Evaluation of the Heavy Metals in Tonic Creams using the Wet Acid and Dry Ashing Methods

Abstract

It has recently been discovered that long term exposure to heavy metals such as mercury (Hg), lead (Pb), cadmium (Cd), and nickel (Ni) causes some health which are carcinogenic, behavioral abnormalities and sterility. This study is aimed at determining the concentration of Pb, Cd, Zn, Mn, Cr, Cu and Ni in skin cosmetics, particularly in toning creams. Samples were purchased from Oja-Oba market in Akure City of Ondo state, Nigeria. All the heavy metals under study were quantified using atomic absorption spectroscopy (AAS) after wet digestion and dry ashing methods. The following metals were found through wet digestion, Cu (3.90-12.05), Zn (3.50-7.10), Mn (9.90-12.50), Cd (0.00-0.35), Ni (1.05-2.25), Pb (0.10-1.80) and Cr (0.6-4.1) while dry ashing recorded, Cu (7.15-10.70), Zn (6.40-13.85), Mn (10.60-14.90), Cd (0.35-0.55), Ni (3.40-4.70), Pb (0.30-0.55) and Cr (0.85-1.00) mg/kg. It was observed that the concentrations of those metals in the creams investigated were below the maximum permissible limits set by WHO. Significant differences (p < 0.05) of the levels of heavy metals were found between some of the creams posing risks of a combination of creams as well as continual usage. It is, therefore, necessary to indicate the levels of heavy metals on the labels of these cosmetics so the users can be aware.