Protecting food with poison - Ecotoxicity of agrochemicals and pharmaceuticals.

Chemicals reach the environment through human activities, such as agriculture or animal husbandry. Emissions could be intentional, as pesticide application of crops, or inadvertently, such as pharmaceutical residues in wastewater effluents.

Chicken manure is occasionally used as a cheap fertilizer in aquaculture pond farms to increase productivity and profitability. Depending on local regulation and production strategy, animal manures can contain substantial amounts of antibiotics and other pharmaceuticals used for raising animals. The benefits of this practice, however, have not been clearly established in relation to the potential adverse consequences.

Production data from Egyptian fish farms in Study I, show that chicken manure fertilization promotes eutrophication, without increasing fish yields or clear benefits for the producers.
Additionally, qPCR assays show that the fertilization correlates with increased abundance of antibiotic resistance genes in pond sediment. Antibiotics emitted to the environment can induce bacteria resistance and promote selection of resistant genotypes.

Study II capture the effects of antibiotics emitted throughout the value chain of agri-food products, and life cycle assessment (LCA) is investigated for this purpose. LCA is a framework to assess environmental impacts throughout the value chain of products. This thesis presents an approach to quantify potential antibiotics resistance enrichment in the environment within LCA. It also discusses an approach to capture the relationship between regional antibiotics use and regional human health impacts.

Characterizations of potential toxic effects of chemicals in LCA are generally drawn from species sensitivity distribution models that describe ecosystem-wide responses to chemical emission. While this provides insights into the toxicity of a chemical, predictions of the “true” ecosystem wide effects will always be shrouded by uncertainty, depending on the availability and quality of data.

Detailed knowledge on adverse effects and the potential hazard chemicals impose are required for stakeholders at global and local scales to make informed decisions on how to regulate the use and emissions of chemicals. Study IV identifies LCA studies where toxicological impacts are evaluated and chemicals in the inventory are classified towards ecotoxicological impact, but where characterizations are missing, which leads to underestimating the impact.

To enhance the precision of ecotoxicological effect assessments for chemicals, Study III gathers an extensive toxicological dataset and present a method to assess the uncertainty associated with ecotoxicological effect calculations. The proposed method opens up for exploring uncertainty in ecotoxicological effect calculations, but data availability is limiting the number of chemicals that can be assessed for ecotoxicological effect and uncertainty. To fill the information on toxic effect of chemicals, Study IV explores quantitative structure-activity relationship (QSAR) models to predict ecotoxicological effect of chemicals. 

This thesis presents some of the many challenges we face when assessing toxicological impacts from chemicals emitted to the environment, and provides methods and recommendations how to better evaluate impacts and uncertainties in toxicological characterization of chemicals.

About this dissertation:

This defence is held in the Vivi Täckholm Auditorium, but you can also join us in Zoom.

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PhD student: Oskar Nyberg

Supervisors: 

Associate Professor Michael Tedengren, Department of Ecology, Environment and Plant Sciences, Stockholm University

Professor Nils Kautsky, Department of Ecology, Environment and Plant Sciences, Stockholm University

PhD Patrik Henriksson, Stockholm Resilience Centre

Opponent:

Professor Peter Fantke, Department of Environmental and Resource Engineering, Technical University of Denmark

Grading committee:

Professor Patrik Andersson, Department of Chemistry, Umeå University

Associate Professor Marlene Ågerstrand, Department of Environmental Sciences, Stockholm University

Professor Michael Gilek, Department of Natural Sciences, Technology and Environmental Studies, Södertörn University

(Reserve) Associate Professor Linda Kumblad, Stockholm University Baltic Sea Centre