From More Data to Actionable Knowledge: Rethinking Ecotoxicological Testing of Micro- and Nanoplastics
Spotlight on Nanna B. Hartmann
Micro- and nanoplastics research has expanded dramatically over the past two decades. Yet a growing volume of scientific literature does not automatically translate into a clearer understanding of environmental hazards and risks. During the InPlasTwin Summer School 2026, Dr Nanna B. Hartmann from the Technical University of Denmark (DTU) addressed this challenge in her lecture “Assessing the Environmental Hazards of Micro- and Nanoplastics: Challenges and Trends in Ecotoxicological Testing.” Her key message was clear: the field is reaching a stage where generating more data is not enough. Progress depends not only on improving the quality, environmental relevance and comparability of ecotoxicological evidence but also on taking the time to synthesise existing data and asking the right questions.
Plastic is not a single material
One of the fundamental challenges is the complexity hidden behind the word “plastic”. Plastic materials consist of synthetic polymers combined with additives, while plastic debris in the environment can occur across different size classes and in multiple forms, including spheres, irregular particles, films and fibres. It may also be classified according to primary or secondary origin.
This diversity extends far beyond particle size and shape. Dr Hartmann highlighted common polymers such as LDPE, HDPE, PP, PET, PVC, PA6, PS, ABS and PC, while drawing attention to the chemical dimension of plastic materials. More than 16,000 chemicals may potentially be used or present in plastics and plastic products; more than 4,200 have been identified as chemicals of potential concern, while hazard data are absent for more than 10,000. Consequently, understanding plastic-associated hazards requires researchers to consider not only the physical particle itself but also its chemical complexity.
What can plastic leachates tell us?
The lecture illustrated this issue through ongoing work comparing the chemical complexity and ecotoxicological effects of leachates from conventional and bioplastic products.
The experimental design compared conventional LDPE with non-biodegradable bio-based LDPE and biodegradable PBAT/starch materials. Water-based leachates and methanol-based extracts were prepared under defined experimental conditions before assessing their biological effects. Importantly, presented results (Vafadar Afshar et al. 2026, manuscript under review) on algae growth-inhibition showed no observed toxic effect for the tested conventional plastics, while toxic effects were observed for the tested bioplastics. This finding should not be interpreted as a general conclusion that conventional plastics are environmentally safe or that bioplastics are inherently more hazardous. Rather, it demonstrates why assumptions based solely on material labels are insufficient. Environmental assessment must examine the actual material, its chemical composition and its biological effects. This is key to avoiding regrettable substitutions.
The challenge of environmental relevance
A major part of Dr Hartmann’s lecture focused on a critical question: How environmentally relevant are the conditions used in microplastics research?
The field has diversified over time, incorporating a wider range of polymers and particle sizes. Nevertheless, important discrepancies remain between laboratory studies and conditions encountered in the environment. The reviewed research on microplastic ingestion in marine planktonic food webs highlights differences in the concentrations and particle shapes used in laboratory studies compared with those observed in the field. Particle shape is particularly illustrative: laboratory studies have relied heavily on beads, whereas field observations encompass a much broader mixture of fragments, fibres, films and other particle types. Environmental realism also involves organism behaviour. Research presented on planktonic copepods showed that organisms may discriminate between food and microplastics, demonstrating why biological responses cannot always be inferred simply from the presence of particles in an exposure system.
Together, these examples underline the need to move beyond highly simplified exposure scenarios and towards experimental approaches that better represent environmentally relevant conditions.
A rapidly growing field - but are we learning fast enough?
The number of scientific publications on microplastics has increased dramatically, expanding from an initial focus on marine environments towards freshwater, terrestrial and atmospheric systems. The ecotoxicity literature on micro- and nanoplastics has likewise grown substantially. Yet this expansion creates its own challenge: an abundance of information can become difficult to integrate when studies use different materials, concentrations, organisms, endpoints and experimental designs. Dr Hartmann therefore emphasised an important principle for environmental risk assessment: the strength of the assessment ultimately depends on the quality of the evidence entering it. Despite numerous studies reporting adverse effects following microplastic exposure, the scientific understanding of microplastic toxicity remains incomplete. The goal should therefore not simply be to increase the number of studies, but to increase their ability to contribute robust and interpretable evidence.
Where do we go from here?
The final part of the lecture moved from diagnosis to direction. Dr Hartmann called for the microplastics research community to “raise the bar” in the quality and risk-assessment applicability of ecotoxicity studies. She also highlighted the need for alternative forms of data sharing, allowing valuable evidence to contribute to knowledge development beyond conventional publication pathways. Modelling can play an important integrative role-but only when it draws on carefully selected, reliable data. This reinforces a central message running through the presentation: integration cannot compensate for weaknesses in the underlying evidence. Finally, the lecture challenged the prevailing scientific culture itself, calling for a change in publishing culture and making an argument for “slow science”, a shift away from prioritising publication volume towards generating evidence that is rigorous, reproducible, environmentally meaningful and genuinely useful for understanding risk – and therefore as a basis for meaningful actions and solutions.
For InPlasTwin, these considerations are particularly relevant. As the project advances methods for detecting, characterising and understanding micro- and nanoplastics associated with biodegradable mulch films, analytical innovation must ultimately connect with a broader question: how can the evidence generated help us understand environmental and biological relevance? The way forward is therefore not simply more microplastics research. It is better-designed research, better-quality evidence and more meaningful integration of that evidence into environmental hazard and risk assessment.
About the expert
Nanna B. Hartmann presented “Assessing the Environmental Hazards of Micro- and Nanoplastics: Challenges and Trends in Ecotoxicological Testing” and “Can You Hear What I Know? Public Communication of Science” during the InPlasTwin Summer School 2026. She is a Professor at DTU Sustain, Technical University of Denmark (DTU). Her contributions to the Summer School combined two complementary perspectives: the scientific challenges of generating robust and environmentally relevant evidence on micro- and nanoplastics, and the responsibility of researchers to communicate complex scientific findings clearly and accurately to different audiences. In her science communication lecture, she particularly emphasised turning facts into meaning, understanding the audience, communicating scientific nuance and uncertainty, and avoiding over-extrapolation and over-simplification.