Health risk assessment for exposure of lead and cadmium in herbal medicines sold in Kalerwe market, Kampala, Uganda

Abstract

Herbal medicine use provides about 80% of primary health care globally. There exists a toxicity risk to the population from consumption of herbal medicines owing to the lack of knowledge on the herbal medicine physicochemical composition. Toxic metals are some of the physicochemical contaminants in herbal medicines. However, there is scarcity of information regarding the toxic metal concentrations in herbal medicines sold on markets in Uganda. This study was aimed at determining the concentrations of lead and cadmium in herbal medicines in Heavy metal( Cadmium) and to determine the attributable health risk to these respective metals.

Methods-One hundred (100) herbal medicine samples were purchased from six (6) recruited herbalists in Kalerwe market. The concentrations of lead and cadmium in herbal medicines were determined following published standard methods on a Flame Atomic Absorption Spectrophotometer. The Chronic Daily Ingestion rate (CDI) of lead and cadmium respectively in herbal medicines, was calculated by substituting the experimentally obtained lead and cadmium concentrations into the published standard equation. The attributable Hazard Quotient (HQ) was calculated by dividing the CDI by the oral reference dose obtained from published tables. The attributable non-carcinogenic risk (Hazard Index, HI) was obtained as a summation of the sample HQ. The attributable cancer risk (Incremental Lifetime Cancer Risk, ILCR) was determined as a product of calculated CDI and the Cancer Slope Factor for each metal got from published tables.

Results-All herbal medicine samples contained lead and cadmium of mean concentration ± SD of 17.055 ± 6.690 ppm and 2.248 ± 1.336 ppm respectively at 95% confidence. Lead had a higher attributable non-carcinogenic risk (Total HI of 26.76 and 17.65 in children and adults respectively) than cadmium (Total HI of 2.79 and 2.21 in children and adults respectively) while cadmium had a higher attributable carcinogenic risk (Total ILCR of 7.60 x 10-4 and 2.99 x 10-3in children and adults respectively) than lead (Total ILCR of 7.81 x10-6 and 2.90 x 10-5 in children and adults respectively).

Conclusions-The study showed gross contamination of herbal medicines by lead and cadmium. Lead generally was higher in concentration than cadmium in all herbal medicines. Consumption of herbal medicines contaminated with both lead and cadmium had intolerable attributable non-carcinogenic risk by each toxic metal. However, cadmium had an intolerable attributable carcinogenic risk whereas lead had a tolerable carcinogenic risk. These findings call for a need to standardise herbal medicines, training and support of herbalists by policy makers and scientists to improve on herbal medicine quality.