Risk analysis of heavy metal contamination in soil, vegetables and fish around Challawa area in Kano State, Nigeria

Abstract

Contamination of soil and water pollution as a result of industrial and agricultural practices in Nigeria is increasing environmental concern. Transfer factor (TF) and risk analysis of four heavy metals (cadmium (Cd), chromium (Cr), lead (Pb) and zinc (Zn)) in five different vegetables: potato, onion, tomato, lettuce and spinach and in fish and water samples around industrial area of Challawa in Kano State, Nigeria were evaluated. A total of 80, 56 and 130 fish, water and vegetables with their individual soils were sampled, respectively, between February and April, 2017. Transfer of heavy metals from soil to vegetables was evaluated using Transfer Factor (TF). Cadmium accumulated the most with the transfer factor (TF) of 6.52E–5–2.88, while Pb had the lowest accumulation with TF of 0.23–0.34. Irish potato had the highest TF (2.88 for Cd). This shows higher level of metals in the soil. Target Hazard Quotient (THQ) was used to determine the potential risk of human exposure as the THQ values in the two species ranged between 1.211.92, 1.883.84, 0.19 and 0.26 and 0.0001 and 0.01 for Cd, Cr, Pb and Zn, respectively. Daily intake of Cd in Challawa water ranged from 0.04 to 0.08; Cr – 0.08–0.10, Pb – 0.03–0.05 and Zn – 0.02–0.03. The average daily intake of metals followed this order Cr > Cd > Pb > Zn. In conclusion, the concentrations of Cd and Cr in water, fish and vegetables were above the permissible limits as the consumption of vegetables and fishes from this river may pose potential human risk, especially to people living around this area.