Zinc bis(benzenesulphinate)

Endpoint summary

Description of key information

in vitro, OECD 442E (hCLAT): positive

in vitro, OECD 442C (DPRA): waiving

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

A study according to OECD guideline 442C to assess key event 1 of skin sensitisation, i.e. the potential of target substance to covalent binding to skin proteins, is not feasible.

Indeed, test substance is a zinc salt and DPRA is not applicable for the testing of metal compound as they are known to react with proteins with mechanisms other than covalent binding.

A study according to OECD guideline 442E (hCLAT) to investigate key event 3 of skin sensitisation, i.e. the potential of target substance to activate monocytes and dendritic cells in the human monocytic leukemia cell line THP-1, was run. Changes in the expression of cell surface markers (CD86 and CD54) were quantified and gave a positive outcome.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

A skin sensitiser refers to a substance that will lead to an allergic response following skin contact. There is general agreement regarding the key biological events underlying skin sensitisation. The existing knowledge of the chemical and biological mechanisms associated with skin sensitisation has been summarised in the form of an Adverse Outcome Pathway (AOP), from the molecular initiating event through the intermediate events to the adverse effect, namely allergic contact dermatitis in humans or contact hypersensitivity in rodents.

Mechanistically based in chemico and in vitro test methods have been considered scientifically valid for the evaluation of the skin sensitisation hazard of chemicals. However, combinations of non-animal methods (in silico, in chemico, in vitro) within the Integrated Approaches to Testing and Assessment (IATA) will be needed to be able to fully substitute for the animal tests currently in use, given the restricted AOP mechanistic coverage of each of the currently available non-animal test methods.

As for target substance, available data is:

- key event 1: not assessable, due to substance features

- key event 2: not assessed.

- key event 3: positive

No assessment on key event 1, i.e. protein binding, could be performed as available test methods are not applicable for the testing of metal compounds. Indeed, metals are known to react with proteins via mechanisms other than covalent binding. Accordingly, an effect on proteins by the metal compound may not be excluded.

The test on key event 3 resulted to be positive; a test on key event 2 was deemed as not necessary, as a negative response would not allow to conclude that the substance is devoid of a skin sensitising potentia.

On these bases, the substance is classified as H317, i.e. substance that may cause an allergic skin reaction, according to the CLP Regulation (EC 1272/2008). Based on available data, no decision on sub-categorisation may be drawn.