Determination of mercury, cadmium, and nickel in henna samples

In most countries around the world, henna (Lawsonia inermis) has been widely used for centuries as a traditional cosmetic and therapeutic plant. However, there is a growing concern about the safety and potential toxicity associated with the use of henna. The research aimed to analyze the levels of mercury (Hg), cadmium (Cd), and nickel (Ni) in 36 henna samples (red, green, black) from both locally produced and imported products commonly used in Iran. The henna samples analysis was carried out using an atomic absorption spectrometry (AAS) system. The level of Hg in all samples was lower than 0.002 µg/g. The levels of Cd and Ni in the samples were at the ranges of 0.25 - 2.05 µg/g (mean = 0.85 µg/g) and 6.7 - 21.8 µg/g (mean = 14.35 µg/g), respectively. The level of Cd in 94.5% of samples was higher than the maximum permissible limits (0.3 µg/g) recommended by the World Health Organization (WHO). To our knowledge, this paper is the first investigation into the level of Hg, Cd, and Ni in Iran's henna. The findings from this study showed that levels of Cd and Ni in henna samples used in Iran were high and seemed to pose a threat to health.