Apparent limitations of OECD TG 431 for classification of acrylic- and methacrylic-based adhesives

For years, the strive for in vitro methods for toxicological assessment suitable to replace animal studies gained progressive importance. OECD Test Guideline (TG) 431 was implemented in 2004, allowing to circumvent animal testing according to OECD TG 404 while reliably predicting skin corrosion potential of many substances and products. However, non-animal assays often show protocol-dependent limitations, that complicate or even prevent the testing of several groups of substances. In this study, the suitability of the OECD TG 431 for assessment of the skin corrosion potential of known acidic, thus often skin corrosive or irritating acrylic and methacrylic acid-based adhesives and monomers, was investigated. The commercially available Phenion® Open Source Reconstructed Epidermis (OS-REp) model, developed at Henkel & Co. KGaA, was used. The EpiDerm™ prediction model was considered most applicable to the Phenion® OS-REp model. All Proficiency Substances listed in OECD TG 431, amongst them six acids, were correctly classified and subcategorized as Skin Corr. 1 A or 1B/C corrosives. The OS-REp model was shown to be suitable for the assessment of skin corrosion potential in accordance with OECD TG 431. However, our results also indicate that acrylic and methacrylic monomer-based adhesives might fall outside the applicability domain of this guideline.