Tin

Endpoint summary

Description of key information

Testing for bioaccumulation is considered to be inappropriate based upon substance type and the use and pattern of environmental exposure.

Additional information

Tin is a natural trace element, and although there is no incontrovertible scientific evidence that tin is an essential element, there are several indications that tin may play a role in physiological and biochemical pathways in animals and humans.

Due to their environmental relevance, virtually all experiments and data related to tin accumulation and bioconcentration in plants and animals deal with organic forms of tin, and not with inorganic Sn-salts. When standard experimental studies on bioaccumulation are not available it is sometimes possible to calculate indicative bioaccumulation factors based on monitoring data. Numerous studies have analysed the levels of tin in aquatic biota in the field, especially in marine systems. However, these studies cannot be used to determine the degree of bioconcentration or bioaccumulation of inorganic tin species in aquatic systems due to the potential presence of organo-tin compounds in the environment. Organo-tin compounds, such as tributyltin, are known to be bioaccumulative and analysis of total tin concentrations in biota will include tin from organo-tin sources. Tributyltin is also persistent under anaerobic conditions, so may be present in the environment for some time after exposure has stopped. It is also possible that metabolism of organo-tin compounds could result in inorganic tin being present in biota. Environmental monitoring data must, therefore, not be used to assess the bioaccumulation potential of tin metal and inorganic tin compounds.

 

Dissolved forms of tin commonly undergo hydrolysis in aqueous systems to form solid precipitates of tin oxides or hydroxides. These solid precipitates are unlikely to be available for bioaccumulation.