Concentrations, sources, and health risks of potentially toxic elements in milled maize

Milling process is an essential step in food processing, which often determines the quality of food accessible to consumers. The contributions of dry and wet milling operations to contamination levels, sources, and health risks of potentially toxic elements (PTEs) in processed maize were evaluated in this study. Maize samples procured from a major market in Ilorin were milled and analyzed for 8 PTEs (Cd, Fe, Pb, As, Mn, Cu, Zn, and Cr) using Atomic Absorption Spectrophotometer. Apart from Cd, Pb, and As, the mean concentrations of other analyzed PTEs were within the permissible limits for PTEs in foodstuffs set by Codex Alimentarius Commission. The mean concentrations of Pb, Mn, and Zn increased from 2.75, 0.78, and 0.46 mg/kg in maize control to 3.03, 0.80, and 0.65 mg/kg in dry-milled maize, respectively, while mean concentrations of Fe, Pb, and Zn increased from 1.33, 2.75, and 0.46 mg/kg in maize control to 1.41, 2.90, and 0.49 mg/kg in wet-milled maize, respectively. The probable PTEs sources in milled maize identified using the positive matrix factorization model include wear of grinding disks; emissions from leaded fuel combustion; lubrication oil leakage during milling; vehicle traffic emissions; application of pesticides and herbicides; use of manure and Zn-enriched fertilizer; and irrigation with industrial wastewater. Assessment of hazard indexes (HIs) and lifetime cancer risks (LCR) revealed that associated health risks of PTEs from consumption of milled maize were insignificant, although HI and LCR results suggest the possibilities of health deterioration in children and adults from long-term consumption of milled maize in Ilorin. This study advocates improvement in maize cultivation and milling processes to avert PTEs contamination.