# Potential Metal Contamination in Foods of Animal Origin--Food Safety Aspects
## 1 Introduction  
Various metals and non-metallic metalloids are an integral part of human civilization due to their widespread occurrence and use in nature. In the past, different metal-based pesticides were used in large quantities on crops to control pests and microorganisms. Due to the rapid development of toxicology, numerous research and studies have demonstrated the high toxicity of certain metals to various organisms living in the environment. Based on these results, the majority of metal-containing pesticides have been restricted or even banned by the competent authorities. However, due to their previous widespread use, the entire biosphere has been contaminated. Furthermore, they have been found in different natural sources. During various industrial processes (e.g., mining, processing industry, etc.) using metal-containing natural sources (ores, stones, rocks, etc. ), environmental areas (water, soil,air) can again be polluted with dust, slag, soot, smoke, particulate matter, and combustion products. Similarly, plants, water, and soil can be contaminated by industrial wastewater emissions. Municipal and industrial emissions from anthropogenic activities are of greater significance than the release of metals of natural environmental origin [1]. The release of toxic heavy metals into the environment began several centuries ago, but it remains highly significant today. The heavy metal contamination of agricultural areas, groundwater, and surface waters can lead to severe environmental pollution, damaging the ecosystem and endangering or destroying the lives of animals and plants. Heavy metals are not biodegradable (rather persistent), they accumulate in living organisms, and they are transformed into more toxic or, in fewer cases, less toxic forms through biochemical processes [2; 3]. Persistent heavy metals (e.g., Hg, Pb, Cd) released into the environment can also enter the bodies of higher animals through the food chain. Organisms at higher trophic levels, such as humans, are thus exposed to higher concentrations of pollutants. Currently, due to their environmental polluting effects and cumulative properties, the enrichment of metals in the food chain is a critical issue from a health protection standpoint. Various metals and heavy metals also occur as natural environmental components, but they primarily enter foods of animal origin and the human body because of anthropogenic activities (e.g., industrial and agricultural activity, household use, transport, waste incineration, etc.). Some metals (e.g., zinc, calcium, cobalt, chromium, copper, selenium, iron) are essential for life in small concentrations; they activate various proteins and enzymes, maintain ion and pH balance, ensure bone and teeth strength, and regulate metabolic homeostasis. The physiological roles of others (e.g., arsenic, mercury, cadmium, nickel, lead, etc.) are currently unknown, although some (e.g., arsenic) may have beneficial effects. Arsenic in small amounts exhibits anabolic effects in animal studies, by inhibiting oxidation, stimulating appetite, increasing body weight gain, and enhancing red bone marrow, thereby increasing the number of erythrocytes and reticulocytes, but it is not established as essential for humans [4; 5; 6; 7]. However, heavy metal exposure has not ceased due to its historical widespread use in plant protection and other industrial processing. The current focus is on the chronic toxic and harmful effects of long-term, low-dose metal exposure and their cumulative nature, which may lead to micro-toxicological alterations, or even mutagenic and carcinogenic effects, immunotoxicity, and reproductive issues [8]. The number of registered chemicals exceeds 10 million, of which 70.000-80.000 are compounds with which humans may come into direct contact [5]. Most of these substances can potentially enter food and adversely affect consumer health.