Prof. Dr. Ruth Freitag, Chair for Process Biotechnology, University of Bayreuth, Germany

Abstract

Biodegradable plastics are increasingly proposed as eco-friendly alternative to standard commodity plastics such as polyethylene. “Compostable” bags and foils based on such materials are sold in supermarkets, e.g. for the collection of organic waste or as foils and containers in food retail. The idea is that bags and wrapping like this can be collected and processed with the biowaste and will quickly degrade during state-of-the-art composting. However, operators of technical compositing plants have complained in the past that they tend to find residues of compostable bags in their composts, while recent research has shown that a considerable fraction of the microplastic (fragments < 1mm) found in quality composts made from organic waste bears the signature of biodegradable materials. Until recently, such small fragments have escaped notice, since fragments smaller 2 mm were not considered in the quality control of composts. However, microplastic is increasingly seen as threat to the environment as well as human health and any microplastic fragment remaining in the compost will enter the environment when the compost is used as fertilizer.

Little is known about the fate of these microplastic fragments in the environment, but further breakdown may depend largely on the exact environmental conditions and the state of the material itself. For instance, biodegradable plastic in the crystalline form has been shown to be much more resistant to further break down that the same material in the amorphous state. The commercially available compostable bags contain a certain amount of crystalline material to fine-tune their mechanical and material properties. Evidence will be presented that the microplastic leaving the plants with the composts is in fact enriched in crystallinity compared to the bags in certain cases, while for other materials the conditions required for composting, such as the elevated temperature necessary for hygenization, may actually aid the transition of an amorphous material into the much more stable crystalline form. Unless more is known about the break down efficiency of biodegradable plastic under conditions of biowaste treatment and in the environment, compostable bags and foils should be used with caution, in particular, since biodegradable materials are not necessarily biobased, so their unrestricted use as welcome alternative to polyethylene may prolong and extend out dependency on fossil resources.

Dr. Fabiana Corami, CNR-ISP · Italian National Research Council · Institute of Polar Sciences, IT

Abstract

Microplastics were unequivocally defined in 2019 thanks to the European Chemical Agency (ECHA, 2019); their size range was also defined, but it has been later reviewed to the extent that it is now comprised between 5 mm and 1 µm (Allen et al., 2022; Casagrande et al., 2024). This is an umbrella definition regarding the size range because transport pathways and the fate of particles in such a size range can be highly different. Plastic particles and other microlitter components (e.g., plastic additives, artificial and natural fibers, paints and varnish, etc.) may be present in a suitable size for the ingestion by biota, particularly invertebrates at the lower layers of the trophic web (mainly particles < 100 µm). Once entering the food web, the particles can undergo bioaccumulation and biomagnification. Because plastic pollution can impact the good environmental status and quality of organisms, the One Health approach (Prata et al., 2021) would also allow consideration of an integrated response aimed at optimizing people's health. Therefore, assessing plastic pollution and the occurrence of other microlitter components below 100 µm will be essential. The Microplastics’ group of the Institute of Polar Sciences, CNR-ISP, together with Ca’ Foscari University, have been investigating microplastics and microlitter, especially those below 100 µm, in several different environmental matrices, i.e., from snow and rain to different species of biota, developing methods for pretreatment and analysis.

Prof. Dr. Sara Villa, University of Milano-Bicocca · Department of Earth and Environmental Sciences – DISAT, IT

Abstract

Plastics are regarded as pervasive contaminants due to the consistent disposal of these materials into the environment, a process that is supported by their global production. The dimensions of plastic items exert a considerable influence on the environmental interactions between plastics and biota, as well as the potential hazard they pose to ecosystems. In general, the impact of smaller plastic items is more pronounced than that of larger ones. The current state of knowledge regarding the environmental levels and effects on biota of nanoplastics (NPs) is still very limited. Polystyrene (PS) is the only plastic polymer that can be readily synthesised in the nanometre size range. Therefore, the observed effects can be attributed almost exclusively to this polymer. The aim is to provide data that will assist in determining whether different NP polymers exhibit comparable toxicity to PS-NPs and whether PS-NPs can be used as a proxy for all other NP polymers.

In this context, we have contributed to the production of evidence regarding the effects of PVC, PE and PS-NPs on individuals of Daphnia magna, both in the short term (48 hours) and in the long term (21 days). A multiple endpoint approach was employed for the purpose of assessing the potential adverse effects of environmentally relevant concentrations of engineered nanospheres. This study examined the impact of the different plastics on a range of endpoints, both at the individual and population levels. The results indicated that PVC exhibited a higher degree of toxicity. The impact on moulting behaviour, morphometric parameters and reproductive fitness has implications for the long-term population dynamics. The data presented here offer new insights into the influence of nanoparticle polymer type on toxicity. Therefore, given that PS does not appear to be the most hazardous polymer, we propose that the use of data on PS toxicity may result in an underestimation of NP hazards.

Dr. Giulia Cesarini, CNR–IRSA · Italian National Research Council · Water Research Institute, IT

Abstract

Plastics pose a significant threat to aquatic habitats worldwide, drawing substantial attention from the scientific community. While freshwater systems are recognized as the primary source of plastic pollution in seas and oceans, they have historically received less focus compared to marine environments. Environmental factors fragment plastics into smaller particles, ranging from macroplastics to nanoplastics, creating a complex pollution problem. The projects conducted aimed to deepen our understanding of plastic behaviour in freshwater ecosystems through a comprehensive, multi-level approach. This approach spanned from the ecosystem level down to individual organisms, analysing the effects of different plastic sizes at each level. At the ecosystem level, the research focused on assessing the transport of floating macroplastics in riverine ecosystems using a standardized methodology. This study also offered recommendations for improving future investigations of plastic pollution. At the community level, the research aimed to collect field data on the role of riparian zones in the distribution of macroplastics and mesoplastics. The occurrence of microplastics was specifically examined in remote mountain environments to assess their presence in isolated areas. Additionally, the research investigated the accumulation of microplastics and associated additives in freshwater bivalves, particularly Anodonta cygnea. Finally, at the organism level, the study explored the teratogenic effects of nanoplastics on freshwater organisms under realistic exposure conditions. Overall, this research enhances our understanding of plastic pollution in freshwater environments, examining its impact from the ecosystem down to the individual level and highlighting the harmful effects of plastics of all sizes.

Dr. Heinrich T.J. Dahms, Eurac Research · Institute for Alpine Environment, IT

Abstract

Microplastic pollution has a worldwide distribution which is so significant, that microplastics can be used in sediment core samples as an indicator for the Anthropocene. After discovering microplastic particles in the oceans, research in marine ecosystems increased significantly, unfortunately, freshwater environments were not similarly investigated. In 2019 only 13% of the total microplastic research conducted was in freshwater environments. This led to an underestimation of microplastic pollution in freshwater ecosystems. As freshwater microplastic research increased, researchers reported concentrations of microplastics similar to those found in marine environments. Microplastics have since been discovered in freshwater environments such as the Amazon River, Danube, Rhine, and the Great Lakes of North America. Critically, the biota that inhabit these freshwater environments have been found to ingest microplastics. Microplastics are ingested by various benthic macroinvertebrates that form a large proportion of the bio-load in freshwater ecosystems. This creates a pathway for microplastics to bioaccumulate into larger predatory organisms, such as fish, birds, and even humans. Unfortunately, the distribution of microplastics through freshwater communities has been under-investigated as many studies tend to focus on microplastics in environmental compartments and not the biota found there. Once ingested, these pollutants could lead to negative health impacts including oxidative stress, increased bioaccumulation of toxicants, immobility, reduced reproduction, and death. Studies have also noted how various polymers and shapes lead to different toxicological effects. This demonstrates the importance of further descriptions of microplastic polymers and shapes in the environment. It is key to determine how microplastics distribute through freshwater ecosystems to identify which ecosystems are most endangered by microplastic pollution.

PhD Candidate Simone Cavazzoli, University of Trento · Dep. of Civil, Environmental and Mechanical Engineering, IT

Abstract

Urban centres release large amounts of microplastics (MPs) into wastewater, which is treated at wastewater treatment plants (WWTPs). Most MPs are concentrated in sewage sludge, though different treatment technologies vary in their removal efficiency. A small fraction of MPs escapes through the effluent, posing risks to ecosystems and human health, as MPs can carry pollutants like organic compounds, heavy metals, and pathogens. When sludge is composted and reused in agriculture, it can reintroduce MPs and hazardous pollutants into the environment. Additionally, mechanical sludge dewatering can release MPs back into the treatment process, leading to potential recirculation within the plant. In this presentation, we will discuss two key research studies examining the role of WWTPs in removing MPs.

The first study applied multiple analytical techniques to investigate MPs (5000 to 10 µm) at various stages of a conventional municipal WWTP. MPs were sampled using an in-situ pump and filter system, with extraction methods consisting in the Fenton reaction and density separation. MPs were then analyzed using FPA-micro FTIR and LDIR, offering detailed insights into their composition, size, shape, and color. TD-GC/MS was employed to quantify the polymer mass and assess the removal efficiency of the plant. While WWTPs significantly reduced MPs by concentrating them in sludge, some MPs still entered water bodies, posing environmental and health risks. This study emphasizes the importance of proper sludge disposal and advanced removal technologies to prevent MP release.

The second study extended the focus to five WWTPs having different treatment technologies: a conventional WWTP, a plant with moving bed bioreactor (MBBR) technology, two plants with tertiary filtration (canvas and stainless steel), and a membrane bioreactor (MBR) filtration. MPs were quantified using TD-GC/MS to assess total polymer mass removal across three size ranges: 300-5000 µm, 10-300 µm, and 2-10 µm. Tertiary treatments maximized MP removal, although conventional processes also performed well. The findings from the first study—such as the need for proper sludge management and optimizing MP removal from effluents—apply here as well. Despite high removal rates, a small but consistent fraction of MPs escapes from WWTPs into the environment, raising ecological and health concerns.