Chromium(3+) neodecanoate

Endpoint summary

Description of key information

Skin sensitizer

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The objective of the key study was to evaluate the in vitro sensitization potential of the test item applied onto 3D human reconstructed epidermis (EpiSkin™) using the SENS-IS assay, based on the quantitative analysis of specific gene biomarkers.

The expression profile of 61 genes divided in three sets were analysed: one set of 23 genes related to the irritation process and the two other sets of genes, named “SENS-IS” and “ARE”, with 21 and 17 biomarkers respectively, involved in skin sensitization.

The expression level of these separate sets of genes was determined by qRT-PCR (quantitative real-time polymerase chain reaction) after a 15 min incubation period with the test item and a 6 hours post-incubation period at 37 °C.

The fold expression of each gene were calculated as a ratio between the mRNA level of test item-treated epidermis versus control (vehicle treated) epidermis.

The results obtained for the positive and negative controls were within acceptance criteria and validated the study, with the exception of DMSO in the experiments 2SI18007.

Considering the number of over-expressed gene in the “SENS-IS” and “ARE” gene groups, the test item gave positive result (more than 7 genes induced) when it was tested diluted at 50% (v/v). Moreover, positive results were also obtained when the test item was tested at 10 % in one experiment out of two and at 100% (not diluted).

Under the experimental conditions of this SENS-IS assay, the test item resut to be a skin sensitizer.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The assessment of skin sensitisation has typically involved the use of laboratory animals. In order to reduce the use of animals on the assessment of toxic effects induced by chemical new strategies have been developed.

Mechanistically-based in chemico and in vitro test methods addressing the first three key events of the skin sensitisation AOP have been adopted for contributing to the evaluation of the skin sensitisation hazard potential of chemicals: the OECD TG 442C describes the Direct Peptide Reactivity Assay addressing the first key event; the OECD 442D assesses keratinocyte activation addressing the second key event and the OECD TG 442E addresses the activation of dendritic cells, the third key event of the skin sensitisation AOP.

This approach couldn't however be followed due to the physico-chemical characteristics of the substance (poorly solubility in all testing vehicles).

For this reason the fourth key event, representing T-cell proliferation indirectly assessed in the murine Local Lymph Node Assay (LLNA), should have been studied.

However as a new in vitro study has been developped in order to assess all biological biomarkers leading to a phenomenon of sensitisation, the test substance was assessed following the method described by the SENS-IS assay (Cottrez F. et al, Toxicology in vitro 29 (2015) 787 -802).

As reported in Annex XI of the REACH Regulation N. 1907 -2006, the results of non-validated in vitro methods are accepted with no further confirmation, if the following conditions are met:

(1) results are derived from anin vitro method whose scientific validity has been established by a validation study, according to internationally agreed validation principles;

(2) results are adequate for the purpose of classification and labelling and/or risk assessment; and

(3) adequate and reliable documentation of the applied method is provided.

All three conditions are fullfilled because:

1) the SENS-IS method has been internally validated (Cottrez F. et al 2016, Toxicology in vitro V.32, 248 -260). Validation study has been submitted to ECVAM and it is under evaluation as declared in the TSAR website (https://tsar.jrc.ec.europa.eu/test-method/tm2011 -11). The only limitation to the formal validation derives from the status of the patented method.

2)The results of the assay lead to a classification according to the CLP. The confirmation is requested only in case of negative results.

3) The study is well documented and performed in the spirit of GLP.

Classification criteria:

A test item is classified as irritant if at least 16/23 genes of the “IRRITATION” group are significantly overexpressed.

A test item is classified as sensitizer if at least 7/17 genes of the “ARE” group, and/or 7/21 genes in the “SENS-IS” group are significantly overexpressed.

Moreover, the results obtained with the different concentrations allow the classification of the test item according to the lowest concentration that gives a positive result (DE> 1.25). Thus, a test item is classified in:

-      category 1A: strong to extreme skin sensitizer, when a positive result is obtained at concentrations of 0.1 and/or 1%,

-      category 1B: weak to moderate sensitizer, whena positive result is obtained at concentrationsof 10 and/or 50%.

A test item is classified as a non-sensitizer when negative results are observed at 100% and at all other analysed concentrations.

According to the classification criteria reported in the SENS-IS assay, the test item can be classified as a sensitizer in class 1B, as more then 7 genes of the SENS-IS groups have been induced at concentrations of 10 % and 50 %.