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- Schönlau, Christine, 1986-
(författare)
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Microplastics in the marine environment and the assessment of potential adverse effects of associated chemicals
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last decade plastics have gained interest by scientists as emerging pollutants particularly in the marine environment due to their ubiquity and persistence. While several studies report the occurrence of microplastics in surface waters globally, there are no harmonized methods to sample and measure microplastics, and the knowledge of toxicological effects in the marine ecosystem is scarce. One of the concerns is that microplastics could transfer hazardous chemicals into organism upon ingestion.In this thesis chemical and bioanalytical methods were combined to address the hypothesis that plastic pollution poses a risk for marine ecosystems by exposure to plastic associated chemicals such as sorbed environmental pollutants, additives, and monomers. Six different pristine plastic polymers were studied which have been deployed in the marine and freshwater system for up to 12 months. Potential adverse effects of plastic associated chemicals were investigated with in vitro reporter gene assays which can be activated by several chemical classes. The main focus was on the aryl hydrocarbon receptor-mediated activity for the assessment of dioxin-like chemicals. Different groups of persistent environmental pollutants, which are present in the aquatic environment, were analyzed by gas chromatographic mass spectrometric methods. The contribution of the targeted chemicals to the measured biological activities was examined by conducting potency balance calculations. A better knowledge about the occurrence of microplastics in the waters surrounding Sweden was gained by sampling surface waters comparing two different sampling techniques, trawl and in-situ pump.The plastic pellets induced bioactivities in most tested reporter gene assays and the activities varied by type of polymer. In the majority of samples the contribution of the targeted environmental pollutants to the observed bioactivities was low. Concentrations of microplastics > 0.3 mm in surface waters around Sweden were observed to be low and the findings of this thesis suggest that the tested polymers with sizes 2-4 mm will not lead to an increased risk for marine ecosystems in terms of exposure to chemicals.
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| 2. |
- Lam, Monika M., 1987-
(författare)
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Characterization of PAC-contaminated soil with the focus on availability, leachability and biological activities
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Current risk assessments of polycyclic aromatic compounds (PACs)-contaminated soil are often based on the 16 priority PAHs and do not consider availability of PACs in soil sufficiently. This may lead to uncertainties of the assessment, since important contaminants can be overlooked and only a small fraction of contaminants is available for the uptake for organisms. The overall aim of this thesis was to develop a refined and enhanced analytical approach based on both chemical and bioassay analysis coupled to passive sampling with polyoxymethylene (POM) and leaching tests that can provide a more comprehensive picture of chemical pollution at PAC-contaminated sites. To achieve this, bioassay-specific relative potency factors (REPs) of PACs were determined for the H4IIE-luc bioassay, detecting AhR-mediated activity, and for the VM7luc4E2 transactivation assay, detecting ER-mediated activity for the use in potency-balance analysis. Results of uptake-experiments of PACs in earthworms and POM suggested that POM is a suitable tool to study availability of AhR and ER agonists in soil. Availability and mobility of PACs in soil were investigated by the use of POM and leaching tests. The results of potency-balance analysis showed that in soil samples, in POM-fractions or in leachates, a large fraction of AhR- or ER-agonists remained unexplained, despite the use of a large number of REPs. In addition, coupling of chemical and biological analysis to passive sampling or leaching tests revealed that only a small fraction of the total mass of PACs in the soil is available or leachable in soil. The results suggests that the use of only the total concentration in soil while ignoring unknown toxicants will lead to great uncertainties in the risk assessment. Therefore, effect-based screening using bioassays, taking availability and mobility of compounds into account, as well as a widened chemical analysis should be included in modern hazard- and risk assessment of PAH contaminated soils.
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| 3. |
- Nilén, Greta, 1989-
(författare)
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Molecular and phenotypical toxicological effects of environmental pollutants and their mixtures : A mechanistic approach
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Current environmental risk assessment of polluted sites primarily relies on single compound evaluation. However, in the environment, organisms are often exposed to complex mixtures of pollutants. To further develop risk assessment of polluted sites and evaluate the risks that mixtures pose to humans and wildlife, a mechanistic understanding of mixture toxicity is needed.The overall aim of this thesis was to increase our knowledge of the toxic effects caused by chemical mixtures and to develop new approaches to investigate the molecular mechanisms underlying such effects. To reach this aim, a comprehensive set of methods was applied, considering molecular and phenotypical alterations as well as chemical analyses.The investigations revealed that the acute toxicity caused by mixtures of the pollutants B[a]P, PFOS, PCB126, and Arsenate is mainly predictable by concentration addition. The results also showed some specific sublethal effects of the various mixtures that were not observed for the single components. In addition, each mixture caused very specific patterns of behavioral alterations, gene expression changes, altered lipid content, and altered organ growth. A complex environmental mixture from soil contaminated with PACs caused for instance behavioral alterations in zebrafish, in addition to dysfunction of genes that are critical for eye development.In summary, this thesis contributes to an increased understanding of the mechanistic pathways underlying the mixture toxicity of selected pollutants and environmental samples. In addition, it provides insights for the development of new approaches that may be included in risk assessment, such as image analysis and effect-directed analysis.
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