Heavy Metal Contamination and Neurotoxicity Risk in Herbal Teas and Spices from Abuja, Nigeria
Adebisi Akinyemi Fagbohun *
Chemistry Advanced Research Center, Sheda Science and Technology Complex, Abuja, Nigeria.
Toba Samuel Anjorin *
Department of Crop Protection, Faculty of Agriculture, University of Abuja, Nigeria.
Mary Sunday Dauda
Chemistry Department, Faculty of Science, University of Abuja, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Herbal teas and spices are widely consumed in Nigeria in both urban and peri-urban societies, such as Abuja, for their nutritional, medicinal, and cultural values. However, contamination with toxic metals poses serious health risks due to their persistence, bioaccumulation, and toxicity even at low concentrations. This study assesses the levels of heavy metals (lead (Pb), cadmium (Cd), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), and copper (Cu)) in herbal teas and spices and evaluates the potential health risks associated with their consumption. Bulked samples of twelve herbal teas and eleven spices were digested and analysed with atomic absorption spectrophotometry (AAS) using standard methods. Analytical results indicate detectable concentrations of all metals in both sample types. In spices, ginger powder (Mn: 598.8 mg kg⁻¹; Cr: 15.13 mg kg⁻¹) and turmeric powder (Mn: 403.8 mg kg⁻¹; Cr: 12.96 mg kg⁻¹) showed the highest contaminant levels. Yellow pepper exhibited elevated Pb (7.89 mg kg⁻¹) and Cd (2.280 mg kg⁻¹), while garlic powder recorded the highest Cr (10.88 mg kg⁻¹). In herbal teas, Top tea contained extremely high Mn (1661 mg kg⁻¹) and Pb (35.12 mg kg⁻¹), whereas Moringa tea had a notably high Pb concentration (77.00 mg kg⁻¹). When compared to WHO/FAO permissible limits (Cd: 0.100 mg kg⁻¹; Co: 0.200 mg kg⁻¹; Cr: 2.000 mg kg⁻¹; Cu: 20.00 mg kg⁻¹; Mn: 0.120 mg kg⁻¹; Ni: 1.630 mg kg⁻¹; Pb: 10.00 mg kg⁻¹), several instances of exceedance were observed, especially for Mn, Cr, and Pb. Health risk assessment revealed that the manganese’s hazard quotient (11.26) surpassed safe limits significantly, indicating a major risk of neurotoxicity, while lead HQ (1.11) slightly exceeded safety thresholds, suggesting potential nervous, renal, and hematopoietic effects. Other metals (Cd, Co, Cr, Cu, Ni) remained below risk levels (HQ < 1). The results confirm substantial contamination in widely consumed spices and teas, with implications for chronic dietary exposure. Regulatory agencies should enforce stricter quality control measures to protect public health. These findings emphasise the urgent need for continuous monitoring, stricter enforcement of food safety standards, and increased public awareness of the dangers of heavy metal exposure through everyday dietary products.
Keywords: Beverages, condiment, metals, toxicity, risk