Letteratura scientifica selezionata sul tema "Chemicals effects"
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Articoli di riviste sul tema "Chemicals effects":
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Rybak, Leonard P. "Hearing: The Effects of Chemicals". Otolaryngology–Head and Neck Surgery 106, n. 6 (giugno 1992): 677–86. http://dx.doi.org/10.1177/019459989210600611.
Abstract (sommario):
Recent studies of human beings exposed to environmental chemicals, as well as experimental animal studies, have identified a number of chemical agents that are commercial products, chemical intermediaries, waste products, or contaminants that are potentially ototoxic. The classes of compounds discussed in this review include organic solvents, asphyxiant gases, and heavy metals that are present in the environment as Industrial pollutants or byproducts. Both human and animal investigations are summarized in discussing the actions of these ototoxic compounds. The suggested gaps in our knowledge are highlighted to help direct future research.
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Giesy, J. P., L. A. Feyk, P. D. Jones, Kurunthachalam Kannan e T. Sanderson. "Review of the effects of endocrine-disrupting chemicals in birds". Pure and Applied Chemistry 75, n. 11-12 (1 gennaio 2003): 2287–303. http://dx.doi.org/10.1351/pac200375112287.
Abstract (sommario):
There have been several case studies of the impact of chemical contaminants on birds at the level of individuals or populations. While many of the chemicals involved in these incidents have been classified as endocrine-disrupting chemicals or endocrine active substances (EASs) the mechanisms by which these chemicals affect birds are not clearly or fully understood.
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Pollis, Rebecca E., Andrew L. Reid e Lenly J. Weathers. "Effects of chemicals microorganisms". Water Environment Research 70, n. 4 (giugno 1998): 915–21. http://dx.doi.org/10.2175/106143098x134532.
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Wheeler, David C., Salem Rustom, Matthew Carli, Todd P. Whitehead, Mary H. Ward e Catherine Metayer. "Assessment of Grouped Weighted Quantile Sum Regression for Modeling Chemical Mixtures and Cancer Risk". International Journal of Environmental Research and Public Health 18, n. 2 (9 gennaio 2021): 504. http://dx.doi.org/10.3390/ijerph18020504.
Abstract (sommario):
Individuals are exposed to a large number of diverse environmental chemicals simultaneously and the evaluation of multiple chemical exposures is important for identifying cancer risk factors. The measurement of a large number of chemicals (the exposome) in epidemiologic studies is allowing for a more comprehensive assessment of cancer risk factors than was done in earlier studies that focused on only a few chemicals. Empirical evidence from epidemiologic studies shows that chemicals from different chemical classes have different magnitudes and directions of association with cancers. Given increasing data availability, there is a need for the development and assessment of statistical methods to model environmental cancer risk that considers a large number of diverse chemicals with different effects for different chemical classes. The method of grouped weighted quantile sum (GWQS) regression allows for multiple groups of chemicals to be considered in the model such that different magnitudes and directions of associations are possible for each group of chemicals. In this paper, we assessed the ability of GWQS regression to estimate exposure effects for multiple chemical groups and correctly identify important chemicals in each group using a simulation study. We compared the performance of GWQS regression with WQS regression, the least absolute shrinkage and selection operator (lasso), and the group lasso in estimating exposure effects and identifying important chemicals. The simulation study results demonstrate that GWQS is an effective method for modeling exposure to multiple groups of chemicals and compares favorably with other methods used in mixture analysis. As an application, we used GWQS regression in the California Childhood Leukemia Study (CCLS), a population-based case-control study of childhood leukemia in California to estimate exposure effects for many chemical classes while also adjusting for demographic factors. The CCLS analysis found evidence of a positive association between exposure to the herbicide dacthal and an increased risk of childhood leukemia.
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Wheeler, David C., Salem Rustom, Matthew Carli, Todd P. Whitehead, Mary H. Ward e Catherine Metayer. "Assessment of Grouped Weighted Quantile Sum Regression for Modeling Chemical Mixtures and Cancer Risk". International Journal of Environmental Research and Public Health 18, n. 2 (9 gennaio 2021): 504. http://dx.doi.org/10.3390/ijerph18020504.
Abstract (sommario):
Individuals are exposed to a large number of diverse environmental chemicals simultaneously and the evaluation of multiple chemical exposures is important for identifying cancer risk factors. The measurement of a large number of chemicals (the exposome) in epidemiologic studies is allowing for a more comprehensive assessment of cancer risk factors than was done in earlier studies that focused on only a few chemicals. Empirical evidence from epidemiologic studies shows that chemicals from different chemical classes have different magnitudes and directions of association with cancers. Given increasing data availability, there is a need for the development and assessment of statistical methods to model environmental cancer risk that considers a large number of diverse chemicals with different effects for different chemical classes. The method of grouped weighted quantile sum (GWQS) regression allows for multiple groups of chemicals to be considered in the model such that different magnitudes and directions of associations are possible for each group of chemicals. In this paper, we assessed the ability of GWQS regression to estimate exposure effects for multiple chemical groups and correctly identify important chemicals in each group using a simulation study. We compared the performance of GWQS regression with WQS regression, the least absolute shrinkage and selection operator (lasso), and the group lasso in estimating exposure effects and identifying important chemicals. The simulation study results demonstrate that GWQS is an effective method for modeling exposure to multiple groups of chemicals and compares favorably with other methods used in mixture analysis. As an application, we used GWQS regression in the California Childhood Leukemia Study (CCLS), a population-based case-control study of childhood leukemia in California to estimate exposure effects for many chemical classes while also adjusting for demographic factors. The CCLS analysis found evidence of a positive association between exposure to the herbicide dacthal and an increased risk of childhood leukemia.
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Liu, Tao, Lei Chen e Xiaoyong Pan. "An Integrated Multi-Label Classifier with Chemical-Chemical Interactions for Prediction of Chemical Toxicity Effects". Combinatorial Chemistry & High Throughput Screening 21, n. 6 (27 agosto 2018): 403–10. http://dx.doi.org/10.2174/1386207321666180601075428.
Abstract (sommario):
Aims and Objective: Chemical toxicity effect is one of the major reasons for declining candidate drugs. Detecting the toxicity effects of all chemicals can accelerate the procedures of drug discovery. However, it is time-consuming and expensive to identify the toxicity effects of a given chemical through traditional experiments. Designing quick, reliable and non-animal-involved computational methods is an alternative way. Method: In this study, a novel integrated multi-label classifier was proposed. First, based on five types of chemical-chemical interactions retrieved from STITCH, each of which is derived from one aspect of chemicals, five individual classifiers were built. Then, several integrated classifiers were built by integrating some or all individual classifiers. Result and Conclusion: By testing the integrated classifiers on a dataset with chemicals and their toxicity effects in Accelrys Toxicity database and non-toxic chemicals with their performance evaluated by jackknife test, an optimal integrated classifier was selected as the proposed classifier, which provided quite high prediction accuracies and wide applications.
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Rivera, Brianna N., Lindsay B. Wilson, Doo Nam Kim, Paritosh Pande, Kim A. Anderson, Susan C. Tilton e Robyn L. Tanguay. "A Comparative Multi-System Approach to Characterizing Bioactivity of Commonly Occurring Chemicals". International Journal of Environmental Research and Public Health 19, n. 7 (23 marzo 2022): 3829. http://dx.doi.org/10.3390/ijerph19073829.
Abstract (sommario):
A 2019 retrospective study analyzed wristband personal samplers from fourteen different communities across three different continents for over 1530 organic chemicals. Investigators identified fourteen chemicals (G14) detected in over 50% of personal samplers. The G14 represent a group of chemicals that individuals are commonly exposed to, and are mainly associated with consumer products including plasticizers, fragrances, flame retardants, and pesticides. The high frequency of exposure to these chemicals raises questions of their potential adverse human health effects. Additionally, the possibility of exposure to mixtures of these chemicals is likely due to their co-occurrence; thus, the potential for mixtures to induce differential bioactivity warrants further investigation. This study describes a novel approach to broadly evaluate the hazards of personal chemical exposures by coupling data from personal sampling devices with high-throughput bioactivity screenings using in vitro and non-mammalian in vivo models. To account for species and sensitivity differences, screening was conducted using primary normal human bronchial epithelial (NHBE) cells and early life-stage zebrafish. Mixtures of the G14 and most potent G14 chemicals were created to assess potential mixture effects. Chemical bioactivity was dependent on the model system, with five and eleven chemicals deemed bioactive in NHBE and zebrafish, respectively, supporting the use of a multi-system approach for bioactivity testing and highlighting sensitivity differences between the models. In both NHBE and zebrafish, mixture effects were observed when screening mixtures of the most potent chemicals. Observations of BMC-based mixtures in NHBE (NHBE BMC Mix) and zebrafish (ZF BMC Mix) suggested antagonistic effects. In this study, consumer product-related chemicals were prioritized for bioactivity screening using personal exposure data. High-throughput high-content screening was utilized to assess the chemical bioactivity and mixture effects of the most potent chemicals.
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Jain, Neha. "Terrorism at Rise with the Chemicals Insight: Use of Chemical Warfare Agents an Issue of Global Concern". Journal of Forensic Chemistry and Toxicology 9, n. 1 (15 giugno 2023): 47–51. http://dx.doi.org/10.21088/jfct.2454.9363.9123.3.
Abstract (sommario):
Crime has led to a worldwide increase with a main weapon of offence including not only a physical object but show the incidences of involvement of chemicals also. Chemical warfare agents are one such example commonly employed by large group of people, mainly violent criminals who not only wants to create a terror or threat in the world but to cause war scale destruction. There are numerous of incidents reported from past showing the involvement of hazardous chemicals for committing crimes. Chemical Warfare Agents (CWA) are synthetic chemicals used in the warfare as weapons, which are highly toxic and lethal to the extent that can cause temporary incapacitation, permanent health damage and even death of the targets. Common examples of these agents are nerve agents, vesicants, incapacitating agents, blood agents, and riots control agents. These agents are variedly classified as per the above-mentioned categories depending onto the effects and adverse effects they poses on human health and on society. The rate of crime commission using these hazardous agents is very rapid, thus making it an issue of serious concern to take measures to prevent innocent individuals.
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Czarnota, Jenna, David C. Wheeler e Chris Gennings. "Evaluating Geographically Weighted Regression Models for Environmental Chemical Risk Analysis". Cancer Informatics 14s2 (gennaio 2015): CIN.S17296. http://dx.doi.org/10.4137/cin.s17296.
Abstract (sommario):
In the evaluation of cancer risk related to environmental chemical exposures, the effect of many correlated chemicals on disease is often of interest. The relationship between correlated environmental chemicals and health effects is not always constant across a study area, as exposure levels may change spatially due to various environmental factors. Geographically weighted regression (GWR) has been proposed to model spatially varying effects. However, concerns about collinearity effects, including regression coefficient sign reversal (ie, reversal paradox), may limit the applicability of GWR for environmental chemical risk analysis. A penalized version of GWR, the geographically weighted lasso, has been proposed to remediate the collinearity effects in GWR models. Our focus in this study was on assessing through a simulation study the ability of GWR and GWL to correctly identify spatially varying chemical effects for a mixture of correlated chemicals within a study area. Our results showed that GWR suffered from the reversal paradox, while GWL overpenalized the effects for the chemical most strongly related to the outcome.
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Boxall, Alistair, Anthony Hardy, Sabine Beulke, Tatiana Boucard, Laura Burgin, Peter Falloon, Philip Haygarth et al. "Impacts of climate change on indirect human exposure to pathogens and chemicals from agriculture". Ciência & Saúde Coletiva 15, n. 3 (maggio 2010): 743–56. http://dx.doi.org/10.1590/s1413-81232010000300017.
Abstract (sommario):
Climate change is likely to affect the nature of pathogens/ chemicals in the environment and their fate and transport. We assess the implications of climate change for changes in human exposures to pathogens/chemicals in agricultural systems in the UK and discuss the effects on health impacts, using expert input and literature on climate change; health effects from exposure to pathogens/chemicals arising from agriculture; inputs of chemicals/pathogens to agricultural systems; and human exposure pathways for pathogens/chemicals in agricultural systems. We established the evidence base for health effects of chemicals/pathogens in the agricultural environment; determined the potential implications of climate change on chemical/pathogen inputs in agricultural systems; and explored the effects of climate change on environmental transport and fate of various contaminants. We merged data to assess the implications of climate change in terms of indirect human exposure to pathogens/chemicals in agricultural systems, and defined recommendations on future research and policy changes to manage adverse increases in risks.
Tesi sul tema "Chemicals effects":
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Meyer, Stephanie Kristen. "Effects of oestrogenic chemicals on the liver". Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3654.
Abstract (sommario):
Our environment and diet contains a variety of man-made endocrine disrupting chemicals which may pose a significant health threat for wildlife and humans. In particular, there is increasing concern regarding the adverse effects caused by xenoestrogens which are believed to trigger many endocrine-related diseases. Since high systemic levels of oestrogens are cholestatic, it was investigated whether xenoestrogens are able to cause adverse hepatic effects in vivo in mouse models and whether these effects are mediated by interaction with the murine oestrogen receptors (ERs). The food dye tartrazine has previously been shown to activate the human ERα and intraperitoneal injection caused cholestasis in mice. In this study, tartrazine failed to activate murine ERα and two murine ERβ variants in vitro suggesting that cholestasis occurred independent of the ERs. Data indicate, however, that tartrazine, its major metabolites and a contaminant inhibited murine dopamine sulfotransferase. Considering the role of sulfotransferases in bile acid secretion, these findings suggest that impairment of bile acid sulfation and subsequent secretion may be a key event in tartrazine-mediated cholestasis. Oral exposure to tartrazine caused inflammation in the liver and gastrointestinal tract in vivo in mice without evidence of cholestatic effects. Several soil extracts prepared from soil samples collected from around an urban landfill site activated human and murine ERα and two murine ERβ variants in vitro. Pooled oestrogenic soil extracts had mild cholestatic effects in a mouse model. Given the cholestatic features of the liver disease primary biliary cholangitis (PBC), which is linked to exposure to xenobiotics associated with a toxic environment and proximities to waste sites, environmental xenoestrogens could be a component of a xenobiotic insult that triggers PBC. These findings indicate that if significant exposure to environmental xenoestrogens occurs, they can have adverse hepatic effects and may be part of a trigger process in cholestatic liver diseases.
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Oliveira, Rhaul. "Effects assessment of chemicals used in aquaculture". Doctoral thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/16297.
Abstract (sommario):
Doutoramento em BiologiaAquaculture provides food and income for millions of families worldwide being an activity with a high growth rate and with a strong potential for further expansion. Both producers and consumers are interested in a sustainable model of aquaculture development covering social, economic and environmental aspects. Such model implies to cope with the environmental impacts generated by aquacultures. The main objective of this work was to evaluate the use of chemicals applied in aquaculture farms and their harmful effects to aquatic organisms. Since more than 80% of global production of aquatic organisms is concentrated in Southwest Asia, special attention was given to the aquaculture in this region, particularly Thailand. Three different types of aquaculture scenarios were studied: shrimp farms and tilapia farms in cages and in earth ponds. Surveys and monitoring campaigns were conducted in several farms and the fate, use and application patterns of chemicals were identified. In cage farms the results indicated overuse/misuse of antibiotics, in shrimp farms the major group of chemicals used were disinfectants whereas in earth pond farms 1,7α-methyltestosterone (MT) was the most used. The results from the monitoring campaigns showed that the excessive use of chemicals was correlated to contamination of the surrounding environment namely with the antibiotics oxytetracycline (OTC) and enrofloxacin (ENR) in the cage farms, and with MT in the earth pond farms. In the laboratory, ecotoxicity assays were performed with antibiotics, disinfectants and pesticides using organisms belonging to different trophic levels. The disinfectants benzalkonium chloride (BKC), chlorhexidine gluconate (ChD) and glutaraldehyde (GA) were tested. BKC and ChD demonstrated to be very toxic to primary and secondary consumers. Moreover, an approach based on the species sensitivity distributions (SSD) was used to estimate the hazardous concentrations for 5 and 50 % of the species after BKC and GA exposure highlighting the sensitivity of primary producers to BKC exposure (HC5 = 10.8 μg/l). In the case of GA, different trophic levels showed similar sensitivities and a general HC5 = 300 μg/l was obtained. Additionally, a probabilistic environmental risk assessment was performed indicating a PAF (potentially affected fraction) of species > 5% for adverse effects of BKC in effluents and surface water. Concerning pesticides, both trichlorfon (TCF) and ivermectin (IVM) were studied. TCF showed to be extremely toxic to daphnids (48h- LC50 = 0.29 μg/l) and affected the acetilcolinesterase activity in D. magna and D rerio. IVM showed to be acutely toxic to D. rerio life stages (96h-LC50 = 18.5 μg/l for juveniles) and affected their development and biomarkers. In chronic exposures, IVM led to changes in the behaviour and growth of D. rerio juveniles (21d-LOEC < 0.25 μg/l). The antibiotics amoxicillin and OTC were not acutely toxic to aquatic organisms but both induced oxidative stress related enzymes of adults and embryos of D. rerio. Globally, most of the tested chemicals showed to compromise at least a particular group of organisms or sub-lethal parameters, requiring further long term studies so that the environmental risk assessment of these compounds can be refined. Lethal and sub lethal effects obtained to non-target organisms suggest a potential biodiversity loss in the aquatic ecosystems which might, thus, compromise the services provided by the ecosystems in a near future. Since the aquaculture relies directly on these services (e.g. high water quality) to succeed, there is an urgent need of control/education measures both in the use of chemicals in aquaculture and monitoring/mitigation of adverse impacts in natural ecosystems.
A aquacultura fornece sustento para milhões de famílias, sendo uma actividade em crescimento e com um forte potencial de expansão em todo o mundo. Há um interesse por parte de produtores e consumidores em desenvolver modelos sustentáveis de aquacultura abrangendo aspectos sociais, económicos e ambientais. Tais modelos implicam lidar com os impactos ambientais gerados pela aquacultura. O principal objectivo deste trabalho foi estudar o uso de produtos químicos usados nas aquaculturas e avaliar os seus efeitos nocivos para organismos aquáticos. Uma vez que mais de 80% da produção mundial de organismos aquáticos está concentrada no sudoeste da Ásia, foi dada especial atenção à aquacultura nessa região, particularmente na Tailândia. Três diferentes cenários foram considerados: aquaculturas de camarão, aquaculturas de tilápias cultivadas em gaiolas e em tanques escavados no solo. Em cada tipo foram realizados inquéritos e campanhas de monitoramento em várias aquaculturas nas quais foram averiguados o uso, destino e forma de aplicação de químicos. Os resultados indicaram o uso excessivo/inapropriado de alguns compostos, nomeadamente de antibióticos (em aquaculturas em gaiolas), de desinfectantes (em aquaculturas de camarão) e de 1,7α-metiltestosterona (MT) (em aquacultura de tilápias em tanques escavados). Os resultados das campanhas de monitorização mostraram que o uso excessivo de produtos químicos resulta na contaminação do meio ambiente com antibióticos (oxitetraciclina (OTC) e enrofloxacina (ENR)) nas aquaculturas em gaiola, e com MT nas aquaculturas de tilápias em tanques escavados. No laboratório, foram realizados ensaios de ecotoxicidade com antibióticos, desinfectantes e pesticidas usando organismos modelo pertencentes a diferentes níveis tróficos. Foram testados os desinfectantes, cloreto de benzalcónio (BKC), gluconato de clorexidina, e glutaraldeído (GA) sendo que os dois primeiros demonstraram ser muito tóxico para consumidores primários e secundários. Para uma análise integrada foi utilizada uma abordagem baseada nas distribuições de sensibilidade das espécies (DSE) com a qual se estimaram as concentrações perigosas (CP) para 5% e 50% das espécies após e exposição ao BKC e GA. O grupo dos produtores primários foi o grupo mais sensível à exposição ao BKC com CP5% = 10,8 μg/l enquanto para GA não foram encontradas diferenças de sensibilidade entre os grupos tróficos e, assim sendo, um valor geral de CP5% = 300 μg/l foi obtido. Além disso, uma análise probabilística dos riscos ambientais indicou uma fracção de espécies potencialmente afectada (FAPE) pelo BKC > 5% em efluentes e águas superficiais. Os pesticidas estudados foram o trichlorfon (TCF) e a ivermectina (IVM). O TCF foi extremamente tóxico para dafnídeos (48h-LC50 = 0,29 μg/l) e afectou também a actividade de acetilcolinesterase em D. magna e D. rerio. A IVM foi tóxica para adultos, juvenis e embriões de D. rerio (96h- CL50 = 18,5 μg/l para os juvenis) afectando o seu desenvolvimento e actividade de biomarcadores. Em exposições crónicas, IVM causou alterações no comportamento e crescimento em D. rerio juvenis (21d-LOEC <0,25 μg/l). Os antibióticos amoxicilina e OTC apresentam baixa toxidade para os organismos aquáticos, mas ambos induziram enzimas relacionadas estresse oxidativo em adultos e embriões de D. rerio. Em geral, a maioria dos químicos testados apresentaram toxicidade para algum grupo de organismo da cadeia trófica ou tiveram efeito a nível de parâmetros sub-letais, sendo portanto recomendados estudos de exposição crónica para que se possa refinar a avaliação de risco ambiental destes compostos. Os efeitos letais e sub-letais observados nos organismos não-alvo sugerem que pode haver uma perda da biodiversidade nos ecossistemas aquáticos, e assim, comprometer os serviços prestados pelos ecossistemas num futuro próximo. Sendo o sucesso da aquacultura dependente directo destes serviços (por exemplo, água de alta qualidade), há uma necessidade urgente de medidas de controlo/educação, tanto no uso de produtos químicos na aquacultura e monitoramento/mitigação dos impactos negativos destes nos ecossistemas naturais.
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Goats, Geoffrey Charles. "Assessment of the effects of toxic chemicals upon earthworms". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37706.
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Merritt, Rebecca L. "The effects of environmental chemicals on glioblastoma cell growth". Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3475.
Abstract (sommario):
Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains vii, 78 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 70-78).
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Li, Jing Adela, e 李晶. "Temperature-dependent toxic effects of selected chemicals on marine organisms". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/211051.
Abstract (sommario):
Anthropogenically driven climate change not only results in rising of sea temperature but also leads to more frequent and longer-lasting cold and heat waves. Meanwhile, coastal marine ecosystems are constantly challenged by increasing threats of chemical pollution. Temperature and chemical stressors can jointly affect the livelihood of marine organisms, but their combined effects are still poorly understood. Therefore, this study aimed to investigate the effects of thermal stress and chemical exposure on the marine medaka Oryzias melastigma, copepod Tigriopus japonicus and rotifer Brachionus koreanus. The four selected chemical contaminants included copper sulphate pentahydrate (Cu), dichlorophenyltrichloroethane (DDT), triphenyltin chloride and copper pyrithione. It was hypothesized that marine organisms are more susceptible to chemical exposure at both cold and warm extremes.
In vivo acute ecotoxicity tests were conducted over a wide temperature range to ascertain the relationship between thermal stress and chemical toxicity. For O. melastigma larvae, the lowest toxicity occurred at an optimum temperature range; the chemical toxicity further increased with temperature increase or decrease from this optimum, and exacerbated at extremely low and high temperatures. For T. japonicus and B. koreanus, the chemical toxicity generally increased with increasing temperature. Such inter-species dissimilarities were possibly due to differences in the uptake route, detoxification mechanism, avoidance behaviour and physiological response between the fish and the copepod or rotifer.
Experiments were conducted to evaluate the temperature-dependent physiological and biochemical responses, and thermal tolerance of O. melastigma larvae. The growth in the fish larvae showed an inverse and negatively skewed V-shape relationship with temperature, with a significant reduction in performance at both low and high thermal extremes. A mismatch between demand and supply of oxygen and energy under extremely cold and warm conditions was probably the primary cause of growth inhibition and metabolic impairment, leading to a temporary adaptation by a shift to anaerobiosis and an induction of heat shock proteins (HSPs).
Temperatures at both cold and warm extremes increased toxicities of DDT and Cu to O. melastigma larvae, resulting in restricted growth and interrupted oxygen consumption rate. The fish larvae modulated their metabolic pathway and produced stress proteins (i.e., HSPs and metallothioneins) for adaptation to the combined stress. However, such responses were disrupted by combinations of thermal extremes, in particular high temperature, and high chemical concentration. Most importantly, both DDT and Cu exposure significantly reduced the thermal tolerance of the fish larvae.
The interacting effect of temperature and Cu was also investigated on T. japonicus. The results showed that their combined effect could significantly reduce the survival, lengthen the developmental time and change the sex ratio of the copepod. Transcriptions of several stress-related genes (i.e., glutathione reductase, glutathione S-transferases and HSPs) in the adult T. japonicus were significantly affected by the joint-effect of temperature and Cu exposure, implying that these genes played essential roles in protecting the cellular integrity against the stresses.
This study advanced the understanding on the temperature-dependent toxicity of chemical contaminants to marine organisms, and provided valuable information and empirical models for deriving water quality criteria of chemical contaminants at various temperatures.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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Oliveira, Eva Lima de Castro. "Ecotoxicological bioassays to evaluate the effects of chemicals in soil". Master's thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/801.
Abstract (sommario):
Mestrado em Toxicologia e EcotoxicologiaA utilização de compostos químicos e os consequentes efeitos em distintos compartimentos ambientais tem despertado muito interesse nos últimos anos.O aparecimento de Produtos de Higiene Pessoal no ambiente tem sido considerado como uma questão a ser colocada no domínio ambiental. A sua presença no ambiente ocorre devido á excessiva utilização por parte dosconsumidores e à sua incompleta remoção das estações de tratamento de águas residuais. Nessas estações os efluentes tratados e lamas sãonovamente reintroduzidos no ambiente e na maioria dos casosafectam os organismos residentes nas comunidades locais. Um outro tipo de compostos que também têm recebido atenção especial é os Hidrocarbonetos Policíclicos Aromáticos (HPAs), que desde a sua primeira aparição no solo, despertaramgrande curiosidade. Estes compostos são derivados da combustão incompletade compostos contendo carbono e hidrogénio e do processo diagénese. Com estetrabalho pretendemos avaliar a toxicidade do Triclosan num conjuntode organismos-teste terrestres, lumbricideos (Eisenia andrei), colêmbolos (Folsomia candida), enquitraideos (Enchytraeus albidus), incluindo dois tipos de plantas superiores (Triticum aestivum e Brassica rapa). Os parâmetros avaliados foram a germinação e crescimento das plantas e a sobrevivência/reprodução dos restantes organismos. Também foi realizado um ensaio de bioacumulação para avaliar o comportamento cinético de um HPA, o fenantreno em E. albidus. Para a determinação da concentração de fenantreno nos organismos bem como nos extractos de solo dois métodos foram usados: um por fluorescência e outro por cromatografia gasosa com espectometria demassa acoplado. Os resultados obtidos para a bateria de testes mostram uma relação dose-resposta para todas as espécies estudadas, Eisenia andrei é a que demonstra ser mais sensível, com um valor de CE50de aproximadamente 4mg/kg; a sensibilidade para cada espécie por ordem decrescente é a seguinteE. andrei> B. rapa> E. albidus > F. candida > T. aestivum. Verificou-se que os enquitraideos podem acumular e ser afectados por uma variedade decompostos orgânicos e inorgânicos, tais como os HPAs (fenantreno). Os parâmetros cinéticos estimados para o fenantreno foram 4.4 g solo/g organismo dia-1 para a taxa de assimilação (a) e 0,305 dia-1 para a taxa de eliminação (ke), o factor de bioacumulação calculado é de 14.3 para E. albidus.Todos os ensaios foram realizados com um solo padronizado Lufa 2.2. No âmbito geral, os testes ecotoxicológicos realizados, revelam a importânciade incluir diversas espécies, abrangendo diferentes níveis tróficos, devido á distinta sensibilidade dos organismos e modos de acção dos diferentes químicos. ABSTRACT: The usage of chemicalcompounds and their effects in the different environmental compartments have received a special attention in recent years. The occurrence of Personal Care Products (PCPs) in the environment hasbeen recognised as one of emerging issues in environmental chemistry. The widespread presence of PCPs in the environment is due to their extensive usefor direct use by the consumer and incomplete removal in wastewater treatment plants (WWTPs). WWTPs produce aqueous effluents for dischargeback into the environment, and sewage sludge and in a number of cases mayaffect the living organisms. Although Polycyclic Aromatic Compounds (PAHs) have received special attention since they were found in soils for the first time.PAHs are a class of several hundreds individual compounds containing at leasttwo condensed rings. They are produced by the incomplete combustion ofcompounds containing C and H, and diagenesis. With this study we assessed the toxicity of Triclosan in several standardized test organisms and parameters:seed emergence and growth of two terrestrial plants (Triticum aestivum and Brassica rapa); survival and reproduction of earthworms (Eisenia andrei), collembolans (Folsomia candida) andenchytraeids (Enchytraeus albidus). The results for the test battery shows a dose-response relationship for the all organisms tested and Eisenia andreiwas the most sensitive specie, with an EC50value of approximately 4mg/kg; with species chronic sensitivity decreasing from E. andrei > B. rapa > E. albidus > F. candida > T. aestivum. The overall results from the selected ecotoxicologicaltests, showed the importance of including species from different trophic levels due to the different species sensitivities and chemicals mode of action.Moreover, also the use of chronic endpoints is recommended.In the case of the PAH phenantrene (PHE), a study was performed in E. albidus, assessing the effects at the survival and reproduction, plus the bioaccumulation, to analysethe toxicokinetic behaviour of this chemical. Enchytraeus can accumulate and may be affected by PHE. Estimated kinetic parameters were 4.4g soil/g worm day-1 for the assimilation rate (a) and 0,305 day-1 for the elimination rate constant (ke), bioaccumulation factor was 14.3. In a general trend, the ecotoxicological tests performedshow the importance, of study different trophic levels, including different species, due to the different sensibility of the organisms and different chemicals modes of action. 6
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Ribeiro, Fabianne de Araújo. "Combined effects of chemicals and ultraviolet radiation on Daphnia magna". Master's thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/871.
Abstract (sommario):
Mestrado em Ecologia, Biodiversidade e Gestão de EcossistemasO ambiente natural está frequentemente exposto a vários tipos de estresses, que podem ser de carácter químico, físico ou biológico, originados da actividade humana e dos processos de alteração climática. Os pesticidas são geralmente usados em práticas agrícolas para controlar doenças em vegetais e o aparecimento de pragas, e podem ser levados do solo para os sistemas aquáticos adjacentes aos locais de aplicação, onde representam um factor de stress para os organismos não-alvo. Além das exposições a químicos, o ambiente está sofrendo as consequências dos processos de alterações climáticas. Uma destas consequências é o aumento da radiação ultravioleta que chega à superfície terrestre devido à diminuição da concentração de ozono na estratosfera. O presente trabalho teve como objectivo principal elucidar alguns padrões e comportamentos biológicos relativamente a mudanças no ambiente. Para isto, com o intuito de prever as interacções entre stressores naturais e químicos, a radiação ultravioleta (RUV) e o fungicida carbendazim foram escolhidos como fontes de stressores natural e químico, respectivamente, e foram aplicados em combinação, como um exemplo das possíveis condições adversas que podem ser encontradas no ambiente. Os efeitos isolados da radiação ultravioleta em Daphnia magna foram avaliados através da utilização de uma lâmpada artificial de RUV, à qual os organismos foram expostos por um período máximo de 5 horas. Os experimentos de combinação entre RUV e carbendazim foram conduzidos com exposição constante ao químico, e uma única dose de radiação ultravioleta. Os parâmetros analisados foram sobrevivência, actividade alimentar, reservas energéticas e produção de juvenis de Daphnia magna. Para prever os efeitos das combinações, um dos modelos utilizados na análise de misturas de químicos e combinação de químicos com stressores naturais foi o utilizado. O modelo da Acção independente (AI) assume que ambos os componentes da combinação têm diferentes modos de acção, e actuam de forma independente sobre o organismo. Os efeitos são avaliados de acordo com as probabilidades de não-resposta do organismo a ambos os componentes da combinação. Há ainda outras formas de interacção entre os componentes da combinação que podem produzir um efeito mais severo (sinergismo) ou menos severo (antagonismo); os efeitos podem ser também dependentes do nível da dose aplicada ou do rácio entre os dois componentes da combinação Os resultados da exposição de Daphnia magna à radiação ultravioleta somente demonstraram um decréscimo na sobrevivência, na actividade alimentar e na produção de juvenis, com valores de dose-efeito muito próximos para todos os parâmetros, o que pode ser explicado pela diferença da sensibilidade deste organismo à radiação, de acordo com a idade em que são expostos. Os resultados das combinações entre carbendazim e RUV para o parâmetro sobrevivência foram bem ajustados ao modelo da acção independente, e não demonstraram nenhum desvio. Para a reprodução e a actividade alimentar, houve um desvio dependente do rácio entre os componentes, que demonstrou maior toxicidade para o carbendazim quando a radiação ultravioleta era o item dominante na combinação. Este estudo mostra a importância da avaliação de combinações entre químicos e stressores naturais. Neste caso, espera-se que o aumento na radiação aumente a sensibilidade dos organismos, como a Daphnia magna quando expostos a stressores químicos, como o fungicida carbendazim.
The natural environment and wildlife are often exposed to several chemicals, physical and biological stressors originated from human activities and climate changes. Pesticides are often used to control plant disease and pest in agricultural practices, and can runoff from the soil to adjacent aquatic systems, where it represents a stress factor for non-target organisms. In addition to chemical exposures, the natural environment is suffering from climate change processes. One of the consequences of that is the increasing amount of ultraviolet radiation reaching the earth’s surface due to depletion on stratospheric ozone. The present work aimed to elucidate some biological behaviors and patterns regarding changes in the environment. For that, to predict interactions between natural stressors and toxicants to Daphnia magna, the ultraviolet radiation (UVR) and the pesticide carbendazim were chosen as the source of natural and chemical stressors, respectively and were employed in combination with each other as an example of possible stress conditions that can be found worldwide in the environment. Single effects of ultraviolet radiation on Daphnia magna were assessed using an artificial UV source, by exposing the organisms to UV and visible light simultaneously, to a maximum period of 5 hours. Combined experiments of carbendazim and ultraviolet radiation were conducted with a constant chemical exposure and a single UVR dose. The parameters analyzed were survival, feeding activity, energy budget and offspring production of Daphnia magna. To predict effects of combined exposures, one of the reference models used for analysis of mixture toxicity and combination of chemical and natural stressor was applied. The Independent Action (IA) model assumes that both components of the combination have different modes of action, and act independently from each other; the effects of the combinations are based on the probabilities of nonresponse of the organism to both stressors. There are some deviations from the independent action model which can cause a more severe effect (synergism), or a less severe effect (antagonism); they might be also dose-level dependent or dose-ratio dependent. Results from single exposure of Daphnia magna to ultraviolet radiation showed a decrease in survival, feeding activity and offspring production, with similar dose-effect values, due to differences in the sensibility of the organism to UVR according to their age. Combined exposures of carbendazim and UVR for survival endpoint fitted to the IA model, showing no deviation patterns, while the response of reproduction and feeding activity were dose-ratio dependent, indicating a higher toxicity of carbendazim when ultraviolet radiation was the dominant item in the combination. This study shows the importance of evaluate the combined effects of chemicals and natural stressors. In this case, UVR increase is expected to enhance the sensitivity of organisms as D. magna when exposed to chemical stressors like the fungicide carbendazim.
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Ferreira, Nuno Gonçalo de Carvalho. "The effects of chemicals in isopods: a multi-organizational evaluation". Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14095.
Abstract (sommario):
Doutoramento em BiologiaThe global aim of this thesis was to evaluate and assess the effects of a pesticide (dimethoate) and a metal (nickel), as model chemicals, within different organization levels, starting at the detoxification pathways (enzymatic biomarkers) and energy costs associated (energy content quantification, energy consumption and CEA) along with the physiological alterations at the individual and population level (mortality), leading to a metabolomic analysis (using liquid 1H-NMR) and finally a gene expression analysis (transcriptome and RT-qPCR analysis). To better understand potential variations in response to stressors, abiotic factors were also assessed in terrestrial isopods such as temperature, soil moisture and UV radiation. The evaluation performed using biochemical biomarkers and energy related parameters showed that increases in temperature might negatively affect the organisms by generating oxidative stress. It also showed that this species is acclimated to environments with low soil moisture, and that in high moisture scenarios there was a short gap between the optimal and adverse conditions that led to increased mortality. As for UV-R, doses nowadays present have shown to induce significant negative impact on these organisms. The long-term exposure to dimethoate showed that besides the neurotoxicity resulting from acetylcholinesterase inhibition, this stressor also caused oxidative stress. This effect was observed for both concentrations used (recommended field dose application and a below EC50 value) and that its combination with different temperatures (20ºC and 25ºC) showed different response patterns. It was also observed that dimethoate’s degradation rate in soils was higher in the presence of isopods. In a similar study performed with nickel, oxidative stress was also observed. But, in the case of this stressor exposure, organisms showed a strategy where the energetic costs necessary for detoxification (biomarkers) seemed to be compensated by positive alterations in the energy related parameters. In this work we presented for the first time a metabolomic profile of terrestrial isopods exposed to stressors (dimethoate and niquel), since until the moment only a previous study was performed on a metabolomic evaluation in nonexposed isopods. In the first part of the study we identify 24 new metabolites that had not been described previously. On the second part of the study a metabolomic profile variation of abstract non-exposed organism throughout the exposure was presented and finally the metabolomic profile of organisms exposed to dimethoate and nickel. The exposure to nickel suggested alteration in growth, moult, haemocyanin and glutathione synthesis, energy pathways and in osmoregulation. As for the exposure to dimethoate alterations in osmoregulation, energy pathways, moult and neurotransmission were also suggested. In this work it was also presented the first full body transcriptome of a terrestrial isopod from the species Porcellionides pruinosus, which will complement the scarce information available for this group of organisms. This transcriptome also served as base for a RNA-Seq and a RT-qPCR analysis. The results of the RNA-Seq analysis performed in organisms exposed to nickel showed that this stressor negatively impacted at the genetic and epigenetic levels, in the trafficking, storage and elimination of metals, generates oxidative stress, inducing neurotoxicity and also affecting reproduction. These results were confirmed through RT-qPCR. As for the impact of dimethoate on these organisms it was only accessed through RT-qPCR and showed oxidative stress, an impact in neurotransmission, in epigenetic markers, DNA repair and cell cycle impairment. This study allowed the design of an Adverse Outcome Pathway draft that can be used further on for legislative purposes.
Os efeitos negativos de contaminantes de origem antropogénica que aparecem no meio ambiente têm um impacto negativo muitas vezes em organismos considerados benéficos. Dentro deste grupo de organismos podemos incluir os isópodes terrestres, detritivorous, cuja função se baseia na fragmentação de matéria vegetal, que poderão posteriormente ser facilmente colonizados por bactérias e os seus nutrientes incorporados nos solos. Para avaliar os efeitos de contaminantes em isópodes terrestres, mais concretamente na espécie Porcellionides pruinosus, foram usados como modelos o metal níquel e o pesticida dimetoato, fazendo uma abordagem em diferentes níveis organizacionais. O trabalho iniciou-se pela avaliação do impacto a nível das vias de destoxificação (biomarcadores enzimáticos) e reservas energéticas (quantificação das reservas, consumo energético e alocação da energia celular), juntamente com alterações a nível dos indivíduos e da população (mortalidade), passando por uma análise de metabolómica (usando 1H-RMN de líquidos) e finalmente uma análise da expressão génica (transcriptoma e RT-qPCR). De forma a melhor entender as variações que podem ocorrer oriundas de variações de fatores abióticos, foi também realizado um estudo sob os efeitos da variação de temperatura, humidade do solo e radiação UV em isópodes terrestres. A avaliação feita a nível dos biomarcadores bioquímicos, quantificação das reservas e parâmetros energéticos demonstrou que o aumento da temperatura iria afectar negativamente os organismos devido ao stress oxidativo gerado. Tendo em conta que esta espécie está aclimatada a ambientes com solos com humidades baixas, a exposição a solos com humidades superiores mostrou a existência de um pequeno intervalo entre o que são consideradas condições óptimas e condições bastante adversas, sendo aí verifica uma elevada mortalidade. Os efeitos da radiação UV demonstraram que as doses que actualmente chegam à superfície do planeta constituem uma ameaça para os isópodes terrestres. A avaliação feita à toxicidade do dimetoato em biomarcadores bioquímicos, reservas e parâmetros energéticos, demonstrou que além da toxicidade já esperada (inibição da enzima acetilcolinesterase), este stressor induz igualmente stress oxidativo. Este efeito foi observado para ambas as concentrações usadas (dose recomendada de aplicação em campo e dose próxima do EC50) e que a sua combinação com diferentes temperaturas (20ºC resumo e 25ºC) dava origem a diferentes padrões de resposta. Também foi observado que a taxa de degradação do dimetoato era superior em solos com a presença de isópodes. Num estudo semelhante ao anterior, realizado com níquel, foi observada toxicidade induzida por stress oxidativo. No entanto os organismos expostos a este stressor apresentam uma estratégia em que os custos energéticos associados à destoxificação (biomarcadores bioquímicos) parecem ser compensados com alterações positivas a nível dos parâmetros energéticos. Neste trabalho é apresentado pela primeira vez o perfil metabolómico de isópodes terrestres expostos a dimetoato e níquel, sendo que até à data apenas um estudo tinha apresentado o perfil metabólico de isópodes em situação de homeostasia. Na primeira parte do estudo é apresentado o perfil metabólico que identifica 24 novos metabolitos que ainda não tinham sido descritos anteriormente. Numa segunda parte é apresentada uma variação do perfil de organismos não expostos ao longo do ensaio e finalmente são apresentadas as variações metabólicas em organismos expostos a dimetoato e a níquel. Os resultados mostraram que ambos os stressores causaram alterações que eram dependentes da concentração e do tempo. Quando expostos a níquel os organismos evidenciam alterações ao nível do crescimento, muda e síntese de hemocianina e glutationas, alterações ao nível das vias energéticas e na osmorregulação. Em relação aos efeitos da exposição a dimetoato, foram observadas alterações a nível da osmorregulação, das vias energéticas e na muda, mas também ao nível da neurotransmissão. Neste trabalho é apresentado pela primeira vez um transcriptoma completo de um isópode terrestre, da espécie Porcellionides pruinosus. Este transcriptoma veio complementar a atual, mas parca, informação disponível sobre este grupo de organismos. Tendo como base o transcriptoma, foi posteriormente realizada uma análise de RNA-Seq e de RT-qPCR. A análise de RNA-Seq foi realizada apenas em organismos expostos a níquel e mostrou que este stressor tem um impacto ao nível genético e epigenético, no transporte, acumulação e eliminação de metais, gera stress oxidativo, neurotoxicidade e afecta também a reprodução. Estes resultados foram confirmados pela análise feita através de RT-qPCR. Em relação aos efeitos de dimetoato nestes organismos a nível genómico, a sua avaliação foi apenas realizada através de RT-qPCR. Foi observado que este stressor gera stress oxidativo, neurotoxicidade, tem um impacto em marcadores epigenéticos, na reparação de ADN e provoca alterações a nível da divisão celular. Este estudo permitiu a realização de uma “Adverse Outcome Pathway” (AOP) que poderá ser usada mais tarde para fins legislativos.
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Lough, Kerry Frances. "The Short and Long-term Effects of Herbicide Application in Maine Clearcuts on Ant Communities (Hymenoptera: Formicidae)". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/LoughKF2003.pdf.
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Czarnota, Jenna. "Modeling Spatially Varying Effects of Chemical Mixtures". VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4361.
Abstract (sommario):
Cancer incidence is associated with exposures to multiple environmental chemicals, and geographic variation in cancer rates suggests the importance of accommodating spatially varying effects in the analysis of environmental chemical mixtures and disease risk. Traditional regression methods are challenged by the complex correlation patterns inherent among co-occurring chemicals, and the applicability of geographically weighted regression models is limited in the setting of environmental chemical risk analysis. In comparison to traditional methods, weighted quantile sum (WQS) regression performs well in the identification of important environmental exposures, but is limited by the assumption that effects are fixed over space. We present an extension of the WQS method that models spatially varying chemical mixture effects called local weighted quantile sum (LWQS) regression, and assess through a simulation study its ability to identify important environmental risk factors over space. We use two different approaches to estimate the LWQS model based on variable subspaces. One uses an ensemble of variable subsets of the same size, and the other selects the best subset over a range of candidate subset sizes according to the model goodness-of-fit. We assess the performance of both estimation methods in simulated scenarios that incorporate increasingly complex levels of spatial dependency in the model, and consider correlation patterns from observed exposure data. The results demonstrate that LWQS has the ability to replicate spatially dependent mixture effects and can correctly identify important exposures in a mixture of environmental chemicals. In all scenarios, the best subset approach correctly chose an index containing only the important chemicals and improved on the accuracy of the chemical importance weights in comparison with the ensemble solutions. Future work will evaluate if the ensemble subset approach has better relative performance with larger chemical mixtures of highly correlated components.
Libri sul tema "Chemicals effects":
1
Ministers, Nordic Council of, a cura di. Health effects of selected chemicals. Copenhagen: Nordic Council of Ministers, 1992.
2
1934-, Richardson Mervyn, e Gangolli S, a cura di. The Dictionary of substances and their effects. Cambridge: Royal Society of Chemistry, 1994.
3
Sanot͡skiĭ, I. V. Long-term effects of chemicals on the organism. Moscow: Centre of International Projects, 1986.
4
S, Rainbow P., Hopkin Stephen P e Crane Mark, a cura di. Forecasting the environmental fate and effects of chemicals. Chichester: Wiley, 2001.
5
Jorma, Toppari, e Denmark Miljøstyrelsen, a cura di. Male reproductive health and environmental chemicals with estrogenic effects. København K, Denmark: Ministry of Environment and Energy, Denmark, Danish Environmental Protection Agency, 1995.
6
Theo, Colburn, Vom Saal Frederick S e Short Polly, a cura di. Environmental endocrine-disrupting chemicals: Neural, endocrine, and behavioral effects. Princeton, NJ: Princeton Scientific Publishing, 1998.
7
Geological Survey (U.S.), a cura di. Physical and chemical properties and health effects of thirty-three toxic organic chemicals. [Reston, Va.?]: U.S. Dept. of the Interior, Geological Survey, 1987.
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Kolb, Meyers Vera, a cura di. Teratogens: Chemicals which cause birth defects. Amsterdam: Elsevier, 1988.
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Meeting, American Chemical Society. Environmental epidemiology: Effects of environmental chemicals on human health. A cura di Draper William M. 1952- e American Chemical Society. Division of Environmental Chemistry. Washington, DC: American Chemical Society, 1994.
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B, Vouk Velimir, Scientific Group on Methodologies for the Safety Evaluation of Chemicals., International Council of Scientific Unions. Scientific Committee on Problems of the Environment. e International Program on Chemical Safety., a cura di. Methods for assessing the effects of mixtures of chemicals. Chichester [West Sussex]: Published on behalf of the Scientific Committee on Problems of the Environment (SCOPE) of the International Council of Scientific Unions (ICSU), and the International Program on Chemical Safety (IPCS) of the World Health Organization (WHO), the United Nations Environment Programme (UNEP) and the International Labour Organization (ILO) by Wiley, 1987.
Capitoli di libri sul tema "Chemicals effects":
1
Van Leeuwen, C. J. "Ecotoxicological Effects". In Risk Assessment of Chemicals, 175–237. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-015-8520-0_6.
2
Traas, T. P., e C. J. Van Leeuwen. "Ecotoxicological Effects". In Risk Assessment of Chemicals, 281–356. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6102-8_7.
3
van den Bercken, Joep. "Membrane Effects of Neurotoxic Chemicals". In Recent Advances in Nervous System Toxicology, 87–89. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0887-4_5.
4
Harrison, P. T. C. "Health effects of environmental chemicals". In Pollution, 500–523. Cambridge: Royal Society of Chemistry, 2007. http://dx.doi.org/10.1039/9781847551719-00500.
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Biedenkopf, Katja. "Chemicals: Pioneering Ambitions with External Effects". In European Union External Environmental Policy, 189–208. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60931-7_10.
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Ghorai, Soma Mondal, e Hardeep Kaur. "Immunomodulatory Effects of Endocrine-Disrupting Chemicals". In Immunomodulators and Human Health, 463–509. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-6379-6_16.
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Zhang, Bo, Marc von Keitz e Kenneth Valentas. "Thermal Effects on Hydrothermal Biomass Liquefaction". In Biotechnology for Fuels and Chemicals, 511–18. Totowa, NJ: Humana Press, 2008. http://dx.doi.org/10.1007/978-1-60327-526-2_48.
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Hardon, Anita. "Chemical Futures". In Critical Studies in Risk and Uncertainty, 281–310. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-57081-1_9.
Abstract (sommario):
AbstractHere we turn to the strategies that young people use to prevent chemical harms, not just those related to single chemicals but also those related to the feedback loops and compounding effects generated by the multiplicity of chemicals in daily life. Chemical Futures takes as an example youth activists in France, the Générations Cobayes, and their mobilization against endocrine-disrupting chemicals. We examine what contributes to the relative invisibility of toxic risk, pointing especially to the role of corporations in generating uncertainty about scientific evidence. The ChemicalYouth project engaged in a range of collaborative, youth-led projects that demonstrate the many ways youth may be engaged in “harm reduction from below.” We suggest that a ChemicalYouth 2.0 project might involve a wider range of researchers, advisors, and laboratories, to make more visible the multiple toxicities that make up young people’s everyday lives. Finally, we argue that governments should team up with youth and complement their efforts with “harm reduction from above” initiatives to regulate unsafe chemicals and support youths’ efforts to observe the effects of chemicals on their bodies and share information with others.
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Edwards, Clive A., e Patrick J. Bohlen. "The Effects of Toxic Chemicals on Earthworms". In Reviews of Environmental Contamination and Toxicology, 23–99. New York, NY: Springer New York, 1992. http://dx.doi.org/10.1007/978-1-4612-2890-5_2.
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Roberts, Celia. "Toxic Chemicals and Their Effects on Reproduction". In How Gender Can Transform the Social Sciences, 177–84. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-43236-2_18.
Atti di convegni sul tema "Chemicals effects":
1
Curren, Morgan, Anton Kaiser, Stephanie Adkins, Ali Qubian, Huda Al-Enezi, Heba Sana, Mohammed Al-Murayri e Mojdeh Delshad. "Effects of CEOR Chemicals on Asphaltene Precipitation". In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 2018. http://dx.doi.org/10.2118/191747-ms.
2
Seger, Brian, Ming Ma e Gaston Larrazabal. "Understanding the Carbon Balance and pH effects in CO2 Electrolysis Devices". In International Conference on Electrocatalysis for Energy Applications and Sustainable Chemicals. València: Fundació Scito, 2020. http://dx.doi.org/10.29363/nanoge.ecocat.2020.001.
3
M. Entov, V., I. S. Ginzburg e E. V. Teodorovich. "Irreversible adsorption and dispersion effects in progagation of thin slugs of chemicals". In IOR 1991 - 6th European Symposium on Improved Oil Recovery. European Association of Geoscientists & Engineers, 1991. http://dx.doi.org/10.3997/2214-4609.201411284.
4
Joshi, Girish, Amol Pote e Shripad Umale. "Investigation of effects of chemicals on strength and durablity of hardended concrete". In 2ND INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS BEHAVIOUR AND CHARACTERIZATION: ICAMBC_2021. AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0073212.
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Aliti, Liridon, e Simon I. Andersen. "Improving Oil-In-Water Treatment by Optimization of Production Chemicals". In International Petroleum Technology Conference. IPTC, 2024. http://dx.doi.org/10.2523/iptc-24282-ea.
Abstract (sommario):
Abstract The removal of oil droplets from water heavily depends on the ability for these to coalesce into larger drops to overcome size limitation of equipment such as centrifuges, hydrocyclones, gas flotation etc. The composition of PW is a mixture of oily compounds, inorganics from the formation and production chemicals. Chemicals have a significant impact on the stabilization of oil droplets but variations in salinity also plays a role. The repulsion of droplets has detrimental effect on the treatment. In this paper we aim to quantify this in order to develop optimization tools. Methods, Procedures, Process: The quantification of droplet coalescence and impact of chemistry is obtained through specially designed microfluidic chips. Droplets are recorded using high speed cameras. Using image analysis coalescence efficiency is quantified. Partitioning of chemicals between water and oil which is affected by both salinity and oil type and measured by capillary electrophoresis. This is analyzed using capillary electrophoresis. Real PW samples and chemicals are obtained from offshore Denmark. Coalescence events are recorded while varying oil type and also diluting the PW to understand which constituents lead to stability of drops and hence potential adverse effects in water treatment. Results, Observations, Conclusions: The fundamental Bancroft´s rule describes that the component favorable dissolved in one phase will stabilize droplets in this continuous phase. Hence compounds primarily soluble in water stabilize oil droplets in the water treatment system, and can lead to poor water quality - potentially having an adverse effect on sizing of equipment. Accordingly specifically water-in-oil (WiO) emulsion breakers can have a detrimental effect when overdosed, as more is not better. When different water streams are commingled before treatment there might be potential cases where one stream despite its apparent low content of oil-in-water (OiW) can stabilize droplets in another stream. We present data based on microfluidics and analysis of partitioning coefficients using a variety of real PWs and production chemicals from O&G production in the Danish North Sea. This clearly indicates that the main issue is related to water constituents, but that oily polar components have a large impact as well on stability. The qualitative information is linked to quantification using the hydrophilic Lipophilic Deviation theory which can then be used to optimize potential scenarios of synergistic and antagonistic effects of chemicals and PW constituents on water quality. Discussion will also aim understanding mixing rules for quantification in multicomponents mixtures based on surface chemical insight. Novel/Additive Information: We apply both novel microfluidics and novel analytical techniques for production chemical partitioning measurements.
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Almorihil, Jawaher, Aurélie Mouret, Isabelle Hénaut, Vincent Mirallès e Abdulkareem AlSofi. "Produced Water Quality: The Effects of Different Separation Methods for Water and Chemical Floods". In SPE Middle East Oil & Gas Show and Conference. SPE, 2021. http://dx.doi.org/10.2118/204650-ms.
Abstract (sommario):
Abstract Gravity settling represents the main oil-water separation mechanism. Many separation plants rely only on gravity settling with the aid of demulsifiers (direct or reverse breakers) and other chemicals such as water clarifiers if they are required. Yet, other complementary separation methods exist including filtration, flotation, and centrifugation. In terms of results and more specifically with respect to the separated produced-water, the main threshold on its quality is the dispersed oil content. Even with zero discharge and reinjection into hydrocarbon formations, the presence of residual oil in the aqueous phase represents a concern. High oil content results into formation damage and losses in injectivity which necessitates formation stimulations and hence additional operational expenses. In this work, we investigated the effects of different separation techniques on separated water quality. In addition, we studied the impact of enhanced oil recovery (EOR) chemicals on the different separation techniques in terms of efficiency and water quality. Based on the results, we identified potential improvements to the existing separation process. We used synthetic well-characterized emulsions. The emulsions were prepared at the forecast water: oil ratio using dead crude oil and synthetic representative brines with or without the EOR chemicals. To clearly delineate and distinguish the effectiveness of different separation methods, we exacerbated the conditions by preparing very tight emulsions compared with what is observed on site. With that, we investigated three separation techniques: gravity settling, centrifugation, and filtration. First, we used Jar Tests to study gravity settling, then a benchtop centrifuge at two speeds to evaluate centrifugation potential. Finally, for filtration, we tested two options: membrane and deep-bed filtrations. Concerning the water quality, we performed solvent extraction followed by UV analyses to measure the residual oil content as well as light transmission measurements in order to compare the efficiency of different separation methods. The results of analyses suggest that gravity settling was not efficient in removing oil droplets from water. No separation occurred after 20 minutes in every tested condition. However, note that investigated conditions were severe, tighter emulsions are more difficult to separate compared to those currently observed in the actual separation plant. On the other hand, centrifugation significantly improved light transmission through the separated water. Accordingly, we can conclude that the water quality was largely improved by centrifugation even in the presence of EOR chemicals. In terms of filtration, very good water quality was obtained after membrane filtration. However, significant fouling was observed. In the presence of EOR chemicals, filtration lost its effectiveness due to the low interfacial tension with surfactants and water quality became poor. With deep-bed filtration, produced water quality remained good and fouling was no longer observed. However, the benefits from media filtration were annihilated by the presence of EOR chemicals. Based on these results and at least for our case study, we conclude that centrifugation and deep-bed filtration techniques can significantly improve quality of the separated and eventually reinjected water. In terms of the effects of EOR chemicals, the performance of centrifugation is reduced while filtrations are largely impaired by the presence of EOR chemicals. Thereby, integration of any of the two methods in the separation plant will lead to more efficient produced-water reinjection, eliminating formation damage and frequent stimulations. Yet, it is important to note that economics should be further assessed.
7
Walker, Dallin S., Steve J. Baedke e Joel P. Maynard. "THE EFFECTS OF DEICING CHEMICALS ON THE AQUEOUS CHEMISTRY OF BIG SPRING, HARRISONBURG, VA". In Joint 69th Annual Southeastern / 55th Annual Northeastern GSA Section Meeting - 2020. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020se-344722.
8
Liman, Mubarak L., Yamusa Bello Yamusa, Bilkisu Danjuma, Abubakar Sani e Yusuf Walliyullah. "Effect of Chemicals on Compressive Strength of Plastic-Laterite Interlock Paving Blocks". In The 2nd International Conference on Civil Infrastructure and Construction. Qatar University Press, 2023. http://dx.doi.org/10.29117/cic.2023.0106.
Abstract (sommario):
This research centres on the need to develop a simple but sustainable material for the utilization of the quantum of plastic wastes that litter our environment. The research uses waste plastics and laterite soil and converts them into construction materials (interlock blocks) with the help of the densifier, thereby reducing the plastic waste, which is a key contributor to environmental pollution. Literature has shown that concrete structure is prone to chemical actions; the durability of conventional concrete bricks gets affected by chemical effects. The chemicals may cause cracking of concrete, rutting, and deterioration of the structure. In the same vein, the plastic-laterite interlock bricks might not be free from such defects due to chemical action. Therefore, this research looks into the effects of different chemical curing conditions on the compressive strength of plastic-laterite paving blocks. Varying proportions of plastic wastes and laterite soil were mixed and processed into composite bricks and subjected to different chemical treatments; in acid, base, oil, and water for 3, 14, and 28 days relative to a concrete brick control. It was observed that samples cured in acid solution gave the lowest compressive strength, while those in base solution gave the highest. The paving interlock blocks made from polyethylene/laterite composite registered relative performance compared to concrete interlock bricks control. If made and put into use, these blocks will reduce construction costs, assist in environmental sustainability and improve circular economic growth. Therefore, using this innovative approach will bolster infrastructural projects and checkmate plastic pollution within our environment.
9
Lin, Lixing, Tayfun Babadagli e Huazhou Andy Li. "Understanding the Dynamics of Matrix-Fracture Interaction for Suitable Fracturing Fluid Design and Chemical EOR in Unconventional Oil/Gas Recovery". In SPE Canadian Energy Technology Conference and Exhibition. SPE, 2024. http://dx.doi.org/10.2118/218032-ms.
Abstract (sommario):
Abstract The effects of chemical additives on mitigating water-blocking and improving oil recovery were experimentally examined for gas-water and oil-water systems in spontaneous imbibition cells. In these attempts, two factors are critically important: (1) Understanding the physics of the interaction, whether it is co- or counter-current, and (2) characteristics of the chemical additives to suitably orient the interaction for specific purposes (accelerate/decelerate matrix-fracture interactions). Co- and counter-current imbibition experiments were conducted on sandstone rock samples using various oil samples (viscosities between 1.37 and 54.61 cP) as well as gas (air). The selected new-generation chemical additives include deep eutectic solvents, cationic/anionic/nonionic surfactants, inorganic and organic alkalis. We observed that the functionality of the chemicals varied depending on the fluid type, interaction type (co- or counter-current), and application purposes. For instance, chemicals such as cationic surfactant CTAB significantly reduced water invasion into the gas-saturated sandstone cores during fracturing, while chemicals such as a nonionic surfactant (Tween 80) provided considerable oil recovery improvement in the oil-saturated sandstone cores. The surface tension and wettability of the rock surface are crucial factors in determining the suitability of chemicals in mitigating water blockage. In terms of the oil recovery, certain chemical additives, such as O342 and Tween 80, may result in a lower recovery rate in the early stage because their strong ability in IFT reduction but could lead to a higher ultimate recover factor by altering the wettability. Additionally, the introduction of chemicals resulted in notable spontaneous emulsification, especially in counter-current imbibition, thereby enhancing oil recovery. The spontaneous emulsification and its stability are influenced by factors such as oil drop size, boundary condition, interaction type, IFT, wettability, as well as rock surface charges. The results have implications for understanding the physics and dynamics of matrix-fracture interactions in co and counter-current conditions. Additionally, they offer practical insights for selecting appropriate chemical additives in hydraulic fracturing fluid design and enhancing oil recovery in unconventional reservoirs.
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Ibrahim, H. D., e T. O. Odedele. "Prediction of Toxicity Effects of Oil Field Chemicals Using Adaptive Genetic Neuro-Fuzzy Inference Systems". In SPE Western Regional Meeting. Society of Petroleum Engineers, 2018. http://dx.doi.org/10.2118/190039-ms.
Rapporti di organizzazioni sul tema "Chemicals effects":
1
Foust, C. B., G. D. Griffin, N. B. Munro e M. L. Socolof. Guidance on health effects of toxic chemicals. Safety Analysis Report Update Program. Office of Scientific and Technical Information (OSTI), febbraio 1994. http://dx.doi.org/10.2172/10136228.
2
Clement, Michael, Sage Broderick e Marty Garton. Toxic Industrial Chemical / Material Intelligence Tool (TICMINT) user guide. Engineer Research and Development Center (U.S.), novembre 2023. http://dx.doi.org/10.21079/11681/47924.
Abstract (sommario):
The Toxic Industrial Chemical / Material Intelligence Tool (TICMINT) is a web application that provides critical chemical and toxicological information to users quickly and efficiently for the purpose of enacting safe maneuvers in areas of operations. It provides an in-depth look at the makeup, properties, and hazardous effects of nearly 400 toxic chemicals of interest. It also provides background on the chemical makeup of a bevy of building materials, enabling soldiers in areas of operation to determine the toxicological risks associated with the combustion of those materials in their environment. This document’s purpose is to demonstrate the functionality of the TICMINT web application and provide instructional material for those managing its content.
3
Hicks, R. J., e P. Van Voris. Review and evaluation of the effects of xenobiotic chemicals on microorganisms in soil. [139 references]. Office of Scientific and Technical Information (OSTI), febbraio 1988. http://dx.doi.org/10.2172/5406358.
4
Ellis, James L., e Margaret G. Filbert. Development of an In Vitro Model Assay System for the Evaluation of the Effects of Toxic Chemicals on Human Airways. Fort Belvoir, VA: Defense Technical Information Center, marzo 1994. http://dx.doi.org/10.21236/ada285074.
5
Moghissi. L51914 Interdependent Effects of Bacteria Gas Composition and Water Chemistry on Internal Corrosion. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), aprile 2002. http://dx.doi.org/10.55274/r0010433.
Abstract (sommario):
A recent Office of Pipeline Safety survey found that corrosion caused 17 to 20 percent of pipeline failures. Of those corrosion failures, roughly half resulted from internal corrosion. In pipelines, internal corrosion is caused by produced (carry-over) or condensed water that contains dissolved gas and/or bacteria. In many cases, chemicals with inhibiting or biocidal properties are added to mitigate corrosion. The internal corrosion in many systems occurs under slowly flowing conditions at ambient temperatures (e.g., relatively low temperature of about 15.5�C (60�F)). The overall objectives of this project were to determine the influence of microbial consortia typically found in condensed water, produced water, and hydrocarbons on the internal corrosion of steel pipeline exposed to CO2, H2S, and O2. To accomplish these objectives, a multi-year project was planned. For the first year, the specific objectives were to assemble a chemostat system capable of maintaining a mixed biofilm consortium of bacteria implicated in MIC of steels under the pressures encountered in gathering lines, identify the type of microbial populations inside pipelines and conditions under which internal MIC has been observed, and perform a limited number of corrosion tests to evaluate the effects of these bacteria on corrosion.
6
Belkin, Shimshon, Sylvia Daunert e Mona Wells. Whole-Cell Biosensor Panel for Agricultural Endocrine Disruptors. United States Department of Agriculture, dicembre 2010. http://dx.doi.org/10.32747/2010.7696542.bard.
Abstract (sommario):
Objectives: The overall objective as defined in the approved proposal was the development of a whole-cell sensor panel for the detection of endocrine disruption activities of agriculturally relevant chemicals. To achieve this goal several specific objectives were outlined: (a) The development of new genetically engineered wholecell sensor strains; (b) the combination of multiple strains into a single sensor panel to effect multiple response modes; (c) development of a computerized algorithm to analyze the panel responses; (d) laboratory testing and calibration; (e) field testing. In the course of the project, mostly due to the change in the US partner, three modifications were introduced to the original objectives: (a) the scope of the project was expanded to include pharmaceuticals (with a focus on antibiotics) in addition to endocrine disrupting chemicals, (b) the computerized algorithm was not fully developed and (c) the field test was not carried out. Background: Chemical agents, such as pesticides applied at inappropriate levels, may compromise water quality or contaminate soils and hence threaten human populations. In recent years, two classes of compounds have been increasingly implicated as emerging risks in agriculturally-related pollution: endocrine disrupting compounds (EDCs) and pharmaceuticals. The latter group may reach the environment by the use of wastewater effluents, whereas many pesticides have been implicated as EDCs. Both groups pose a threat in proportion to their bioavailability, since that which is biounavailable or can be rendered so is a priori not a threat; bioavailability, in turn, is mediated by complex matrices such as soils. Genetically engineered biosensor bacteria hold great promise for sensing bioavailability because the sensor is a live soil- and water-compatible organism with biological response dynamics, and because its response can be genetically “tailored” to report on general toxicity, on bioavailability, and on the presence of specific classes of toxicants. In the present project we have developed a bacterial-based sensor panel incorporating multiple strains of genetically engineered biosensors for the purpose of detecting different types of biological effects. The overall objective as defined in the approved proposal was the development of a whole-cell sensor panel for the detection of endocrine disruption activities of agriculturally relevant chemicals. To achieve this goal several specific objectives were outlined: (a) The development of new genetically engineered wholecell sensor strains; (b) the combination of multiple strains into a single sensor panel to effect multiple response modes; (c) development of a computerized algorithm to analyze the panel responses; (d) laboratory testing and calibration; (e) field testing. In the course of the project, mostly due to the change in the US partner, three modifications were introduced to the original objectives: (a) the scope of the project was expanded to include pharmaceuticals (with a focus on antibiotics) in addition to endocrine disrupting chemicals, (b) the computerized algorithm was not fully developed and (c) the field test was not carried out. Major achievements: (a) construction of innovative bacterial sensor strains for accurate and sensitive detection of agriculturally-relevant pollutants, with a focus on endocrine disrupting compounds (UK and HUJ) and antibiotics (HUJ); (b) optimization of methods for long-term preservation of the reporter bacteria, either by direct deposition on solid surfaces (HUJ) or by the construction of spore-forming Bacillus-based sensors (UK); (c) partial development of a computerized algorithm for the analysis of sensor panel responses. Implications: The sensor panel developed in the course of the project was shown to be applicable for the detection of a broad range of antibiotics and EDCs. Following a suitable development phase, the panel will be ready for testing in an agricultural environment, as an innovative tool for assessing the environmental impacts of EDCs and pharmaceuticals. Furthermore, while the current study relates directly to issues of water quality and soil health, its implications are much broader, with potential uses is risk-based assessment related to the clinical, pharmaceutical, and chemical industries as well as to homeland security.
7
Van Voris, P., D. A. Tolle e M. F. Arthur. Experimental terrestrial soil-core microcosm test protocol. A method for measuring the potential ecological effects, fate, and transport of chemicals in terrestrial ecosystems. Office of Scientific and Technical Information (OSTI), giugno 1985. http://dx.doi.org/10.2172/6059663.
8
Wolf, Eva. Chemikalienmanagement in der textilen Lieferkette. Sonderforschungsgruppe Institutionenanalyse, 2022. http://dx.doi.org/10.46850/sofia.9783941627987.
Abstract (sommario):
The World Summit on Sustainable Development in Johannesburg in 2002 set the goal of minimising the adverse impacts of chemicals and waste by 2020. This goal has not been achieved yet. Therefore, other approaches are needed to prevent, minimise, or replace harmful substances. One possible approach is this master thesis which deals with the challenges that the textile importer DELTEX is facing with regard to a transparent communication of chemicals used and contained in the product in its supply chain. DELTEX is bound by legal regulations and requirements of its customer and must ensure that there are no harmful substances in the garments. For each order, the customer requires a chemical inventory from DELTEX which contains the chemical substances and formulations used (so-called "order-wise chemical inventory"). Currently, the suppliers are not willing to pass this on to DELTEX. As a result, DELTEX is faced with the problem of having no knowledge of the materials used in the garments and is thus taking a high risk. The structure of this study is based on the transdisciplinary "delta analysis" of the Society for Institutional Analysis at the University of Applied Sciences Darmstadt. This compares the target state with the actual state and derives a delta from the difference. Based on this, suitable design options are to be developed to close the delta. The study defines the target state on the basis of normative requirements and derives three criteria from this, which can be used to measure design options. By means of guideline-based interviews with experts, an online survey and literature research, it examines the current state. The analysis shows that the relevant actors are in an unfavourable incentive and barrier situation. The textile supply chain can be seen as a complex construct in which a whole series of production sites (often in developing and emerging countries where corruption and low environmental standards exist) carry out many processing steps. Chemicals are used at almost all stages of processing, some of which have harmful effects on people and the environment. At the same time, factory workers in the production countries are under enormous price and time pressure and often have insufficient know-how about chemical processes. DELTEX is dependent on its main customer and therefore has little room for price negotiations. To close this delta, the study formulates design options on macro, meso and micro levels and measures them against the developed criteria. None of the measures completely meets all the criteria, which is why a residual delta remains. The study concludes that not one, but rather a combination of several design options at all levels can achieve the target state. For DELTEX, an alliance with other textile importers, membership in the Fair Wear Foundation, strengthening the relationship with its suppliers and cooperation with another customer are recommended. Furthermore, the use of material data tools that support proactive reporting approaches such as a Full Material Declaration is recommended. The study is carried out from the perspective of the textile importer DELTEX. The results can therefore only be applied to the entire textile supply chain to a limited extent.
9
Schoten, Eert. HELLE: Health Effects of Low Level Exposures/ Gezondheidseffecten van lage blootstellingniveaus [International workshop: Influence of low level exposures to chemicals and radiation on human and ecological health]. Office of Scientific and Technical Information (OSTI), novembre 1998. http://dx.doi.org/10.2172/765246.
10
Campobasso, Marissa, Musa Ibrahim, Amanda Chisholm, Julia Miazek e Martin Page. pH pivoting for algae coagulation : bench-scale experimentation. Engineer Research and Development Center (U.S.), maggio 2024. http://dx.doi.org/10.21079/11681/48611.
Abstract (sommario):
Harmful algal blooms (HABs) threaten recreational waters and public supplies across the US, causing detrimental economic and environmental effects to communities. HABs can be mitigated with dissolved air flotation (DAF) treatment, which requires addition of pH-sensitive charged chemicals to neutralize algae, allowing them to attach to microbubbles and float to the surface. During HAB events and photosynthesis, algae raise the pH to levels that are not ideal for DAF. Traditionally, pH is reduced with a strong acid; however, this adds operational cost and permanently adjusts the water’s pH. This study assessed an approach that might allow for infusing CO₂ from diesel-powered electricity generators into the water prior to DAF treatment. It was hypothesized that formation of carbonic acid could temporarily reduce the pH. Results showed that 2.5%–5.0% CO₂ mixed within compressed air can achieve pH levels between 6–7 in algal water with an initial pH of 9–11 and alkalinity of 150 mg/L as CaCO₃. Further, dosing CO₂ before chemical addition yielded a 31% improvement in water clarification. Returning the pH back to natural levels was not achieved using ambient air microbubbles; however, coarse bubble air spargers should be tested to provide more volumetric capacity for CO₂ absorption.