MICROBIAL CONTAMINANTS AND LEVEL OF HEAVY METALS CONCENTRATION OF SELECTED VEGETABLES IRRIGATED WITH WASTEWATER IN HARAR TOWN, KEBELE 05 VEGETABLE FARM, EASTERN ETHIOPIA

Abstract

Food safety issues are of growing concern to consumers globally because of the risks associated with consumption of foods contaminated with heavy metals and pathogenic microbes. In Harar town, kebele 05 vegetable farm is known to produce vegetables irrigated with wastewater. To what extent these vegetables are contaminated with heavy metals and pathogens was not known. Thus, a laboratory based cross sectional study was conducted from October 2016 to January 2017 to assess the extent of heavy metal and microbial contamination of vegetables. Accordingly, a total of 72 samples from four leafy vegetables namely lettuce (Lactuca sativa), spinach (Spinacea oleracea), kale (Brassica carinata)) and cabbage (Brassica oleracea) were examined. The results revealed that the mean values in all vegetables were 9.5x107 CFU/g for total aerobic mesophilic bacterial count, 4.3x106 CFU/g for total coliform and 4.6x105 CFU/g for fecal coliform count. These leafy vegetables were also examined for some pathogenic bacteria (Salmonella, Shigella and Campylobacter species) and infective parasitic stages (Ascaris lumbricoides eggs, Entamoeba histolytica and Giardia lamblia cysts). Salmonella, Shigella and Campylobacter species were isolated in 12.5%, 9.7% and 2.8%, respectively, of all vegetables. Ascaris lumbricoides eggs was the predominant (43.1%) intestinal parasitic stage detected in the present study, followed by Entamoeba histolytica (25%) and Giardia lamblia cysts (15.3%). Lead, Cadmium, and Chromium concentration was determined using atomic absorption spectrophotometry. In all the vegetables, the mean concentrations of Pb, Cd and Cr were 0.17, 0.62 and 1.78 mg/kg, respectively in all vegetables. Cd was found in level more than the maximum limit recommended by FAO/WHO but the level of lead was within the normal range for all vegetables. Chromium was found also within the normal range in all vegetables except in lettuce. The findings of this study have important information on the implications of public health by transmission of pathogenic bacteria and heavy metal among vegetable consumers of Harar town and the surroundings. Thus, it is recommended that the concerned public health authorities need to create awareness in the community and discouraging the use of untreated wastewater for cultivating vegetables.