**Abstract**

Aflatoxins, a carcinogenic group of mycotoxins, are naturally occurring toxic fungi that cause illness in both animals and humans. Predominantly found in hot and humid areas, aflatoxins are generated by Aspergillus fungi and are found in a large percentage of the world's food supply. Aflatoxin B1 (AFB1), being the most potent of the over 18 aflatoxins discovered, is most noted for its role in the development of hepatocellular carcinoma (HCC) in humans and animals, unfortunately, many features of the illnesses it causes and the mechanisms that produce them, remain unexplained. This review examined AFB1 metabolism; its epoxidation and DNA adduction, its correlations to cancer initiation and the mechanisms that underpin it, the synergistic interactions with stunted growth associated with AFB1 intake and kwashiorkor, involvement of oxidative stress and reactive oxygen species. Its harmful effects, including growth retardation, starvation, and immunotoxicity, were also discussed, delving into new findings of AFB1 contamination in worldwide food sources. This review indicated that AFB1 is commonly found in high concentrations in food supplies, notably in maize. To lessen the global burden of AFB1 toxicity, data gathered through this review emphasized the necessity to apply novel and existing techniques to prevent these toxins on other diseases.

**Keywords:** aflatoxin, toxicology, teratogenicity, malnutrition, kwashiorkor, oxidative stress

### **1. Introduction**

Mycotoxins are unrelated structural secondary metabolites produced by various molds, most of which belong to one of three genera; Aspergillus, Penicillium, or Fusarium [1]. There are two kinds of mycotoxin-producing fungi; field fungi, such as Fusarium species, produce mycotoxins on crops that are still growing, and storage fungi, such as Aspergillus and Penicillium species which produce mycotoxins after the crops have been harvested [2].

Aflatoxins, and being widespread in many human foods, are the biggest threat to food safety. Aflatoxins, since their discovery, have been found to be highly toxic to humans; being linked to liver cancer in humans for instance. Being common in agricultural products, such as maize, groundnut, millets, and their derivatives serving as the primary carriers, aflatoxins are prevalent in tropical and subtropical countries, posing high risks as food and feed pollutants, resulting in an excessive frequency of several deadly chronic diseases and aflatoxicosis epidemics [3].

## **2. Occurrence in food**

The FAO's forecast for world cereal production in 2021 has been reduced by 2.1 million tonnes since November, to 2 791 million tonnes, still 0.7 percent (19.2 million tonnes) higher than the previous year's output and a new high. However, the forecast for world coarse grains production remains 1.4 percent higher on an annual basis. In the case of wheat, recent reports from Brazil and the United Kingdom of Great Britain and Northern Ireland indicating smaller harvests than expected have resulted in a slightly lower global production forecast, now pegged at 769.6 million tonnes, reinforcing an expected 1 percent year-over-year decline. In the case of rice, government estimates in Pakistan show that a record crop was harvested this season, defying FAO predictions of a minor decline in output due to water restrictions in several areas. This change, when combined with a yield-based increase for the United States of America, compensates for somewhat lower output projections in Thailand [4]. These figures demonstrate the significance of cereals and other grains in the world food supply. AFB1, on the other hand, is known to infect cereals and grains products, as well as other commonly consumed foods like groundnuts, dried fruits, and spices. The studies that found AFB1 contamination in these commodities are listed below.

#### **2.1 Maize**

Maize has the highest observed concentrations of AFB1. In Croatia, Pakistan, and the Democratic Republic of Congo, maximum AFB1 levels >1000 g/kg were discovered (2072, 1405.3, and 1401.45 μg/kg, respectively). For the investigation in the Democratic Republic of Congo, samples were evaluated after harvest, during transportation, and lastly at the market. The incidence of AFB1 infection increased considerably between freshly harvested maize (32%), and market samples (100%) [5]. Both examinations that used Pakistani samples discovered high levels of contamination. Maximum values of 1405.3 μg/kg were discovered in Lahore, Pakistan, while maximum levels of 409.3 μg/kg were discovered in Punjab, Pakistan [6]. The maize samples were collected during an unusually hot and dry season, according to the Croatian study, which could explain why the levels were so high (2072 μg /kg) [7]. In investigations into maize contamination, 46.1% of samples tested positive for AFB1, with an average maximum concentration of 553.9 μg/kg [8].

#### **2.2 Rice**

AFB1 contamination in rice has recently been identified in various Asian nations. Aflatoxin-producing fungus and aflatoxins were discovered in 187 rice samples in

*Aflatoxins: Toxicity, Occurrences and Chronic Exposure DOI: http://dx.doi.org/10.5772/intechopen.105723*

a Brazilian analysis. In these samples, 383 Aspergillus fungus strains were found, with 17% of those strains capable of producing type B aflatoxins. AFB1 contamination was discovered in 14% of rice samples, with AFB1 levels ranging from 0 to 63.32 μg/kg [9]. 230 rice samples were collected from various locations in Brazil during an outbreak in 2007–2009, according to another study. Many samples were contaminated with mycotoxins like ochratoxin A, deoxynivalenol, and zearalenone, and up to 180.74 g/kg of AFB1 was found [10]. AFB1 was detected in 56 of the 199 rice samples examined in Canada, with concentrations ranging from 7.1 to 7.1 μg/ kg. AFB1 levels in Chinese rice ranged from 0.1 to 136.8 g/kg, with fumonisin B1 infection found in several of the samples. Ecuadorian rice samples had amounts as high as 47.4 grams per kilogram, while Iran and India reported levels as high as 6.3 and 308 grams per kilogram, respectively [11]. Three distinct investigations on rice contamination with AFB1 were conducted in Pakistan. AFB1 contamination was discovered in 35 percent, 52 percent, and 95.4 percent of the samples, with maximum AFB1 levels of 21.3, 32.9, and 24.54 μg/kg, respectively, in these three studies. Rice samples from Sweden and Malaysia were also found to be contaminated with AFB1 [11].

#### **2.3 Wheat/Sorghum/Cereals**

In a few recent studies, AFB1 has been discovered in wheat, sorghum, and cereals. Even though it was only evaluated in a few trials, sorghum had the highest average frequency of AFB1 contamination (67.3%) and the second-highest average maximum concentration (83.6 μg/kg) of all food products [12]. Wheat had the lowest average maximum concentration of 6.0 μg/kg, although having the highest AFB1 contamination rate (44.8%) [13].

#### **2.4 Groundnuts**

The contamination of groundnuts with AFB1 has been studied. Peanuts are the most commonly contaminated groundnuts; however, pistachios and hazelnuts have also been discovered to be contaminated. AFB1 was found in ten of twentyone peanut butter samples in a Japanese study, albeit the amounts were not higher than 2.59 μg/kg. Aflatoxin contamination was not found in unprocessed peanut samples, which were also analyzed in the study [11]. The occurrence of AFB1 was investigated in three different areas of China in one study. AFB1 contamination was discovered in 100 percent of the peanut samples tested in this study, however at modest levels (up to 0.7 g/kg). Malaysia has also identified peanut contamination, with levels as high as 15.33 μg/kg. Groundnut contamination was investigated in Burkina Faso and Mozambique in a study. Burkina Faso had moderate AFB1 levels of up to 15.5 μg/kg, whilst Mozambique had high AFB1 levels of up to 123 μg/kg [11]. Turkey's groundnuts were the topic of two separate studies in 2014 and 2016. Contamination was discovered in 16.9% of the 302 samples tested in the previous study, with AFB1 levels ranging from 0.16 to 368 μg/kg. In the latter study, only 6.5 percent of the 170 samples tested positive for AFB1 contamination, with values ranging from 0.09 to 10.6 μg/kg [14]. Thailand samples revealed a low percentage of groundnut contamination (9%), whereas Zimbabwe samples had high AFB1 levels of up to 175.9 g/kg, although having a low degree of contamination (12.5%) [15].

## **2.5 Fruits/spices**

Although fruits and spices have been studied, they are not a source of AFB1 exposure. Spices (cumin, black pepper, and chili pods/powder) had the second-highest average frequency of contamination (64.4%), as well as the highest average maximum AFB1 concentration (25.4 μg/kg) [11]. Dried fruits (such as figs, raisins, currants, sultanas, plums, dates, and apricots) had the second-lowest frequency (36.0%) and average maximum value of 16.3 μg/kg [16].

## **2.6 Reports of AFB1 occurrence in food commodities**

Table for rice


#### Table for maize


#### Table for wheat

