Risk assessment for skin sensitization using read-across with in silico tools: A case study with 2-hydroxyethyl methacrylate (HEMA)

Abstract

 While cosmetics can enrich people's lives, they can also pose health hazards to users in some cases. The causes are many and varied, but one of the main causes is skin sensitization. Nevertheless, some ingredients with known skin sensitization potential, such as certain fragrance ingredients and residual monomers present in functional polymers, cannot be avoided when improving the functionality of cosmetics. Assessing the acceptable amount of these ingredients in cosmetics is useful to minimize the possibility of skin sensitization. One such assessment approach is the Quantitative Risk Assessment (QRA)2 for dermal sensitization, proposed by RIFM. Although QRA2 was originally developed as a risk assessment tool for fragrance ingredients, this method is potentially useful for assessing other non-fragrance ingredients.

 In this study, a skin sensitization risk assessment was conducted for 2-hydroxyethyl methacrylate (HEMA), a residual monomer in certain polymers that is considered to be the causative ingredient of gel nail allergy. Using the QRA2 approach, we assessed a scenario where a HEMA-containing polymer is formulated in a nail polish. Since there is no known LLNA EC3 value for HEMA, its sensitization intensity was estimated based on known data of analogues and read-across prediction by in silico tools. We checked the consistency of our LLNA EC3 estimation with existing results of GPMT or in vitro skin sensitization tests. Here, we present the exposure assessment of nail polish and the read-across assessment, and hope to start a discussion on the validity of our approach.