Levels of Some Heavy Metals in the Leaves of Henna Plant (Lawsonia inermis) within Lamu County, Kenya

Abstract

Henna plant scientifically known as Lawsonia inermis is an ethno botanical plant used majorly for preparation of dye called henna. The plant contains a pigment called Laws one which makes it suitable for preparation of henna used in painting or beautification of body parts. Henna painting of body parts is an art of beautification which is commonly practised by the people of Lamu County and other parts of the world. However, high levels of toxic heavy metals such as lead (Pb), Cadmium (Cd) and Nikel (Ni) commonly found in henna products pose health threat to users. One of the sources of heavy metals in cosmetic henna products is the henna leaves. The aim of the study was to determine the level of heavy metals; Lead (Pb), Cadmium (Cd) and Nickel (Ni) in henna leaves within Lamu County in order to assess their suitability as raw material for henna products with respect to the international standard limits. A total of 60 henna leaf samples were randomly selected from Mpeketoni, Amu, Pate and Kiunga sampling sites within Lamu County 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 least and highest mean levels (ppm) of heavy metals in the henna leaf samples were as follows: 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). The pattern of overall mean level of heavy metal accumulation in the henna leaves followed the order: Pb > Ni > Cd. No significant difference in the overall mean level of lead (p=0.155), cadmium (p=0.577) and nickel (p=0.355) in the henna leaves was noted. Among all the sampling sites, a significant difference in the level of nickel (p=0.021) was recorded only within Mpeketoni site. From the results of the study, it showed that henna leaves from Lamu County formed a good raw material for henna products due to their low level of lead, cadmium and nickel in comparison to the standard limits by WHO. Effective quality control measures, proper selection of raw material as well as good manufacturing practises should be enhanced so as to minimise the levels of these metals in henna products.