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.
