Health Risk Analysis of Heavy Metals (Cr, Fe, Hg & Ni) in Edible Vegetables in Yala Urban Area of Cross River State, Nigeria

Abstract

Aim: The aim of the study was to determine concentration of heavy metals in the soil and edible vegetables planted consumed Yala Urban Area of Cross River State, Nigeria, ascertained the level of metals contamination and the possible health risk or implication.
 Sampling: Forty eight (48) soil and edible vegetable samples (6 of each kind of the 8 vegetables) were collected randomly from Yala Urban Area of Cross River State. The eight vegetables considered for the study were Amaranthus spp., Corchorus olitorius, Murraya koenigii, Ocimum grattissimum, Solanum melongena, Talinum triangulare, Telferia occidentalis and Vernonia amygdalina. They were collected between January and March for dry season, and July and September for rainy season of the year. 
 Methodology: The samples were digested and analyzed for the Cr, Fe, Hg and Ni (heavy metals) concentration using Flame Atomic Absorption Spectrometer (AAS) in the Chemistry Laboratory, University of Calabar.
 Results: The results showed that the mean concentration of the metals in the soil in mgkg-1 ranged from (0.063 - 0.108) and (0.049 - 0.104) in rainy and dry seasons respectively for Cr, and (0.026 - 0.124) and (0.013 - 0.119) in rainy and dry season respectively for Fe. The mean concentration accumulated by the vegetables ranged from (0.037- 0.063) and (0.029 - 0.066) in rainy and dry season respectively for Cr and (0.012- 0.071) and (0.008- 0.086) in rainy and dry season respectively. Hg and Ni were neither detected in the soil nor in the vegetables. The trend of the metals in both the soil and vegetable was in the order: Cr > Fe> Hg> Ni. The Target Hazard Quotients were all less than 1, indicating no health risk.
 Conclusion: These results suggest that there is no significant difference between the amount of metals in the soil or that accumulated by the vegetables in rainy and dry seasons of the year. Also the amount of metals accumulated by most of the vegetables was directly proportional to the amount present in the soil where they are planted. These results indicate that the concentration of Cr, Fe, Hg and Ni in the soil and vegetables were still low and within the permissible limits of WHO/FAO. Thus, the consumption of the vegetables in the area may not pose any risk at the moment.