested, Cr(VI) formation is dominated by the reduction potential of the metals. The oxides of Ca(2+) with high reduction potential favored the oxidation of Cr(III), same for K(+). The other two basic metals, Fe2O3 and MgO with lower reduction potentials reacted with Cr(III) to form the corresponding chromites at the temperatures above 600°C. Coal combustion experiments in drop-tube furnace have confirmed the rapid capture of Cr vapors, either trivalent or hexavalent, by CaO into solid ash. The existence of HCl in flue gas favored the vaporization of Cr as CrO2Cl2, which was in turn captured by CaO into chromate. Both Fe2O3 and MgO exhibited less capability on scavenging the Cr(VI) vapor. Particularly, MgO alone exhibited a low capability for capturing the vaporized Cr(III) vapors. However, its co-existence with CaO in the furnace inhibited the Cr(VI) formation. This is beneficial for minimizing the toxicity of Cr in the coal combustion-derived fly ash.

Surfactant Sensitized Calix[4]arenes Fluorescence Quenching Method for Speciation of Cr(VI)/Cr(III) in Water Samples

The surfactant sensitized spectrofluorimetry for speciation of chromium (Cr(VI)/Cr(III)) was developed. The analytical procedure was that the fluorescence intensity of l4,10,16,22-tetramethoxyl resorcinarene carboxylic acid derivatives (TRCA) could be selectively quenched by Cr(VI) and the fluorescence quenching value (ΔF=FTRCA-FCr(VI)-TRCA) was increased in cetyltrimethylammonium bromide (CTAB). The main influence factors on the fluorescence quenching (ΔF) were investigated in detail. Under the optimal conditions, the linear range of calibration curve for the determination of Cr(VI) was 0.10~5.00 μg/mL, and the detection limit was 0.024 μg/mL with RSD=2.10% (c=1.0 μg/mL, n=3). The concentration of Cr(III) was calculated by subtracting Cr(VI) from the total chromium determined after oxidizing Cr(III) to Cr(VI). The preliminary sensitized mechanism was discussed with the inclusion constant (K) of TRCA-Cr(VI), the fluorescence quantum yield of TRCA, and IR spectra characterization. The method has been applied to the speciation analysis of Cr(VI)/Cr(III) in water samples.

Transcriptomic analysis provides insights on hexavalent chromium induced DNA double strand breaks and their possible repair in midgut cells of Drosophila melanogaster larvae

Hexavalent chromium [Cr(VI)] is a well known mutagen and carcinogen. Since genomic instability due to generation of double strand breaks (DSBs) is causally linked to carcinogenesis, we tested a hypothesis that Cr(VI) causes in vivo generation of DSBs and elicits DNA damage response. We fed repair proficient Drosophila melanogaster (Oregon R(+)) larvae Cr(VI) (20.0μg/ml) mixed food for 24 and 48h and observed a significant (p<0.05) induction of DSBs in their midgut cells after 48h using neutral Comet assay. Global gene expression profiling in Cr(VI)-exposed Oregon R(+) larvae unveiled mis-regulation of DSBs responsive repair genes both after 24 and 48h. In vivo generation of DSBs in exposed Drosophila was confirmed by an increased pH2Av immunostaining along with the activation of cell cycle regulation genes. Analysis of mis-regulated genes grouped under DSB response by GOEAST indicated the participation of non-homologous end joining (NHEJ) DSB repair pathway. We selected two strains, one mutant (ligIV) and another ku80-RNAi (knockdown of ku80), whose functions are essentially linked to NHEJ-DSB repair pathway. As a proof of principle, we compared the DSBs generation in larvae of these two strains with that of repair proficient Oregon R(+). Along with this, DSBs generation in spn-A and okr [essential genes in homologous recombination repair (HR) pathway] mutants was also tested for the possible involvement of HR-DSB repair. A significantly increased DSBs generation in the exposed ku80-RNAi and ligIV (mutant) larvae because of impaired repair, concomitant with an insignificant DSBs generation in okr and spn-A mutant larvae indicates an active participation of NHEJ repair pathway. The study, first of its kind to our knowledge, while providing evidences for in vivo generation of DSBs in Cr(VI) exposed Drosophila larvae, assumes significance for its relevance to higher organisms due to causal link between DSB generation and Cr(VI)-induced carcinogenesis.

Hexavalent chromium-induced alteration of proteomic landscape in human skin fibroblast cells

Hexavalent chromium [Cr(VI)] generated during industrial processes is carcinogenic. Although much is known about the deleterious effects caused by reactive oxygen species generated during the reduction of Cr(VI) after its absorption by biological systems, the precise mechanisms underlying Cr(VI) cytotoxicity remain poorly defined. Here, we analyzed, at the global proteome scale, the perturbation of protein expression in GM00637 human skin fibroblast cells upon exposure to potassium dichromate (K₂Cr₂O₇). We were able to quantify ∼4600 unique proteins, among which ∼400 exhibited significant alterations in expression levels upon a 24-h treatment with 0.5 μM K₂Cr₂O₇. Pathway analysis revealed the Cr(VI)-induced perturbation of cholesterol biosynthesis, G-protein signaling, inflammatory response, and selenoprotein pathways. In particular, we discovered that the K₂Cr₂O₇ treatment led to pronouncedly elevated expression of a large number of enzymes involved in de novo cholesterol biosynthesis. Real-time PCR analysis revealed the increased mRNA expression of selected genes involved in cholesterol biosynthesis. Consistently, K₂Cr₂O₇ treatment resulted in marked increases in cellular cholesterol level in multiple cell lines. Moreover, the Cr(VI)-induced growth inhibition of cultured human cells could be rescued by a cholesterol-lowering drug, lovastatin. Together, we demonstrated, for the first time, that Cr(VI) may exert its cytotoxic effect, at least partly, through the up-regulation of enzymes involved in de novo cholesterol biosynthesis and the resultant increase of cholesterol level in cells.

Outline of occupational chromium poisoning in China

The present study analyzed the feature of occupational chromium poisoning in China since the 1980s. The collected data were acquired from 18 previous surveys of chromium poisoning in 14 cities of China. The method of risk assessment was applied to calculate the relative risk and 95% CI, p < 0.05 was considered as a significant risk. The results showed that nasal disease was the most common sign of occupational chromium poisoning, and the prevalence rate of nasal disease was 17.83% in total population of 6,998. Further, the risk analysis showed that occupational chromium poisoning led to an increased risk of lung or liver cancer in male workers due to the definite carcinogenicity of hexavalent chromium. Significantly, an increased risk of spontaneous or threatened abortion was also found in female workers. In conclusion, these studies suggest that early detection of impaired reproductive function or impaired lung or liver function in female or male workers is essential for controlling occupational chromium poisoning in China.

Optimization of bioleaching conditions for metal removal from CCA-treated wood by using an unknown Polyporales sp. KUC8959

The purpose of this study was to investigate the effect of extraction conditions (i.e., culture filtrate concentration, extraction temperature, and extraction time) on the removal of metals from chromated copper arsenate (CCA)-treated wood particles by using an unknown Polyporales sp. KUC8959. As the first research, a 20-run central composite design using response surface methodology was applied to optimize the system and construct the models, which predicted metal removal by bioleaching. The coefficients of determination of fitted models were 0.874-0.989, which indicated that the models can predict the metal removal yield accurately under various conditions. The Cu removal model suggested that the following conditions, culture filtrate concentration of 45.8%, extraction temperature of 34.2 °C, and extraction time of 20.6 h, were required for maximal removal of Cu (82.1%). The model predicted that extraction conditions of increased severity would result in complete removal of Cr and As from CCA-treated wood particles. In order to confirm actual metals removal efficiency, metals extraction was subsequently conducted under optimal bioleaching condition evaluated in this study. By applying the model, we demonstrated 83.9% Cu, 96.0% Cr, and 99.3% As removal from treated wood particles.

Accumulation of chromium in pak choi ( L.) grown on representative chinese soils

Anthropogenic chromium (Cr) pollution in soils poses a great threat to human health through the food chain. It is imperative to understand Cr accumulation properties in common vegetables because the proportion of vegetables consumed has increased with the improvement of living standards. This study investigated Cr accumulation in pak choi ( L.) grown on six representative agricultural soils in China. Chromium concentration in the edible parts of pak choi generally increased with soil Cr concentrations following the order: Ustic Cambosols > Periudic Argosols > Mollisols > Calcaric Regosols > Stagnic Anthrosols > Udic Ferrisols. Simple correlation analysis indicated that Cr concentration in pak choi was significantly correlated with the total Cr, Mehlich-3-extractable Cr, and Cr(VI). Stepwise multiple regression analysis also demonstrated that the phytoavailability of Cr was strongly correlated with the extractable fraction by Mehlich-3, total Cr concentration, soil organic matter, and Fe(II). Critical Cr concentrations in these six soils were evaluated for pak choi based on the maximum safe level for daily intake of Cr. Total soil Cr can be used as Cr thresholds for potential dietary toxicity in pak choi. Mehlich-3-extractable Cr is most suitable to be used as Cr thresholds for Periudic Argosols, Udic Ferrisols, Mollisols, and Ustic Cambosols, with values of 20.7, 15.8, 21.2, and 20.4 mg kg, respectively, whereas Cr(VI) is most suitable for Calcaric Regosols and Stagnic Anthrosols, with values of 26.5 and 28.0 mg kg, respectively.

Model for evaluation of the phytoavailability of chromium (Cr) to rice (Oryza sativa L.) in representative Chinese soils

Anthropogenic chromium (Cr) pollution in soils poses a great threat to human health through the food chain. It is imperative to understand Cr phytoavailability to rice (Oryza sativa L.), which is a major staple food crop for the largest population of people on Earth. This study was aimed to establish a model for evaluation of the phytoavailability of Cr to rice in six representative Chinese soils based on soil properties. Simple correlation analysis indicated that Cr concentration in polished rice was significantly correlated with total Cr, Mehlich-3 extractable Cr, and Cr(VI) in soil. Stepwise multiple regression analysis also demonstrated that the Cr phytoavailability was strongly correlated with soil total Cr, Mehlich-3 extractable Cr, Cr(VI) concentration, soil organic matter, Fe(II), and particle size distribution. Critical Cr concentrations in the six soils were evaluated for rice based on the maximum safe level for daily intake of Cr. Mehlich-3 extractable Cr are the most suitable Cr thresholds for Periudic Argosols, Udic Ferrisols, Mollisols, and Ustic Cambosols with values of 1.54, 0.56, 0.42, and 2.18 mg kg(-1), respectively, while Cr(VI) are adequate thresholds for Calcaric Regosols and Stagnic Anthrosols with values of 0.68 and 0.84 mg kg(-1), respectively.

Study of the thermodynamics of chromium(III) and chromium(VI) binding to iron(II/III)oxide or magnetite or ferrite and magnanese(II) iron (III) oxide or jacobsite or manganese ferrite nanoparticles

Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4±0.9 nm (Fe3O4) and 15.5±0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative.

Lead, mercury, cadmium, chromium, nickel, copper, zinc, calcium, iron, manganese and chromium (VI) levels in Nigeria and United States of America cement dust

This study was aimed at investigating the relative abundance of heavy metals in cement dust from different cement dust factories in order to predict their possible roles in the severity of cement dust toxicity. The concentrations of total mercury (Hg), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), manganese (Mn), lead (Pb), iron (Fe) and chromium (VI) (Cr (VI)) levels in cement dust and clinker samples from Nigeria and cement dust sample from the United States of America (USA) were determined using graphite furnace atomic absorption (GFAAS), while Zn and Ca were measured by flame atomic absorption spectrophotometry (FAAS), and Cr (VI) by colorimetric method. Total Cu, Ni and Mn were significantly higher in cement dust sample from USA (p<0.05), also, both total Cr and Cr (VI) were 5.4-26 folds higher in USA cement dust compared with Nigeria cement dust or clinker (p<0.001). Total Cd was higher in both Nigeria cement dust and clinker (p<0.05 and p<0.001), respectively. Mercury was more in both Nigeria cement dust and clinker (p<0.05), while Pb was only significantly higher in clinker from Nigeria (p<0.001). These results show that cement dust contain mixture of metals that are known human carcinogens and also have been implicated in other debilitating health conditions. Additionally, it revealed that metal content concentrations are factory dependent. This study appears to indicate the need for additional human studies relating the toxicity of these metals and their health impacts on cement factory workers.

Chromium(VI) but not chromium(III) species decrease mitoxantrone affinity to DNA

Binding of mitoxantrone (MXT) to double-stranded DNA has been investigated as a model drug-DNA binding system to evaluate the effects of various forms of chromium on the binding properties. We have found that Cr(III), which binds strongly to DNA, does not affect the MXT affinity to DNA. In contrast, Cr(VI), in the form of chromate ions CrO(4)(2-), decreases the MXT affinity to DNA despite electrostatic repulsions with phosphate-deoxyribose chains of DNA. The MXT-DNA binding constant was found to decrease from (1.96 ± 0.005) × 10(5) to (0.77 ± 0.018) × 10(5) M(-1) for Cr(VI) concentration changing from 0 to 30 μM. The influence of Cr(VI) on MXT-DNA binding has been attributed to the oxidation of guanine residue, thus interrupting the intercalation of MXT into the DNA double helix at the preferential CpG intercalation site. This supposition is corroborated by the observed increase in the MXT binding site size from 2 bp (base pairs) to 4-6 bp in the presence of Cr(VI). The measurements of the MXT-DNA binding constant and the MXT binding site size on a DNA molecule have been carried out using spectroscopic, voltammetric, and nanogravimetric techniques, providing useful information on the mechanism of the interactions.

Transcriptome profiling of genes differentially modulated by sulfur and chromium identifies potential targets for phytoremediation and reveals a complex S-Cr interplay on sulfate transport regulation in B. juncea

A differential display cDNA-AFLP derived technique was used to identify gene transcripts regulated by chromium (Cr) in relation to sulfur (S) nutrition in Brassica juncea. Twelve-day old plants were grown with 200 μM sulfate (+S), without sulfate (-S), with 200 μM sulfate plus 200 μM chromate (+S+Cr), or without sulfate plus 200 μM chromate (-S+Cr). Forty-four combinations of degenerate primers were assayed, which allowed the detection of 346 Transcript-Derived Fragments (TDFs) differentially regulated by Cr and S at times 0, 10 min, 1 h, 24 h. Eight sulfate transporters were identified, whose transcript abundance was dependent on the levels of plant S-compounds. For some of these transporters, a tight coordinated regulation of gene expression was observed in response to Cr. The MapMan analysis revealed a differential pattern of gene expression between +S+Cr and -S+Cr plants for several other transcripts and highlighted an overlap among responses to metals, defence against pathogens and senescence, hence suggesting the existence of common mechanisms of gene regulation. Among the identified gene transcripts, those involved in S metabolism and proteolitic processes may represent potential targets of genetic engineering in efforts to increase Cr accumulation and tolerance in plant species employed in phytoremediation techniques.

Spectroscopic analyses of pollutants in water, sediment and fish

Water ways in Egypt is suffering from continual discharge without adequate treatment especially in the Delta and greater Cairo area. Accordingly water, sediments and catfishes were collected from El Mouheet El Youmna drain in Giza. Cd, Cr, Pb and Zn were determined furthermore the molecular structure of sediment and catfish were conducted with FTIR spectroscopy. Although studied metals were lower in water, higher values are recorded in sediment and catfish samples. FTIR shows possible interaction among metals and organic structures mainly proteins. The bioaccumulation of Pb and Cd proportion was significantly increased in the liver tissues of catfish. A correlation coefficient among sediment and fish liver metals accumulation exist. This infers that the waste assimilation capacity for the drain is high, a phenomena that could be ascribed to dilution, sedimentation and continual water exchange. Furthermore, the genotoxicity affect in catfish genomic corroborates the genus diagnostic markers which attributed to long pollution. This is an indication that agriculture and industrial wastes discharged into the drain has badly a significant effect on the ecological balance.

Evidence of Cr(VI) formation during analysis of leather Proposal of an alternative method of analysis through the ion-chromatographic approach and post-column reaction

The formation of Cr(VI) in Cr(III) tanned leather, in neutral and alkaline solution, has been demonstrated by means of crossed experiments using different pH buffers, ethylenediaminetetraacetic acid as Cr(III) complexing agent and NaCl solutions. According to the found results the composition of the extracting solution suitable to extract Cr(VI) amount present in leather was pH 4.4 (which is also the tanned leather natural pH) and 5% NaCl (w/v). Interferences coming from coloured compounds have been eliminated with suitable SPE cartridges. A new protocol for the analysis of Cr(VI) based on ion chromatography and a diphenylcarbazide post-column reaction has been implemented. The use of a large volume injection loop (500mul) allowed to obtain a very low quantification limit (0.15mgkg(-1)) despite the low amount of leather extracted (0.2g with respect to 2.0g used by the IUC 18 official method). Evidence of the transient nature of Cr(VI) in leather requires using the external calibration procedure for the correct quantification of the species.

Examination of distribution of trace elements in hair, fingernails and toenails as alternative biological materials. Application of chemometric methods

The aim of this study was to find correlations between several studied elements and analyzed materials as well as the application and validation of an analytical method to determine trace elements in hair, fingernails and toenails of healthy volunteers (normal concentration). The method developed covers washing, mineralization and ICP-MS determination of 10 elements (Ca, Cd, Co, Cr, Cu, Fe, Mg, Ni, Pb and Zn) in hair and nails. Concentrations of the selected elements in hair, fingernails and toenails were measured for 24 women and 18 men. Furthermore, a chemometric approach (Principal Component Analysis, PCA) was employed to evaluate the correlations between concentrations of the elements in hair and nails and between these materials. Until now PCA has not been frequently applied in handling and interpretation of the results of analysis of biological materials. However, the results of the present investigation show the high potential of PCA in extraction of valuable information from analytical measurements. Additionally, PCA has become a useful tool for visualization of the obtained results. Moreover, the cluster analysis (CA) was used to group the samples according to gender, taking into account two different groups of elements: essential and toxic.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Reduction kinetics of hexavalent chromium in soils and its correlation with soil properties

The toxicity of chromium (Cr) to biota is related to its chemical forms and consequently to the redox conditions of soils. Hexavalent Cr[Cr(VI)] may undergo natural attenuation through reduction processes. In this study, the reduction kinetics of Cr(VI) in seven soils and its relationships with soil properties were investigated with laboratory incubation experiments. The results indicate that the reduction of Cr(VI) can be described by a first-order reaction. The reduction rates of Cr(VI) in the seven soils decreased in the order: Udic Ferrisols > Stagnic Anthrosols > Calcaric Regosols > Mollisol > Typic Haplustalf > Periudic Argosols > Ustic Cambosols. Simple correlation analysis revealed that the reduction of Cr(VI) in soils was positively related to organic matter content, dissolved organic matter content, Fe(II) content, clay fraction, and to the diversity index of the bacterial community but negatively correlated with easily reducible Mn content. Using stepwise regression, the reduction of Cr(VI) in soil could be quantitatively predicted by the measurement of dissolved organic matter content, Fe(II) content, pH, and soil particle size distribution, with a fitting level of 95.5%. The results indicated that the reduction of Cr(VI) in natural soils is not controlled by a single soil property but is the result of the combined effects of dissolved organic matter, Fe(II), pH, and soil particle size distribution.

Bioremediation and tolerance of humans to heavy metals through microbial processes: a potential role for probiotics?

The food and water we consume are often contaminated with a range of chemicals and heavy metals, such as lead, cadmium, arsenic, chromium, and mercury, that are associated with numerous diseases. Although heavy-metal exposure and contamination are not a recent phenomenon, the concentration of metals and the exposure to populations remain major issues despite efforts at remediation. The ability to prevent and manage this problem is still a subject of much debate, with many technologies ineffective and others too expensive for practical large-scale use, especially for developing nations where major pollution occurs. This has led researchers to seek alternative solutions for decontaminating environmental sites and humans themselves. A number of environmental microorganisms have long been known for their ability to bind metals, but less well appreciated are human gastrointestinal bacteria. Species such as Lactobacillus, present in the human mouth, gut, and vagina and in fermented foods, have the ability to bind and detoxify some of these substances. This review examines the current understanding of detoxication mechanisms of lactobacilli and how, in the future, humans and animals might benefit from these organisms in remediating environmental contamination of food.