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En Afrique Sub-Saharienne, les problématiques de contamination de la ressource en eau par les pesticides et les résidus pharmaceutiques commencent à être mises en évidence. La problématique de la thèse porte sur la caractérisation de l’impact des activités humaines sur la qualité de la ressource en eau, par l’étude de la contamination par les pesticides et les résidus pharmaceutiques. Le site d’étude choisi est le bassin versant de la Méfou, qui draine la capitale du Cameroun, Yaoundé. Dans un premier temps, le site est caractérisé par ses spécificités environnementales (relief, occupation des sols) et sociodémographiques afin d’identifier les pressions anthropiques. Les pratiques d’agriculture urbaine, et en particulier le maraîchage intensif dans les bas-fonds entraîneraient l’utilisation massive de pesticides. L’absence d’assainissement efficace et les multiples latrines, drains et fosses septiques constitunt autant de sources diffuses de contamination par les résidus de médicaments. En prenant le cas des pesticides, une méthode cartographique a permis de confirmer l’hypothèse selon laquelle les parcelles agricoles pourraient être identifiées comme des sources de pollution diffuses de pesticides via le ruissellement. La méthode multicritère SIRIS-Pesticides de l’INERIS (Institut National de l’Environnement Industriel et des Risques) appliquée sur deux scénarios de pratiques agricoles indique un potentiel transfert des pesticides ciblés vers les eaux de surface. Afin de conforter ces hypothèses, deux diagnostics de pollution ont été réalisés entre 2015 et 2018 en saisons pluvieuses, couplant des méthodes d’échantillonnages ponctuels et passifs. Une liste de 32 pesticides et de 24 résidus pharmaceutiques a été recherchée dans les eaux de surface et les eaux souterraines du bassin de la Méfou. Les résultats généraux indiquent (i) de fortes concentrations en herbicides et en anti-inflammatoires non stéroïdiens ainsi que la détection et la quantification d’une large gamme de composés recherchés, (ii) une contamination bien plus marquée en milieu urbain qu’en milieu péri-urbain, (iii) un risque environnemental à ces concentrations pour deux herbicides (diuron et atrazine) et (iv) la contamination de certains points d’eau souterraine (forages, puits, sources) par les résidus pharmaceutiques. Une enquête sociologique réalisée autour des points d’eau de prélèvement a permis d’identifier les enjeux liés à l’utilisation de cette ressource en eau. La contamination des eaux souterraines pourrait entraîner une exposition potentielle des populations aux résidus pharmaceutiques présents dans leur eau de boisson. Les résultats principaux constituent donc une base d’information sur les pressions anthropiques, les niveaux de contamination et les enjeux liés à l’eau à Yaoundé. Ils soulèvent des questionnements sur (i) les transferts des pesticides et des résidus médicamenteux dans l’hydrosystème de la Méfou, et (ii) à propos de l’exposition et des risques sanitaires potentiels posés par leur occurrence et leurs niveaux de contamination dans la ressource en eau. / Demographic growth and urbanization create pressure on water resources. Among urban contaminants, pesticides and pharmaceuticals can be discharged into the aquatic environment through agricultural activities and untreated waste waters. Their presence is also reported in global water bodies. Measured contamination levels can have ecotoxicological effects on aquatic organisms as well as on human populations. In Sub-Saharan Africa, these problems are beginning to be highlighted. Local agricultural practices and consumption of pharmaceuticals lead to specific concerns.The aim of this thesis is to identify and characterize the impacts of human activity on the quality of the water resource in urban Sub-Saharan Africa, by analyzing pesticide and pharmaceutical contamination. The study area was the Méfou watershed that drains the political capital of Cameroon, Yaoundé (Center Region).First, the study area was characterized by its environmental (reliefs, land use) and socio-demographic specificities to identify anthropogenic pressures. Urban agricultural practices and in particular the intensive market gardening in the humid lowlands involves the use of massive amounts of pesticides. The absence of a sewage system and the numerous pit-latrines, drains and septic tanks are the sources of diffuse pharmaceutical contamination.Using the example of pesticides, a contaminated runoff mapping method based on susceptibility maps (from the IRIP method) confirmed that some treated plots located in situations that favor runoff were sources of diffuse pesticide contamination. Several areas in the study basin can accumulate this polluted runoff. Next, the multi-criteria SIRIS-Pesticides method from INERIS was applied based on two agricultural scenarios constructed with data sources from the literature. Results pointed to the potential transfer of pesticides from crops to both surface and groundwater.To reinforce these hypotheses, two water quality surveys were conducted in the rainy season between 2015 and 2018, combining grab and passive sampling. Thirty-two pesticides and twenty-four pharmaceuticals were searched for in surface and groundwater in the Méfou watershed. The main results indicate that (i) high concentrations of herbicides and analgesics were detected and quantified in the water samples along with a wide range of targeted compounds; (ii) the contamination pattern showed that the urban area is more polluted than the peri-urban area of Yaoundé; (iii) the measured concentrations pose an environmental risk, in particular the herbicides atrazine and diuron; and (iv) some groundwater sampling points used for drinking water were contaminated by the targeted pharmaceuticals.A social survey conducted in March 2018 around the sampling points identified the risks related to water use. The lack of a sewage system and the discharge of untreated waste water into the immediate surroundings facilitate contamination of the sampling sites. As groundwater is used as an alternative to the tap water network in Yaoundé, the population is also exposed to the risk of pharmaceutically contaminated drinking water.The main results provide baseline information about anthropogenic pressures, contamination levels and related issues in Yaoundé. They raise questions about (i) the transfer of contaminants in the Méfou hydrosystem and (ii) population exposure and potential health risks due to their presence and to the levels of contamination of the water resources.

Graduation date: 1996

A two generation laboratory study was conducted on a captive population of American kestrels (Falco sparverius) to investigate the possible teratogenic effects of the pesticide Dicofol. Paired females were exposed to three levels of Dicofol. Integrity of the reproductive tract of the resulting embryos were examined. Viable eggs were hatched and these birds were permitted to breed the following year. Breeding performance for these birds was measured based on their ability to form pair bonds and exhibit normal behaviour in the presence of a mate. Clutch completion, fertility, hatchability and number of hatchlings reared to fledging were used as reproductive parameters. Females dosed with 20 ppm Dicofol laid eggs that were significantly (p $<$ 0.05) thinner than eggs of control birds. Male embryos from dosed females were significantly (p $<$ 0.05) different from control chicks. Feminization was confirmed by the presence of primordial germ cells. Second generation adults showed altered reproductive parameters related to their parental dose groups. / Rank-order trials were conducted on second generation males based on parental dose levels to determine the aggressiveness of these individuals when placed in a competitive arena. Primary perch sites and food items were obtained by control birds significantly (p $<$ 0.05) more often than exposed males.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 140-149).

M.Sc. (Zoology) / Please refer to full text to view abstract