Monitoring of essential and toxic metals in imported herbal teas marketed in selected cities in Southern Nigeria: A health risk assessment study

Abstract

Teas are the most consumed beverage worldwide after water, and its consumption among Nigerians has increased over the past decades due to its documented health potentials. The objective of this study was to investigate the levels of heavy metals (Pb, Ni, Cr, Zn, Fe and Cu) in herbal teas and also to estimate human health risk associated with their consumption. Twenty eight samples of commonly consumed herbal tea bags were purchased from major supermarkets in Port-Harcourt, Yenagoa and Owerri in Southern Nigeria. They were digested, ashed and analysed using atomic absorption spectroscopy (AAS). Heavy metal concentration varied among the different brands of herbal teas in the study whereas the concentrations of Cd, Cr and Ni in some herbal teas were higher than the permissible limit in China. The estimated daily intake (EDI) of heavy metals via consumption of herbal teas showed that Fe contributed the most to the daily intake of metals while Pb contributed the least. The mean average of EDI of heavy metals were 0.657, 0.118, 0.014, 0.014, 0.008 and 0.0009 mg/kg/day Bw in the order of Fe > Zn > Cu > Cr > Ni > Pb respectively. The THQ and HI values were < 1. In conclusion, the study suggests that the risk level of heavy metal exposure via consumption of herbal teas is low with no significant health implications to consumers and may not pose a threat to food safety.

Key words: Herbal teas, food safety, health risk assessment, THQ, EDI, HI, toxic metals