**1. Introduction**

### **1.1 Aflatoxins**

Aflatoxins (AFs) are a group of mycotoxins produced by *Aspergillus* species mainly by *A. flavus* and *A. parasiticus* [1] and to a lesser extent, by *A. bombycis*, *A. ochraceoroseus*, *A. nomius*, and *A. pseudotamari* [2]. Eighteen AFs have been identified so far, but the ones with major significance are aflatoxin B1 (AFB1), aflatoxin B2, aflatoxin G1, aflatoxin G2, aflatoxin M1, and aflatoxin M2 [1, 3]. AFs are difuranocoumarin molecules that are produced by the polyketide pathway of fungi. Molecular differences among AF groups exist; for example, the B-aflatoxins exhibit a cyclopentane ring while the G-aflatoxins have a lactone ring (**Figure 1**) [3]. In addition to that, B-aflatoxins display blue fluorescence under ultraviolet light, while G-aflatoxins exhibit a yellow-green one.

**Figure 1.** *Aflatoxins molecular structures.*

*Aspergillus* species are very diverse and can adapt to a wide range of environmental conditions [4] but mainly they are found in hot humid climates typically in tropical and subtropical regions, most significantly, between 40°S and 40°N latitude [5]. *Aspergillus* sp. optimal growth happens at a temperature of 25°C with a minimum water activity of 0.75, however, their secondary metabolites production starts at 10–12°C with the most toxic metabolites produced at 25°C with 0.95 water activity [1]. Those growth patterns differ between different strains of *Aspergillus* sp., for example, optimal growth temperature of the most significant strains, *A. flavus* and *A. parasiticus*, occurs at 33°C and 35°C, respectively [6, 7].

On-field, normally, *A. flavus*, that naturally colonize the aerial parts of the plant including leaves and flowers, produces B aflatoxins while *A. parasiticus*, which are usually found in the soil environment, produce B and G aflatoxins. As for aflatoxin M1 and M2 they are produced *in vivo* as the hydroxylated metabolites of aflatoxins B1 and B2, respectively. Naturally, the colonization rate of *Aspergillus sp.* and the degree of contamination with AFs are determined by several factors including; temperature, aw, and humidity. Additionally, contamination is promoted due to stress or physical damage to the crop especially due to drought episodes, insect infestation, rain showers during pre-harvest, poor harvest timing, and insufficient drying before storage [1]. *Aspergillus* species can further colonize the crop during storage, specifically under uncontrolled conditions that allow their domination such as increased humidity and temperature. Many types of crops and plants that are used as a source of human food or animal feed are prone to colonization by *Aspergillus* sp. and subsequent contamination with AFs, such as wheat, barley, maize, rice, sorghum, soy, peanuts, nuts, oilseeds, legumes, spices, herbs, etc. [1, 2, 8–10].

#### *1.1.1 Aflatoxin B1 (AFB1)*

Among all identified aflatoxins, AFB1 is considered the most common and it accounts for almost 75% of worldwide AF contamination in food and feed [3].

#### *Aflatoxins in the Era of Climate Change: The Mediterranean Experience DOI: http://dx.doi.org/10.5772/intechopen.108534*

AFB1 production is the result of a complex biosynthetic pathway that involves at least 27 enzymatic reactions [11]. The genes responsible for enzymatic coding are grouped in a cluster and their expression depends on two cluster-specific regulators: *aflR* and *aflS* [11]. Additional genes are also involved in the pathway including *aflD* [11]. AFB1 is the most potent carcinogen among all mycotoxins [12, 13]. It is also the most hepatotoxic and hepatocarcinogenic agent, therefore, it poses the highest concern for food safety and health. Worldwide, AFB1 have been the main aflatoxin causing most cases of aflatoxicoses. According to Paulin et al., AFB1 can cause "acute toxicity, chronic toxicity, carcinogenicity, teratogenicity, genotoxicity, and immunotoxicity" [1]. Many epidemiological studies have demonstrated AFB1 as the major contributor to hepatocarcinoma cases [14] and it had been estimated that 4.2–28.2% of HCC cases worldwide are caused by AFB1 [15]. And due to its well-documented carcinogenicity, the IARC classified AFB1 as carcinogenic to humans (group 1) [16].

Upon intake of contaminated food, AFB1 gets rapidly absorbed through a passive mechanism in the gastrointestinal tract. It is then metabolized in the liver where it gets converted by cytochrome P-450 into aflatoxin-8, 9-epoxide, hydroxylated into a less potent form AFM1, and demethylated into aflatoxin P1 that is excreted in the urine [12, 14]. The resulting epoxide is highly reactive so it binds to DNA or protein molecules. Binding to a protein molecule in the liver eventually causes hepatotoxicity while binding to a DNA molecule affects the genetic code through transversion of a guanine (G) molecule to thymine (T), therefore, mutating the P53 gene that codes for tumor suppression hence allowing the formation of tumors and leading eventually to hepatocellular carcinoma (HCC) (**Figure 2**) [12, 14, 17].

#### *1.1.2 Aflatoxin M1 (AFM1)*

AFM1 is the hydroxylated metabolite of AFB1 formed in the liver (**Figures 2** and **3**). Once produced, it gets absorbed by the mammary glands and secreted in the milk of mammals. AFM1, therefore, contaminates milk and dairy products such as cheese and yogurt due to its capacity to stay intact during milk pasteurization, treatment, and fermentation [18]. AFM1 is less toxic than AFB1 and possess 2–10% of its carcinogenic potency [19]. Nevertheless, AFM1 is capable of binding to DNA leading eventually to hepatocellular carcinoma. The findings of many studies that discussed the carcinogenicity of AFM1 led to its reclassification as carcinogenic to human (group 1) by the IARC in 2002 after it was for long classified as possibly carcinogenic to humans (group 2B) [16]. AFM1 presents a particular risk for infants and children due to the vulnerability of their immune systems, their low body weights, and their high consumption of milk.

#### **1.2 Health effects of AFs**

Aflatoxins' presence is recognized as a global food safety concern by the World Health Organization since they exhibit several toxic effects on animals and humans. The diseases caused by exposure to aflatoxins are referred to as "aflatoxicosis" that could be acute or chronic. The toxic effects exhibited by AFs depend on several factors such as age, gender, intake dosage, exposure duration, and nutritional status. Acute aflatoxicosis is prevalent when individuals are exposed to food contaminated with high doses of AFs and its symptoms include abdominal pain, vomiting, diarrhea, pulmonary edema, cerebral edema, anorexia, fatty liver, jaundice, depression, and photosensitivity [20]. Acute poisoning is more prevalent in developing countries due

to the increased risk of contamination of staple food, lack of food security, absence of AF awareness, and lack of regulatory limits. For example, in Eastern Kenia in 2004, acute liver failure was diagnosed in 317 individuals of which 125 people died later due to acute aflatoxicosis caused by consuming contaminated home-grown maize [21]. Acute aflatoxicosis presents a risk to animals, as well, due to their exposure to AFs through contaminated feed, and the susceptibility varies among different species. Acute aflatoxicosis in animals lead to several complications including decreased

#### *Aflatoxins in the Era of Climate Change: The Mediterranean Experience DOI: http://dx.doi.org/10.5772/intechopen.108534*

weight gain, reduction in egg or milk production, decreased feed conversion, and increased vulnerability to infectious diseases [20].

Chronic aflatoxicosis, on the other hand, is caused by being exposed to low doses of AFs for an extended period and results in immune suppression and cancer. The liver is the primary target organ for AFs and chronic consumption could lead to liver cancer, especially when coupled with hepatitis B and/or C virus since those viruses interact synergistically with AF causing an increased risk of hepatocellular carcinoma (HCC) [21]. Many toxicological studies demonstrated the carcinogenicity of AFs in many species including mice, rats, hamsters, monkeys, and ducks. AFs have been demonstrated as mutagenic compounds that can alter DNA leading to changes in chromosomes and mutations in genetic codes [22]. Enough evidence, therefore, lead to the classification of AFs as "group 1 carcinogen to humans" by the IARC [16]. AFs can also lead to other liver diseases such as cirrhosis and hepatomegaly [21]. Additionally, chronic exposure to AFs have been shown to affect immunity through decreased antibody production, reduced cell-mediated immunity, and decreased resistance to fungal, bacterial, and parasitic secondary infection [20, 21]. AFs exposure may also lead to low birth weights since exposure can occur in the uterus through a trans-placental pathway. Impaired child growth can be also caused by being exposed to AFs, especially since exposure is higher in children due to their low body weights which leads to more toxic effects. For example, a follow-up study in Benin showed that there was a strong negative correlation between aflatoxin-albumin adducts and height increase in children over 8 months period [23, 24]. Similarly, in the Gambia, a follow-up study demonstrated a strong effect of AF exposure during pregnancy on the infant's growth rate during their first year of life [24, 25].

### **2. The Mediterranean region**

#### **2.1 Region and climate**

The Mediterranean is an intercontinental sea located between Europe, North Africa, and Western Asia [26]. Its surface area covers around 2.5 million km2 and is surrounded by a total of 22 countries including Lebanon, Cyprus, Egypt, Morocco, Spain, Italy, France, etc. [27, 28].

The Mediterranean climate is characterized by mild wet winters and warm dry sunny summers with temperature and humidity variations among different countries [28]. The sea itself is surrounded by vast land areas and acts as a heat reservoir and a source of moisture for them [28]. The climate in the North and South Mediterranean differs mainly due to the fact that the former includes countries with a west coastal climate (e.g. Spain, Turkey, Cyprus) while the latter includes countries with a subtropical desert climate (e.g. Morocco, Syria) [28, 29]. The summer duration range from 2 to 7 months starting from North to South region.

#### **2.2 Agricultural sector**

Agriculture in the Mediterranean countries plays a crucial role in the economy as it provides a main source of income and employment, and ensures food security in the region. Around 28% of the Mediterranean land is devoted to agriculture with discrepancies between different countries depending on economic development, industrialization, urbanization, etc. [30].

Agriculture in the Mediterranean basin depends on irrigation, especially in the long hot dry summer seasons. Precipitation across the region is also subject to high inter-annual and seasonal variations, therefore, making it essential for farmers to provide irrigation to maintain crop diversification and assure high quality and yields of crops. Generally, around 21% of cultivated agricultural lands in the area are irrigated, with the main irrigation system being surface irrigation despite its low efficiency.

The Mediterranean region has some unique environmental characteristics that shape its agricultural production. First, its seasonal variation is characterized by rainy mild winters and long hot dry summers. Second, its terrain, in which the presence of coastal plains that support summer agriculture are backed up by low hills or mountains that help provide at sometimes snow water for irrigation in the summer.

Climate patterns also affect agricultural products along the Mediterranean Basin, for example, temperate crops can be cultivated in rainy seasons, while sub-tropical crops can be grown in summer seasons. Several agricultural commodities are produced in the Mediterranean region, first, traditional permanent crops like olives, grapes, fruits, vegetables, and dates. Most of the grapes grown in the Mediterranean region are used for wine production, additionally, grapes are also cultivated for table grapes, currants, and sultanas. Similarly, olives are used to produce olive oil and which amounts to 99% of the world's output with the main producers being Italy, Spain, and Greece [30]. As for fruits and vegetables, the Mediterranean basin production accounts for approximately 16% and 13% of the world's fruits and vegetable production, respectively. The Mediterranean region also accounts for 85% of world hazelnut output, 36% of dates, 55% of pulses, etc. [30].

Second, cereals are produced in the region specifically wheat, maize, barley, and rice which contribute to 90% of cereal production [31]. While most of the Mediterranean countries produce cereals, their yields are not enough for local consumption, therefore, most of the countries depend on imports and store cereals for long durations to ensure an adequate and continuous supply. On an overall scale, 16% of total world wheat output is produced in the Mediterranean, with France being the main producer and the only exporter country followed by Turkey, Spain, Italy, and Egypt [30].

#### **2.3 Aflatoxins in the Mediterranean**

The climate of the Mediterranean is in general inductive to fungal attacks and mycotoxin production, in addition to other factors, such as prevalence of pests, irrigation systems, droughts, agricultural practices, storage techniques, etc. Generally, the most important mycotoxins in the Mediterranean basin are aflatoxins, ochratoxin A, trichothecenes, and fumonisins with variations in the type and level of each mycotoxin in each country and in different regions [32]. Aflatoxin contamination specifically of dried fruits is most frequent in the southern and eastern parts of the basin including African and Asian countries [32]. Crops such as peanuts, pistachios, and maize are also reported to be contaminated with aflatoxins in the Mediterranean basin [32].

AFM1 is also frequent in Mediterranean countries and has been reported in many studies among different countries due to the presence of AFB1 in the feed either due to field contamination or improper storage practices.

#### **2.4 Aflatoxins regulations in Mediterranean countries**

Previous studies done in the Mediterranean region have showed a frequency of aflatoxins contamination specifically AFB1 and AFM1. As a control measure,

