19. Tin, Sn

The harmfulness of tin (Sn) on the environment depends on the chemical form in which it occurs. In general, organic Sn compounds are more toxic than metallic tin and inorganic tin compounds. Some studies suggest that tin is an essential trace element for animals and perhaps for humans, but no consensus exists in this regard. Concentrations of inorganic tin in the air, soil, and water are usually low, apart from those areas with naturally high Sn content and regions surrounding tin processing plants. The toxic activity of Sn, caused by environmental exposure to tin, has not been reported in plants, animals, or humans. From an ecotoxicological point of view, the most important compounds are the organotins, mostly due to their androgenic activity and contribution to the increasing number of imposex individuals between marine vertebrates and invertebrates. Literature data about the bioaccumulation of inorganic tin in land ecosystems is very limited, especially in relation to mammals. Also, most of the data concerning the aptitude of some species of animals and biological parameters to be used as bioindicators and biomarkers of environmental exposure to tin usually relate to marine habitats and organic forms of this element. It seems that the problem of land habitat pollution with tin is not well elucidated.