Abstract
Background.Trace metals from anthropogenic activities have been found to occur in tea brands and pose potential human health risks to consumers.Objectives.The present study assessed the concentrations of trace metals in green, black and herbal tea brands using a modified Community Bureau of Reference sequential extraction method.Methods.Fifteen (15) Camellia sinensis and eight (8) herbal tea samples commonly consumed in Nigeria were collected and analyzed for trace metals. The concentrations of cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) in extract fractions were analyzed using microwave plasma atomic emission spectroscopy (MP-AES).Results.Trace metals were detected in all of the samples investigated. The concentrations of trace metals in 4 stages (soluble/exchangeable/carbonates bound fraction, reducible fraction, oxidizable fraction, residual fraction) of sequential and pseudo-total metal extraction procedures are presented. The concentrations of Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn in the exchangeable/carbonate bound fraction for green tea ranged between 0.27–1.47, ND-0.33, ND-0.44, 7.05–33.04, 0.23–0.69, ND-0.51, ND-0.16 and 0.18–1.99 mg/kg, ND-0.73, 0.15–0.36, 0.36–0.59, 1.38–30.07, 0.15–0.54, 0.05–0.76, 0.15–0.34 and 0.27–0.77 mg/kg and 0.54–0.64, 0.25–0.41, 0.35–0.47, 18.72–23.98, 0.30–0.55, 0.15–0.21, 0.15–0.23 and 0.30–0.48 mg/kg for hebal tea, respectively.Conclusion.The metal content in the investigated tea indicated low to enhanced concentrations. Locally produced black teas recorded relatively low trace metal contents compared to the green and herbal tea samples. The most bioavailable trace metal was Mn, while Zn was most preferably bound to the residual fraction. Cadmium, Cr, Cu, Ni, Pb, and V were distributed at varied concentrations among other extractable phases. Daily consumption of the investigated tea products may expose consumers to potentially toxic metals as well as essential elements.Competing Interests.The authors declare no competing financial interests.
Highlights
Trace metals are chemical elements which naturally occur at low concentrations in the environment and are required at very low levels in living systems, but are toxic at enhanced levels.[1,2,3] This includes elements such as cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), molybdenum (Mo), manganese (Mn), nickel (Ni), and zinc (Zn)
The concentrations of Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn determined through sequential extraction procedure in twenty-three (23) branded tea samples (11 green tea, 8 herbal tea, 4 black tea) are presented in Tables 2 – 3
The present study examined the trace metal contents of each tea type, imported and locally produced for the Nigerian market
Summary
Trace metals are chemical elements which naturally occur at low concentrations in the environment and are required at very low levels in living systems, but are toxic at enhanced levels.[1,2,3] This includes elements such as cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), molybdenum (Mo), manganese (Mn), nickel (Ni), and zinc (Zn). Elemental contamination has been of growing concern in environmental matrices such as soil, sediment, water, medicinal plants, fruits and vegetables, and particulate matter in the atmosphere.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] Foodstuff, beverages and consumer products like cigarettes have been shown to have enhanced levels of toxic trace metals.[16,17,18] Essential trace elements including Cu, Fe, Mn and Zn are required for the proper functioning of enzymes in the body; they become toxic when their concentrations are enhanced and begin to accumulate in body tissues Nonessential trace metals such as Cd and Pb are toxic to the human. Low and high molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in commercially sold green tea and herbal products.[19,20]
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