Evaluation of Heavy Metals and Microbial Contamination in Herbal Medicines Used for Chronic Illnesses in Nairobi Metropolis

Abstract

The World Health Organization estimates that 70-80% of the world’s population uses herbal medicines for their primary health care needs. Herbal medicines may be contaminated with toxic metals, microbes and pesticide residues among other contaminants. In spite of their popularity and immense contribution to the primary health care, many African countries lack or have insufficient quality control systems to assure the safety of these products. This study sought to evaluate marketed herbal products for two important quality parameters, heavy metals and microbial contamination, in Nairobi metropolis that comprises of Nairobi City County and sections of Kiambu, Kajiado and Machakos Counties. Experimental Herbal medicine samples used for the management of chronic illnesses namely diabetes, human immunodeficiency virus/acquired immune deficiency syndrome, rheumatoid arthritis, peptic ulcer disease, tuberculosis, cancer and hypertension were obtained from pharmacies, open-air markets and supermarkets within Nairobi metropolis. Heavy metals namely lead, cadmium, mercury and arsenic were quantitatively determined using inductively coupled plasma mass spectrometry. Microbial analysis was performed according to the British pharmacopeia, 2017 specifications for herbal medicines. Principal component analysis was performed in order to detect potentially harmful herbal medicines using Origin Pro 9.1 software (OriginaLab Corporation, MA, USA) while quantitative risk assessment was conducted to evaluate the potential public health risk posed by consumption of herbal medicines using target quotient and cancer risk methodology as elaborated by the United States Environmental Protection Agency. Results and Discussion A total of 89 herbal products were sampled for this study. A large proportion of the samples (42, 47.2%) were collected from Nairobi City County because it is the core distributive centre of the other metropolis regions. The remaining 47 samples (52.8%) were from the other three counties. Among the 89 samples, 55 (61.8%) had no both brand name and list of ingredients while 8 (9.0%) had brand name without list of ingredients. Only 26 (29.2%) samples had both brand name and list of ingredients. All the 89 samples were subjected to elemental analysis, whereby 33 (37.08%), 19 (21.35%), 3 (3.37%) and 2 (2.25%) contained lead, mercury, arsenic and cadmium, respectively, above the United States Pharmacopeia, (2018) permissible limits. A two-tailed test of significance showed no correlation between the levels of analysed metals. Analysis of variance using the F-statistic also showed that the content of the metals in the herbal products were significantly different at 0.05 level (p=0.3093). Risk analysis identified arsenic and mercury as being of greatest risk for non-cancerous toxicity with hazard index of greater than 1. Cancer risk (CR) and total cancer risk (TCR) higher than 104 were identified in some samples. Arsenic was found to be the contributor of the CR in some samples. Eighty six samples were subjected to microbial analysis, where 14 (16.3%) had no visible growth while 72 (83.7%) exhibited growth of microorganisms and were subjected to test for specified microorganisms. Thirty nine (54.17%) of the 72 samples did not comply with the BP 2017 specifications. Twenty nine (33.72%) and 26 (36.1%) failed enumeration and test for specified micro-organisms, respectively. Conclusion and Recommendation The study revealed significant contamination with heavy metals and microorganisms in the herbal products. Mercury and arsenic were identified to pose the greatest non-cancer risk to consumers of herbal medicines with a two-fold higher risk in children than adults. The cancer risk was ascribable to arsenic. Judicious use of herbal medicines in children and adults is recommended. Chronic use of these products may lead to bioaccumulation of the contaminants that may inadvertently have serious health implications. This underscores need for proper regulation of herbal products to ensure only those products that comply with standard quality specifications get to the market.