Consumption of vegetables play important role in human health (Henning et al., 2017; Sanlier & Guler, 2018). They provide required minerals and vitamins for better health (Conner et al., 2017; Wallace et al., 2020). Moreover, vegetables supply dietary fiber, and fiber intake is linked to a lower incidence of cardiovascular disease and obesity (Slavin & Lloyd, 2012). Besides, they are essential factors for the prevention and control of other non-communicable diseases including cancer (Farvid et al., 2020; Kerschbaum & Nüssler, 2019; Marmot, 2018; Valcke et al., 2017). However, Ethiopia is one of the developing countries with limited access and consumption of fresh and healthy vegetables (Haji, 2008; Hunde, 2017). In this regard, the urban community has better access and consumption than the rural (Demissie, Ali, & Zerfu, 2009). About sixty percent of Addis Ababa vegetable demand met by urban farmers since the early 1940s (Van Rooijen, Biggs, Smout, & Drechsel, 2010; Alebel Bayrau Weldesilassie, 2008).
In and near Addis Ababa, varieties of vegetables are growing by smallholder farmers. These farmers use the Akaki River as their main water source for irrigation without established modern irrigation mechanisms (Van Rooijen et al., 2010). Due to scarcity of freshwater, partially treated and untreated effluent of wastewater from numerous industries and other gray water from the habitat of the Addis Ababa city is currently used for irrigation purpose as other developing urban areas practiced (Gashaye, 2020; Janeiro, Arsénio, Brito, & van Lier, 2020; Ungureanu, Vlăduț, & Voicu, 2020). As all streams of Addis Ababa, the Akaki River is enormously polluted by anthropogenic impacts from upstream to down (Alemu, 2017; Alebel B Weldesilassie, Boelee, Drechsel, & Dabbert, 2011; Woldetsadik, Drechsel, Keraita, Itanna, & Gebrekidan, 2017). Although the Akaki River water is suspected to be the source of contamination to vegetables and the environment, nearly 1,300 smallholder farmers are engaging to cultivate and irrigate different vegetables consumed by the residents of Addis Ababa (Van Rooijen et al., 2010).
Water quality is one of the important criteria to determine the intended purposes of a river (Misaghi, Delgosha, Razzaghmanesh, & Myers, 2017; Şener, Şener, & Davraz, 2017). The quality of river water is explained by its physical, chemical, and biological constitutes (Kebede et al., 2020; Zhang, Meng, Xia, Wu, & She, 2018). The bacteriological quality of river water is a good indication to monitor irrigation water. As a result, many countries have set microbial quality standards based on their contexts. For instance, World Health Organization set the limit of fecal coliform bacteria for unrestricted irrigation as less than 1000 per 100 ml but for restricted irrigation, the recommended limit is about 105 fecal coliform bacteria per 100 ml (U. J. Blumenthal, Mara, Peasey, Ruiz-Palacios, & Stott, 2000; WHO, 2006). However, the irrigation practice of smallholder farmers in the urban area of Addis Ababa is traditional and a flooding type(Van Rooijen et al., 2010). So that, in this study the cut-off point for the status of contamination level was taken according to the guideline limit of 103 fecal coliform bacteria/100 ml to monitor the irrigation water quality. A study conducted in the Akaki River indicated that the fecal coliform bacteria level of irrigation water is above the WHO recommended limit for unrestricted irrigation (Woldetsadik, Drechsel, Keraita, Itanna, Erko, et al., 2017).
Growing evidence suggests that vegetable consumption is getting attraction by many people particularly in the urban community (Raaijmakers, Snoek, Maziya-Dixon, & Achterbosch, 2018; Raymond, Diduck, Buijs, Boerchers, & Moquin, 2019; Roberts & Shackleton, 2018). The recent popularity of vegetables could be its health advantage and low energy density (Hölzel, Tetens, & Schwaiger, 2018; Shrestha, Haramoto, & Shindo, 2017). However, most urban farmers use untreated or partially treated wastewaters along with high-polluted river like Akaki River (Gashaye, 2020; Gutierrez et al., 2019; Wang et al., 2018; Woldetsadik, Drechsel, Keraita, Itanna, Erko, et al., 2017), which received both liquid and solid wastes from the nearby dwellers and industries operating near to its watershed (Amare, 2019; Yilma, Kiflie, Windsperger, & Gessese, 2019). Hence, microbiologically contaminated rivers could affect the health of farmers on the one hand and consumers of fresh vegetables that are irrigated with contaminated water on the other hand. For instance, the prevalence of perceived illness like intestinal nematodes, diarrhea, and skin disease among farmers working on irrigation farms within and around Addis Ababa were varied significantly between the wastewater and freshwater areas and the prevalence was higher for farmers who are working in downstream than upstream wastewater farm areas (Alebel B Weldesilassie et al., 2011).
Among diarrheal-causing pathogens, Salmonella, Shigella, Escherichia coli, and Cryptosporidium are mentioned (Kundu, Wuertz, & Smith, 2018; Luna-Guevara, Arenas-Hernandez, Martínez de la Peña, Silva, & Luna-Guevara, 2019). Pathogenic Escherichia coli strain causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome in humans (Luna-Guevara et al., 2019). Overall, consumption of freshly produced vegetables particularly those eaten raw is caused by foodborne illness (Carstens, Salazar, & Darkoh, 2019; Mun, 2020; Shrestha et al., 2017).
There have been well-documented evidence on freshly produced vegetables related foodborne illness internationally (Luna-Guevara et al., 2019; Mritunjay & Kumar, 2017) and different remedial approaches have been designed to mitigate the effect of wastewater use in urban farming globally (Banach & van der Fels-Klerx, 2020; Woldetsadik, Drechsel, Keraita, Itanna, & Gebrekidan, 2018; Yao et al., 2019). Besides, limited researches in the current study area conducted specifically on fecal coliform distribution on Lettuce and river water (Woldetsadik, Drechsel, Keraita, Itanna, Erko, et al., 2017). However, there is no adequate information about the microbial quality of Akaki River water and different fresh produced vegetables in and near Addis Ababa; particularly, concerning the effect of the wet and dry period, the incidence of Total coliform, Faecal coliform, Aerobic Plate Count of vegetable, E.coli, and non-E.coli of irrigated water. Therefore, this study is aimed to evaluate the microbial contamination of irrigation water and freshly produced vegetables and their perceived health risk.