ELEMENTAL IMPURITIES IN REGISTERED HERBAL SUPPLEMENTS IN NIGERIA: A LOOK AT MERCURY, ANTIMONY AND TIN

Abstract

The use of traditional and alternative medicine has increased worldwide. Although heavy metal poisoning has been associated with traditional medicines, little is known about the exposure to heavy metal toxins from herbal supplements consumed in Nigeria. This study determined the concentrations of mercury, antimony and tin in orallyadministered herbal supplements commonly sold in Nigeria. Twenty four different Nigerian Herbal supplements (NHS) were randomly sampled from herbal medicines stores in the Niger Delta in December, 2010. They were analyzed for mercury, antimony and tin contents and to ascertain their compliability with the recommended limits of the World Heath Organization (WHO), European Union (EU) and the United States Environmental Protection Agency (USEPA). Herbal supplements were ashed before digestion using conc. aqua regia, HCl:HNO 3 (3:1) and mercury, antimony and tin were assayed with AAS 205A. The highest levels of mercury, antimony and tin were 0.01945mg/l (super cleanser capsules), 0.00381mg/l (Super clean capsules), 0.00926mg/l (Reliva Caplets) respectively, whereas lowest levels of mercury and tin were 0.00488mg/l (Eroxil 5000 syrup) and 0.00205mg/l (Evans Bitters). About 29.2% of the sampled NHS had non-detectable levels of antimony. The solid samples (tablets, caplets and soft gels) had the highest concentrations of mercury, antimony and tin. One hundred percent of the sampled NHS violated the permissible limits of 0.001mg/l and 0.002mg/l for mercury and tin as recommended by WHO and EU respectively. Also, 79.2% and 33.3% of the samples exceeded the 0.006mg/l and 0.002mg/ml as recommended by USEPA for mercury and antimony respectively. One hundred per cent of the NHS was found to be below the limits of 0.005mg/l as prescribed by EU and WHO for Antimony. It is feared that indiscriminate use of these supplements may constitute a significant source of mercury and tin exposure and should therefore be considered a public health problem especially in chronic exposure/ingestion given the resurgence of interest. The public health hazards from ingestion of these supplements should be identified and disclosed by in-depth risk assessment.