Heavy Metal Contamination of Market Garden Vegetables and Estimation of the Potential Health Risk Associated with Their Consumption in Bouaké, Côte d’Ivoire

Abstract

In Côte d’Ivoire, urban market gardening frequently develops in wetlands subjected to anthropogenic pressures that may promote trace metal (TM) contamination of crops. The Gonfreville market gardening site in Bouaké, located downstream of a textile industry, represents a potentially concerning context. This study aimed to characterise the contamination of Ipomoea batatas and Allium cepa leaves by copper (Cu), nickel (Ni), chromium (Cr), lead (Pb), and cadmium (Cd), and to assess potential health risks associated with their consumption. The study was conducted during the dry season on four plots, using a limited sampling design comprising eight vegetable samples analysed by atomic absorption spectrometry. Potential exposure and health risks were assessed using estimated daily intake (EDI), hazard quotient (HQ), individual excess lifetime cancer risk (IER), and a theoretical health impact indicator based on assumed exposure parameters. Chromium showed the highest concentration, reaching 59.01 mg/kg, while Pb and Cd concentrations in Ipomoea batatas leaves ranged from 1.93–5.29 and 0.60–1.12 mg/kg, respectively, exceeding the Codex Alimentarius reference limits of 0.30 and 0.20 mg/kg. HQ values indicated potential non-carcinogenic concerns for Cd and Cu in some exposure scenarios, while IER values for Cr and Pb exceeded the reference threshold. Extrapolation of IER to Bouaké’s total population yielded theoretical health impact estimates of up to 56,878 and 32,174 additional cases for Cr associated with Allium cepa and Ipomoea batatas, respectively. These estimates are theoretical calculations based on assumed exposure parameters and should not be interpreted as observed cases or epidemiological predictions. Despite the limited sampling design and exposure uncertainties, the findings support strengthened monitoring of soils, irrigation water, and vegetables at the site.