Assessment of the toxicity of novel partially biobased polymers in zebrafish embryos and two zooplankton species.
Supervisor: Amaia Orbea (UPV/EHU)
Plastic use is ubiquitous with daily life in the 20th century. Produced from fossil fuels, these polymers can be designed to possess a variety of favorable features, a characteristic exploited for the development of astounding technology, packaging, and biomedicine. But the amazing development and range of use  of plastic polymers has created a problem, namely plastic pollution. There is much evidence of the  hazard of petroleum based polymers to terrestrial and aquatic systems and environments and the  damages are still being uncovered. The proposal of bio-based alternatives to common polymers has  gained much attention because of their environmentally friendly and renewably sourced nature. Despite  the already growing use of bio-polymers worldwide, information about the toxicity of these bio-based  polymers is not yet comprehensive. It is important to assess the environmental impact of these bio-based  materials before advertising or endorsing them to the global market. In the present study, the toxicity of  different partially bio-based nanoparticle suspensions was evaluated in aquatic organisms: 1) Partially  bio-based polyurethane nanoparticle suspensions with and without crystal nanocellulose CNC)  reinforcement and 2) Partially biobased pressure sensitive adhesives (PSA1 and PSA1) differing in the  colloidal stabilization. Acute and sublethal toxicity of WBPU nanoparticle suspensions was assessed in  zebrafish embryos (Danio rerio) and the zooplankton Artemia and rotifer Brachionus plicatilis. PSA1  and PSA2 toxicity were assessed with zebrafish embryos. WBPU suspensions did not cause acute  toxicity in zebrafish embryos, malformations, hatching delays, or cell death in zebrafish embryos. This  was also the case for PSA1 and PSA2 except there was an increase in fluorescence intensity  measurement at 0.01 mg/L in PSA1 which denotes cell death. There was higher mortality in zebrafish  exposed to PSA1 but this effect may have been exaggerated due to the egg quality of the spawning couples used. Artemia mortality was not affected by exposure to WBPU and rotifer assays were rendered unusable because of population growth and compound aggregation. However, WBPU caused a decrease in the ingestion of both artemia and rotifers. Additionally, CNC alone caused a decrease in artemia ingestion rate. Despite the problems with the study, the assessment with zebrafish embryos and zooplankton at least shows some pattern of general low acute toxicity and the effects on sublethal endpoints of waterborne exposure to the partially biobased WBPU and PSA nanoparticle suspensions. The conclusions of this study are as varied as the literature concerning these types of compounds. Regardless, size and exposure media likely play large roles in nanopolymer toxicity, but it is difficult toascertain the underlying mechanisms of their toxicity through studies such as these. Further investigations of the molecular forces driving the toxicity of nanopolymers in aquatic organisms are needed.