Occupational respiratory exposures to irritating and sensitizing volatile compounds deriving from cleaning products

Recent findings suggest an association between exposure to cleaning products and respiratory dysfunctions including asthma. However, little information is available about quantitative airborne exposures of professional cleaners to volatile organic compounds deriving from cleaning products. During the first phases of the study, a systematic review of cleaning products was performed. Safety data sheets were reviewed to assess the most frequently added volatile organic compounds. It was found that professional cleaning products are complex mixtures of different components (compounds in cleaning products: 3.5 ± 2.8), and more than 130 chemical substances listed in the safety data sheets were identified in 105 products. The main groups of chemicals were fragrances, glycol ethers, surfactants, solvents; and to a lesser extent phosphates, salts, detergents, pH-stabilizers, acids, and bases. Up to 75% of products contained irritant (Xi), 64% harmful (Xn) and 28% corrosive (C) labeled substances. Hazards for eyes (59%), skin (50%) and by ingestion (60%) were the most reported. Monoethanolamine, a strong irritant and known to be involved in sensitizing mechanisms as well as allergic reactions, is frequently added to cleaning products. Monoethanolamine determination in air has traditionally been difficult and air sampling and analysis methods available were little adapted for personal occupational air concentration assessments. A convenient method was developed with air sampling on impregnated glass fiber filters followed by one step desorption, gas chromatography and nitrogen phosphorous selective detection. An exposure assessment was conducted in the cleaning sector, to determine airborne concentrations of monoethanolamine, glycol ethers, and benzyl alcohol during different cleaning tasks performed by professional cleaning workers in different companies, and to determine background air concentrations of formaldehyde, a known indoor air contaminant. The occupational exposure study was carried out in 12 cleaning companies, and personal air samples were collected for monoethanolamine (n=68), glycol ethers (n=79), benzyl alcohol (n=15) and formaldehyde (n=45). All but ethylene glycol mono-n-butyl ether air concentrations measured were far below (<1/10) of the Swiss eight hours occupational exposure limits, except for butoxypropanol and benzyl alcohol, where no occupational exposure limits were available. Although only detected once, ethylene glycol mono-n-butyl ether air concentrations (n=4) were high (49.5 mg/m3 to 58.7 mg/m3), hovering at the Swiss occupational exposure limit (49 mg/m3). Background air concentrations showed no presence of monoethanolamine, while the glycol ethers were often present, and formaldehyde was universally detected. Exposures were influenced by the amount of monoethanolamine in the cleaning product, cross ventilation and spraying. The collected data was used to test an already existing exposure modeling tool during the last phases of the study. The exposure estimation of the so called Bayesian tool converged with the measured range of exposure the more air concentrations of measured exposure were added. This was best described by an inverse 2nd order equation. The results suggest that the Bayesian tool is not adapted to predict low exposures. The Bayesian tool should be tested also with other datasets describing higher exposures. Low exposures to different chemical sensitizers and irritants should be further investigated to better understand the development of respiratory disorders in cleaning workers. Prevention measures should especially focus on incorrect use of cleaning products, to avoid high air concentrations at the exposure limits. - De récentes études montrent l'existence d'un lien entre l'exposition aux produits de nettoyages et les maladies respiratoires telles que l'asthme. En revanche, encore peu d'informations sont disponibles concernant la quantité d'exposition des professionnels du secteur du nettoyage aux composants organiques volatiles provenant des produits qu'ils utilisent. Pendant la première phase de cette étude, un recueil systématique des produits professionnels utilisés dans le secteur du nettoyage a été effectué. Les fiches de données de sécurité de ces produits ont ensuite été analysées, afin de répertorier les composés organiques volatiles les plus souvent utilisés. Il a été mis en évidence que les produits de nettoyage professionnels sont des mélanges complexes de composants chimiques (composants chimiques dans les produits de nettoyage : 3.5 ± 2.8). Ainsi, plus de 130 substances listées dans les fiches de données de sécurité ont été retrouvées dans les 105 produits répertoriés. Les principales classes de substances chimiques identifiées étaient les parfums, les éthers de glycol, les agents de surface et les solvants; dans une moindre mesure, les phosphates, les sels, les détergents, les régulateurs de pH, les acides et les bases ont été identifiés. Plus de 75% des produits répertoriés contenaient des substances décrites comme irritantes (Xi), 64% nuisibles (Xn) et 28% corrosives (C). Les risques pour les yeux (59%), la peau (50%) et par ingestion (60%) était les plus mentionnés. La monoéthanolamine, un fort irritant connu pour être impliqué dans les mécanismes de sensibilisation tels que les réactions allergiques, est fréquemment ajouté aux produits de nettoyage. L'analyse de la monoéthanolamine dans l'air a été habituellement difficile et les échantillons d'air ainsi que les méthodes d'analyse déjà disponibles étaient peu adaptées à l'évaluation de la concentration individuelle d'air aux postes de travail. Une nouvelle méthode plus efficace a donc été développée en captant les échantillons d'air sur des filtres de fibre de verre imprégnés, suivi par une étape de désorption, puis une Chromatographie des gaz et enfin une détection sélective des composants d'azote. Une évaluation de l'exposition des professionnels a été réalisée dans le secteur du nettoyage afin de déterminer la concentration atmosphérique en monoéthanolamine, en éthers de glycol et en alcool benzylique au cours des différentes tâches de nettoyage effectuées par les professionnels du nettoyage dans différentes entreprises, ainsi que pour déterminer les concentrations atmosphériques de fond en formaldéhyde, un polluant de l'air intérieur bien connu. L'étude de l'exposition professionnelle a été effectuée dans 12 compagnies de nettoyage et les échantillons d'air individuels ont été collectés pour l'éthanolamine (n=68), les éthers de glycol (n=79), l'alcool benzylique (n=15) et le formaldéhyde (n=45). Toutes les substances mesurées dans l'air, excepté le 2-butoxyéthanol, étaient en-dessous (<1/10) de la valeur moyenne d'exposition aux postes de travail en Suisse (8 heures), excepté pour le butoxypropanol et l'alcool benzylique, pour lesquels aucune valeur limite d'exposition n'était disponible. Bien que détecté qu'une seule fois, les concentrations d'air de 2-butoxyéthanol (n=4) étaient élevées (49,5 mg/m3 à 58,7 mg/m3), se situant au-dessus de la frontière des valeurs limites d'exposition aux postes de travail en Suisse (49 mg/m3). Les concentrations d'air de fond n'ont montré aucune présence de monoéthanolamine, alors que les éthers de glycol étaient souvent présents et les formaldéhydes quasiment toujours détectés. L'exposition des professionnels a été influencée par la quantité de monoéthanolamine présente dans les produits de nettoyage utilisés, par la ventilation extérieure et par l'emploie de sprays. Durant la dernière phase de l'étude, les informations collectées ont été utilisées pour tester un outil de modélisation de l'exposition déjà existant, l'outil de Bayesian. L'estimation de l'exposition de cet outil convergeait avec l'exposition mesurée. Cela a été le mieux décrit par une équation du second degré inversée. Les résultats suggèrent que l'outil de Bayesian n'est pas adapté pour mettre en évidence les taux d'expositions faibles. Cet outil devrait également être testé avec d'autres ensembles de données décrivant des taux d'expositions plus élevés. L'exposition répétée à des substances chimiques ayant des propriétés irritatives et sensibilisantes devrait être investiguée d'avantage, afin de mieux comprendre l'apparition de maladies respiratoires chez les professionnels du nettoyage. Des mesures de prévention devraient tout particulièrement être orientées sur l'utilisation correcte des produits de nettoyage, afin d'éviter les concentrations d'air élevées se situant à la valeur limite d'exposition acceptée.

Heat capacity measurements on the equiatomic compounds in Ni-X (X = Al, In, Si, Ge and Bi) and M-Sb (with M = Ni, Co and Fe) systems

Molar heat capacities of the binary compounds NiAl, NiIn, NiSi, NiGe, NiBi, NiSb, CoSb and FeSb were determined every 10 K by differential scanning calorimetry in the temperature range 310-1080 K. The experimental results have been fitted versus temperature according to C-p = a + b . T + c . T-2 + d . T-2. Results are given, discussed and compared to estimations found in the literature. Two compounds, NiBi and FeSb, are subject to transformations between 460 and 500 K. (C) 1999 Elsevier Science Ltd. All rights reserved.

Low molecular weight carboxylic acids in oxidizing porphyry copper tailings

The distribution of low molecular weight carboxylic acids (LMWCA) was investigated in pore water profiles from two porphyry copper tailings impoundments in Chile (Piuquenes at La Andina and Cauquenes at El Teniente mine). The objectives of this study were (1) to determine the distribution of LMWCA, which are interpreted to be the metabolic byproducts of the autotroph microbial community in this low organic carbon system, and (2) to infer the potential role of these acids in cycling of Fe and other elements in the tailings impoundments. The speciation and mobility of iron, and potential for the release of H+ via hydrolysis of the ferric iron, are key factors in the formation of acid mine drainage in sulfidic mine wastes. In the low-pH oxidation zone of the Piuquenes tailings, Fe(III) is the dominant iron species and shows high mobility. LMWCA, which occur mainly between the oxidation front down to 300 cm below the tailings surface at both locations (e.g., max concentrations of 0.12 mmol/L formate, 0.17 mmol/L acetate, and 0.01 mmol/L pyruvate at Piuquenes and 0.14 mmol/L formate, 0.14 mmol/L acetate, and 0.006 mmol/L pyruvate at Cauquenes), are observed at the same location as high Fe concentrations (up to 71.2 mmol/L Fe(II) and 16.1 mmol/L Fe(III), respectively). In this zone, secondary Fe(111) hydroxides are depleted. Our data suggest that LMWCA may influence the mobility of iron in two ways. First, complexation of Fe(III), through formation of bidentate Fe(III)-LMWCA complexes (e.g., pyruvate, oxalate), may enhance the dissolution of Fe(III) (oxy)hydroxides or may prevent precipitation of Fe(III) (oxy)hydroxides. Soluble Fe(III) chelate complexes which may be mobilized downward and convert to Fe(II) by Fe(III) reducing bacteria. Second, monodentate LMWCA (e.g., acetate and formate) can be used by iron-reducing bacteria as electron donors (e.g., Acidophilum spp.), with ferric iron as the electron acceptor. These processes may, in part, explain the low abundances of secondary Fe(III) hydroxide precipitates below the oxidation front and the high concentrations of Fe(II) observed in the pore waters of some low-sulfide systems. The reduction of Fe(III) and the subsequent increase of iron mobility and potential acidity transfer (Fe(II) oxidation can result in the release of H+ in an oxic environment) should be taken in account in mine waste management strategies.

Strategies of "Pseudomonas aeruginosa" to overcome copper limitation

Summary Copper is an important trace element and micronutrient for living organisms as it is the cofactor of several enzymes involved in diverse biological redox processes such as aerobic respiration, denitrification and photosynthesis. Despite its importance, copper may be poorly bioavailable in soils and aquatic environments, as well as in the human body, especially at physiological or alkaline pH. In this work, we have investigated the strategies that the versatile bacterium and opportunistic pathogen Pseudomonas aeruginosa has evolved to face and overcome copper limitation. The global response of the P. aeruginosa to copper limitation was assessed under aerobic conditions. Numerous iron uptake functions (including the siderophores pyoverdine and pyochelin) were down-regulated whereas expression of cioAB (encoding an alternative, copper-independent, cyanide-resistant ubiquinol oxidase) was up-regulated. Wild type P. aeruginosa was able to grow aerobically in a defined glucose medium depleted of copper by a copper chelator, whereas a cioAB mutant did not grow. Thus, P. aeruginosa relies on the CioAB enzyme to cope with severe copper deprivation. A quadruple cyo cco1 cco2 cox mutant, which was deleted for all known heme-copper terminal oxidases of P. aeruginosa, grew aerobically, albeit more slowly than did the wild type, indicating that the CioAB enzyme is capable of energy conservation. However, the expression of a cioA'-'lacZ fusion was less dependent on the copper status in the quadruple mutant than in the wild type, suggesting that copper availability might affect cioAB expression indirectly, via the function of the heme-copper oxidases. These results suggest that the CioAB enzyme can be used as a by-pass strategy to overcome severe copper limitation and perform aerobic respiration even if virtually no copper is available. The PA0114 gene, which encodes a protein of the SCOT/SenC family, was found to be important for copper acquisition and aerobic respiration in low copper conditions. A PA0114 (sent) mutant grew poorly in low copper media and had low terminal oxidase activity with TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine), but expressed the CioAB enzyme at elevated levels. Addition of copper reversed these phenotypes, suggesting that periplasmic copper capture by the SenC protein is another strategy that helps P. aeruginosa to adapt to copper deprivation. RESUME Le cuivre est un micronutriment important pour les organismes vivants. Il représente le cofacteur de plusieurs enzymes impliquées dans une multitude de processus biologiques tels que la respiration aérobie, la dénitrification et la photosynthèse. Malgré son importance, le cuivre peut être peu disponible dans les sols, les environnements aquatiques et le corps humain, spécialement à pH physiologique ou alcalin. Dans ce travail nous avons étudié les stratégies développées par la bactérie pathogène opportuniste Pseudomonas aeruginosa PAO1 afm de faire face et de surmonter le manque de cuivre. La réponse globale de P. aeruginosa à la carence de cuivre a été analysée dans des conditions aérobie. Les résultats obtenus ont montré que plusieurs gènes impliqués dans l'acquisition du fer, tels que les gènes codant pour les sidérophores (pyoverdine et pyochéline), étaient réprimés, tandis que l'expression de l'opéron cioAB, codant pour l'oxydase terminale insensible au cyanure (CIO), était augmentée. La souche sauvage P. aeruginosa est capable de croître dans un milieu où la concentration en cuivre est limitée, due à la présence d'un chélateur spéciftque de cuivre, tandis que le mutant cioAB ne croît pas dans ces conditions. Nous avons conclu que P. aeruginosa nécessite l'oxydase terminale CIO pour faire face à la carence en cuivre. Un quadruple mutant affecté dans toutes les oxydases dépendantes du cuivre (cyo ccol cco2 cox) et appartenant aux oxydases de type hème-cuivre, peut croître en aérobie, néanmoins plus lentement que la souche sauvage, ce qui montre que l'enzyme CIO est capable de conserver l'énergie. L'expression de la fusion rapportrice cioA'-'IacZ chez le quadruple mutant est moins dépendante de la disponibilité de cuivre que chez la souche sauvage. Ces résultats suggèrent que la disponibilité de cuivre influence l'expression de cioAB d'une façon indirecte, par le biais des oxydases terminales de type héme-cuivre. Il est donc possible qu'en cas de carence de cuivre, P. aeruginosa utilise l'enzyme CIO comme stratégie afin de surmonter ce manque et de réaliser la respiration aérobie. Nous avons démontré que le gène PA0114, codant pour une protéine appartenant à la famille SCO1/SenC, est important dans l'acquisition et dans la respiration aérobie dans des environnements où le cuivre est présent en faible concentration. En ces conditions, la croissance du mutant senC est faible; de plus, l'activité des oxydases terminales en présence du donneur d'électrons TMPD (N,N,N,N'-tetraméthyl-p-phénylenediamine) est basse. Toutefois, l'addition de cuivre au milieu de culture permet de restaurer le phénotype du type sauvage. Ces résultats montrent que la protéine SenC est capable d'acquérir le cuivre et représente donc une autre stratégie chez P. aeruginosa pour s'adapter à un manque de cuivre.

Metal concentrations in soils around the copper smelter and surrounding industrial complex of Port Kembla, NSW, Australia

Anthropogenic emissions of metals from sources such as smelters are an international problem, but there is limited published information on emissions from Australian smelters. The objective of this study was to investigate the regional distribution of heavy metals in soils in the vicinity of the industrial complex of Port Kembla, NSW, Australia, which comprises a copper smelter, steelworks and associated industries. Soil samples (n=25) were collected at the depths of 0-5 and 5-20 cm, air dried and sieved to < 2 mm. Aqua regia extractable amounts of As, Cr, Cu, Ph and Zn were analysed by inductively coupled plasma mass spectrometry (lCP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Outliers were identified from background levels by statistical methods. Mean background levels at a depth of 0-5 cm were estimated at 3.2 mg/kg As, 12 mg/kg Cr, 49 mg/kg Cu, 20 mg/kg Ph and 42 mg/kg Zn. Outliers for elevated As and Cu values were mainly present within 4 km from the Port Kembla industrial complex, but high Ph at two sites and high Zn concentrations were found at six sites up to 23 km from Port Kembla. Chromium concentrations were not anomalous close to the industrial complex. There was no significant difference of metal concentrations at depths of 0-5 and 5-20 cm, except for Ph and Zn. Copper and As concentrations in the soils are probably related to the concentrations in the parent rock. From this investigation, the extent of the contamination emanating from the Port Kembla industrial complex is limited to 1-13 km, but most likely <4 km, depending on the element; the contamination at the greater distance may not originate from the industrial complex. (C) 2003 Elsevier B.V. All rights reserved.

Evaluation of the toxicity of different metal compounds in the developing brain using aggregating cell cultures as a model.

To evaluate their toxicity in the developing brain, eight metal compounds, [bismuth sodium tartrate (BiNA-tartrate), CdCl(2), CoCl(2), HgCl(2), dimethyl mercury, NiCl(2), TlCl and triethyltin chloride (TET)] were tested in aggregating cell cultures of foetal rat telencephalon. The compounds were applied to the cultures continuously, either during an early developmental stage (between days 5 and 14) or during and advanced stage of maturation (between days 24 and 34). Changes in the activities of cell type-specific enzymes were used as a criterion for toxicity. A general cytotoxic effect was observed after treatment with either CdCl(2), HgCl(2) or TET at 10(-6)m, and with TlCl at 10(-5)m. Selective effects were found with BiNa-tartrate and dimethylmercury. CoCl(2) did not modify the parameters tested, whereas a stimulant effect was found with NiCl(2). The effects of several compounds were development dependent: HgCl(2), TET and TlCl were more toxic in immature cultures, whereas BiNa-tartrate, dimethylmercury and NiCl(2) were more effective in differentiated cultures.

Increased vulnerability of neurones and glial cells to low concentrations of methylmercury in a prooxidant situation.

Using reaggregating rat brain cell cultures at two different stages of differentiation, we examined the biochemical effects of a 10-day treatment with nanomolar concentrations of methylmercuric chloride (monomethylmercury), in the presence or absence of promoters of hydroxyl radical formation (10 microM copper sulphate plus 100 microM ascorbate). A decrease in total protein content accounted for the general cytotoxicity of these compounds, whereas selective effects were assessed by determining the activities of cell type-specific enzymes. Methylmercury, up to 100 nM, as well as the copper ascorbate mixture, when applied separately, induced no general cytotoxicity, and only slight effects on neuronal parameters. However, when applying 100 nM methylmercury and the copper-ascorbate mixture together, a drastic decrease in neuronal and glial parameters was found. Under these conditions, the content of reactive oxygen species, assessed by 2',7'-dichlorofluorescin oxidation, increased greatly, while the activities of antioxidant enzymes decreased. In the presence of copper and ascorbate, differentiated cultures appeared more resistant than immature ones to low methylmercury concentrations (1-10 mM), but did undergo similar changes in both cell type-specific and antioxidant enzyme activities at 100 nM methylmercury. These results suggest that in prooxidant conditions low doses of mercury can become much more deleterious for the central nervous system.

Induction of apoptosis by mercury compounds depends on maturation and is not associated with microglial activation

The earliest sign of neurotoxicity observed after exposure of three-dimensional brain cell cultures to low concentrations of mercury compounds is a microglial reaction. We hypothesized that an induction of apoptosis by mercury compounds could be an activating signal of the microglial reaction. Aggregating brain cell cultures of fetal rat telencephalon were treated for 10 days with either mercury chloride or monomethylmercury chloride at noncytotoxic concentrations during two developmental periods: from day 5 to 15, corresponding to an immature stage, and from day 25 to 35 corresponding to a mature stage. Apoptosis was evaluated by the TUNEL technique. It was found that both mercury compounds caused a significant increase in the number of apoptotic cells, but exclusively in immature cultures exhibiting also spontaneous apoptosis. Double staining by the TUNEL technique combined with either neuronal or astroglial markers revealed that the proportion of cells undergoing apoptosis was highest for astrocytes. Furthermore neither an association nor a colocalization was found between apoptotic cells and microglial cells. In conclusion, it appears that the induction of apoptosis by mercury compounds in immature cells is only an acceleration of a spontaneously occurring process, and that it is not a directly related to the early microglial reaction.

Synthesis of a non-peptidic PET tracer designed for α5β1 integrin receptor.

Arginine-glycine-aspartic acid (RGD)-containing peptides have been traditionally used as PET probes to noninvasively image angiogenesis, but recently, small selective molecules for α5 β1 integrin receptor have been developed with promising results. Sixty-one antagonists were screened, and tert-butyl (S)-3-(2-((3R,5S)-1-(3-(1-(2-fluoroethyl)-1H-1,2,3-triazol-4-yl)propanoyl)-5-((pyridin-2-ylamino)methyl)pyrrolidin-3-yloxy)acetamido)-2-(2,4,6-trimethylbenzamido)propanoate (FPMt) was selected for the development of a PET tracer to image the expression of α5 β1 integrin receptors. An alkynyl precursor (PMt) was initially synthesized in six steps, and its radiolabeling was performed according to the azide-alkyne copper(II)-catalyzed Huisgen's cycloaddition by using 1-azido-2-[(18)F]fluoroethane ([(18)F]12). Different reaction conditions between PMt and [(18)F]12 were investigated, but all of them afforded [(18)F]FPMt in 15 min with similar radiochemical yields (80-83%, decay corrected). Overall, the final radiopharmaceutical ([(18)F]FPMt) was obtained after a synthesis time of 60-70 min in 42-44% decay-corrected radiochemical yield.

Geochemical evolution of active porphyry copper tailings impoundments : from alkaline deposition towards acidification

J. Smuda: Geochemical evolution of active porphyry copper tailings impoundments Thesis abstract Mine waste is the largest volume of materials handled in the world. The oxidation of sulfidic mine waste may result in the release of acid mine drainage (AMD) rich in heavy metals and arsenic to the environment, one of the major problems the mining industry is facing today. To control and reduce this environmental impact, it is crucial to identify the main geochemical and hydrological processes influencing contaminant liberation, transport, and retention. This thesis presents the results of a geochemical, mineralogical and stable isotope study (δ2H, δ18O, δ34S) from two active porphyry copper tailings impoundments in Mediterranean (Carén tailings impoundment, El Teniente mine, Central Chile) and hyper-arid climate (Talabre tailings impoundment, Chuquicamata, Northern Chile) from the deposition in alkaline environment (pH 10.5) towards acidification after several years of exposure. The major hydrological results were the identification of vertical contaminant and water transport in the uppermost, not water-saturated zone, triggered by capillary rise due to evaporation, and infiltration downwards due to new tailings deposition, and of horizontal transport in the groundwater zone. At the surface of the sedimented tailings, evaporation of pore water led to the precipitation of Na-Ca-Mg sulfates (e.g., gypsum, tenorite), in hyper-arid climate also halite. At the Carén tailings impoundment, renewed deposition in a 4-week interval inhibited a pH decrease below neutral values and the formation of an efflorescent salt crust. At the Talabre tailings impoundment, deposition breaks of several years resulted in the formation of acidic oxidation zones in the timeframe of less than 4 years. This process enabled the transport of liberated Cu, Zn, and Fe via capillary rise to the surface, where these metals precipitated as heavy-metal sulfates (e.g., devilline, krohnkite) and chlorides (eriochalcite, atacamite). Renewed depositing may dissolve efflorescent salts and transport liberated elements towards the groundwater zone. This zone was found to be highly dynamic due to infiltration and mixing with water from different sources, like groundwater, catchment water, and infiltration from superficial waters. There, Cu was found to be partially mobile due to complexation with Cl (in Cl-rich groundwater, Talabre) and dissolved organic matter (in zones with infiltration of catchment water rich in dissolved organic matter, Carén). A laboratory study on the isotopic fractionation of sulfur and oxygen of sulfate in different minerals groups (water-soluble sulfates, low- and high-crystalline Fe(III) oxyhydroxides) contributed to the use of stable isotopes as tracer of geochemical and transport processes for environmental studies. The results highlight that a detailed geochemical, stable isotope and mineralogical study permits the identification of contamination processes and pathways already during the deposition of mine tailings. This knowledge allows the early planning of adequate actions to reduce and control the environmental impact during tailings deposition and after the closing of the impoundment. J. Smuda: Geochemical evolution of active porphyry copper tailings impoundments Résumé de these Les déchets miniers constituent les plus grands volumes de matériel gérés dans le monde. L'oxydation des déchets miniers sulfuriques peut conduire à la libération de drainages miniers acides (DMA) riches en métaux et arsenic dans l'environnement, ce qui est l'un des principaux problèmes de l'industrie minière aujourd'hui. Pour contrôler et réduire ces impacts sur l'environnement, il est crucial d'identifier les principaux processus géochimiques et hydrologiques influençant la libération, le transport et la rétention des contaminants. Cette thèse présente les résultats d'une étude géochimique, minéralogique et des isotopes stables (δ2H, δ18O, δ34S) sur des déchets miniers de 2 sites de dépôt actifs en climat méditerranéen (Dépôt de déchets de Carén, mine de El Teniente, Centre du Chili) et en climat hyper-aride (Dépôt de déchets de Talabre, mine de Chuquicamata, Nord du Chili). L'objectif était d'étudier l'évolution des déchets de la déposition en milieu alcalin (pH = 10.5) vers l'acidification après plusieurs années d'exposition. Le principal résultat hydrologique a été l'identification de 2 types de transport : un transport vertical de l'eau et des contaminants dans la zone non saturée en surface, induit par la montée capillaire due à l'évaporation et par l'infiltration subséquente de la déposition de sédiments frais ; et un transport horizontal dans la zone des eaux souterraines. À la surface des déchets, l'évaporation de l'eau interstitielle conduit à la précipitation de sulfates de Na-Ca-Mg (ex. gypse, ténorite) et halite en climat hyper-aride. Dans le site de Carén, une nouvelle déposition de déchets frais à 4 semaines intervalle a empêché la baise du pH en deçà des valeurs neutres et la formation d'une croûte de sels efflorescentes en surface. Dans le site de Talabre, les fentes de dessiccation des dépôts ont entraîné la formation d'une zone d'oxydation à pH acide en moins de 4 ans. Ce processus a permis la libération et le transport par capillarité de Cu, Zn, Fe vers la surface, où ces éléments précipitent sous forme de sulfates de métaux lourds (ex., dévilline, krohnkite) de chlorures (ex. ériochalcite, atacamite). Une nouvelle déposition de sédiments frais pourrait dissoudre ces sels et les transporter vers la zone des eaux souterraines. Cette dernière zone était très dynamique en raison du mélange d'eaux provenant de différentes sources, comme les eaux souterraines, l'eau de captage et l'infiltration des eaux superficielles. Egalement dans cette zone, le cuivre était partiellement mobile à cause de la formation de complexe avec le chlore (dans les zone riche en Cl, Talabre) et avec la matière organique dissoute (dans les zones où s'infiltre l'eau de captage riche en matière organique, Carén). Une étude en laboratoire sur le fractionnement des isotopes stables de sulfure et d'oxygène des sulfates dans différents groupes de minéraux (sulfates hydrosolubles, sulfures de oxy-hydroxyde de Fe(III) faiblement ou fortement cristallins) a permis d'apporter une contribution à leur utilisation comme traceurs dans l'étude des processus géochimiques et de transport lors d'études environnementales. Les résultats montrent qu'une étude détaillée de la géochimie, des isotopes stables et de la minéralogie permet d'identifier les processus et les voies de contamination déjà pendant la période de dépôt des déchets miniers. Cette connaissance permet de planifier, dès le début de l'exploitation, des mesures adéquates pour réduire et contrôler l'impact sur l'environnement pendant la période de dépôts de déchets miniers et après la fermeture du site.

Comparison of the developmental effects of two mercury compounds on glial cells and neurons in aggregate cultures of rat telencephalon.

A three-dimensional cell culture system was used as a model to study the influence of low levels of mercury in the developing brain. Aggregating cell cultures of fetal rat telencephalon were treated for 10 days either during an early developmental period (i.e., between days 5 and 15 in vitro) or during a phase of advanced maturation (i.e., between days 25 and 35) with mercury. An inorganic (HgCl2) and an organic mercury compound (monomethylmercury chloride, MeHgCl) were examined. By monitoring changes in cell type-specific enzymes activities, the concentration-dependent toxicity of the compounds was determined. In immature cultures, a general cytotoxicity was observed at 10(-6) M for both mercury compounds. In these cultures, HgCl2 appeared somewhat more toxic than MeHgCl. However, no appreciable demethylation of MeHgCl could be detected, indicating similar toxic potencies for both mercury compounds. In highly differentiated cultures, by contrast, MeHgCl exhibited a higher toxic potency than HgCl2. In addition, at 10(-6) M, MeHgCl showed pronounced neuron-specific toxicity. Below the cytotoxic concentrations, distinct glia-specific reactions could be observed with both mercury compounds. An increase in the immunoreactivity for glial fibrillary acidic protein, typical for gliosis, could be observed at concentrations between 10(-9) M and 10(-7) M in immature cultures, and between 10(-8) M and 3 x 10(-5) M in highly differentiated cultures. A conspicuous increase in the number and clustering of GSI-B4 lectin-binding cells, indicating a microglial response, was found at concentrations between 10(-10) M and 10(-7) M. These development-dependent and cell type-specific effects may reflect the pathogenic potential of long-term exposure to subclinical doses of mercury.

Adaptation of aerobically growing Pseudomonas aeruginosa to copper starvation.

Restricted bioavailability of copper in certain environments can interfere with cellular respiration because copper is an essential cofactor of most terminal oxidases. The global response of the metabolically versatile bacterium and opportunistic pathogen Pseudomonas aeruginosa to copper limitation was assessed under aerobic conditions. Expression of cioAB (encoding an alternative, copper-independent, cyanide-resistant ubiquinol oxidase) was upregulated, whereas numerous iron uptake functions (including the siderophores pyoverdine and pyochelin) were expressed at reduced levels, presumably reflecting a lower demand for iron by respiratory enzymes. Wild-type P. aeruginosa was able to grow aerobically in a defined glucose medium depleted of copper, whereas a cioAB mutant did not grow. Thus, P. aeruginosa relies on the CioAB enzyme to cope with severe copper deprivation. A quadruple cyo cco1 cco2 cox mutant, which was deleted for all known heme-copper terminal oxidases of P. aeruginosa, grew aerobically, albeit more slowly than did the wild type, indicating that the CioAB enzyme is capable of energy conservation. However, the expression of a cioA'-'lacZ fusion was less dependent on the copper status in the quadruple mutant than in the wild type, suggesting that copper availability might affect cioAB expression indirectly, via the function of the heme-copper oxidases.

Comprehensive approach for the detection of antifungal compounds using a susceptible strain of Candida albicans and confirmation of in vivo activity with the Galleria mellonella model.

An efficient screening strategy for the identification of potentially interesting low-abundance antifungal natural products in crude extracts that combines both a sensitive bioautography assay and high performance liquid chromatography (HPLC) microfractionation was developed. This method relies on high performance thin layer chromatography (HPTLC) bioautography with a hypersusceptible engineered strain of Candida albicans (DSY2621) for bioactivity detection, followed by the evaluation of wild type strains in standard microdilution antifungal assays. Active extracts were microfractionated by HPLC in 96-well plates, and the fractions were subsequently submitted to the bioassay. This procedure enabled precise localisation of the antifungal compounds directly in the HPLC chromatograms of the crude extracts. HPLC-PDA-mass spectrometry (MS) data obtained in parallel to the HPLC antifungal profiles provided a first chemical screening about the bioactive constituents. Transposition of the HPLC analytical conditions to medium-pressure liquid chromatography (MPLC) allowed the efficient isolation of the active constituents in mg amounts for structure confirmation and more extensive characterisation of their biological activities. The antifungal properties of the isolated natural products were evaluated by their minimum inhibitory concentration (MIC) in a dilution assay against both wild type and engineered strains of C. albicans. The biological activity of the most promising agents was further evaluated in vitro by electron microscopy and in vivo in a Galleria mellonella model of C. albicans infection. The overall procedure represents a rational and comprehensive means of evaluating antifungal activity from various perspectives for the selection of initial hits that can be explored in more in-depth mode-of-action studies. This strategy is illustrated by the identification and bioactivity evaluation of a series of antifungal compounds from the methanolic extract of a Rubiaceae plant, Morinda tomentosa, which was used as a model in these studies.