Yes / Pesticide contamination is a global issue, affecting nearly 44% of the global farming population, and disproportionately affecting farmers and agricultural workers in developing countries. Despite this, global pesticide usage is on the rise, with the growing demand of global food production with increasing population. Different types of porous materials, such as carbon and zeolites, have been explored for the remediation of pesticides from the environment. However, there are some limitations with these materials, especially due to lack of functional groups and relatively modest surface areas. In this regard, metal-organic frameworks (MOFs) provide us with a better alternative to conventionally used porous materials due to their versatile and highly porous structure. Recently, a number of MOFs have been studied for the extraction of pesticides from the environment as well as for targeted and controlled release of agrochemicals. Different types of pesticides and conditions have been investigated, and MOFs have proved their potential in agricultural applications. In this review, the latest studies on delivery and extraction of pesticides using MOFs are systematically reviewed, along with some recent studies on greener ways of pest control through the slow release of chemical compounds from MOF composites. Finally, we present our insights into the key issues concerning the development and translational applications of using MOFs for targeted delivery and pesticide control.

Thesis (PhD (Food Science))--University of Stellenbosch, 2007. / Thermal pasteurisation failures in the dairy industry have often been found to cause end-products of poor quality and short shelf-life. Therefore, alternative methods to eliminate microbial contaminants in raw milk are being studied. Ultrasonication is one such non-thermal technology that could offer the dairy industry an alternative to traditional pasteurisation. The main objective of this dissertation was to evaluate the use of high-power lowfrequency ultrasound (20 kHz, 750 W, 124 μm) applied in batch mode to eliminate a selection of spoilage and potentially pathogenic microbes, commonly associated with milk. These included Gram-positive and negative microbes, comprising of rods and cocci, an endospore-former, and a yeast (Escherichia coli, Bacillus cereus, Chryseobacterium meningosepticum, Lactobacillus acidophilus, Lactococcus lactis, Listeria monocytogenes, Micrococcus luteus, Pseudomonas fluorescens and Saccharomyces cerevisiae). Three strains of E. coli (1 x 106 cfu.ml-1) tested, viz. ATCC 11775, a wild strain from raw milk, and an O157:H7 strain from milk were sensitive to ultrasonication. Complete elimination of viable cells occurred within 10 min. Viable counts of P. fluorescens were reduced by 100% within 6 min of ultrasonication and L. monocytogenes was reduced by 99.0% within 10 min. Lactococcus lactis was reduced by 97.0% and M. luteus, B. cereus and C. meningosepticum by 88.0%, 87.0% and 85.0% respectively. Lactobacillus acidophilus showed the most resistance to ultrasound with only 78.0% of viable cells being eliminated. Under similar conditions, S. cerevisiae was reduced by 99.7%. Microbial cell morphology, size and Gram status did not necessarily influence the efficacy of ultrasonication. Sterile saline solution and UHT milk were used as the suspension media, and the reputed protective effect of milk fat was not observed under the parameters used in this study. A higher wave amplitude (100%; 124 μm) was found to be more efficient in eliminating microbes than a lower wave amplitude (50%; 62 μm). Pulsed-ultrasonication did not enhance the efficiency of ultrasonication indicating that standing waves were absent. Limited success was achieved by ultrasonication itself, and the long batch treatment time (10 min or more) was found to be unrealistic for industrial implementation. Hence the simultaneous application of ultrasound and heat (thermoultrasonication) was examined. Thermo-ultrasonication proved to be more effective than either an ultrasonic or heat treatment with all viable M. luteus cells being eliminated within 4 min (100% amplitude at 72°C). Similarly, to eliminate E. coli and Lb. acidophilus from milk, only 2 min and 4 min thermo-ultrasonication was required, respectively. Bacillus cereus endospores remained resistant and after a 10 min thermo-ultrasonic treatment only 78.04% were eliminated. During this investigation both extensive surface (SEM) and internal (TEM) cell damage caused by ultrasonication were observed in E. coli, Lb. acidophilus and S. cerevisiae. Hence ultrasonication physically/mechanically damages these microbial cells causing cell death/injury. Microbial proteins and DNA released from cells into the environment after an ultrasonic treatment was measured and an increase in released microbial proteins and DNA was found to be indicative of a decrease in the number of viable cells, providing that the initial cell concentration was high enough. It was, however, not possible to correlate the concentration of released microbial proteins and DNA with the exact number of viable cells eliminated, rendering it an ineffective quality indicator for the industry. Ultrasonication had no statistically significant influence on the protein, fat and lactose content of both raw and pasteurised milk. The somatic cell count of raw and pasteurised milk was found to decrease after ultrasonication. Unlike with heating, activity of alkaline phosphatase and lactoperoxidase were not reduced by ultrasonication. Hence neither enzyme can be used to indicate a successful ultrasonic treatment of milk. This study has demonstrated that ultrasonication offers a viable alternative to pasteurisation as it is effective in eliminating microbes, and does not alter native milk components. However, to attain a more effective killing, thermo-ultrasonication is recommended for the treatment of milk to be used for the production of different dairy products.

L’estuaire de la Gironde est affecté par une pollution polymétallique historique provenant de son bassin versant (affluent du Lot). L’analyse de 320 échantillons de sédiments couvrant l’ensemble de la surface estuarienne nous a permis d’établir les premières cartographies à haute résolution spatiale de la contamination métallique des sédiments de surface. Elles révèlent des zones d’accumulation préférentielle des ETM au niveau de la zone des îles en amont de l’estuaire et du chenal nord en aval de l’estuaire. Le facteur de contrôle dominant cette répartition est la granularité des sédiments.L’estimation des stocks métalliques potentiellement re-mobilisables, des facteurs d’enrichissement et de la toxicité potentielle du cocktail des ETM prioritaires nous ont permis d’évaluer un risque de toxicité faible à moyen des ETM vis-à-vis du biota. La contamination en ETM des bassins versants affluents de l’estuaire de la Gironde inclus dans le périmètre du SAGE Estuaire a été appréhendée en couplant sous SIG les caractéristiques typologiques de 57 bassins versants et la géochimie des sédiments prélevés à l’exutoire de ces bassins.Les anomalies les plus importantes concernent les bassins proches de l’agglomération bordelaise et correspondent au cortège des « traceurs urbains » : Ag, Cd, Cu, Hg, Sb et Zn, ainsi que Cu pour les bassins viticoles. L’étude des variations temporelles et spatiales des concentrations en ETM sur les chenaux drainant deux bassins versants agricoles montre des apports ponctuels ou chroniques en Ag,As, Cu et U attribués aux activités anthropiques. Les zones de marais jouent un rôle important dans la spéciation des ETM en lien avec les transformations de la matière organique (e.g. As). Des expérimentations de laboratoire ont permis de caractériser les processus affectant les ETM issus des sols agricoles lors de leur transfert et de leur transport dans les systèmes aquatiques. Les phénomènes de relargage à long terme de Cu soulignent le rôle important des colloïdes organiques dans la mobilité et la biodisponibilité potentielle de cet élément. / The Gironde estuarine system is impacted by historic polymetallic pollution due to mining and smelting activities in the upper watershed. Based on a high spatial resolution sampling strategy, wepropose the first maps of trace element (TE) contamination in the surface sediment at the estuarine scale. The highest TE concentrations occurred in the North Channel in the downstream estuary and inthe island zone in the upper estuary. Estimation of potentially releasable TE fraction, of enrichment factors and a comparison between measured TE concentrations and sediment quality guidelines allow us to class a major part of the estuary as a low to medium priority zone in terms of potential toxicityfor aquatic organisms.The TE contamination in the intra-estuarine watersheds included in a project of water quality management of the Gironde estuary (SAGE), was assessed for 57 watersheds by coupling into GIS,typological characteristics of the watersheds and geochemical analyses of stream sediments. Highest anomalies were found for urban watersheds for which urban tracers were identified as Ag, Cd, Cu, Hg,Sb and Zn, and for vineyard watersheds with Cu. A study of temporal and spatial variations of TEconcentrations in two small agricultural watersheds lead us to identify inputs from point and diffusive sources, especially for Ag, As, Cu and U related to anthropogenic activities. Marsh areas also play an important role in TE reactivity mainly due to organic matter transformations. In laboratory experiments simulating the transportation of TE from agricultural soils to aquatic systems and the maturing process of soil particles in the stream help us to identify processes responsible for TE release in the environment. Long term release of copper was mainly attributed to organic colloid transformation which implies an increase in the mobility, and consequently, the potential bioavailability/toxicity of Cu for aquatic organisms.

Particle contamination control is a critical issue for the semiconductor industry. In the near future, this industry will be concerned with the chemical identities of contaminant particles as small as 0.01 pm in size. Therefore, analytical techniques with both high chemical sensitivity and spatial resolution are required. Transmission electron microscopy (TEM) provides excellent spatial resolution and yields structural and compositional information. It is rarely used, however, due to the difficulty of sample preparation. The goals of this research are to promote the use of TEM as an ultrafine particle analysis tool by developing new sample preparation methods, and to exploit the new TEM techniques for analysis of particles in semiconductor processing fluids. A TEM methodology for the analysis of particulate contaminants in fluids with an elemental detectability limit as low as 0.1 part per trillion (ppt), and a particle concentration detectability limit as low as 1 particle/ml for particles greater than 0.2 pm was developed and successfully applied to the analysis of particles in HF, H202, de-ionized (DI) water, and on the surface of an electronic device. HF samples from three manufacturers were examined. For HF (B), the maximum particle concentration was 8.3 x 103 particles/ml. Both a viscous material and lath-shaped particles were observed. The Sb concentration was less than 0.6 part per billion (ppb). HF (C) was the cleanest. CaF2 and TiO2 particles were identified in HF (D). For H2 02, iron and tin oxides and hydroxides were identified. The maximum particle concentration was 990 particles/ml. The Sn and Fe concentrations were less than 0.3 ppb. Spherical and dendritic particles were observed. For DI water, spherical and dendritic particles (<2 particles/ml), and particles containing Fe or Si with concentrations less than 0.1 ppt were observed. Contaminants on an electronic device surface were also analyzed. Clusters of small particles were determined to be a mixture of aluminum oxides and aluminum silicates.

Mycobacterium avium ssp. paratuberculosis (MAP) est l'agent causal de la paratuberculose, maladie entérique, chronique et incurable des ruminants, avec un impact économique important. Une meilleure compréhension des facteurs de risque associés à l'introduction de la maladie dans un troupeau est essentielle pour sa prévention. L’amélioration des tests diagnostiques est aussi importante pour son contrôle. L’introduction des nouveaux animaux dans le troupeau et la présence et contact des différentes espèces sauvages et domestiques avec les vaches, semblent être des facteurs de risques d’introduction de la maladie. Nous avons réalisé une revue systématique dont l`objective était de recueillir l’information pertinente pour répondre à la question sur l’importance de ces facteurs et leur impact sur l’introduction de la maladie dans un troupeau. D`un autre côté, la détection de MAP dans les fèces par culture bactérienne demeure la méthode diagnostique de choix malgré les facteurs qui l`affectent. Une série de 3 étapes est requise afin de confirmer la présence du MAP : (1) culture (2) coloration, et (3) confirmation du MAP par PCR (si détecté à l´étape 2). Certains échantillons fécaux présentent une particularité en raison de leur forte charge de micro-organismes. Ces contaminants peuvent interférer avec la croissance et la détection de MAP. Une étude visant à : a) estimer l'impact des certain covariables sur les résultats de la culture de MAP parmi l`analyse rétrospective d`un banque des données et b) évaluer la possibilité d'optimiser le processus de diagnostic du MAP en effectuant l'analyse PCR sur les cultures déclarées comme contaminées a été réalisée. / Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of paratuberculosis an enteric, chronic and incurable disease of ruminants, with a major economic impact. A better understanding of the risk factors associated with the introduction of the disease in a herd, is essential for its prevention. Improving diagnostic tests are also important for the control. The introduction of new animals into the herd and the presence and contact of wild and domestic species with cattle, appear to be a risk factor for disease introduction. We conducted a systematic review to obtain relevant information to answer the question about the importance and impact of these factors on the introduction of the disease into a herd. On the other hand, the detection of MAP in feces by bacterial culture remains the diagnostic method of choice despite of the factors that can affect it. A series of 3 steps are required to confirm the presence of MAP: (1) culture (2) acid fast stain (3) MAP confirmation by PCR (if detected in step 2). Some fecal samples exhibit a particularity due to their normal heavy load of micro-organisms. These contaminants can interfere with the growth and detection of MAP. A study to: a) assess the impact of some covariables on the culture results by a retrospective analysis of a databank and b) to evaluate the possibility to optimize MAP diagnostic process by performing a PCR analysis on cultures declared as contaminated was realized.

Depuis la seconde moitié du XXème siècle, l’industrialisation, l’urbanisation croissante, les transports et les pratiques agricoles ont entraîné une contamination généralisée des écosystèmes et des modifications profondes dans la composition et la structure des paysages. Ces changements majeurs induisent des perturbations physiologiques et comportementales des organismes et ont des effets négatifs sur la biodiversité. L’Abeille mellifère (Apis mellifera) est au coeur de cette problématique : 1/ les colonies d’abeilles déclinent dramatiquement depuis quelques années en Europe et aux Etats-Unis, et 2/ les abeilles sont reconnues comme d’excellentes sentinelles pour évaluer la contamination environnementale grâce à leurs caractéristiques physiologiques et biologiques. C’est dans ce contexte, que des abeilles, du miel et du pollen récoltés dans l’Ouest de la France ont été analysés pour évaluer leurs contaminations et la présence dans l’environnement d’hydrocarbures aromatiques polycycliques, de plomb, de pesticides et de médicaments vétérinaires. Les échantillons ont été prélevés dans 18 ruchers de contextes paysagers différents (ville, bocage, culture et insulaire) sur 4 périodes (printemps, début d’été, milieu d’été et début d’automne) en 2008 et en 2009. Les résultats d’analyses toxicologiques mettent en évidence des sensibilités différentes en fonction du polluant environnemental, de la matrice étudiée, de la période de prélèvements et du contexte paysager. En dépit de ces différences, le plus souvent propres à chaque rucher, notre étude montre une contamination généralisée des matrices apicoles quels que soient le paysage et la période considérés. Même si les concentrations mesurées sont généralement faibles, cette pression par les xénobiotiques s’ajoute à, voire amplifie l’action des nombreux autres stresseurs environnementaux qui menacent la survie des abeilles en général. / Since the middle of the twentieth century, industrialization, growing urbanization, transports and agricultural practices let to an ecosystem overall contamination and to profound modifications in landscape structure and composition. Those major changes cause physiological and behavioral damages on organisms and have adverse effects on biodiversity. Honey bee (Apis mellifera) is in the central point of this problematic: 1/ bees colonies are recently dramatically declining both in Europe and USA, and 2/ bees are recognized as appropriate sentinels to assess the environmental contamination due to their physiological and biological characteristics. In this context, honeybees, honey and pollen sampled from West France, were analyzed to monitor their contamination and the presence in the environment of polycyclic aromatic hydrocarbons, lead, pesticides and veterinary drugs. Samples were collected in eighteen apiaries from different landscape context (urban, rural-grassland, rural-cultivated and island) during four periods (spring, early summer, middle summer, early autumn) over 2008 and 2009. Toxicological analysis results show different sensitiveness according to the environmental pollutant, the studied matrix, the period and the landscape context. Despite such differences, most often specific to each apiary, our study shows an overall contamination of beehive matrices in all landscapes and during all periods. Even if the measured concentrations are generally low, this xenobiotic pressure is added to, even increases, the effect of many other environmental stressors which threaten the survival of bees in general.

L’assemblage des satellites dans des salles propres est actuellement surveillé, afin de garantir leur fiabilité, via des compteurs optiques de particules qui indiquent la quantité de particules par volume d’air prélevé dans la salle. Cependant, pourquoi mesurer la quantité de particules qu’il y a dans l’air alors que c’est la propreté des surfaces qui est importante ? La complexité des phénomènes de transport et de sédimentation des particules rend la simulation, la prédiction ou la prévention de ces phénomènes particulièrement difficile. L’objectif de cette thèse, qui s’est déroulée au Centre National d’Etudes Spatiales (CNES), est de proposer une méthode de mesure de la contamination particulaire locale et surfacique. Deux axes sont privilégiés dans ce but. En premier lieu, une évaluation des phénomènes de contamination et des moyens de mesure existants est proposée en abordant les spécificités du domaine du spatial. Les études théoriques et expérimentales rassemblées dans ce mémoire et le bilan des interrogations restantes tracent un portrait clair de l’état des connaissances actuelles dans ce domaine. Cet état de l’art amène à la définition d’un besoin pour la première fois clairement exprimé. Un tour d’horizon des moyens métrologiques s’appuyant sur cette évaluation préalable permet d’étudier avec précision les possibilités de développement d’un capteur. Finalement, cette thèse démontre que l’objectif de mesure de particules de 1 µm avec un moyen actif et en temps-réel est atteint avec une méthode de détection optique par transmission du signal lumineux. En second lieu, cette thèse s’attache donc aux caractéristiques du capteur dont les spécifications ont été étudiées et précisées en première partie. Si le développement du capteur est encore au stade initial, les perspectives de valorisation industrielle sont clairement établies. Ce mémoire s’appuie donc sur une recherche de fond sur la théorie de la contamination particulaire et les phénomènes physiques d’interaction entre les particules et leur environnement pour définir une méthode de mesure optique fiable, validée par la simulation, et faisant l’objet d’un dépôt de brevet. / The assembly of the satellites in clean rooms is currently monitored, in order to guarantee their reliability, via optical counters of particles which indicate the quantity of particles per volume of air in the room. However, why measure the quantity of particles in the air whereas it is the cleanliness of surfaces which is important? The complexity of the phenomena of transport and sedimentation of the particles makes the simulation, the prediction or the prevention of these phenomena particularly difficult. The objective of this thesis, which proceeded at the Centre National d’Etudes Spatiales (CNES), is to propose a method of measurement of the local and surface particulate contamination. Two axes are privileged to this end. Initially, an evaluation of the phenomena of contamination and existing methods of measurement are proposed by approaching space field specificities. The theoretical and experimental studies gathered in this memory and the assessment of the remaining interrogations trace a clear portrait of the state of current knowledge in this field. This state of the art brings to the definition of a need for the first time clearly expressed. A review of the metrological methods being based on this preliminary evaluation makes it possible to study with precision the possibilities of development of a sensor. Finally, this thesis shows that the goal of active and real-time measurement of particles of 1 µm is achieved with a method of optical detection by transmission of the light signal. In the second place, this thesis attempts to describe the characteristics of the sensor whose specifications were studied and specified in first part. If the development of the sensor is still at the initial stage, the prospects for industrial valorization are clearly established. This memory is thus based on a background research on the theory of the particulate contamination and the physical phenomena of interaction between the particles and their environment to define a method of optical measurement reliable, validated by simulation, and being the object of a patent filling.

Ce travail porte sur la formulation de nouveaux gels permettant de détecter visuellement par changement de couleur une contamination radioactive surfacique α ou γ. Un film mince de gel (< 1mm) est pulvérisé sur la paroi et est facilement récupéré après séchage. Des gels de gomme de xanthane transparents, viscoélastique et contenant des colorants radiosensibles ont été formulés. Des irradiations γ de colorants organiques et de complexe coloré Fer (II)- Xylénol orange dans des gels de silice et de xanthane ont été effectuées. Les mécanismes et les vitesses d'oxydation par radiolyse ont été précisés en fonction de la dose absorbée. Notamment, le xylénol orange et l'erioglaucine sont les deux colorants les plus radiosensibles. Le gel Fer (II)- Xylénol orange- Xanthane, noté FXX, a permis de révéler une tache contamination de 137Césium (émetteur γ d'activité0 = 20 KBq) au bout de 48 heures par oxydation du complexe coloré xylénol orange- Fe (II). Par ailleurs, ce même gel a permis de détecter une contamination surfacique de 239plutonium (émetteur α d'activité0 = 3720 Bq) au bout d'une journée.Pour la récupération après séchage, l'ajout de la silice dans le gel de xanthane a permis de mettre en évidence un résidu final qui délamine à faible concentration en silice ou qui fracture à une concentration élevée en silice. Enfin, l'ajout d'acide (> 2 M) a conduit à un séchage partiel du gel afin d'obtenir un film humide récupérable. / This work deals with the formulation of new gels to detect visually radioactive surface contamination α or γ by color changing. A thin gel film (<1mm) is sprayed onto the wall and is easily recovered after drying, Transparent, viscoelastic polymer xanthan gels and with radiosensitive dyes were selected.γ irradiation of organic dyes and colored complex Fe (II)- xylenol orange in silica and Xanthan gel were performed. Mechanisms and kinetics of oxidation by radiolysis were identified as a function of absorbed dose. The gel iron (II)-xylenol orange- Xanthane, noted FXX, revealed a spot of contamination by 137cesium (γ emitter of Activity0 = 20 KBq) after 48 hours by oxidation of the complex xylenol orange- ion (II). Moreover, the same gel detected a surface contamination by 239plutonium (transmitter Activity0 = 3720 Bq) after one day.For recovering after drying, the addition of silica to xanthan gel helped highlight a final dry residue delaminates at low concentration of silica or fracture at high silica concentration. However, the addition of acid (> 2 M) led to a partial drying of the gel giving a wet film recoverable.

Made available in DSpace on 2016-08-10T10:44:14Z (GMT). No. of bitstreams: 1 MARIANA BERNARDES BORGES BENCHIMOL.pdf: 15746292 bytes, checksum: 6f409bc1d98f40023f1239cbe314ec0c (MD5) Previous issue date: 2011-08-30 / This study was conducted in the Araguaia and Tocantins basins in the State of Goiás, during the drought period, and aimed to evaluate the content of polluting metals: aluminum, cadmium, lead, copper, chromium, iron, manganese and zinc in different trophic levels of fishes, and to compare the concentrations of these metals between the different trophic levels, sampling sites and between the two basins. Tests for determining the concentration of metals were performed by atomic absorption spectrometry, flame mode (AAS-flame). The similarity of the median concentrations of metal pollutants between trophic groups, between sampling sites and between basins was investigated by nonparametric Kruskal-Wallis test. The metals that most contributed to the pollution of basins studied were aluminum and manganese, possibly due to soil typical of the region (Oxisol) and the type of handling close to watercourses. The highest concentrations of metals were found in the Araguaia basin. There was significant difference in the levels of aluminum, iron and zinc between the basins. The trophic level most affected by metal pollution was the insectivore. Significant difference in the concentrations of pollutant metals (except lead) between trophic levels was observed. The data analysis indicates that the source of metal contamination of fish is the sediment of the aquatic environment. Results show a possible contamination of fish Araguaia and Tocantins basins with metal pollutants. Human activities observed in these basins appear to contribute to these results. / Esse estudo foi realizado nas bacias dos rios Araguaia e Tocantins, no Estado de Goiás, durante o período de estiagem, e teve como objetivo avaliar o teor de metais poluentes: alumínio, cádmio, chumbo, cobre, cromo, ferro, manganês e zinco em diferentes níveis tróficos de peixes, bem como comparar as concentrações destes metais entre os diferentes níveis tróficos, locais de coleta e entre as duas bacias hidrográficas. As análises para a determinação da concentração dos metais foram realizadas por espectrometria de absorção atômica, modalidade chama (EAA chama). A similaridade das concentrações medianas de metais poluentes entre os grupos tróficos, entre os locais de coleta e entre as bacias foi investigada pelo teste não-paramétrico de Kruskal-Wallis. Os metais que mais contribuíram para a poluição das bacias estudadas foram o alumínio e o manganês, possivelmente em decorrência do solo típico da região (Latossolo) e do tipo de manejo próximo aos cursos d água. As maiores concentrações de metais foram encontradas na bacia do rio Araguaia. Observou-se diferença significativa nos teores de alumínio, ferro e zinco entre as bacias. O nível trófico mais afetado pela poluição por metais foi o insetívoro. Diferença significativa nas concentrações de metais poluentes (exceto para o chumbo) entre os níveis tróficos foi verificada. Análises dos dados indicam que a fonte de contaminação dos peixes por metais é o sedimento do ambiente aquático. Resultados mostram uma possível contaminação de peixes das bacias dos rios Araguaia e Tocantins com metais poluentes. As atividades antrópicas observadas nestas bacias parecem contribuir para esses resultados.

Os metais de relevância toxicológica provenientes de fontes naturais e antropogênicas continuamente entram no ecossistema aquático causando sérios problemas à saúde humana e ambientais devido a sua toxicidade, longa persistência, bioacumulação e biomagnificação na cadeia alimentar. A contaminação de peixe e produtos da pesca por metais é de interesse da saúde pública. No Brasil, o Ministério da Saúde estabelece o limite máximo de tolerância (LMT) de 1,0 mg/kg para o arsênio em peixe e produtos da pesca e 0,5 mg/kg para o mercúrio, e 1,0 mg/kg em peixe predadores. O LMT não foi estabelecido para arsênio inorgânico, metilmercúrio e selênio. Este trabalho tem por objetivo avaliar a presença de arsênio total, arsênio inorgânico, mercúrio total, metilmercúrio e selênio em amostras de peixe cação comercializadas na cidade de São Paulo e analisar os resultados em relação à avaliação do risco. O arsênio total e o selênio foram determinados através de mineralização por via seca das amostras e quantificação utilizando absorção atômica com gerador de hidretos (FI-HG-AAS). O arsênio inorgânico foi determinado através de digestão ácida das amostras e posterior mineralização por via seca e quantificação utilizando FI-HG-AAS. O mercúrio total foi determinado através de digestão assistida por microondas em meio ácido e posterior quantificação do mercúrio total por espectrometria de fluorescência atômica com geração de vapor frio em fluxo contínuo (CV-AFS). O metilmercúrio foi determinado através de extração ácida das amostras e quantificação utilizando HPLC-termo-oxidação-CV-AFS. Os valores de As total nas amostras de cação analisadas variaram de 8,4 a 134,1 mg/kg (peso seco) e 2,1 a 33,5 mg/kg (peso úmido) e os valores de As inorgânico variaram de 0,013 a 0, 738 mg/kg (peso seco) e 0,0033 a 0,1845 mg/kg (peso úmido). Os valores de Hg total variaram de 0,7 a 14,6 mg/kg (peso seco) e 0,18 a 3,65 mg/kg (peso úmido). Os valores de metilmercúrio variaram de 0,46 a 8,67 mg/kg (peso seco) e 0,12 a 2,17 m/kg (peso úmido). Os valores de selênio variaram de 0,5 a 2,6 mg/kg (peso seco) e 0,13 a 0,65 mg/kg (peso úmido). Os valores de razão molar entre Hg e Se variaram de 0,28 a 5,39 (Hg:Se), e a média foi igual a 1,69. O PTWI para o arsênio inorgânico é 15 &#181;g/kg de peso corpóreo (WHO, 1989), e assumindo uma média de peso corpóreo de 65kg, a ingestão de arsênio inorgânico proveniente do consumo de cação representa apenas 0,0007% do valor de referência TDI (Ingestão diária tolerável) para média brasileira. O PTWI para o Hg total é 5 &#181;g/kg de peso corpóreo (WHO, 2003) e, a ingestão de Hg total por pessoa por dia proveniente apenas do consumo de cação para a média brasileira representa 0,17% do valor de referência TDI. / Metals of toxicological relevance from natural and anthropogenic sources continuously enter the aquatic ecosystem and cause serious environmental problems to human health and environment due to their toxicity, persistance, bioaccumulation and biomagnification in the food chain. Seafood metal contamination of is a public health interest. In Brasil, the Minister of Health establishes the maximum residue level (MRL) 1.0 mg/kg for arsenic in seafood and 0.5 for mercury and 1.0 for mercury in predator fish. The MRL was not stablished for inorganic arsenic, methylmercury and selenium. The purpose of this study is to evaluate the presence of total arsenic, inorganic arsenic, total mercury, methylmercury and selenium in shark samples commercialized in São Paulo city, and to evaluate their risk. The total arsenic and selenium were determined through sample dry ash and quantification by flow Injection -hydride generation-atomic absorption spectrometer (FI-HG-AAS). The inorganic arsenic was determined through sample acid digestion, ulterior dry ash and quantification by FI-HG-AAS. The total mercury was determined through sample acid digestion in microwave and quantification by atomic f1uorescence spectrophotometer with a cold vapor generator (CV-AFS). Methylmercury was determined by sample acid extraction and quantification by HPLC-termo-oxidation-CV-AFS. The levels of total arsenic vary between 8.4 and 134.1 mg/kg (dry weight) and 2.1 and 33.5 mg/kg (fresh weight) and levels of total inorganic arsenic vary between 0.013 and 0.738 mg/kg (dry weight) and 0.0033 and 0.1845 mg/kg (fresh weight). The levels of total mercury vary between 0.7 and 14.6 mg/kg (dry weight) and 0.18 and 3.65 mg/kg (fresh weight). The levels of methylmercury vary between 0.46 and 8.67 mg/kg (dry weight) and 0.12 and 2.17 m/kg (fresh weight). The levels of selenium vary between 0.5 and 2.6 mg/kg (dry weight) and 0.13 and 0.65 mg/kg (fresh weight). The values of molar reason between Hg and Se vary 0.28 and 5.39 (Hg:Se), and the media was 1.69. The PTWI for inorganic arsenic is 15 &#181;g/kg body weight (WHO, 1989), and assuming an average body weight of 65 Kg, the ingestion of inorganic arsenic from shark ingestion represents only 0,0007% of the reference value TDI (Tolerable daily ingestion) for Brazilian media. The PTWI for total mercury is 5 &#181;g/kg body weight (WHO, 2003) and the ingestion of total mercury per person per day from shark ingestion for Brazilian media represents 0.17% of the reference value TDI.