Assessment of heavy metals (Lead,Arsenic,Cadmium) in yams grown in Kampala wetlands.

Abstract

Yams consumed in Kampala are grown in wetlands around Kampala, which receive untreated industrial wastes, laden with heavy metals. Yams are known to accumulate heavy metals from the soils on which they are grown. Heavy metals are well known for their adverse health effects on humans and there is however poor monitoring mechanism of such food crops in Uganda. This study seeks to establish the safety of yams cultivated in the wetlands around Kampala in terms of heavy metal concentrations. The concentrations of lead, cadmium and arsenic in the yams and the water in which they were grown was determined using Atomic Absorbtion Spectrophotometry. Arsenic wasn’t detected in the analysis but the levels of Cadmium were generally higher than Lead in all the yams obtained from the different wetlands. The concentrations of lead were found to be highest in yams grown in Kasangati wetland and lowest in Lubigi wetland. These followed the order of Lubigi < Kinawataka < Nakivubo < Kirrudu < Kasangati from the lowest Lead concentration to the highest. The levels of Cadmium were also found to be highest in yams grown in Kasangati wetland and lowest in Lubigi Wetland. These followed the order of Lubigi < Kirrudu < Nakivubo < Kinawataka < Kasangati. The Lead Chronic Daily Intake (CDI) values ranged from 0.00172 to 0.00347 mg/kg/day for adults and from 0.00447 to 0.00903 mg/kg/day for children while the Cadmium CDI levels ranged from 0.0130 to 0.0165 mg/kg/day for adults and from 0.0338 to 000429 mg/kg/day for children. The Target Hazard Quotient (THQ) was calculated, the lead THQ for adults in all wetlands was less than one there by below the Provisional Tolerable Weekly Income Values (PTWIV) by the World Health Organisation (WHO) indicating no possible deleterious effects to the adults however the THQ for Lead in children and Cadmium in both adults and children was beyond one implying possible deleterious effects from the obtained levels in the yams. In this study, Cadmium had higher chances for bringing about deleterious effects in the populations of Kampala which consume yams grown in the different wetlands due to its high THQ value. Yams grown in Kampala wetlands were found not to be safe for daily consumption.