Test No. 431: In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method

The present Test Guideline addresses the human health hazard endpoint skin corrosion, following exposure to a test chemical. Skin corrosion is defined as the production of irreversible tissue damage, manifested as visible necrosis of the skin, according to the definition of the Globally Harmonised System for Classification and Labeling of Chemicals.

This Test Guideline describes an in vitro procedure allowing the identification of non-corrosive and corrosive substances and mixtures, based on three-dimensional human skin model which reliably reproduces histological, morphological, biochemical, and physiological properties of the upper layers of human skin, including a functional stratum corneum. The procedure on reconstituted human epidermis is based on the principle that corrosive chemicals are able to penetrate the stratum corneum by diffusion or erosion, and are cytotoxic to the underlying cell layers. Two tissue replicates are used for each treatment (or exposure time), and for controls. Corrosive materials are identified by their ability to produce a decrease in cell viability below defined threshold levels at specified exposure time. Cell viability is measured by enzymatic conversion of the vital dye MTT  into a blue formazan salt that is quantitatively measured after extraction from tissues. Corrosive substances are evidenced by their capacity to reduce cell viability below the defined threshold.

Several validated methods are referenced in the Test Guideline and follow the procedure described above. Some of the methods referenced allow sub-categorisation among corrosive chemicals.

This Test Guideline also includes a set of Performance Standards (PS) for the assessment of similar and modified TER-based test methods.

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