Genotoxicity studies of heavy metals: lead, bismuth, indium, silver and antimony

Antimicrobial mechanism of cuprous oxide (Cu2O) coatings

Some very effective antimicrobial coatings exploit copper or cuprous oxide (Cu2O) as the active agent. The aim of this study is to determine which species is the active antimicrobial - dissolved ions, the Cu2O solid, or reactive oxygen species. Copper ions were leached from Cu2O into various solutions and the leachate tested for both dissolved copper and the efficacy in killing Pseudomonas aeruginosa. The concentration of copper species leached from Cu2O into aqueous solution varied greatly with the composition of the aqueous solution. For a range of solution buffers, killing of P. aeruginosa was highly correlated with the concentration of copper in the leachate. Further, 10 µL bacterial suspension droplets were placed on Cu2O coatings, with or without a polymer barrier layer, and tested for bacterial kill. Killing occurred without contact between bacterium and solid, demonstrating that contact with Cu2O is not necessary. We therefore conclude that soluble copper species are the antimicrobial agent, and that the most potent species is Cu+. The solid quickly raises and sustains the concentration of soluble copper species near the bacterium. Killing via soluble copper ions rather than contact should allow copper coatings to kill bacteria even when fouled, which is an important practical consideration.

Association of chromosomal abnormalities with prenatal exposure to heavy metals: A nested case-control study in high-risk pregnant women in China

Prenatal exposure to heavy metals causes multiple hazards to fetal growth and development. Epidemiological studies on the association between heavy metals and fetal chromosomal abnormalities (CAs) are lacking. We conducted a nested case-control study in a cohort of high-risk pregnant women in China from September 2018 to June 2021. A total of 387 participants were diagnosed with fetal CAs in the case group and 699 were diagnosed with a normal karyotype in the control group. Amniotic fluid concentrations of 10 metals (barium, cobalt, antimony, manganese, ferrum, copper, selenium, strontium, vanadium, and chromium) were measured using inductively coupled plasma-mass spectrometry. We applied quantile g-computation and weighted quantile sum regression to assess the overall effect of metal mixtures and identify metals with significant weight. Logistic and Poisson regression analyses were used to estimate the effects of metals on CAs and CAs subtypes. Our results showed that the metal mixture concentrations were positively associated with the risk of fetal CAs. In adjusted logistic models, Sb was associated with fetal CAs (OR=1.15, 95% CI: 1.02-1.30), and revealed a linear dose-response relationship between Sb level and the risk of fetal CAs. Additionally, the exploratory analysis revealed that Sb levels were associated with Klinefelter syndrome (OR=1.452, 95% CI: 1.063-1.984) and Turner syndrome (OR=1.698; 95% CI,1.048-2.751). Our study revealed that metal mixtures are associated with a higher risk of fetal CAs and that this association may be driven primarily by Sb. Moreover, we provide a genetic perspective on the effects of heavy metals on sexual development in humans.

Association of multi-metals exposure with intelligence quotient score of children: A prospective cohort study

BACKGROUND

Associations between most single metals and children's intelligence quotient (IQ) scores have been evaluated in previous studies. However, associations between multi-metal exposures and children's IQ scores have not been analyzed.

OBJECTIVES

To assess the joint effects of lead (Pb), manganese (Mn), antimony (Sb), tin (Sn) and titanium (Ti) co-exposure on children's IQ scores.

METHODS

A prospective cohort study was conducted in Shimen and Huayuan, Hunan Province, China. Urine metals levels were measured by inductively coupled plasma mass spectrometry (ICP-MS) at baseline. Children's IQ scores were repeatedly measured at baseline and follow-up following the method of Raven's Standard Progressive Matrices (SPM) and standardized as z scores. We fitted linear regression models and Bayesian kernel machine regression (BKMR) models to investigate the associations of metal levels with children's IQ scores after adjusting for covariates.

RESULTS

A total of 633 participants aged 7-10 years completed the survey. Urinary Pb (β = -0.028, P = 0.022) and urinary Ti (β = -0.0003, P = 0.001) were inversely associated with children's IQ scores. The BKMR analyses revealed significant negative overall effects of the five metals on children's IQ scores when all the metals were above their median levels, while significant positive associations were shown when all the metal concentrations were below their median levels. The model also showed negative trends of Sn and Ti on children's IQ. Furthermore, Ti and Sn had a synergistic relationship, with a decline in IQ score when Sn exposure was relatively high. The urinary Sn concentration was significantly higher but the urinary Ti concentration was significantly lower in participants from the Shimen area than in those from the Huayuan area. Decreasing trends of the overall effects were observed in both the Shimen and Huayuan areas.

CONCLUSION

Our findings revealed that multi-metal exposures caused a decline in children's IQ scores according to traditional linear regression models and the BKMR model. Our results provide some evidence of the association between multi-metal exposure and children's IQ. Meanwhile, interactions between multi-metal exposures on children's IQ should be given more attention.

Complex Mechanisms of Antimony Genotoxicity in Budding Yeast Involves Replication and Topoisomerase I-Associated DNA Lesions, Telomere Dysfunction and Inhibition of DNA Repair

Antimony is a toxic metalloid with poorly understood mechanisms of toxicity and uncertain carcinogenic properties. By using a combination of genetic, biochemical and DNA damage assays, we investigated the genotoxic potential of trivalent antimony in the model organism Saccharomyces cerevisiae. We found that low doses of Sb(III) generate various forms of DNA damage including replication and topoisomerase I-dependent DNA lesions as well as oxidative stress and replication-independent DNA breaks accompanied by activation of DNA damage checkpoints and formation of recombination repair centers. At higher concentrations of Sb(III), moderately increased oxidative DNA damage is also observed. Consistently, base excision, DNA damage tolerance and homologous recombination repair pathways contribute to Sb(III) tolerance. In addition, we provided evidence suggesting that Sb(III) causes telomere dysfunction. Finally, we showed that Sb(III) negatively effects repair of double-strand DNA breaks and distorts actin and microtubule cytoskeleton. In sum, our results indicate that Sb(III) exhibits a significant genotoxic activity in budding yeast.

The toxicology of gallium oxide in comparison with gallium arsenide and indium oxide

Gallium arsenide (GaAs) and indium oxide (In₂O₃) are used in electronic industries at high and increasing tonnages since decades. Gallium oxide (Ga₂O₃) is an emerging wide-bandgap transparent conductive oxide with as yet little industrial use. Since GaAs has received critical attention due to the arsenic ion, it seemed reasonable to compare its toxicology with the respective endpoints of Ga₂O₃ and In₂O₃ toxicology in order to find out if and to what extent arsenic contributes. In addition, the toxicology of Ga₂O₃ has not yet been adequately reviewed, Therefore, this review provides the first evaluation of all available toxicity data on Ga₂O₃. The acute toxicity of all three compounds is rather low. Subchronic inhalation studies in rats and mice revealed persistent pulmonary alveolar proteinosis (PAP) and/or alveolar histiocytic infiltrates down to the lowest tested concentration in rats and mice, i.e. 0.16 mg Ga₂O₃/m³. These are also the predominant effects after GaAs and In₂O₃ exposure at similarly low levels, i.e. 0.1 mg/m³ each. Subchronic Ga₂O₃ exposure caused a minimal microcytic anemia with erythrocytosis in rats (at 6.4 mg/m³ and greater) and mice (at 32 and 64 mg/m³), a decrease in epididymal sperm motility and concentration as well as testicular degeneration at 64 mg/m³. At comparable concentrations the hematological effects and male fertility of GaAs were much stronger. The stronger effects of GaAs are due to its better solubility and presumed higher bioavailability. The database for In₂O₃ is too small and subchronic testing was at very low levels to allow conclusive judgements if blood/blood forming or degrading and male fertility organs/tissues would also be targets.

Antimony and its compounds: Health impacts related to pulmonary toxicity, cancer, and genotoxicity

Although occupational exposure to antimony and its compounds can produce pulmonary toxicity, human carcinogenic impacts have not been observed. Inhalation studies with respirable antimony trioxide particles administered to rats and mice have, however, induced carcinogenic responses in the lungs and related tissue sites. Genotoxicity studies conducted to elucidate mechanism(s) for tumor induction have produced mixed results. Antimony compounds do not induce gene mutations in bacteria or cultured mammalian cells, but chromosome aberrations and micronuclei have been observed, usually at highly cytotoxic concentrations. Indirect mechanisms of genotoxicity have been proposed to mediate these responses. In vivo genotoxicity tests have generally yielded negative results although several positive studies of marginal quality have been reported. Genotoxic effects may be related to indirect modes of action such as the generation of excessive reactive oxygen species (ROS), altered gene expression or interference with DNA repair processes. Such indirect mechanisms may exhibit dose-response thresholds. For example, interaction of ROS with in vivo antioxidant systems could yield a threshold for genotoxicity (and cancer) only at concentrations above the capacity of antioxidant defense mechanisms to control and/or eliminate damage from ROS.

Metallic air pollutants and breast cancer heterogeneity

BACKGROUND

Emerging evidence suggests airborne metals may be associated with breast cancer risk. However, breast cancer is heterogenous and associations with heavy metals vary by subtype. Heavy metals possess both carcinogenic and xenoestrogenic properties which may be related to different tumor etiologies. Therefore, we tested for etiologic heterogeneity, using a case-series approach, to determine whether associations between residential airborne metal concentrations and breast cancer differed by tumor subtype.

METHODS

Between 2005 and 2008, we enrolled incident breast cancer cases into the Breast Cancer Care in Chicago study. Tumor estrogen and progesterone receptors status was determined by medical record abstraction and confirmed immunohistochemically (N = 696; 147 ER/PR-negative). The 2002 USEPA's National Air Toxics Assessment census-tract estimates of metal concentrations (antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel and selenium) were matched to participants' residences of the same year. Adjusted logistic regression models were used to examine whether the airborne heavy metal associations differed by tumor ER/PR status. Principal component analysis was performed to assess associations by metal co-exposures.

RESULTS

Comparing the highest and lowest quintiles, higher concentrations of antimony (odds ratio[OR]: 1.8, 95% confidence interval[CI]: 0.9, 3.7, P-trend: 0.05), cadmium (OR: 2.3, 95% CI: 1.2, 4.4, P-trend: 0.04) and cobalt (OR: 2.0, 95% CI: 0.9, 4.4, P-trend: 0.04) were associated with ER/PR-negative breast cancer. Mixture analysis using principal components suggested co-exposures to multiple airborne heavy metals may drive associations with tumor receptor status.

CONCLUSIONS

Among women diagnosed with breast cancer, metallic air pollutants were associated with increased odds of developing ER/PR-negative breast cancer.

Biological, biochemical and genotoxic effects of Sb in the midge Chironomus sancticaroli Strixino and Strixino, 1981 (Diptera: Chironomidae)

In aquatic systems, antimony (Sb) is found in the water column and associated with sediment particles being bioavailable to organisms. Consequently, toxic effects have been detected in benthic invertebrates, but the toxicity after Sb exposure in Chironomidae have not been investigated. Were investigated DNA damage, activities of cholinesterase (ChE), alpha and beta esterase (EST-α, EST-β), glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) and lipid peroxidation after acute (48 h) and subchronic exposure (8 d). We also investigated the effects of subchronic (8 d) on development of larvae and chronic (25 d) Sb exposure on emergence and size of adults of Chironomus sancticaroli. Were analyze Sb nominal concentrations ranged from 0.5 to 800 μg.L^-1. Genotoxic effects occurred at higher concentrations upon acute (50, 800 μg.L^-1) and subchronic exposure (50 μg.L^-1). Acute exposure increased ChE, EST-α, EST-β, and GST activities. Subchronic Sb exposure increased EST-α activity at 0.2 μg.L^-1 and GST activity at 5 μg.L^-1. CAT activity increased at all concentrations while increasing lipid peroxidation levels were observed (1 μg.L^-1, 5 μg.L^-1 and 50 μg.L^-1), indicating oxidative stress. All concentrations of Sb delayed larval development and decreased the number of emerging adults. At high concentrations (50, 500, 800 μg.L^-1), the emerging adults were smaller. In conclusion, these varying genotoxic, biochemical and biological effects of Sb make a notable impact on the reproduction and population dynamics of C. sancticaroli.

Occurrence of 44 elements in human cord blood and their association with growth indicators in newborns

There is growing concern about environmental pollution produced by elements, including "emerging" contaminants, such as rare earth elements (REE) and other trace elements (TE), which are extensively and increasingly employed in the manufacture of consumer electronics. Previous research has shown that prenatal exposure to some elements (mainly heavy metals) may be associated with decreased fetal growth and other adverse birth outcomes. Recent studies have also shown that environmental exposure to REE and TE may be related to adverse effects on human health. This cross-sectional study, which included nearly 92% of the births in 2016 in La Palma (Canary Islands, Spain; n = 471), aimed to evaluate the potential adverse health effects exerted by a wide range of elements on newborns. We quantified the levels of 44 elements (including 26 REE and TE) in their umbilical cord blood. Our results showed low or very low levels of most elements. We found an inverse association between antimony (Sb) and birth weight (Spearman's r = -0.106, p = 0.021). A similar trend was observed between nickel (Ni) and birth weight and between chromium (Cr) and birth length, although in this case the significance was borderline. Bismuth appeared as a risk factor for having a birth weight below the tenth percentile in the univariate (OR = 3.30; 95% CI = 1.25-8.78; p = 0.017) and multivariate analyses (OR = 5.20; 95% CI = 1.29-20.91; p = 0.020). When assessing the effect of element mixtures, the sum of Cr, Ni, and Sb appeared as a risk factor for having a birth weight below the tenth percentile in the univariate (OR = 2.41; 95% CI = 1.08-5.35; p = 0.031) and multivariate analyses (OR = 3.84; 95% CI = 1.42-10.39; p = 0.008). Our findings suggest that some inorganic elements-isolated or in mixture-are associated to a lower fetal growth. Additional research is needed to understand the role of inorganic pollutants on fetal development.

Heavy Metals' Effect on Susceptibility to Attention-Deficit/Hyperactivity Disorder: Implication of Lead, Cadmium, and Antimony

Background: Heavy metals are known to be harmful for neurodevelopment and they may correlate to attention deficit/hyperactivity disorder (ADHD). In this study, we aim to explore the relationships between multiple heavy metals (manganese, lead, cadmium, mercury, antimony, and bismuth), neurocognitive function, and ADHD symptoms. Methods: We recruited 29 patients with ADHD inattentive type (ADHD-I), 47 patients with ADHD hyperactivity/impulsivity type (ADHD-H/I), and 46 healthy control children. Urine samples were obtained to measure the levels of the aforementioned heavy metals in each child. Participants’ cognitive function and clinical symptoms were assessed, respectively. Results: We found ADHD-H/I patients demonstrated the highest antimony levels (p = 0.028), and ADHD-I patients demonstrated the highest cadmium levels (p = 0.034). Antimony levels were positively correlated with the severity of ADHD symptoms that were rated by teachers, and cadmium levels were negatively correlated with the Full Scale Intelligence Quotient. Lead levels were negatively correlated with most indices of the Wechsler Intelligence Scale for Children–Fourth Edition (WISC-IV), but positively correlated with inattention and hyperactivity/impulsivity symptoms (p < 0.05). Conclusion: Lead, cadmium and antimony were associated with susceptibility to ADHD and symptom severity in school-age children. Eliminating exposure to heavy metals may help to prevent neurodevelopmental disorders in children.

Sub-inhibitory concentrations of heavy metals facilitate the horizontal transfer of plasmid-mediated antibiotic resistance genes in water environment

Although widespread antibiotic resistance has been mostly attributed to the selective pressure generated by overuse and misuse of antibiotics, recent growing evidence suggests that chemicals other than antibiotics, such as certain metals, can also select and stimulate antibiotic resistance via both co-resistance and cross-resistance mechanisms. For instance, tetL, merE, and oprD genes are resistant to both antibiotics and metals. However, the potential de novo resistance induced by heavy metals at environmentally-relevant low concentrations (much below theminimum inhibitory concentrations [MICs], also referred as sub-inhibitory) has hardly been explored. This study investigated and revealed that heavy metals, namely Cu(II), Ag(I), Cr(VI), and Zn(II), at environmentally-relevant and sub-inhibitory concentrations, promoted conjugative transfer of antibiotic resistance genes (ARGs) between E. coli strains. The mechanisms of this phenomenon were further explored, which involved intracellular reactive oxygen species (ROS) formation, SOS response, increased cell membrane permeability, and altered expression of conjugation-relevant genes. These findings suggest that sub-inhibitory levels of heavy metals that widely present in various environments contribute to the resistance phenomena via facilitating horizontal transfer of ARGs. This study provides evidence from multiple aspects implicating the ecological effect of low levels of heavy metals on antibiotic resistance dissemination and highlights the urgency of strengthening efficacious policy and technology to control metal pollutants in the environments.

The toxicology of indium oxide

Indium oxide (In₂O₃) is a technologically important semiconductor essentially used, doped with tin oxide, to form indium tin oxide (ITO). It is poorly soluble in all so far tested physiologic media. After repeated inhalation, In₂O₃ particles accumulate in the lungs. Their mobilization can cause significant systemic exposure over long periods of time. An increasing number of cases of severe lung effects (characterized by pulmonary alveolar proteinosis, emphysema and/or interstitial fibrosis) in workers of the ITO industry warrants a review of the toxicological hazards also of In₂O₃. The database on acute and chronic toxicity/carcinogenicity/genotoxicity/reproductive toxicity as well skin/eye irritation and sensitization is very limited or even lacking. Short-term and subchronic inhalation studies in rats and mice revealed persistent alveolar proteinosis, inflammation and early indicators of fibrosis in the lungs down to concentrations of 1 mg/m³. Epidemiological and medical surveillance studies, serum/blood indium levels in workers as well as data on the exposure to airborne indium concentrations indicate a need for measures to reduce exposure at In₂O₃ workplaces.

The relative sensitivity of freshwater species to antimony(III): Implications for water quality guidelines and ecological risk assessments

Antimony (Sb) is a pollutant in many jurisdictions, yet its threat to aquatic biota is unclear. Water quality guidelines (WQGs) for Sb are not well established and large uncertainty factors are commonly applied in derivation. We constructed freshwater species sensitivity distributions (SSDs) for Sb(III) using available acute toxicity data sourced from temperate and tropical regional studies. A tiered ecological risk assessment (ERA) approach using risk quotients (RQs) was applied for characterisation of risks presented by Sb(III) concentrations measured in the freshwater environment. Multiple parametric models were fitted for each SSD, with the optimal model used to derive the 5% hazardous concentration (HC5), defined as protective of 95% of species, and the corresponding predicted no effect concentration (PNEC). The HC5 values for whole and temperate SSDs were estimated at 781 and 976 μg L^-1 Sb(III), respectively, while the PNECs for both datasets were 156 and 195 μg L^-1 Sb(III), respectively. Due to limited tropical data, a temperate-to-tropic extrapolation factor of 10 was used to estimate an interim PNEC for tropical regions of 20 μg L^-1 Sb(III). Based on published freshwater Sb(III) concentration values across a range of locations, potential ecological risks posed by Sb(III) in some freshwater systems studied would be classified as medium to high risk, but the majority of locations sampled would fall into the low ecological risk category. Our results facilitate the understanding of toxic effects of Sb(III) to freshwater species but also demonstrate that data for Sb ERA are extremely limited.

Indium acetate toxicity in male reproductive system in rats

Indium, a rare earth metal characterized by high plasticity, corrosion resistance, and a low melting point, is widely used in the electronics industry, but has been reported to be an environmental pollutant and a health hazard. We designed a study to investigate the effects of subacute exposure of indium compounds on male reproductive function. Twelve-week old male Sprague-Dawley rats were randomly divided into test and control groups, and received weekly intraperitoneal injections of indium acetate (1.5 mg/kg body weight) and normal saline, respectively, for 8 weeks. Serum indium levels, cauda epididymal sperm count, motility, morphology, chromatin DNA structure, mitochondrial membrane potential, oxidative stress, and testis DNA content were investigated. The indium acetate-treated group showed significant reproductive toxicity, as well as an increased percentage of sperm morphology abnormality, chromatin integrity damage, and superoxide anion generation. Furthermore, positive correlations among sperm morphology abnormalities, chromatin DNA damage, and superoxide anion generation were also noted. The results of this study demonstrated the toxic effect of subacute low-dose indium exposure during the period of sexual maturation on male reproductive function in adulthood, through an increase in oxidative stress and sperm chromatin DNA damage during spermiogenesis, in a rodent model.

Maternal exposure to alkali, alkali earth, transition and other metals: Concentrations and predictors of exposure

Most studies of metals exposure focus on the heavy metals. There are many other metals (the transition, alkali and alkaline earth metals in particular) in common use in electronics, defense industries, emitted via combustion and which are naturally present in the environment, that have received limited attention in terms of human exposure. We analysed samples of whole blood (172), urine (173) and drinking water (172) for antimony, beryllium, bismuth, cesium, gallium, rubidium, silver, strontium, thallium, thorium and vanadium using ICPMS. In general most metals concentrations were low and below the analytical limit of detection with some high concentrations observed. Few factors examined in regression models were shown to influence biological metals concentrations and explained little of the variation. Further study is required to establish the source of metals exposures at the high end of the ranges of concentrations measured and the potential for any adverse health impacts in children.

Genotoxicity of indium tin oxide by Allium and Comet tests

Genotoxic effects of indium tin oxide (ITO) were investigated on root cells of Allium cepa by employing both Allium and Comet assays. A. cepa roots were treated with the aqueous dispersions of ITO at 5 different concentrations (12.5, 25, 50, 75, and 100 ppm) for 4 h. Exposure of ITO significantly increased mitotic index, and total chromosomal aberrations by the Allium test. While chromosome laggards, stickiness, disturbed anaphase-telophase and anaphase bridges were observed in anaphase-telophase cells, c-metaphase and binuclear cells were observed in other cells. A significant increase in DNA damage was also observed at all concentrations of ITO by the Comet assay. These results indicate that ITO exhibits genotoxic activity in A. cepa root meristematic cells.

Assessment of mutagenic, genotoxic, and cytotoxic potential of water samples of Harike wetland: a Ramsar site in India using different ex vivo biological systems

Harike is a wetland of international importance under the Ramsar Convention. The present study entails the investigation of mutagenic, genotoxic and cytotoxic effect of surface water samples collected from five different areas of the Harike wetland by using the histidine reversion point mutation assay in Salmonella typhimurium (TA98 and TA100) strain with or without S9, bioluminescence mutagenicity assay using Vibrio harveyi (A16) strain, plasmid-nicking assay using pBR322 and 3(4,5-dimethyl-thiazol-2-yl)2,5-diphenyl-tetrazolium bromide assay as well as confocal imaging studies using Chinese hamster ovarian cell line, respectively. It was observed that although, the water sample of all the areas of wetland demonstrated mutagenic, genotoxic as well as cytotoxic activity, the effect was quite significant with the water samples from River Satluj and Khatan area (i.e. reservoir mainly contains Satluj water). The metal analysis of water samples was also conducted with atomic absorption spectrophotometer. The mutagenicity, genotoxicity and cytotoxicity of water samples emerged to be correlated with metal concentration. The source of toxic components seems to be associated with various industrial effluents and agricultural run-off. The results of the present study carry great importance in documenting the water quality monitoring data of the wetland.

Indium chloride-induced micronuclei via reactive oxygen species in Chinese hamster lung fibroblast V79 cells

We study the cytotoxicity of indium chloride (InCl₃) in Chinese hamster lung fibroblasts, the V79 cells, using MTT assay. The results showed that InCl₃ did not induce significant cytotoxicity at various concentrations tested. In addition, the frequency of micronuclei (MN) was assayed to evaluate the genotoxic effects of InCl₃ in V79 cells. InCl₃ at concentrations ranged 0.1-1 μM significantly increased MN frequency in a concentration-dependent manner. Both catalase and superoxide dismutase at concentrations of 75 and 150 μg/mL significantly inhibited InCl₃-induced MN. Similarly, Germanium oxide (GeO₂) and dimercaprol expressed antigenotoxic effects. From these findings, it is concluded that InCl₃ is a potent genotoxic chemical, which may be mediated partly by inducing oxidative stress. The significance of this study shows that the workers in the semiconductor factories should be cautious in exposing to the hazardous genotoxic InCl₃.

Antimicrobial activity of metals: mechanisms, molecular targets and applications

Metals have been used as antimicrobial agents since antiquity, but throughout most of history their modes of action have remained unclear. Recent studies indicate that different metals cause discrete and distinct types of injuries to microbial cells as a result of oxidative stress, protein dysfunction or membrane damage. Here, we describe the chemical and toxicological principles that underlie the antimicrobial activity of metals and discuss the preferences of metal atoms for specific microbial targets. Interdisciplinary research is advancing not only our understanding of metal toxicity but also the design of metal-based compounds for use as antimicrobial agents and alternatives to antibiotics.

Migration of antimony from PET trays into food simulant and food: determination of Arrhenius parameters and comparison of predicted and measured migration data

Migration experiments with small sheets cut out from ovenable PET trays were performed in two-sided contact with 3% acetic acid as food simulant at various temperatures. The fraction of diffusible antimony (Sb) was estimated to be 62% in the PET sample under study. Apparent diffusion coefficients of Sb in PET trays were determined experimentally. Measurement of migration between 20 and 150°C yielded a linear Arrhenius plot over a wide temperature range from which the activation energy (E(a)) of 188 ± 36 kJ mol(-1) and the pre-exponential factor (D(0)) of 3.6 × 10(14) cm(2) s(-1) were determined for diffusing Sb species. E (a) was similar to previously reported values for PET bottles obtained with a different experimental approach. E (a) and D (0) were applied as model parameters in migration modelling software for predicting the Sb transfer in real food. Ready meals intended for preparation in a baking oven were heated in the PET trays under study and the actual Sb migration into the food phase was measured by isotope dilution ICP-MS. It was shown that the predictive modelling reproduces correctly experimental data.

pH and Antimicrobial Activity of Portland Cement Associated with Different Radiopacifying Agents

Objective. The aim of this study was to evaluate the antimicrobial activity and pH changes induced by Portland cement (PC) alone and in association with radiopacifiers. Methods. The materials tested were pure PC, PC + bismuth oxide, PC + zirconium oxide, PC + calcium tungstate, and zinc oxide and eugenol cement (ZOE). Antimicrobial activity was evaluated by agar diffusion test using the following strains: Micrococcus luteus, Streptococcus mutans, Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans. After 24 hours of incubation at 37°C, inhibition of bacterial growth was observed and measured. For pH analysis, material samples (n = 10) were placed in polyethylene tubes and immersed in 10 mL of distilled water. After 12, 24, 48, and 72 hours, the pH of the solutions was determined using a pH meter. Results. All microbial species were inhibited by the cements evaluated. All materials composed of PC with radiopacifying agents promoted pH increase similar to pure Portland cement. ZOE had the lowest pH values throughout all experimental periods. Conclusions. All Portland cement-based materials with the addition of different radiopacifiers (bismuth oxide, calcium tungstate, and zirconium oxide) presented antimicrobial activity and pH similar to pure Portland cement.

Genotoxicity of sediment extracts of the Berre lagoon (France)

To evaluate the genotoxic risk that contaminated sediment could constitute for benthic organisms, three contaminated (VA, VC and VN) and one uncontaminated (RN) sediment samples were collected in the Berre lagoon (France). Potentially bioavailable contaminants in sediments were obtained using sediment extraction with synthetic seawater adjusted to pH 4 or pH 6, simulating the range of pH prevailing in the digestive tract of benthic organisms. The genotoxic activities of these extracts were evaluated by three short-term bioassays: the Salmonella mutagenicity test using the Salmonella typhimurium strain TA102, the alkaline comet assay and the micronucleus assay on the Chinese Hamster Ovary cells CHO-K1. Results of the Salmonella mutagenicity assay detected a mutagenic response for RN extract at pH 6, and for VA extract at pH 4. Results of the comet and micronucleus assays detected low genotoxic/clastogenic activities for VA and VC extracts at pH 6 and higher activities for RN, VA and VC extracts at pH 4. To identify if metals (Al, Fe, Mn, As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) were involved in these genotoxic activities, their concentrations were determined in the extracts, and their speciation was assessed by thermodynamic calculations. Results showed that extracts from sites VA, VC and VN generally presented the highest trace metal contents for both extractants, while the site RN presented lower trace metal contents but the highest Fe and Mn contents. Thermodynamic calculations indicated that Fe, Mn, As and in a lower extend Co, Ni and Zn were mainly present under free forms in extracts, and were consequently, more likely able to induce a genotoxic effect. Results globally showed no correspondence between free metal contents and genotoxic activities. They suggested that these positive results could be due to uncharacterized compounds, acting as direct genotoxic agents or enhancing the genotoxic properties of analyzed metals.

Multiple metals exposure and neurotoxic risk in bald eagles (Haliaeetus leucocephalus) from two Great Lakes states

In the present study, the authors determined concentrations of several elements (As, Cd, Co, Cu, Cr, Mn, Pb, Sb, Zn) in the brains and livers of 46 bald eagles (Haliaeetus leucocephalus) from two Great Lakes states, Michigan and Minnesota. To explore whether exposures are of neurological concern, the authors assessed their associations with neurochemical receptors (N-methyl-D-aspartate [NMDA] and γ-aminobutyric acid A [GABA(A)]) and enzymes (glutamine synthetase [GS] and glutamic acid decarboxylase [GAD]) that play critical roles in vertebrate neurobehavior and reproduction. For most elements, levels in the livers and brains did not differ between region and gender. Hepatic Pb levels averaged 33.1 ppm (dry wt), 30.4% of all carcasses exceeded proposed avian Pb thresholds (>26.4 ppm), and in 30.8% of the birds examined evidence of Pb pellets or fragments was found. Significant changes in the activities of GS and GAD were related to brain concentrations of several metals (Pb, Cd, Co, Cu, Zn). No relationships were found among any of the nine elements and NMDA or GABA(A) receptor levels. When combined with the authors' previous study on these same eagles that showed Hg-associated alterations in GS, GAD, and NMDA receptor levels, the present research suggests that bald eagles are exposed to various elements, especially Pb and Hg, that are capable of causing changes in GABAergic and glutamatergic neurotransmission. The functional significance of these neurochemical changes warrants attention.

Using In(III) as a promoter for glycosylation

InCl(3), InBr(3), and In(OTf)(3) were tested as promoters in the preparation of glycosides from trichloroacetimidate precursors. A range of protecting groups and of alcohol acceptors were used to determine the versatility of these promoters. Disaccharide formation was demonstrated. In most cases, the In(III) compounds were shown to promote glycosylation better than the widely used promoter BF(3)·OEt(2).

Antimony toxicity

Antimony toxicity occurs either due to occupational exposure or during therapy. Occupational exposure may cause respiratory irritation, pneumoconiosis, antimony spots on the skin and gastrointestinal symptoms. In addition antimony trioxide is possibly carcinogenic to humans. Improvements in working conditions have remarkably decreased the incidence of antimony toxicity in the workplace. As a therapeutic, antimony has been mostly used for the treatment of leishmaniasis and schistosomiasis. The major toxic side-effects of antimonials as a result of therapy are cardiotoxicity (~9% of patients) and pancreatitis, which is seen commonly in HIV and visceral leishmaniasis co-infections. Quality control of each batch of drugs produced and regular monitoring for toxicity is required when antimonials are used therapeutically.

The efficiacy of bismuth subnitrate against genotoxicity and oxidative stress induced by aluminum sulphate

Aluminum (Al) is commonly used in industrial processes and drugs and is thought to induce erythrocytes damage via activation of oxidative stress. Recently, bismuth (Bi)-containing drugs are used in the treatment of various diseases. However, uncertain effects of Bi in blood tissue may participate in the therapeutic efficacy of Bi compounds as related to metals. Hence, this study aimed to determine the roles on human blood cells of the various concentrations of aluminum sulphate (Al2 (SO4)3) and bismuth subnitrate (BSN), separate and together. With this aim, oxidative status was assessed on erythrocytes by measuring following oxidative stress markers: reduced glutathione (GSH), superoxide dismutase (SOD), glucose-6-phosphate dehydrogenase (G-6-PDH) and catalase (CAT). Two chemicals were tested for their ability to induce cytogenetic change in human lymphocytes using assays for chromosome aberrations (CAs) and sister chromatid exchanges (SCEs). Our results showed that high dose of Al2(SO4)3 (20 µg/mL) caused oxidative stress and increased CA and SCE frequencies. Whereas, BSN doses did not change CA and SCE rates. Moreover, it led to changes of antioxidant capacity at different concentrations. After concomitant treatment with Al2(SO 4)3 and BSN, the effects of BSN doses were different on enzyme activities and decreased the genotoxic damage. However, the high dose of BSN and Al2(SO4)3 was shown to enhance the frequencies of CAs and SCEs in a synergistic manner. In conclusion, BSN could be effective in the protection against the blood toxicity of Al 2(SO4)3.