Next-Generation Microplastics – What Happens in the Environment?
Over 400 million tons of plastic (OECD (2024)) are produced every year, and a significant fraction ends up in the environment, where it fragments into microplastics. New polymer materials (Biopolymers, Metallopolymers, Vitrimers) are being developed as alternatives to conventional plastics, aiming to improve sustainability through renewable resources, better degradability, or repairability. However, how these materials change in the environment though aging and how they behave as microplastics is still poorly understood.
Three Exposure Pathways
To better reflect environmental processes, three types of samples were investigated:
- Microplastic particles themselves
- Leaching products released during UV-induced aging
- Leaching products released after aging
This approach allows us to distinguish whether observed effects originate from the material itself or from substances released over time.
Bioassays with Algae – A Sensitive Test System
To assess toxicity, bioassays were conducted using gametes of the green alga Ulva mutabilis. These early life stages are highly sensitive to environmental stress and serve as a suitable model for ecological effects.
Measured endpoints included:
- Survival rates (LC50)
- Physiological stress responses (e.g., chlorophyll a fluorescence)
Aging Increases Toxicity
The results clearly show: aged materials exhibit significantly higher toxicity than non-aged ones. UV exposure alters polymer structures, leading to surface degradation and the release of a wide range of dissolved substances. These leaching products can strongly impair the development of algal gametes and, in some cases, are more toxic than the particles themselves. Notably, substances continue to be released even after the aging process has ended, resulting in prolonged biological effects.
New Materials – New Risks
Functional materials such as metallopolymers also showed toxic effects. While the release of metal ions (e.g., zinc) was observed, the overall toxicity could not be explained by metals alone. This suggests additional contributions from polymer degradation products or combined effects.
Conclusion
It is not only the material itself that matters, but what it becomes over time. For a realistic environmental assessment, microplastics, aging processes, and released substances must be considered together.