Hazard Assessment of Antioxidants as Contaminants of Concern

Antioxidants (AOs) are increasingly detected in the environment, in aquatic organisms, and in human biosamples. Therefore, we performed a comprehensive hazard assessment of more than 500 natural and synthetic AOs by exploring their recalcitrance toward mineralization (not readily biodegradable, NRB), persistence (P), bioaccumulation (B), toxicity (T), mobility (M), and formation of toxic transformation products (TPs). Literature experimental data complemented with in silico predictions revealed that 60% of the AOs classify as NRB and T, out of which 31.6% classify as P and T. Of highest concern according to EU regulations are PBT or PMT compounds, with 4.8% and 2.1% of the AOs studied, respectively, falling into these categories. All AOs classified as PBT or PMT are of synthetic origin and, by majority, primary AOs, i.e., phenolic or amine compounds. Further, most predicted toxic TPs stem from phenolic and amine structures. Natural or nature-identical primary AOs or secondary AOs, e.g., ester or organic sulfur compounds, are less often classified as hazardous. Only 19 AOs were identified as not fulfilling any of the hazard criteria, highlighting the need for more experimental data on AO hazards for regulatory purposes, as well as for further research on safe AO alternatives.