# Hg Content in EU and Non-EU Processed Meat and Fish Foods
## 1 Introduction  
Processed products are now an important part of the human diet. Food processing allows the state of raw materials to be altered to increase their shelf life or change their sensory characteristics [1]. The term \"processing\" refers to a series of operations (e.g., washing, grinding, heating, freezing, filtering, fermentation, extraction, centrifuging, cooking, drying, packaging) carried out on raw materials [1], i.e., all methods and techniques used by the food, beverage, and associated industries to transform whole fresh foods into food products [2]. These processes not only extend the shelf life of a product and maintain its quality but also allow most microorganisms to be eliminated [3]. Although there are many processed foods [4; 5; 6; 7], meat and fish are certainly among the main food matrices subject to processing, given their great importance in the diet, being a source of protein and other nutrients. However, as the consumption of processed food increases, their exposure to different types of hazardous contaminants is also of great concern. They, in fact, may contain more contaminants than natural foods. Such contamination can be of different types: chemical (e.g., from the addition of additives); process (contamination during cooking, heating, or storage of foods or during their transportation); or from the environment [8]. These, representing different sources of contamination, can consistently affect food quality and safety [3; 9]. Among the many contaminants, toxic elements pose a serious threat to human health. They are nonbiodegradable xenobiotics and can accumulate in the environment, eventually reaching food [9; 10; 11]. In fact, it is the ingestion of contaminated food that is a major source of human exposure to toxic elements [9]. For this reason, knowing the degree of pollutioncaused by toxic elements in processed samples is, therefore, crucial to be able to assess the possible risk to which consumers are exposed because of the overuse of such products [12]. Among the toxic elements regulated at the European level is mercury, a metal present in liquid form and silivery-white in color, which is highly toxic to the environment and living beings [13]. This element can occur in different forms: elemental, inorganic, and organic. Exposure to inorganic Hg can take place through occupation; exposure to organic Hg is mainly by ingestion of food and water [14]. Depending on its form, its characteristics vary in terms of circulation in the ecosystem, accumulation, exposure to the human body, biological effects, and toxicity [15]. However, the primary source of mercury exposure for humans is food. Forms most found in food, albeit at very low levels, are the cation Hg\({}^{2+}\) and organic methylmercury, CH\({}_{3}\)Hg [16]. Only fish products have higher mercury concentrations. CH\({}_{3}\)Hg is the form of mercury of greatest concern because it readily crosses blood-brain and placental barriers and has an extremely high absorption efficiency (>90%) when ingested in food. This partly explains the higher relative risk associated with exposure to CH\({}_{3}\)Hg compared to inorganic Hg species. Less than 10% of inorganic Hg in food is absorbed by the body, while the rest is rapidly excreted within 24 h [17]. The International Agency for Research on Cancer (IARC) does not list elemental mercury and inorganic Hg compounds as human carcinogens (Group 3). However, in 2010, the Panel on Contaminants in the Food Chain (CONTAM) of the European Food Safety Authority (EFSA) indicated a TWI value for inorganic mercury of 4 \(\upmu\)g/kg body weight [18]. In contrast, methylmercury compounds are grouped in the category \"possibly carcinogenic\" (Group 2B) [19], with a TWI of 1.3 \(\upmu\)g/kg body weight/week [16; 20]. CH\({}_{3}\)Hg binds to the sulfhydryl groups of proteins and accumulates in organisms [21].