Assessment of Heavy Metal Concentration in Some Vegetables in Lafia, Southern Guinea Savannah, Nigeria

Abstract

A study was conducted in Lafia, Nasarawa State, Nigeria, to evaluates the concentrations of heavy metals, cadmium (Cd), copper (Cu), lead (Pb), selenium (Se), and zinc (Zn) in vegetables cultivated within the area. The edible portions of four vegetables, amaranth, okra, pumpkin, and tomato were collected from three locations, Bukan Sidi, Maraba, and Shabu, for heavy metal analyses. The concentrations of these metals were determined using standard laboratory procedure and compared against established safety standards set by FAO/WHO. Results indicated that cadmium levels ranged from 0.01 to 0.29 mg/kg, with the highest concentration in okra from Maraba, yet all values were well below the maximum limit of 2.4 mg/kg. Copper concentrations varied between 0.12 and 0.40 mg/kg, with the highest in tomato from Maraba, remaining within the permissible limit of 2.5 mg/kg. Lead levels ranged from 0.08 to 0.27 mg/kg, with the highest detected in pumpkin from Maraba, all within the FAO/WHO limit of 0.5–30 mg/kg. Selenium levels fluctuated between 0.11 and 0.47 mg/kg, with elevated values in tomatoes from Shabu and Bukan Sidi, but still below the maximum permissible limit of 5–19 mg/kg. Zinc concentrations ranged from 0.50 to 0.73 mg/kg, with the highest in okra from Bukan Sidi, significantly below the safety threshold of 20–100 mg/kg. The findings reveal that the heavy metal concentrations in the vegetables are generally within safe limits, reflecting minimal environmental pollution in Lafia. The low levels of cadmium, in particular, suggest limited soil and water contamination, aligning with previous studies indicating the influence of reduced industrial emissions and cleaner agricultural practices. The research recommends the continued consumption of vegetables produced in the study locations and advocates for regular monitoring to detect any potential future contamination.