Concentrations of Heavy Metals and Pesticide Residues in Leafy Vegetables and Implications for Peri-urban Farming in Nairobi, Kenya

Abstract

The primary objective of this study was to assess the levels of heavy metals, nitrate, and pesticide residues in kale (Brassicaolaracea var. olecephala), a leafy vegetable. The study was conducted in three peri-urban sites in Nairobi, Kenya, where the use of wastewater irrigation is pervasive. The results indicated elevated levels of boron (B), cobalt (Co), chromium (Cr), copper (Cu), lead (Pb), zinc (Zn) and nickel (Ni) in vegetables irrigated with wastewater in two sites. High loadings of the heavy metals Ni, arsenic (As), Pb, Cr, Cu, and Zn into agricultural soils were demonstrated to be from chicken manure. Nitrate levels were within acceptable daily intakes. Residues of diazinon, cypermethrin, biternol, and profenofos pesticides exceeded permissible maximum residue limits in kale at one site. Study findings suggest that consumers of vegetables grown in wastewaterirrigated soils may ingest significant amounts of heavy metals and pesticides. Considering these findings, reducing heavy metal deposits into soils should be a strategic aim of soil protection policies in Kenya.

Assessment of bio-availability of Cd, Pb, As and Tl via Gastric/Intestinal Digestion in Plants Collected From Different Kenyan Regions

“…Botanical names, common names, local names and parts of the Medicinal plants used in the study The ve plant species with As concentrations of <0.2 mg/kg from both study regions were W. ugandensis, V. auriculifera, M. indica, A. abyssinica and A. hockii. The plants could be releasing low amounts of arsenic to the body of the plant As are similar to those in different ora of less than 0.01 to 0.4 mg/kg reported by different authors(Karanja et al 2012;Zhu et al 2013) Tadesse et al (2019). reported As levels in different plants collected from Awash river basin in Ethiopia as ranging from not detected to 0.009 mg/kg.…”

Consumer Demand for Value-added Products of African Indigenous Vegetables in Coastal Kenya: The Case of Sun-dried and Frozen Cowpea Leaves

“…At the same time, the tolerance of most AIVs to a wide spectrum of abiotic and biotic stresses makes them more suited to smallholders' low-input production techniques than their exotic counterparts, which frequently require pesticides and fertilizers and an adequate supply of water to perform well. Interest in AIVs is being further driven by health consciousness among the more affluent urban consumers who associate these vegetables with a low risk of pesticide and pathogen contamination (Karanja, Njenga, Mutua, Lagerkvist, Kutto, & Okello, 2012).…”

Assessment of the contamination of Lactuca sativa L. (lettuce) and Lycopersicon esculentum (tomato) by pesticides: Case of market gardeners in Ouagadougou

“…Similar observations were made in other countries in the subregion. For instance, in Kenya, Karanja et al [18] found excessive levels of diazinon, profenofos, and cypermethrin in leafy vegetables. However, in Benin, similar concentrations of dichlorodiphényltrichloroéthane and lindane were found in samples by Diop et al [13].…”