Aflatoxin: Managing A Stubborn Threat To Global Food Safety

Aflatoxins are a group of secondary metabolites  that   can be highly toxic, mutagenic and most importantly, carcinogenic. They are produced  primarily by species of the fungal genus called Aspergillus under  favourable conditions of humidity, temperature  and matrix integrity (is the food item healthy of not, whole or broken?) The regular species are Aspergillus flavus and Aspergillus parasiticus . Aflatoxins are categorized based on fluorescence and source. The B  and G aflatoxins  give blue and green colour respectively on UV light, while M group is specifically located in the milk of livestock. Both B and G categories are dietary aflatoxins .Ordinarily they are all colourless, tasteless and odourless.

Aflatoxin contamination of crops is a global  food safety concern. The most dangerous form is Aflatoxin B1 (AFB1), classified as a Group 1 carcinogen by the International Agency for Research on Cancer, IARC, which is the technical arm of the WHO. Generally many  food items are susceptible(1.)  however, notable candidate  crops include  maize, groundnuts, tree nuts, and spices on which contamination happens  before harvest and during storage under poor conditions.   (2, 3 )

For food brands, processors, and exporters, aflatoxins represent a dual risk: severe public health consequences and strict regulatory enforcement. In 2024 alone, the EU rejected 127 shipments from Africa due to aflatoxin levels exceeding 2 ppb  for AFB1. For consultants and auditors, understanding aflatoxin risk is now a core compliance skill for food safety, sustainability, and ESG(Environmental, Social and Governance) audits.

Geography

Aflatoxin contamination is not random. It clusters in tropical and subtropical regions with high heat and humidity. High-risk zones  are:

Sub-Saharan Africa like Ghana, Nigeria, Kenya, Tanzania, Senegal where  maize and groundnuts show 60-90% contamination rates. This is why the  various national regulatory agencies like NAFDAC (Nigeria) and KEBS (Kenya) enforce strict testing.

South/Southeast Asia comprising  India, Thailand and Vietnam with  spices, dried chilies, and pistachios being  major export rejection points. Some parts of the US are also recorded to experience  aflatoxin on farm and store. Significant work has been done on the Arizona field with regard to tree nuts, and cotton

Latin America with maize and peanut exports face EU/US border controls.

Low-risk zones include temperate regions like Northern Europe and Canada having a minimal pre-harvest risk but  could invite  post-harvest risk if imports are stored improperly.

For brands sourcing globally, geography is the first risk filter. For example, a peanut butter brand sourcing from west Africa may  face substantially  higher audit risk than one sourcing from the US.

Impact of Climate Change

As in other mycotoxins, climate change is making aflatoxin risk significant  and expanding its range  (4, 5)

The 3 mechanisms associated with climate change are:

Higher temperatures: A. flavus grows fastest at 28-35°C. As West Africa warms, more crops hit this range during growing season. Some  predictions  suggest  a 20% increase in contamination risk in Nigeria by 2030.

Drought stress: Water-stressed maize and groundnuts crack, allowing fungal spores to enter.Both  drought and heat combine to potentiate aflatoxin production,

Unpredictability: In recent times, regions previously “too cold” like Southern Europe are now reporting A. flavus in maize. For auditors, “climate risk” is no longer future talk. Clients must now ask suppliers: “What’s your drought mitigation plan?” If none, then the risk score goes up.

Recent taxonomic advances have expanded the list of known aflatoxin-producing fungi beyond Aspergillus flavus and A. parasiticus. Phylogenetic studies now confirm at least 18 species within Aspergillus section Flavi as aflatoxigenic, including newly described species such as A. korhogoensis from West Africa (6) and A. pseudocaelatus from South America  These cryptic species are morphologically identical to non-toxigenic strains, creating false-negative risks for labs using only visual or TLC methods. Molecular identification targeting aflatoxin biosynthesis genes such as aflR, nor-1, and omtA is now required for regulatory compliance. Climate change is therefore  driving range expansion of section Flavi species into temperate zones, increasing detection complexity for import/export audits (7, 8)

Detection

Effective interventions  rest on reliable detection and quantitation techniques. Detection methods range from field tests to lab confirmation:

Field screening involves  ELISA kits, lateral flow strips with sensitivity of about  5 ppb Many of these give results in  less than 20min.

Laboratory confirmation involving Thin Layer chromatography TC, High Performance Liquid Chromatography  HPLC  and LC/MS-MS  This can detect  about  0.1 ppb. Because of the sensitivity, it is usually recommended and required for EU/US export certificates.

The Polymerase Chain Reaction ,PCR is used to detects fungal DNA, since aflatoxin occurrence depends on the thriving of the fungus.. The MALDI-TOF technique is now the Gold standard for fungal identification due to its speed, low cost per sample and high accuracy.

Health Impacts

Aflatoxin is a silent killer partly because of the difficulty in detection ordinarily. Acute exposure repeatedly at low doses incites aflatoxicosis. In 2004 Kenya outbreak recorded  317 cases and 125 deaths from contaminated maize. Symptoms  express as liver failure, jaundice, or death in days.

Chronic exposure at  low doses over  many years can lead to  liver cancer. AFB1 metabolizes in liver to AFB1-8,9-epoxide which binds DNA. The WHO has estimated 25% of global liver cancer cases are aflatoxin-related, mostly in Africa  and  Asia.

In children symptoms observed include stunted growth  and  immune suppression. Some studies in tropical Africa  revealed that very a high aflatoxin exposure  can lead to double the stunting rates. For infant food brands, this is a regulatory flashpoint . Therefore any claim like “100% natural, safe for kids” on a maize product label  without proof of aflatoxin testing is a compliance red flag.

Regulations and Impact on International Trade

As a result of the health impact to human and animals, aflatoxins are one of the top  reasons food shipments are rejected at borders across the globe  For Aflatoxin B1, the EU set limit is 2 ppb(parts per billion) and 4ppb for total aflatoxins . The FDA in the USA accepts 20ppb for total aflatoxins in maize and  nuts

The EU rejected about 2,200 consignments  between 2020 and 2024, which averagely cost  $50,000 in lost goods  shipping, per rejection. The Rapid Alert System for Food and Feed RASFF is an effect step for European member states that ensures a preemptive action against contaminated imported shipments. In Africa, the instruments for enforcing regulations are relatively weak, leading to a freer circulation of toxic food items.

Apart from rejection, recall costs can  kill brands sometimes leading to a sharp drop in stock. For ESG audits, “supply chain mycotoxin risk” is now a scored item.

The Codex Alimentarius Commission  sets global baseline. 15 ppb total aflatoxins for most nuts. Countries can be stricter. Nigeria  adopts the  Codex standard  and enforcement  now includes  random market raids for  aflatoxin testing with penalties for  violators.

Intervention Strategies

It is very difficult, if not completely impossible to attain zero-level howver, biological control measures have been reported as effective (9) Aflatoxin risk but it can be managed  at 3 levels:

Pre-harvest: Drought-tolerant seeds, proper spacing, timely harvest and biological control like Aflasafe are all effective measures Aflasafe is a non toxigenic A. flavus strain that outcompetes toxic strains.6 Nigeria saw 80% reduction in maize after use(Ranajit (10). The product employs a ‘fungus-fight’ approach.7 In the US, the fields of Arizona witnessed a successful bio-control using same mode of action. The product is Aflaguard  with Aspergillus favus strain AF36 (11)which  is approved for organic use against pistachio, peanuts, almond and corn .

Post-harvest. The use of fast drying to at most 13% moisture within 48hrs as well as proper storage in hermetic bags like PICS bags have been confirmed as reliable . Keeping the storage environment well ventilated and devoid of any other contaminant is also crucial.

Processing. Physical sorting  by removing  visibly mouldy food items  and the use of  laser  sorters to remove damaged kernels are an attraction to exporters, processors and even domestic consumers. Roasting may reduce AFB1 by 40-60% but doesn’t eliminate it . Activated clay binders  and charcoal are effectively used in animal feed but not for human food.

A winning recommendation is  a combination of Awareness, Good Agricultural Practice (GAP), HACCP, ,Capacity building and a soup of Interventions. Generally, the chemical solution is now being discouraged due to inherent hazards

References

_{1.Esan A; S O Fapohunda; CN Ezekiel; M Sulyok and R Krska 2020 Distribution of fungi and their toxic metabolites in melon and sesameseeds marketed in two major producing states in Nigeria. Mycotoxin Research https://doi.org/10.1007/s12550-020-00400-0}

_{2.Adewunmi ,A A and  Stephen O. Fapohunda 2019. Mycotoxins in Nigerian  cereals and public health implications. Recent Advances in Food Science; 2(4): 200-216}

_{3.Adewunmi A, Stephen O Fapohunda, OlumidecAfolabi and Abiodun Joseph. 2021: Occurrence of mycotoxigenic fungi in guinea corn oleand pearl millet marketed in South west Nigeria. Recent Advances in Food Science 4(3) 341-357}

_{4.Fapohunda S O and A AAdewunmi 2019Climate Change and Mycotoxins–The African Experience. Croatian Journal of Food Science and Technology 11(2)DOI: 10.17508/CJFST.2019.11.2.09}

_{5.Esan A and Fapohunda  S O (2020)Fusarium toxins, climate change and food security Recent Advances in Food Science Open access 3 (3)332-340}

_{6.Carvajal-Campos, A ,AmaLethiciaManizan  ID , SouriaTadrist , David KoffiAkaki ,RoseKoffi-Nevry , Geromy G. Moore , Stephen O. Fapohunda , A Sylviane Bailly, Didier Montet , Isabelle P. Oswald  ID , Sophie Lorber, Catherine Brabet and Olivier Puel(2017). Aspergilluskorhogoensis, a Novel Aflatoxin Producing Species from the Côte d’Ivoire. Toxins  9, 353; doi:10.3390/toxins9110353  1-22}

_{7.Sharma, A.K., Kumar, A., & Rijal, R. (2025). Phylogenetic studies and distinction of aflatoxin-producing Aspergillus species in section Flavi, Ochraceorosei and Nidulantes: A review. Gene, 937, 149151. https://doi.org/10.1016/j.gene.2024.14915}

_{8. Schamann, A., et al. (2024). Comparative analysis of the genomes and aflatoxin production patterns of three species within Aspergillus section Flavi reveals an undescribed chemotype. Communications Biology, 7, 1134. https://doi.org/10.1038/s42003-024-06738-w}

_{9,Fapohunda S. O, Esan A O.  andAnjorin S. T (2017)Biological Control of Mycotoxins : an Update  World Veterinary Journal7 (4) 117-127}

_{10.Cotty PJ.1990. Effect of atoxigenic strains of Aspergillus flavus on aflatoxin contamination of developing cottonseed. Plant Dis. 1990;74(3):233–235. doi: 10.1094/PD-74-0233.}

_{11.Bandyopadhyay R, Atehnkeng J, Ortega-Beltran A, Akande A, Falade TDO and Cotty PJ (2019) “Ground-Truthing” Efficacy of Biological Control for Aflatoxin Mitigation in Farmers’ Fields in Nigeria: From Field Trials to Commercial Usage, a 10-Year Study. Front. Microbiol. 10:2528. doi: 10.3389/fmicb.2019.02528}