Titanium carbide MXenes – Early identification of safety, sustainability and regulatory issues

Abstract

Two-dimensional (2D) carbides and nitrides, collectively known as MXenes, are advanced materials known for their unique properties, including exceptional electrical conductivity, large surface area, and tuneable surface functionalities. MXenes have gained significant attention, due to their potential in energy storage, biomedicine, and environmental remediation. However, the safe and sustainable implementation of these materials is hindered by critical gaps in safety, sustainability, and regulatory data. This study applies the OECD's Early4AdMa anticipatory risk governance tool to systematically identify potential risks and challenges associated with titanium carbide (Ti₃C₂) MXenes, the most extensively studied of the MXenes. We highlight critical uncertainties around human health and environmental impacts, stemming from discrepancies in acute toxicity studies, insufficient data on pulmonary exposure, genotoxicity, and long-term effects, and limited understanding of environmental fate and ecotoxicity. These knowledge gaps are sustained by the lack of harmonised guidance on sample preparation and dosimetry tailored to the unique morphology of MXenes. Moreover, life-cycle assessments demonstrate the high environmental cost of conventional synthesis methods, underlining the need for greener, energy-efficient alternatives and sustainable innovation approaches. In addition to addressing these knowledge gaps, a key follow-up action is the evaluation of the need to update regulatory guidance documents related to material characterization relevant for such 2D materials (e.g., lateral size, layers, and terminal groups) to ensure comprehensive risk assessment. The present study not only identifies actions to improve the safety and sustainability of Ti₃C₂ MXenes, but also provides a basis for the evaluation of other emerging materials.