Semiconductor manufacturing is one of the most advancing, growing and evolving industries. The production of semiconductors presents several challenges, both technologically and environmentally. The amount and complexity of the chemical substances utilized in the manufacturing process has been growing exponentially, and new chemicals are often introduced to the process and the environment. Two steps of this process play a special important role in the introduction of new chemical and demand of natural resources: Chemical Mechanical Planarization (CMP) and Photolithography.Wastewaters from the semiconductor manufacturing are complex and have several chemicals in different concentrations. Heavy metals, acids, chelators, surfactants and other chemicals are found in semiconductor effluents. Part of the scope of this study is to evaluate and remediate wastewaters produced in semiconductor manufacturing.During the development of this project it was found that copper can be successfully removed and recovered from CMP wastewaters by the use of a sulfate reducing bioreactor and a crystallization reactor, promoting precipitation of copper sulfides on the surface of silica sand. High removal and recovery efficiencies were found as result of the study. Another finding include that citrate is a readily biodegradable compound which can be successfully utilized as electron donor for anaerobic processes such as methanogenesis and sulfate reductions. However other important chelator, like EDTA, can cause toxicity to these microorganisms and affect important biological processes. PFOS is an important chemical for the semiconductor industry; however, the physical and chemical properties make this compound persistent in the environment and bioaccumulative. New substitutes for PFOS were tested and evaluated for their environmental impact. It was found that perfluorination plays an important role in the chemical properties of PFOS and removal of this characteristic improves the environmental performance of the new substitutes. Evaluation of these new chemicals was also performed by simulation and modeling. The software utilized in this study identified properties like toxicity and octanol-water partition coefficient accurately. On the other hand biodegradability was poorly estimated and new models are suggested for evaluation of this property for compounds with characteristics similar to the ones studied here (specifically high fluorination).

Les substances perfluoroalkylées (PFAS) sont des composés synthétiques utilisés dans une multitude de domaines pour leurs propriétés hydrofuges, antiadhésives et antitaches exceptionnelles. Cependant, ces contaminants, dont la neurotoxicité a été démontrée dans les études in vitro et in vivo, sont capables de traverser la barrière placentaire et d’atteindre le fœtus en développement. Bien qu’une multitude d’études épidémiologiques aient été conduites pour examiner l’association entre l’exposition prénatale aux PFAS et le neurodéveloppement des enfants, il n’y a pas de consensus dans la littérature : certaines rapportent des associations délétères, et d’autres protectrices ou nulles. Le but de cette étude est d’évaluer l’association entre l’exposition aux PFAS chez les femmes enceintes et le développement neurocomportemental et social des enfants pendant la petite enfance. Nous avons également examiné si le lien différait entre les filles et les garçons. Les données de l’étude Maternal-Infant Research on Environmental Chemicals (MIREC), une cohorte de grossesse pancanadienne, ont été utilisées. L’exposition prénatale à trois PFAS (acides perfluorooctanoïque (PFOA), perfluorooctanesulfonique (PFOS) et perfluorohexane sulfonique (PFHxS)) ainsi que leur somme (ΣPFAS) a été mesurée dans le plasma maternel prélevé durant le premier trimestre de grossesse. Lorsque les enfants étaient âgés de trois-quatre ans, les mères ont été invitées à remplir deux questionnaires sur leurs enfants : le Behaviour Assessment System for Children–2 (BASC-2), pour évaluer les difficultés émotionnelles et comportementales, et le Social Responsiveness Scale–2 (SRS-2), afin d’évaluer le développement social. À partir des données de 794 paires mère-enfant, des analyses de régressions linéaires multiples, avec ajustement pour des facteurs de confusion, ont été réalisées, et les coefficients d’association ont été calculés pour un doublement des concentrations de PFAS. La modification des associations selon le genre a été examinée au moyen de termes d'interaction et d'analyses stratifiées. Bien que la majorité des associations obtenues soient nulles, pour l’ensemble du groupe étudié, un doublement de l’exposition prénatale aux PFOS était lié à moins de déficits de motivation sociale (β = -1.03; IC : -1.88, -0.17) et le PFHxS à plus de comportements atypiques (β = 0.57; 0.04, 1.11). Cependant, les analyses selon le genre ont révélé que chez les garçons seulement, un doublement de l’exposition prénatale aux PFOA était significativement associée à des scores plus faibles pour les sous-échelles suivantes : indice des symptômes comportementaux, problèmes d'externalisation, agressivité et hyperactivité (β allant de -1.87 à -1.32). Le PFOS et la ΣPFAS étaient aussi liés à moins d’agressivité chez les garçons (β = 1.20; -2.27, -0.13 et β = -1.35; -2.55, -0.15 respectivement). À l’inverse, chez les filles, le PFOA était significativement lié à plus de symptômes d’anxiété, et le PFHxS et la ΣPFAS étaient liés à plus de problèmes de cognition sociale (β allant de 0.90 à 1.81). Dans l’ensemble, les données suggèrent que l’association entre l’exposition prénatale aux PFAS et le développement neurocomportemental et social des enfants semble différer selon le genre : un effet protecteur est observé chez les garçons, tandis qu’il ressort délétère chez les filles. Les résultats obtenus dans cette cohorte canadienne de grande taille corroborent ceux notés dans certaines études épidémiologiques rapportant un lien délétère, lequel est surtout observable chez les filles. / Perfluoroalkyl substances (PFAS) are synthetic compounds used in a wide range of fields for their exceptional water-repellent, non-stick, and stain-resistant properties. However, these contaminants, whose neurotoxicity has been demonstrated in in vitro and in vivo studies, can crossthe placental barrier, and reach the developing fetus. Although numerous epidemiological studies have been conducted to examine the association between prenatal exposure to PFAS and the neurodevelopment in children, there is no consensus in the literature: some report deleterious associations, while others report protective or null associations. The aim of this study is to investigate the association between PFAS exposure in pregnant women and the neurobehavioral and social development of children during early childhood. We also examined whether the association differed between girls and boys. We used data from the Maternal-Infant Research on Environmental Chemicals (MIREC) study, a pan-Canadian pregnancy cohort. Prenatal concentrations of three PFAS (perfluorooctanoic (PFOA), perfluorooctanesulfonic (PFOS) and perfluorohexanesulfonic acids (PFHxS)), as well as their sum (åPFAS), were measured in maternal plasma collected during the first trimester of pregnancy. When the children were three to four years old, mothers were asked to complete two questionnaires about their children: the Behaviour Assessment System for Children-2 (BASC-2) to assess emotional and behavioural difficulties, and the Social Responsiveness Scale-2 (SRS-2) to assess social development. Using data from 794 mother-child dyads, multiple linear regression analyses, with adjustment for confounding factors, were performed and regression coefficients were estimated to assess whether there was an association between each doubling of PFAS concentrations and test scores. Effect modification by child gender was examined using interaction terms and stratified analyses. For the entire study group, although most of the associations found were null, a doubling of prenatal PFOS exposure was linked to fewer social motivation deficits (β = -1.03; CI: -1.88, -0.17), and increased PFHxS was linked to more atypical behaviors (β = 0.57; 0.04, 1.11). However, gender-stratified analyses revealed that in boys only, each doubling of prenatal PFOA exposure was significantly associated with lower scores on the following BASC-2 subscales: Behavioral Symptoms Index, Externalizing Problems, Aggressivity and Hyperactivity (β ranging from -1.87 to -1.32). PFOS and åPFAS were also associated with less aggression in boys (β = 1.20; -2.27, -0.13 and β = -1.35; -2.55, -0.15 respectively). Conversely, in girls only, PFOAwas significantly associated with more symptoms of anxiety, and PFHxS and ∑PFAS were associated with more social cognition problems (β ranging from 0.90 to 1.81). Overall, the data suggest that the association between prenatal PFAS exposure and the neurobehavioral and social development of children appears to differ by gender: a protective effect is observed in boys, while a detrimental effect is seen in girls. The results obtained in this large Canadian cohort are consistent with findings from some epidemiological studies reporting a harmful link predominantly in girls.