Evaluating the trace metal pollution of an urban paddy soil and bioaccumulation in rice (Oryza sativa L.) with the associated dietary risks to local population: a case study of Ilorin, north-central Nigeria

摘要

Trace metal contamination of paddy soil can be of major health concern due to the potential risk involved in metal transfer along the food chain. This study investigates the level of some trace metals in paddy soil and rice and estimates the risks to humans via dietary intake of brown rice among the local population. Bulk concentrations of Cd and Zn (3.72 and 389.2 mg/kg, respectively) in the paddy exceeded the recommended limits for agricultural soils. However, pollution index showed moderate pollution for only Cd that was anthropogenic in origin in the paddy soil. Concentrations of Cu in rice shoot (4.18 mg/kg) and brown rice (3.57 mg/kg) were below the recommended FAO/WHO limits, whereas contents of Cd, Zn and Pb in the brown rice exceeded the limits by multiples of 15.7, 2 and 19.8, respectively. Transfer factor of trace metals in both rice shoot and grain showed the same trend: Cd[Zn[Cu[Pb, and cluster analysis indicated grain Cd content to be directly accumulated in rice grain via root uptake. Estimated daily intake (EDI) of Pb in adults exceeded the FAO/WHO tolerable daily intake (TDI) whereas in children, EDI of Cd and Pb exceeded the TDI by several folds. The hazard quotient for non-cancer effects in adults and children subpopulations was 2.60 and 11.93, respectively, and Cd was the main contributing factor. Therefore, contamination of brown rice from the field by Cd and Pb poses great non-cancer health risks to both adults and children subpopulations, though children are at greater risks.