Trace Elements and Toxic Metals in Environmental Matrices from Mubuku Irrigation Scheme, Uganda: Human Health Implications and Risk Assessment

Environmental contamination of agricultural systems presents a growing public health concern, particularly in resource-limited settings. This study evaluated the levels of heavy metals in vegetables cultivated under the Mubuku irrigation scheme in Uganda and assessed associated human health risks using both deterministic and probabilistic models. Concentrations of arsenic (As), lead (Pb), mercury (Hg), cadmium and others in vegetables, soil and irrigation water were quantified using Inductively Coupled Plasma Optical Emission Spectroscopy. Deterministic risk assessment was performed by calculating the chronic daily intake (CDI), target hazard quotient (THQ), hazard index (HI), and total cancer risk (TCR). A Monte Carlo Simulation (10,000 iterations) was applied for probabilistic risk analysis to capture variability and uncertainty in exposure parameters, offering a more robust, data-driven estimation of risk distribution in the subset of human population studied. Results revealed that concentrations of As, Pb, and Hg in vegetables and multiple metals in irrigation water exceeded WHO/FAO permissible limits. THQ and HI values > 1 indicated significant non-carcinogenic risks, while TCR values in adults exceeded acceptable thresholds, signalling elevated lifetime cancer risk. These findings underscore the critical need for policy reforms, sustainable agricultural practices, environmental monitoring, safer irrigation strategies, and public health interventions to mitigate exposure-mediated health risks.