Determination Of Lead, Cadmium And Nickel In Henna Leaves And Cosmetic Henna Products Within Lamu County, Kenya

ABSTRACT

Lawsonia inermis Linn, commonly known as henna, is an ethno botanical plant which has been used since antiquity for cosmetic and medicinal purposes. Henna painting is an art of beautification which is commonly practised by the people of Lamu County. Heavy metals such as Pb, Cd and Ni are toxic and commonly found in cosmetic products such as henna. The level of these metals in henna leaves and henna products from Lamu is not known. The aim of the study was to determine the level of Pb, Cd and Ni in henna leaves from Lamu so as to identify the source of these metals in the henna products used by the residents of Lamu and in addition to assess the suitability of using the paste and powdered henna products based on their heavy metal content with respect to the standard limits. A total of 120 henna samples were randomly selected and analysed for heavy metals using Flame Atomic Absorption Spectroscopy (FAAS) after acid digestion of the samples. Analysis of variance (ANOVA) using SPSS version 17.0 was used to analyse the data. The lowest and highest mean levels (ppm) of heavy metals in the henna samples were as follows: Henna leaves: Pb (0.04±0.01 to 0.93±0.04), Cd (0.01±0.00 to 0.09±0.01) and Ni (0.01±0.00 to 0.34±0.02). Powdered henna products: Pb (0.16±0.01 to 2.63±0.24), Cd (0.01±0.00 to 1.23±0.03) and Ni (0.13±0.01 to 2.73±0.09). Paste henna products: Pb (0.56±0.06 to 1.32±0.04), Cd (0.02±0.00 to 1.31±0.01) and Ni (0.14±0.02 to 3.01±0.09). From the results, henna leaves recorded the lowest significant levels of heavy metals compared to both powdered and paste henna products with a significant difference noted in the level of Ni (p=0.035) at 95% confidence level. Apart from the henna leaves, the results indicate that more heavy metals were added into the henna products either inadvertently or as formulants. Generally, the powdered henna products recorded their overall mean level of Cd and Pb below the limit of 2 ppm by KeBS as well as Ni below the limit of 1 ppm by Health Canada, hence the products are recommended for use. However, the overall mean level of Ni in paste henna products was above the recommended limit of 1 ppm by Health Canada, hence such products should not be used frequently since they expose the henna users to the toxic effects of Ni. The results of the study can be used to create awareness on the need to minimize or stop the use of heavy metals as formulant in henna products and to reduce the addition of the metals into the products inadvertently during or after the manufacturing process. The henna users can be sensitised on the high level of exposure to heavy metals in various categories and colours of henna products with respect to the set limit by standard bodies.