Assessment of heavy metal concentrations in urban grown vegetables in Thika Town, Kenya

Abstract

Consumption of leafy vegetables grown in urban areas contaminated with heavy metals is a major source of health problems for both humans and animals. This study was conducted to analyze the heavy metal levels in tomato (Lycopersicon esculentum L.) and spinach (Spinacia oleracea L.) grown in Thika town. Heavy metal concentration was analyzed using Atomic Absorption Spectrometry. The mean concentrations of lead (Pb), Zinc (Zn) and cadmium (Cd) in all the samples were more than the maximum permitted concentrations while there was no evidence of copper (Cu) contamination. Heavy metal uptake differences by the vegetables were attributed to plant differences in tolerance. Further Lead (mgkg-1) concentration in the vegetables was above the maximum limit of 0.3 mgkg-1 accepted for human health by World Health Organization (WHO) standards. Due to increased consumption of vegetables by urban communities, we suggest that it is important to treat industrial effluents which are significant sources of heavy metals and phyto-extract excess metals from polluted environments to reduce health risks.