Lead and Total Chromium in Street-Vended Soybean Cake (Awara) from Wudil, Nigeria: Concentrations and Estimated Dietary Exposure

Abstract

Potentially toxic element contamination of ready-to-eat foods is an important food-safety concern because dietary exposure may contribute to cumulative human exposure to environmental contaminants. This study investigated lead (Pb) and chromium (Cr) concentrations in soybean cake (awara) obtained from selected vending locations in Wudil Local Government Area, Kano State, Nigeria, and characterized consumer exposure under defined dietary parameters. Ten awara samples were collected and analyzed using Microwave Plasma Atomic Emission Spectrometry (MP-AES) following acid digestion. Lead was detected in all samples at concentrations of 0.06–0.17 mg/kg, with four samples (40%) exceeding 0.1 mg/kg, which was used as a comparative food-safety benchmark rather than an awara-specific legal limit. Chromium concentrations ranged from 0.06 to 0.14 mg/kg. Estimated daily intake (EDI) was calculated for adults and children using an awara consumption rate of 50 g/day and body weights of 60 and 24 kg, respectively. Lead exposure was characterized using dietary EDI because a health-protective oral reference dose is not currently established for inorganic lead. Chromium exposure was additionally assessed using a Cr(III)-based screening reference dose; however, total chromium was measured and Cr(III) and Cr(VI) were not differentiated, making this assessment conditional on an unverified Cr(III) assumption. Estimated exposures were consistently higher in children due to their lower body weight. The findings demonstrate detectable Pb and Cr contamination in awara and support continued surveillance, investigation of contamination pathways, chromium speciation, and locally derived consumption patterns.