**1. Introduction**

Agriculture is becoming less beneficial to rural farmers in the Sahelian region of West Africa (WA) because of the population explosion, severity and persistence of climate change, scarcity of irrigation infrastructure, degradation of the environment and slow pace of technology change amongst other factors. These challenges have resulted in a large number of rural farmers migrating to cities in search of social and economic opportunities and its accompanying increase in urban food

demand [1, 2]. Most farmers in urban and peri-urban areas have limited land, and so practice farming systems targeted at the production of high-value crops used in urban diets, especially exotic vegetables. These farming systems, known as urban and peri-urban agriculture (UPA), have evolved in different African cities, and in WA involves 20 million people essentially farming for subsistence and/or income generation [3–5]. The contribution of urban agriculture (UA) in strengthening the living conditions of urban Africans is unknown or is seen as a small role in the fight against chronic hunger [6, 7]. The urban population involved in urban UA in Africa is estimated at 50% in Ghana [8, 9], 46% in big cities in Mali [10], 80% of families in Brazzaville, 68% in six Tanzanian cities, 45% in Lusaka, 37% in Maputo, 36% in Ouagadougou and 35% in Yaoundé [11, 12].

In Mali, agriculture contributes about 23% of export earnings and 40% of gross domestic product (GDP) [13], with 5.1% growth rate in 2019 [14]. Vegetable production in Malian cities is usually done on open lands along streams, rivers and roadsides. Due to the inaccessibility of clean irrigation water and the high cost of chemical fertiliser, urban and peri-urban farmers use drainage water and untreated animal waste for production. They are also involved in unselective use of pesticides [15, 16] . These indiscriminate practices negatively affect the health of the population [17–19].

The primary public health problem associated with the consumption of vegetables produced using untreated irrigation water in WA include contamination with pathogenic microorganisms such as *Escherichia coli* [20]. Helminths transmitted to crops through soil are also responsible for some parasitic diseases prevalent in sub-Saharan Africa (SSA) [18, 21, 22]. Studies in West African countries have generally revealed high levels of harmful microorganisms, heavy metals and pesticide residue in irrigation water and vegetables [23–25] far exceed recommended levels set by World Health Organisation (WHO) [26] and International Commission of Microbiological Specifications for Foods (ICMSF) [27]. Many authors [16, 19, 28] also reported high contamination levels of lettuce with pesticide residue and *Salmonella* species in WA. Other biological and chemical contaminants of water for UPA in WA include dye effluents from textile dyeing activities and industrial and domestic waste. The effective wastewater treatment published by WHO [26] is impracticable in most parts of SSA due to high cost. Wastewater treatment for urban vegetable production is therefore currently not a realistic option for WA, and banning the use of untreated irrigation water will also threaten many livelihoods, affect urban vegetable supply, and will therefore be-contrary to poverty alleviation. In order to mitigate these problems, the characteristic of UPA has been reviewed for major cities in SSA countries such as Ghana [29], Burkina Faso [30], Kenya [31], Nigeria [32] etc. The present chapter reviews the identification of pathway and levels of vegetables contamination and also the identification of interventions employed to reduce public health risk without compelling farmers to change their cropping system or water sources.

### **2. Material and methods**

For this study, research was conducted using scientific papers, books, reports and statistical data from WHO to quantify the level of vegetable contamination and determine key points where necessary interventions could be applied to reduce public health risks in SSA. The concept is based on the biological and chemical identification of irrigation waters, fertilisers and vegetables, pre- and post-harvest risk management *Microbial and Chemical Contamination of Vegetables in Urban and Peri-Urban Areas… DOI: http://dx.doi.org/10.5772/intechopen.107453*

strategies for pathogens. Microbiological analysis and helminth eggs were done using standard methods of ISO and standard morphological characteristics, respectively. Heavy metals and pesticide residues were quantifying by atomic absorption spectrophotometry and Gas Chromatography, respectively.
