Assessment of Irrigation Water Quality Used for Vegetable Cultivation in Barkin Ladi, Plateau State, Nigeria

Due to increasing freshwater scarcity, farmers in Plateau State increasingly rely on untreated wastewater for irrigation, raising concerns about contamination risks. This study evaluated the physicochemical characteristics, microbial load, heavy metal concentrations, and associated human health risks of irrigation water from multiple sources in Barkin Ladi, Nigeria. Standard analytical methods were employed for physicochemical and microbiological assessments, while heavy metals were quantified using ICP-OES. Most physicochemical parameters fell within acceptable limits. However, microbial counts were significantly elevated, with total bacterial counts ranging from 5.4 × 10⁵ to 1.15 × 10⁶ CFU/mL, total coliforms 0 to 8.2 × 105 CFU/mL, and fungal counts between 3 × 10⁴ to 4.2 × 10⁵ CFU/mL in water—far exceeding recommended safety limits, indicating faecal contamination. Cabbage showed TBC, TCC and TFC values between 7.6 × 10⁵ and 2.31 × 10⁶ CFU/g, 2 × 10⁴ and 1.10 × 10⁶ CFU/g and all with 3 x 104 CFU/g respectively and green pepper from 3.9 × 10⁵ to 1.64 x10⁶ CFU/g, 6 x 104 to 3.8 x 105 and non-detectable levels to 8 × 10⁴ CFU/g respectively. Heavy metal analysis showed that, except for Zn, concentrations exceeded WHO and NAFDAC permissible limits. Cancer risk indices ranged from 0.03 to 0.12 for children and 0.02 to 0.08 for adults, surpassing acceptable thresholds. Arsenic, chromium, and nickel were identified as major contributors to carcinogenic risk. Overall contamination followed the trend: groundwater < surface water < mine water. The findings highlight significant public health risks associated with the use of untreated irrigation water in the study area.