Heavy Metal Contaminants in Popularly-consumed Vegetables of Freetown, Sierra Leone

Abstract

The contamination of the environment with heavy metals is one of the challenges that make up Sierra Leone's environmental problem, with urbanization being one of the main causes; due to the lack of proper waste dumpsites and landfills for infrastructural development, rivers, and streams are polluted. The loss of biodiversity, but river and stream pollution have a significant impact on aquatic life. Animals and plants in contaminated water sources "may perish or reproduce improperly". This study assessed the level of concentration of heavy metals namely; chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), and lead (Pb) in some commonly-consumed vegetables like Manihot esculenta (Cassava) leaves, Ipomoea batatas (Potato) leaves, Amaranthus viridis (African spinach), Corchorus olitorius (Krain krain); Solanum lycopersicum (Tomatoes); Cucumis sativus (Cucumber); Brassica oleracea (Cabbage); Abelmoschus esculentus fruits (Okra); Capsicum annuum (Bell Pepper); and Lactuca sativa (Lettuce) which were all purchased at local market places in Freetown. The vegetable samples were analyzed using an X-ray fluorescence machine (XRF) to determine their heavy metal concentration. The goal was to determine the food safety status of the vegetables by comparing the results to the maximum permissible limit (MPL) for vegetables, as set by WHO/FAO. The levels of Zn, Cr, Fe, Cu, and Pb in all vegetable samples varied from 4.70 – 5.69 %; 3.46 – 4.58 %; 4.00 – 4.52 %; 2.87 – 3.42 %; and 0.5 – 1.2 %, respectively. This result indicates that the metals were present at unsafe levels. According to the result, the maximum concentration values are much higher than the MPL value suggested by WHO/FAO for vegetables, implying that eating vegetables from the source market sites in this study may pose a health risk to humans. Heavy metals in vegetables should be monitored on a regular basis to prevent excessive accumulation of these heavy metals in the human food chain. When it comes to vegetable marketing, certain precautions should be implemented.