Assessment of Heavy Metals in Poultry Feeds from the Kampala Metropolitan Area, Uganda

Abstract

This study investigated the concentrations of heavy metals; lead (Pb), cadmium (Cd), chromium (Cr), and copper (Cu) in poultry feeds collected from five locations within the Kampala Metropolitan Area, Uganda: Wakiso (RS01), Kalerwe (RS02), Mukono (RS03), Nakulabye (RS04), and Bweyogerere (RS05). Chromium concentrations were highest in Bweyogerere (10.92 ppm) and Kalerwe (7.05 ppm), likely reflecting contamination from nearby industrial and traffic-related activities. Copper exhibited the greatest spatial variability, with elevated levels in Bweyogerere (48.63 ppm) and Wakiso (40.61 ppm), suggesting both environmental exposure and possible intentional supplementation. Lead concentrations were highest in Bweyogerere (1.16 ppm) and Wakiso (0.92 ppm), though these remained below regulatory limits. Cadmium levels were alarmingly elevated, exceeding both FAO/WHO and EU permissible limits by 2 to over 10 times, particularly in Nakulabye (5.75 ppm), Bweyogerere (5.56 ppm), and Kalerwe (4.44 ppm), indicating severe contamination likely from industrial discharges and improper waste disposal. Statistical analyses confirmed significant differences (p < 0.05) in metal concentrations across sites, with copper showing the highest variation. Estimated Daily Intake (EDI) values for poultry revealed cadmium as the greatest hazard, with Risk Quotients (RQ) exceeding 100 in multiple samples, signaling high toxicity risks. Chromium and lead also exhibited elevated RQs, raising concerns about chronic toxicity and cumulative effects on poultry health, including liver damage, immunosuppression, and growth impairment, corroborated by regional studies from Nigeria and Egypt. Human health risk assessment, based on bioaccumulation factors and poultry consumption rates, showed that EDI values for humans were several orders of magnitude lower than for poultry. Corresponding human RQs for all metals were below unity, suggesting no immediate health threat at current consumption levels. However, cadmium presented the highest relative risk (RQ up to 0.48), highlighting potential long-term health concerns due to its carcinogenicity and renal toxicity, consistent with findings in Uganda and neighboring East African countries.