Guéladio Cissé: Impact sanitaire de l'utilisation d'eaux polluées en agriculture urbaine. Cas du maraîchage à Ouagadougou (Burkina Faso)

PhD-thesis, École Polytechnique Fédérale de Lausanne, co-supervised by Prof Marcel Tanner, Swiss Tropical Institute (1997)

In Ouagadougou and in many similar Sahelian cities the practice of waste-water use for market gardening (maraîchage) is widespread. On the one hand, this practice entails potential sanitary risks, due to the pollution of water; on the other hand, in the Sahelian context, with its rapid urbanization and desertification, it can alleviate nutritional, financial and environmental conditions. Since there is no assessment of real risks of this practice, this research aims at contributing to the better understanding of interactions between the environment and health. The adopted approach is transdisciplinary: starting from an epidemiological perspective, it associates microbiology, socio-anthropology, cartography and geomatics. First, polluted residential areas, market gardening sites and the seasonal variation of the exploited surfaces are mapped. It results that peripheral sectors are more polluted and that the areas of market gardening represent a significant percentage of the total exploited surfaces, a fact that demonstrates the importance of the practice. Secondly, the bacteriological and parasitological pollution in water, soils and plants has been monitored, showing that the levels are mostly above WHO recommended thresholds. Then, through a socio-anthropological approach the author analyses the perceptions and practices of the actors in the chain of market gardening products and evidences the lack of awareness of the farmers. Through an epidemiological approach differences in incidence or prevalence rates between climatic seasons, between farmers and the general population, between market gardening sites, and between sexes, for diarrhea, stomach aches and parasitic infections are assessed. The results are presented as thematic maps, which show the coincidence of market gardening sites, highest polluted environments and highest incidence rates for children diarrhea in the peripheral sectors of Ouagadougou.