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Accueil du site → Doctorat → Allemagne → 2020 → Analytical screening of organic chemicals of emerging concern in western Kenya and their contribution to the prevalence of schistosomiasis

Johann Wolfgang Goethe-Universität (2020)

Analytical screening of organic chemicals of emerging concern in western Kenya and their contribution to the prevalence of schistosomiasis

Faith Jebiwot Kandie

Titre : Analytical screening of organic chemicals of emerging concern in western Kenya and their contribution to the prevalence of schistosomiasis

Auteur : Faith Jebiwot Kandie

Université de soutenance :

Grade : Doktorgrades der Naturwissenschaften 2020

Résumé partiel
In the past decades, the use and production of chemicals has been on the rise globally due to increasing industrialization and intensive agriculture ; resulting in the occurrence and ecotoxicological risks of chemicals of emerging concern (CECs) in the aquatic compartments. Risks include changes in community structure resulting in the dominance of one species and ecosystem imbalance. When dominant disease-causing organisms are in the environment, the disease transmission is increased. For example, host snails for the schistosomiasis, a human trematode disease, are known to be tolerant to pesticide exposure compared to the predators. This would therefore result in an increased abundance of snails which consequently increase the disease transmission in the human population. Kenya, being a low income country faces a lot of challenges with provision of clean water, diseases and sanitation facilities, and increasing population which results in intensive agriculture coupled with pesticide use. Although a lot of research has been carried out on the environmental occurrence and risk of CECs (Chapter 1), most of these studies have been done in developed countries with limited information from Africa. Additionally, research in Africa focused on urban areas with limited number of compounds analyzed and mostly in the water phase, and inadequate information on the effects of CECs on the aquatic organisms. In order to reduce this knowledge gap, this dissertation focused on identification and quantification of CECs present in water, sediment and snails from western Kenya, and the contribution of pesticides to the transmission of schistosomiasis. Chapter 2 gives a summary of the results and discussion of the dissertation. In Chapter 3, a comprehensive chemical analysis was carried out on 48 water samples to identify compounds, spatial patterns and associated risks for fish, crustacean and algae using toxic unit (TU) approach. A total of 78 compounds were detected with pesticides and biocides being the compounds most frequently detected. Spatial pattern analysis revealed limited compound grouping based on land use. Acute risk for crustaceans and algae were driven by one to three individual compounds. These compounds responsible for toxicity were prioritized as candidate compounds for monitoring and regulation in Kenya. In Chapter 4, an extension of Chapter 3 was done to cover the CECs present in snails and sediment from the 48 sites. A total of 30 compounds were found in snails and 78 in sediments with 68 additional compounds being found which were not previously detected in water. Higher contaminant concentrations were found in agricultural sites than in areas without anthropogenic activities. The highest acute toxicity (TU 0.99) was determined for crustaceans based on compounds in sediment samples. The risk was driven by diazinon and pirimiphos-methyl. Acute and chronic risks to algae were driven by diuron whereas fish were found to be at low to no acute risk.

Mots clés  : Freshwater Ecosystems ; Organic micropollutants ; Risk assessment ; Schistosomiaisis ; Western Kenya

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Page publiée le 25 novembre 2021