Ecotoxicological modelling of cosmetics for aquatic organisms: A QSTR approach

In this study, externally validated quantitative structure–toxicity relationship (QSTR) models were developed for toxicity of cosmetic ingredients on three different ecotoxicologically relevant organisms, namely <i>Pseudokirchneriella subcapitata</i>, <i>Daphnia magna</i> and <i>Pimephales promelas</i> following the OECD guidelines. The final models were developed by partial least squares (PLS) regression technique, which is more robust than multiple linear regression. The obtained model for <i>P. subcapitata</i> shows that molecular size and complexity have significant impacts on the toxicity of cosmetics. In case of <i>P. promelas</i> and <i>D. magna</i>, we found that the largest contribution to the toxicity was shown by hydrophobicity and van der Waals surface area, respectively. All models were validated using both internal and test compounds employing multiple strategies. For each QSTR model, applicability domain studies were also performed using the “Distance to Model in X-space” method. A comparison was made with the ECOSAR predictions in order to prove the good predictive performances of our developed models. Finally, individual models were applied to predict toxicity for an external set of 596 personal care products having no experimental data for at least one of the endpoints, and the compounds were ranked based on a decreasing order of toxicity using a scaling approach.