Presence and levels of potential trace elements in lettuce and spring onion grown in Kumasi, Ghana

Abstract

Vegetables are essential for human nutrition and health, and their consumption is increasing dramatically in every part of the world. However, irrigated water used in cultivation is usually not portable. The aim of the study was to determine the presence and level of potential trace elements in lettuce and spring onions grown and sold at Kwame Nkrumah University of Science and Technology (KNUST) and its environs. The Thermo Scientific Niton XL3t XRF Analyzer measured the heavy metal concentrations in the lettuce and spring onions. The samples were taken from three farms on the KNUST campus. The heavy metals determined in the samples were arsenic, cadmium, chromium, mercury, manganese, nickel, and lead. Most heavy metal concentrations determined in the vegetables were above the permissible limit of WHO/RML standards, except for Mn and Ni. However, Ni (88.22 mg/l) in Farm A was above the permissible limit (67.9 mg/l). The contamination of these metals showed a low degree of contamination of heavy metals in lettuce and spring onions from the various farms, except Nickel, which showed moderate contamination from Farm A (3.01 and 2.12 mg/) for lettuce and spring onion, respectively. The estimated daily intake (EDI), health quotient (HQ) and health index (HI) calculated generally indicated that most of the vegetables had low risk to human health, apart from those grown in Farm A, which had values above the permissible limit. However, long-term intake of these vegetables can be harmful due to accumulated effects.