Assessment of Heavy Metal Contents in Some Common Spices Available in the Local Market of North Shewa Zone, Oromia Regional State, Ethiopia

Abstract

The objective of this study was to determine the contents of heavy metals in some common spices commercially available in the North Shewa Zone, Oromia region, Ethiopia. Korarima seed (Aframomum corrorima), ginger rhizome (Zingiber officinale), red pepper fruit (Capsicum annum), and turmeric rhizome (Curcuma longa) samples were randomly collected from the Fiche open market. These spice samples were digested using a mixture of 3 mL of HNO₃ (69-72%) and 1 mL of HClO₄ (70%), where organic components are assumed to decompose into gaseous forms while other heavy metal elements are left in the solution. The contents of heavy metals (Fe, Zn, Cu, Cr, Mn, Ni, Cd, and Pb) in the spices were determined by inductively coupled plasma‒optical emission spectrometry (ICP‒OES). The results obtained showed that the concentrations of heavy metal in the korarima, red pepper, ginger, and turmeric samples in milligrammes per kilogramme of dry weight were in the range of Fe (38.7-98.9), Mn (10.5-257), Zn (7.30-29.2), Cu (1.70-6.50), Cr (5.40-9.70), Cd (1.50-2.90), Pb (14.5-28.4), and Ni (3.90-6.70). The heavy metal contents in korarima, red pepper, ginger, and turmeric samples were compared with the maximum values given by the World Health Organization (WHO). Accordingly, the Fe, Zn, Cu, Cr, Mn, and Ni values in the spice samples were found to be lower than the maximum limit of the WHO, while the levels of Pb and Cd in four spice samples and Mn (only in ginger) were higher than the WHO permissible limit. This study shows that the consumption of korarima, red pepper, ginger, and turmeric may pose a serious health threat to consumers due to the high content of lead, cadmium, and manganese (only in ginger) in spices. Therefore, it is suggested that further study be conducted on spice samples based on the origin of cultivation to determine which hotspot is responsible for high levels of contamination of lead, cadmium, and manganese to protect consumers.

Keywords: Ginger; Heavy metals; ICP‒OES; Korarima; Red pepper; Spice; Turmeric.