Multi-mycotoxin contamination, dietary exposure and health risk assessment of maize consumed in Niger State, Nigeria

Abstract

This study assessed fungal contamination, multi-mycotoxin occurrence and associated health risks in maize consumed in Niger State, Nigeria. A total of 240 individual maize samples were collected across four microclimatic zones and pooled into 32 composite samples stratified by zone, source and maize type to obtain representative contamination profiles for screening-level assessment. Fungal isolation was performed using dilution plating, while mycotoxins were quantified by HPLC (aflatoxins, deoxynivalenol (DON), nivalenol (NIV), and cyclopiazonic acid (CPA)) and ELISA (total fumonisins (FB1, FB2 and FB3), ochratoxin A (OTA), and zearalenone (ZEN)). Aspergillus species, particularly A. flavus and A. parasiticus, predominated, followed by Fusarium and Penicillium. Aflatoxins were detected in all composites (0.03–683 µg/kg). AFB₁ exceeded European Union (EU) limits in 75% of composites, while total aflatoxins exceeded limits in 72%. Total fumonisins exceeded EU limits in 72% of composites and OTA in 56%, whereas CPA, DON, NIV and ZEN occurred less frequently. Co-contamination was common, with up to five toxins detected simultaneously. Dietary exposure estimates indicated the highest exposure for total fumonisins (up to 9125.8 ng/kg bw/day), exceeding the corresponding tolerable daily intake. Margins of exposure (MOE) for aflatoxins and OTA were < 10,000 across demographic groups. Using JECFA cancer potency factors and hepatitis B virus prevalence scenarios (13.6% and 8.1%), estimated aflatoxin-attributable hepatocellular carcinoma incidence ranged from 4.92 to 7.26 cases per 100,000 population per year for AFB₁ and up to 15.39 cases for total aflatoxins. These findings highlight the need for improved pre- and post-harvest control measures.