#WhiteAlert: All you need to know about aflatoxins

Maize farmers dry their maize. Researchers say drying maize on the ground gets it in contact with the soil, where the fungi that causes aflatoxin are found. The fungal infestation is a serious threat to Kenya’s food security, causing a substantial portion of the harvested grains to go to waste. PHOTO | FILE | NATION MEDIA GROUP

What you need to know:

  • Aflatoxin-producing fungi can contaminate crops in the field, at harvest, and during storage.

  • Aflatoxins are odourless, tasteless and colourless, making them silent but lethal poisons.

  • These fungi are also associated with both acute and chronic toxicity in animals and humans, including acute liver damage, liver cirrhosis and liver cancers.

Sunday night exposé by NTV Investigations Desk on aflatoxin contamination of maize products has caused a wave of panic and concern in Kenya.

The ‘White Alert’ highlighted the dangerously high amounts of the fungi, which is known to cause various cancers, in Kenya’s staple food.

The exposé came a day after Kenya Bureau of Standards (Kebs) suspended licences of five maize millers over the sale of aflatoxin-contaminated flour.

The banned brands include Dola, Kifaru, Starehe, Jembe and 210.

It has also emerged that the government and its agencies have over the past two decades presided over slow aflatoxin-poisoning of Kenyans— with most of the foods in the local market now containing dangerous levels of the fungi.

In the wake of these shocking revelations, there is need to understand what aflatoxins are and how to stay safe.

Here is a brief guide to aflatoxins and aflatoxin poisoning.

  • What is Aflatoxin?

Aflatoxin belongs to a group of fungal toxins known as mycotoxins, and is widespread or commonly found in agricultural products and food such as maize (corn), peanuts, cottonseed, and tree nuts.

Aflatoxin is the secondary metabolite produced by specific strains of Aspergillus that is produced by fungi that grow on grains that are not dried or stored in proper conditions.

This means that they thrive in warm and moist conditions.

According to the World Health Organisation (WHO), aflatoxins pose a significant economic burden, causing an estimated 25 percent or more of the world’s food crops destroyed annually.


Aflatoxin is classified into a number of subtypes— including B1, B2, G1 and G2 that are distinguished by their fluorescent colour under ultraviolet light.

Aflatoxins are odourless, tasteless and colourless, making them silent but lethal poisons.

Chemically, they are stable in foods and resistant to degradation under normal cooking procedures, thus it is difficult to eliminate aflatoxin once it is produced.

A research study conducted by Centre for Food Safety reveals aflatoxin-producing fungi can contaminate crops in the field, at harvest, and during storage.

These fungi are also associated with both acute and chronic toxicity in animals and humans, including acute liver damage, liver cirrhosis and liver cancers.

Government health officials destroy aflatoxin-infested maize in a past incident. FILE PHOTO | NATION MEDIA GROUP

  • What are the levels of aflatoxin in food?

Aflatoxins are found in most countries in the world, if not all. However, studies have shown that there are higher risks of aflatoxins in developing or underdeveloped countries as compared to the developed world.

A possible explanation for this could be the lack of proper infrastructure or handling methods of agricultural products that encourages the growth of aflatoxin-causing fungi.

Developed countries also use chemical processes to remove aflatoxins in foods such as nuts, corn, grains and milk.

Despite this, most foods do still contain very small amounts of aflatoxins that have raised concerns over the possible long-term effects of the poison, even in small amounts.

Foods that are susceptible to aflatoxin contamination include:

•       Cereals and cereal products such as maize, wheat, rice, barley, sorghum, cottonseed, pumpkin seeds and tree nuts

•       Peanuts and peanut products

•       Vegetable oil and fat

•       Poultry and poultry products such as eggs

•       Products from infected animals such as meat and milk

•       Some fruits and vegetables

•       Some herbs and spices

  • How are humans exposed to aflatoxin?

The primary method of aflatoxin exposure is eating contaminated plant products (such as maize) or by consuming meat or dairy products from animals that fed on contaminated feed.

Another likely exposure is when farmers and other agricultural workers inhale dust generated during the handling and processing of contaminated crops and feeds.

  • What are the recent outbreaks of aflatoxin exposure?

In 1974, a major outbreak of hepatitis due to aflatoxin was reported in the states of Gujrat and Rajasthan in India, resulting in an estimated 106 deaths.

In Kenya, the first recorded acute outbreak was reported in 1981, when 12 people died after eating aflatoxin-contaminated food.

The most recent incident took place in Tanzania in 2016, where there were more than 53 cases and eight deaths reported.

A recent research in Kenya revealed that the aflatoxin outbreaks followed poor harvests of maize that had been damaged and made susceptible to mould by drought.

From January to June 2004, 317 people sought hospital treatment for symptoms of liver failure, and 125 died.

  • What are the effects of aflatoxin on human beings?

Exposure to aflatoxins by human beings is associated with an increased risk of cancer, particularly liver cancer.

Once consumed into the human body, the aflatoxin is incorporated into the DNA to form complexes that colonise the liver, leading to the development of mutations that later manifest as cancer.

Studies have also shown that children are particularly affected by aflatoxin exposure, which is associated with stunted growth, delayed development, liver damage, and liver cancer. They also cause reduced efficiency of immunisation in children that lead to enhanced risk of infections.

Short-term or immediate effects caused by an aflatoxin breakout can cause symptoms such as abdominal pain, vomiting, convulsions, edema, pulmonary edema, haemorrhaging, digestion complications, coma and death.

According to the WHO, large doses of aflatoxins lead to acute poisoning (aflatoxicosis) that can be life threatening, usually through damage to the liver

It should be noted that aflatoxicosis is not contagious and drugs and antibiotics do little to help.

Aflatoxicosis damages the liver more than any other organ and also suppresses the immune system.

  • How can aflatoxin be detected?

There are two principal techniques that have been used most often to detect levels of aflatoxin in human beings.

The first method is measuring the AFB1-guanine adduct present in the urine.

The presence of this breakdown product indicates exposure to aflatoxin B1 in the last 24 hours.

However, this technique measures only recent exposure. Due to the half-life of this metabolite, the level of AFB1-guanine measured may vary from day to day, based on diet, it is not ideal for assessing long-term exposure.

The second technique that has been used is a measurement of the AFB1-albumin adduct level in the blood serum.

This approach provides a more integrated measure of exposure over several weeks or months.

Dr Isaiah Muchilwa demonstrates to Purity Jerotich and Sylvia Okello how his mootle checks moisture levels in cereals, vegetables and fruits. According to him, most farmers rely on the sun to dry their maize yet being in the tropics makes the country receive a lot of rains. PHOTO | STANLEY KIMUGE | NMG

  • How can aflatoxin be controlled?

According to the WHO, control measures are required both pre- and postharvest.

In a publication released in February 2018, WHO says that the most long-term, stable solution to controlling pre-harvest aflatoxin contamination is through enhancing the ability of the crop to resist fungal infection and/or prevent production of aflatoxins by the invading fungus.

This can be achieved through plant breeding or through genetic engineering of crops of interest.

However, these processes are laborious and time consuming.

Effective, sustainable and universally applicable pre-harvest intervention strategies are needed.

WHO further notes that post-harvest interventions include preventive measures to address adequate storage conditions— moisture, temperature, mechanical or insect damage, and aeration— which influence contamination and toxin production by mould.

Other measures, such as chemical decontamination or use of enter sorbents, can be used to remove aflatoxins from already contaminated foodstuffs.

  • How can you prevent aflatoxin exposure?

In order to reduce the exposure to aflatoxin, consumers should observe the following measures:

While buying the product:

•       Always purchase from reliable and reputable retailers.

•       Make sure you observe whether foods are stored in cool condition.

•       Reject any unclean, opened or damaged package.

•       Check the storage conditions of your retailer.

While storing the product:

•       Maintain a dry and cool environment (temperature preferably below 20°C and relative humidity below 80 percent)

•       Avoid direct sunlight

•       Watch out the durability of the products

•       Avoid stocking up excessive foods

While consuming the product:

•       Consume foods within the designated "best before date".

•       Discard any foods that look mouldy, damped, shrivelled and discoloured

•       Ensure that your diet is diverse as this not only helps to mitigate aflatoxin exposure, but also improves health and nutrition.


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