Assessment of heavy metals (Lead, Arsenic, Cadmium) in raw sugarcane grown in wetlands of Kampala

Abstract

Sugarcane is a major cash crop around the world. In Uganda, it is one of the popular snacks commonly sold in urban areas of Uganda with a variety of nutritional, industrial and health benefits. However, sugarcanes have the potential to be unsafe for consumption by humans since they are capable of accumulating heavy metals when grown in contaminated soils around highly industrialized places. Studies have shown that urbanization in Kampala has led to utilization of unsuitable places for cultivation like wetlands and around highly industrialized places with contaminated soils. This study was done to assess the safety status, regarding lead, arsenic, cadmium concentration, of raw sugarcane grown in Nakivubo and Lubigi wetlands as compared to dryland-grown sugarcane and WHO permissible limits. The level of contamination of these wetlands with these metals was also compared. The study was a cross-sectional study with random sampling from the two wetlands. Two sugar cane samples were harvested from each wetland and from Lungujja as the dry land control. One soil sample from both the wetlands and the dry land was also obtained and the amount of heavy metals in each was quantified. Samples were prepared using wet acid digestion procedure and analyzed by atomic absorption spectrometry using the Agilent 240 AAS model of machine. Nakivubo wetland sugarcane had both lead and cadmium concentration above the WHO permissible limits. Lubigi wetland sugarcanes had only lead concentration above WHO permissible limit of 0.3mk/kg. Arsenic was almost undetectable in all sugarcane samples and thus assumed to be 0. The THQ for lead and cadmium in Nakivubo wetland sugarcanes was 0.01 and 0.22 respectively while the EDI for lead and cadmium of the same sugarcanes was 0.003 and 0.004mg/kg-day respectively and these were both below the oral reference dose per day. The BCF for lead and cadmium in the same sugarcanes was 0.216 and 0.026mg/kg respectively. The THQ for lead and cadmium in Lubigi wetland sugarcanes was 0.003 and 0 respectively while the EDI for lead and cadmium of the same sugarcanes was 0.001 and 0 mg/kg-day respectively. Both EDI’s for both the metals were below the permissible daily intake limits of the respective metals. The BCF for lead and cadmium in these sugarcanes was 0.216 and 0.030mg/kg respectively. In general, the cumulative health assessment showed that the sugarcane juice from sugarcanes in both wetlands could pose a negligible heath risk and therefore could not cause a threat if consumed in the normal standard amounts per day throughout an individual’s lifetime. Based on these findings, the sugarcaneswere therefore safe for consumption however, this may also be unlikely if the sample space of sugarcanes was bigger than the one used for this study.