Tin

Carcinogenicity

Description of key information

According to  column 2 (specific rules for adaptation from column 1) point 8.9.1, under Annex X of the regulation EC no. 1907/2006, a study may be proposed if:

- the substance has a widespread dispersive use or there is evidence of frequent or long-term human exposure; and

- the substance is classified as mutagen category 3 or there is evidence from the repeated dose study(ies) that the substance is able to induce hyperplasia and/or pre-neoplastic lesions.

As the substance was found to be non-mutagenic from the conclusions of the genetic toxicity tests, and no neoplastic histopathology was noted in the repeated dose studies, and there are no such known reports in humans in the public domain, testing for this endpoint is not required.

Furthermore, in the supporting information provided by Oppenheimer BS et al. (1956), tin foil discs failed to produce any response when subcutaneously implanted; in addition, several other metal foils all from a similar position to tin in the periodic table induced tumours in mice.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Data waiving:

other justification

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Data waiving:

other justification

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Data waiving:

other justification

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No 1272/2008, the substance does not require classification with respect to carcinogenicity as the available data indicates that there is no reason for concern.

Additional information

Oppenheimer BS et al. (1956) was provided as supporting data only. The study was not performed in compliance with GLP or a current guideline, and the level of reporting lacked some detail; as such the study was assigned a reliability score of 4 under the criteria of Klimisch et al. (1997).

In accordance with point 8.9.1., column 2 (specific rules for adaptation from column 1) of Annex IX, regulation EC no. 1907/2006, the study may be proposed if:

the substance has a "widespread dispersive use" or there is evidence of frequent or long term human exposure, AND the substance is classified as germ cell mutagen category 2 or there is evidence from the repeated dose study(ies) that the substance is able to induce hyperplasia and/or pre-neoplastic lesions.

Although use maybe considered widespread and dispersive, the material is not mutagenic and does not cause proliferative lesions (McRae, 2010, Robertson, 1960). Hence carcinogenicity work is not triggered.

It can be seen from the toxicokinetic data (which utilised extreme exposures), when put into the context of normal human background dietary exposure and plasma concentrations, that metalic tin would not be absorbed by the oral route to any detectable degree under normal occupational exposure conditions (see the toxicokinetics, metabolism and distribution section i.e. absorption for risk assessment purposes can be considered zero). The additional pathology conducted in the acute inhalation toxicity study (Gaunt, 2009) also showed that there would be no practical systemic absorption of metallic tin, via the inhalation or for that matter dermal routes of exposure. Tin did not exhibit any toxic effects in the 28 day oral gavage study in rats up to the limit dose of 1000 mg/kg bw/day. The substance has no significant solubility. Industrial working practices and food standards ensure that the the potential for exposure is extremely limited (see Waivers for Subchronic and Chronic toxicity) There is no anticipated consumer exposure where tin is in massive solid metallic form either pure or in an alloy).

There are no effects anticipated from the structure of metallic tin (metallic tin is anyway an inorganic substance), and there are no other dangerous properties anticipated that would notionally only manifest after chronic dosing.

Available human data also rules out any long term toxicological effects including tumours. Robertson J (1960) studied stannosis (tin oxide induced pneumoconiosis) in workers from a tin smelting works. Even with positive X-ray findings, workers with many years of exposure suffered no health effects, deposition of the dust in the lungs did not lead to a fibrous response (i.e. no adverse pathological effects), indicating no cellular interaction. Observations were performed on workers exposed later in the production line, such as ingot casters exposed to pure molten tin, which reports that there is little dust or fume exposure during this process and changes were not observed in these workers. Though the working conditions are not comparable to today’s practices (much improved), it gives a worst case scenario of exposure during various points of the lifecycle of tin metal.