Xavier Cousin

Microplastic toxicity ? It's complicated

Xavier Cousin is an INRAE senior scientist working at IFREMER. After an initial training in molecular and developmental biology, X. Cousin has progressively developed his activity centred on the understanding of the effects of stressors on fish physiology, especially pollutants. He is focusing on functions or processes, in particular behaviour and reproduction, essential functions for individuals  to contribute to population and on the identification of underlying molecular mechanisms. He has also been involved in the development of an OECD Technical Guideline for assessment of estrogenic activity in vivo (TG EASZY in validation) and has extensive experience of OECD TG 236 using zebrafish or adapted to marine medaka. In the last years, he has coordinated or has been involved in national and EU projects aiming at understanding the effects of lifelong exposure to several pollutants mixtures on fish physiology and the consequences on their offspring over several generations and more recently three projects dedicated to microplastics and one project dedicated to the understanding of early endocrine disruption on fish.

Microplastics (MPs) occurrence in aquatic environment follows the increase in plastic production and emission in the environment and concerns about impact of MPs on aquatic ecosystem increase accordingly. MPs do not however designate something homogeneous but an extremely heterogeneous set of particles. Variety comes from the polymers and additives which compose them, their shape, their size etc. Additional complexity is due to the property of MPs to transport adsorbed pollutants or microorganism fixed during their stay in the environment.

Based on examples from Ephemare project (JPI-Oceans) and other works, I will show how fish exposures to MPs can last during their whole life, including at sensitive early stages. Using experimental approaches, acute tests corresponding to regulatory tests, conclude to the absence of toxicity of MPs in most cases, including upon exposure to irrelevant concentrations of MPs.  On the contrary, chronic long term exposures to low concentrations of MPs can lead to major biological disruptions which may have dramatic consequences at population level. Beyond the issue posed by MPs already present in the aquatic environment, this raises the question of the toxicity assessment of alternatives to conventional plastics.