ORIGINAL ARTICLE 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 Clement O. Ogunkunle 1,4 · Mayank Varun 2 · Mahboob A. Jimoh 3 · Kehinde S. Olorunmaiye 1 · Paul O. Fatoba 1 Received: 11 March 2016 / Accepted: 14 October 2016 © Springer-Verlag Berlin Heidelberg 2016 Abstract 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 investi- gates 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 concentra- tions of Cd and Zn (3.72 and 389.2 mg/kg, respectively) in the paddy exceeded the recommended limits for agricul- tural 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 mul- tiples 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. Keywords Trace metal · Brown rice · Health hazard · Estimated daily intake · Metal pollution Introduction Trace metals are ubiquitous in the environment either from natural or anthropogenic source and can contaminate soils with consequential transfer along the food chains via plant uptake. This can eventually affect human health and well- being (Ahmed et al. 2015a; Islam et al. 2015a). Some of these trace metals (e.g., Cu and Zn) are essential for growth and development of plants and humans but can become toxic at elevated concentrations (Ahmed et al. 2015b; Rahman et al. 2014). However, other trace metals like Cd and Pb are very toxic at low concentrations and readily contaminate the soil component of the ecosystem (Islam et al. 2015b). They are considered potential human car- cinogens and are reportedly associated with etiology of several diseases, especially cardiovascular, kidney, nervous system, blood and bone diseases (Zhuang et al. 2009). Cultivation of food crops for human consumption on contaminated soil can lead to uptake and excessive accu- mulation of trace metals in edible parts of plants (McBride, 2007). Excessive accumulation of trace metals may potentially pose health risk to humans since the major route of metals exposure to humans is through soil–food crop pathway via dietary intake (Kachenko and Singh 2006; Sharma et al. 2007). Trace metal contamination of paddy soils is of interest due to its use for the cultivation of rice. & Clement O. Ogunkunle seyeogunkunle@gmail.com 1 Environmental Biology Unit, Department of Plant Biology, University of Ilorin, Ilorin 240003, Nigeria 2 St John’s College, Agra, Agra 282 002, India 3 Plant Biology Unit, Department of Biological Sciences, Osun State University, Osogbo, Nigeria 4 Bergische Universitat Wuppertal, 42097 Wuppertal, Germany 123 Environ Earth Sci (2016)75:1383 DOI 10.1007/s12665-016-6203-3