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Aim <p>Aflatoxin contamination of food crops remains a critical public health challenge in tropical regions, requiring robust risk management and data-driven surveillance. This study assessed the seasonal prevalence and spatial distribution of aflatoxins in melon seeds (<i>Citrullus lanatus</i> var. <i>colocynthis</i>) across eight Nigerian states (Oyo, Ekiti, Nasarawa, Kogi, Kwara, Lagos, Ogun, and the Federal Capital Territory).</p> Methods <p>Composite samples (n = 41) were collected from formal and informal markets during wet and dry seasons. Fungal taxa were identified using culture-based methods, while aflatoxins B₁, B₂, G₁, and G₂ were quantified using thin-layer chromatography (TLC) coupled with densitometric scanning. Statistical, spatial, and risk analyses including chi-square tests, Mann–Whitney U test, Global Moran’s I, Getis-Ord Gi*, Monte Carlo simulation (10,000 iterations), and generalized linear modeling were applied.</p> Key findings <p><i>Rhizopus oryzae</i> (42.3%) and <i>Aspergillus flavus</i> (38.6%) were the most prevalent fungal isolates (χ<sup>2</sup> test, <i>p</i> &lt; 0.001). Total aflatoxin concentrations were significantly higher during the wet season (mean: 207.5&#xa0;µg/kg) compared to the dry season (mean: 25.55&#xa0;µg/kg; Mann–Whitney U = 12.0, <i>p</i> &lt; 0.004), with 50% of wet-season samples exceeding the European Union regulatory limit of 5&#xa0;µg/kg. Spatial analysis revealed significant clustering of contamination (Global Moran’s I = 0.41, <i>p</i> = 0.02), with Getis-Ord Gi* identifying high-intensity hotspots in Ekiti (Z = 3.12) and Oyo (Z = 2.87). A 10,000-iteration Monte Carlo simulation projected elevated potential lifetime cancer risks, particularly among children, with estimated intakes reaching 5.21&#xa0;ng/kg bw/day (95% UI: 3.87–6.98). Generalized linear modeling identified relative humidity and informal market storage as key determinants of contamination heterogeneity.</p> Implications <p>The co-occurrence of high aflatoxin levels and toxigenic <i>Aspergillus flavus</i> highlights a significant food safety risk driven by environmental and post-harvest handling conditions, particularly during the wet season.</p> Conclusion/recommendation <p>These findings provide a quantitative basis for prioritizing targeted risk management interventions, including improved storage practices and humidity control, and underscore the importance of evidence-based surveillance systems to mitigate aflatoxin exposure in Nigerian food systems.</p>

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Spatiotemporal and seasonal surveillance with risk assessment and multimarket analysis of aflatoxin contamination in Citrullus lanatus melon seeds across six Nigerian states

  • 期刊论文

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  • 发表日期：

    2026年6月23日

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  • Simeon Kolawole Odetunde,
  • Abimbola Ayodeji Orukotan,
  • Afeez Olabisi Yusuf

摘要

Aim

Aflatoxin contamination of food crops remains a critical public health challenge in tropical regions, requiring robust risk management and data-driven surveillance. This study assessed the seasonal prevalence and spatial distribution of aflatoxins in melon seeds (Citrullus lanatus var. colocynthis) across eight Nigerian states (Oyo, Ekiti, Nasarawa, Kogi, Kwara, Lagos, Ogun, and the Federal Capital Territory).

Methods

Composite samples (n = 41) were collected from formal and informal markets during wet and dry seasons. Fungal taxa were identified using culture-based methods, while aflatoxins B₁, B₂, G₁, and G₂ were quantified using thin-layer chromatography (TLC) coupled with densitometric scanning. Statistical, spatial, and risk analyses including chi-square tests, Mann–Whitney U test, Global Moran’s I, Getis-Ord Gi*, Monte Carlo simulation (10,000 iterations), and generalized linear modeling were applied.

Key findings

Rhizopus oryzae (42.3%) and Aspergillus flavus (38.6%) were the most prevalent fungal isolates (χ2 test, p < 0.001). Total aflatoxin concentrations were significantly higher during the wet season (mean: 207.5 µg/kg) compared to the dry season (mean: 25.55 µg/kg; Mann–Whitney U = 12.0, p < 0.004), with 50% of wet-season samples exceeding the European Union regulatory limit of 5 µg/kg. Spatial analysis revealed significant clustering of contamination (Global Moran’s I = 0.41, p = 0.02), with Getis-Ord Gi* identifying high-intensity hotspots in Ekiti (Z = 3.12) and Oyo (Z = 2.87). A 10,000-iteration Monte Carlo simulation projected elevated potential lifetime cancer risks, particularly among children, with estimated intakes reaching 5.21 ng/kg bw/day (95% UI: 3.87–6.98). Generalized linear modeling identified relative humidity and informal market storage as key determinants of contamination heterogeneity.

Implications

The co-occurrence of high aflatoxin levels and toxigenic Aspergillus flavus highlights a significant food safety risk driven by environmental and post-harvest handling conditions, particularly during the wet season.

Conclusion/recommendation

These findings provide a quantitative basis for prioritizing targeted risk management interventions, including improved storage practices and humidity control, and underscore the importance of evidence-based surveillance systems to mitigate aflatoxin exposure in Nigerian food systems.