Exploring the toxicity of the new emerging toxicant 6PPD-Quinone to environmental microorganisms.

Abstract

International audienceThis study examines the toxicity of the newly discovered molecule 6PPD-Quinone (6PPD-Q) to selected environmental microorganisms. After decades of intense research, this molecule, derived from a very common antioxidant (6PPD) used as a car tyre protector, has recently been identified as the main cause of the death of Coho salmon in the north-western United States, and is suspected to be a common toxicant worldwide through tyre treading. 6PPD-Q is produced by the ozone oxidation of 6PPD during the ageing of tyre particles after deposition on roads. The 6PPD-Q produced in this way at low concentrations can accumulate in surface waters after storm water runoff, resulting in acute mortality of salmon migrating to urban streams. In this context, we assessed the toxicity of a wide range of 6PPD-Q concentrations through its intrinsic oxidative potential, and through the response of single-cell microorganisms commonly found in the environment (3 bacterial species, a yeast, an algal strain and an amoeba) by cell tracking with various modern techniques. To assess the mechanisms involved in 6PPD-Q toxicity, particular attention was paid to model bacteria and their capacity for resistance (role of efflux pumps in the response to the toxicant) and degradation of the molecule, monitored by LC-MS/MS. Overall, our results showed that 6PPD-quinone had no or limited impact on all microorganisms tested, at the realistic concentrations tested. For some bacteria and yeasts, a slight inhibition of growth was observed with some concentrations, while other organisms were not impacted at all or were even stimulated by the presence of 6PPD-quinone, probably used as a carbon source by these organisms. Further investigations are needed to assess the potential chronic effects of 6PPD-Q on microbial communities in natural waters and on their ecosystem services