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 Printable version |
Health risks of urban agriculture development around small dams in Ouagadougou |
Cahiers Agricultures. Volume 11, Number 1, 31-8, Janvier - Février 2002, Cultures irriguées et santé
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 Résumé
Article gratuit
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Author(s) : Guéladio Cissé, Mathieu Kientga, Boureïma Ouédraogo, Marcel Tanner |
Summary : Ouagadougou, the capital city of Burkina Faso, is crossed by a network of rivers and channels through which rainwater is flooding. There are also some water dams getting water from this network during the rainy season and retaining water until the dry season. This gives an essential opportunity for a wide range of human activities, mainly agricultural. The urban agricultural sites in Ouagadougou use several water resources for irrigation, mainly from wells, channels, and dams. However, the largest homegardening activities are undertaken in areas close to dams.
All water resources in the Sahelian context are submitted to high risks of contamination by different kinds of pollution. The potential of risks related to the use of polluted water in agriculture led the World Health Organization to prescribe guidelines in 1989, indicating a limited level of microbiological contamination for different cases, particularly when the vegetables are likely to be consumed uncooked, the threshold being 1,000 FC/100 ml. It was then very relevant to assess whether water from dams in Ouagadougou is presenting a level of contamination under or above the thresholds set up by WHO. The aim of the study presented here is to assess the levels of microbiological pollution of irrigation with water from dams in Ouagadougou, as well as the health risks associated with such practice.
The microbiological approach made it possible to monitor the bacteriological (faecal coliforms) and parasitological (helminth and protozoan eggs) water pollution levels. Water samples were taken in four homegardening areas representing, all year round, between 49 and 56% of the exploited surfaces in the city, including two sites close to dams (Tanghin and Boulmiougou).
A weekly microbiological follow-up conducted during two successive years (1994-1995) allowed 174 water samples from dams (84 from Boulmiougou, 90 from Tanghin) and 172 samples of water from wells (82 and 90, respectively) to be tested. Most of the time, the bacteriological water pollution levels were found to be above the thresholds recommended by WHO for the watering of vegetables likely to be consumed uncooked (1,000 FC/ 100 ml). There was no significative difference between the two dam sites of Tanghin and Boulmiougou. Water from canals or channels (Abattoir and Canal Central sites) proved to be more polluted, both bacteriologically and parasitologically, than water from wells and dams (Boulmiougou and Tanghin sites). The homegardening sites with the most parasite-polluted beds were those of Abattoir (79% of the samples) and Canal Central (75%) which correspond to the sites with irrigation water that are also the most polluted.
Therefore, the health risks must not be underestimated, even on homegardening sites close to dams. An epidemiological approach coupled with a microbiological approach in the same period in Ouagadougou made it possible to assess differences in incidence or prevalence rates between farmers and the general population for diarrhoea, stomach aches and various parasitic infections. Particularly, some results showed that the group of farmers (sampled from all the homegardening sites), both children and adults, have in a very significant way, higher prevalence rates than those of the general population as far as Ankylostoma are concerned (10.80 ± 6.68% against 1.40 ± 0.43% among children; 40.60 ± 7.38% against 14.90 ± 5.09% among adults).
These results show that water dams in sahelian cities constitute a very big opportunity for urban agricultural farmers both in terms of quantity and quality, as they present the lowest health risks regarding the bacteriological and parasitological water pollution levels. |
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