ASSESSMENT OF HEAVY METALS CONTENT OF SOME PLANT BASED MEDICINES IN PARTS OF SOUTHERN NIGERIA, WEST AFRICA

The concentration levels and human health risk of iron, cadmium, zinc, nickel, copper and lead were determined in 25 popularly consumed types of commercially available herbal drugs in Southern Nigeria. In each type, three brands were selected and analysed. The study area was divided into five sampling zones (A – E) and the herbal drugs were categorized into five clusters based on their advertised usage. The samples were digested using HNO₃: HClO₄ mixture in the ratio of (4:1) and metals analysis were carried out using Atomic Absorption spectrophotometer. The results showed the concentration of the metals in the ranges: Fe ­= 4.524 ± 0.011 to 70. 121 ± 0.002 µg/g; Cd = 0.012 ± to 0.620 ± 0.002 µg/g; Zn = 0.03 ± 0.01 to 42.010 ± 3.40 µg/g; Cu = 0.160 ± 0.000 to 66.21 ± 2.11 µg/g and Pb = BDL to 22.011 ± 0.850 µg/g. The provisional weekly intake (PWI) of the metals did not exceed the recommended provisional weekly tolerable intake (PTWI) except nickel in 5 samples. The heavy metal pollution index (HMPI) in the five sampling locations indicated a trend: D > C > E > B > A. Seventeen brands of the studied herbal drugs had Fe, Cd, Ni, Cu and Pb levels higher than the WHO/FAO limits. Consumption of these studied herbal drugs ought to be monitored regularly to prevent toxic metals poisoning due to elevated levels of these metals.