Some elements in small concentrations are vital for the normal functioning of the human body, but in high concentrations they can pose a threat to its development and normal functioning, this is the case of manganese. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Manganese is found at low levels in virtually all diets and plays an essential role as a cofactor in many enzymatic reactions in humans and other organisms. This element exists in different forms, both physical and chemical, in the earth's crust, in water and in particulate matter in the atmosphere. Due to its outer electron shell configuration, it can donate up to 7 electrons (USEPA, 1984[1]) and assume different oxidation states, but in living organisms Mn is found mainly as Mn2+, Mn3+ and possibly as Mn4+ (Archibald and Tyree, 1987[2]). While essential biological functions related to Mn depend on its oxidation state, little is known about how the oxidation state of high Mn exposures influences cellular uptake and function/toxicity (Reaney, 2002). Ingestion of manganese is the main route of human exposure, although inhalation also occurs, predominantly in occupationally exposed groups. Regardless of intake, Mn levels in biological tissues remain stable thanks to homeostatic mechanisms that effectively regulate the absorption and excretion of this metal. It is also known, however, that chronic exposure to high levels of manganese (Mn) in air causes adverse neurological, reproductive, and respiratory effects ( Mergier et al., 1994 , Bader et al., 1999 , Aschner and Dorman, 2006 ). , ). This was discovered as early as 1837 when Couper observed neurological problems in workers employed in grinding manganese oxide used in the production of bleaching powder (Guilarte 2010). Industrial emissions are the main source of anthropogenic release of manganese into the air, especially dust and smoke containing manganese dioxide and manganese tetroxide – mainly occurring during ore mining, crushing and smelting, as well as during steel production (Schiele, 1991). Alternative sources of manganese incorporation into the air are the combustion of fossil fuels and the resuspension of manganese-containing soils (ATSDR, 2000[3]). Several studies of exposure cases related to mining and manufacturing activities have found a relationship between inhalation of Mn and an increased risk of a broad spectrum of clinical symptoms. Among others, some nonspecific neurological symptoms such as postural instability, mood and psychiatric changes (e.g., depression, agitation, hallucinations) have been reported (Mena et al., 1967), and activation or acceleration of disease-like symptoms Parkinson's disease (PD) (Rodier, 1955; Tanaka & Lieben, 1969; Huang et al., 1989, 1998; Roels et al., 1987a, 1992; Wang et al., 1989; Mergler et al., 1994; Hochberg et al., 1996; Bader et al., 1999), such as bradykinesia, rigidity, tremor, gait disturbances, postural instability and dystonia and/or ataxia (Josephs et al., 2005). However, for some researchers, this relationship remains questionable, taking into account current clinical, toxicological and epidemiological evidence, which is not conclusive regarding the existence of such a relationship, based on the fact that out of 1 million welders worldwide and as of 2007, only approximately 15 case reports describing clinical neurological symptoms in exposed individuals had been published in the medical literature. The numerous epidemiological studies conducted on welders over the last half century have focused.