Manganese is also used in portland cement mixtures. Manganese is an important element for human health, essential for development, metabolism, and the antioxidant system. Nevertheless, excessive exposure or intake may lead to a condition known as manganism, a neurodegenerative disorder that causes dopaminergic neuronal death and symptoms similar to Parkinson's disease. The classes of enzymes that have manganese cofactors is large and includes oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases, lectins, and integrins. The reverse transcriptases of many retroviruses (though not lentiviruses such as HIV) contain manganese. The best-known manganese-containing polypeptides may be arginase, the diphtheria toxin, and Mn-containing superoxide dismutase (Mn-SOD).
Methylcyclopentadienyl manganese tricarbonyl combustion in gasoline, MMT is classified as an acute toxicant by the oral, dermal, and inhalation routes of exposure under the European Union's Classification, Labeling and Packaging Regulation (EC/1272/2008), implementing the Global Harmonized System (GHS) of Classification and Labeling. The US ATSDR (Agency for Toxic Substances and Disease Registry) notes that MMT is very unstable in light and degrades to a mixture of less harmful substances and inorganic manganese in less than 2 minutes. Therefore, human exposure to MMT prior to combustion in gasoline would not likely occur at significant levels. Regarding occupational exposure to the raw concentrated chemical prior