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Improved models for sub-categorising skin corrosion using reconstructed human epidermis models under OECD test guideline No 431

Understanding the potential skin corrosion of a substance is an important test in many industries including the chemical (e.g., REACH and TSCA), the pesticide (plant protection products and biocides), and the cosmetics and personal care industries. The classification and labelling of chemicals for skin corrosion is also essential under the Global Harmonized System (GHS) of classification and labeling and the EU Classification, Labeling and Packaging (CLP) Regulation. According to these regulations, skin corrosives are categorised as Category 1 substances. These can be further sub-categorised depending on the severity of the effect. The sub-categories are important requirements under transportation guidelines and the restrictions imposed upon it, with the transport of Category 1A chemicals being more costly and stringent than for Category 1B or 1C chemicals.

In vitro assessment of skin corrosion potential, performed according to OECD Test Guideline 431, is now becoming a standard technique, with animal testing only being required in special scenarios. Within this test guideline, there are four accepted reconstructed human epidermis models to determine whether a test article is corrosive or non-corrosive (EpiDermTM, EpiSkinTM, SkinEthicTM RHE and epiCS®). Although all these models have limitations in terms of sub-categorisation, EpiSkinTM SCT is considered to be the preferred method for sub-categorisation into Category 1A, or Category 1B/1C.

A recent paper by the European Commission’s Joint Research Centre (JRC) (Desprez B et al., 2015) evaluates different prediction models for analysing the data from 80 chemicals tested in the OECD TG 431 method using the four recommended reconstructed skin models. The findings of this paper indicate that by using newly developed prediction models, an improvement was achieved in the sub-categorisation of Category 1A and 1B/1C, and that comparable accuracy was observed between the four recommended skin models. Based on these results, the JRC commented that OECD TG 431 should be revised to incorporate a new prediction model to enable a broader range of skin models to be used in the sub-categorization of corrosive materials.

Learn more about in vitro skin corrosion testing.