Human exposure to nano- and microplastics (NMPs) has raised major societal concerns, yet no framework to assess the risks of NMPs for human health exists. A substantial proportion of plastic produced worldwide is not properly disposed and persists in the environment for decades while degrading. Plastic degradation generates a size continuum of fragments, including nano- and microplastic particles, with numerous associated environmental pollutants and plastic additives, and microbial communities colonising their surfaces. The ubiquitous presence of NMPs, their availability for uptake by organisms and their potential to act as vectors for toxicants and pathogens render risk assessment a priority on the political agenda at the global level. We provide a new, fully integrated risk assessment framework tailored to the specificities of NMPs, enabling an assessment of current and future human health risks from NMPs. The framework consists of four novel paradigms to the traditional risk assessment methodology. These paradigms deal with techniques in NMP analysis, gaps in empirical data, theoretical and modelling approaches and stakeholder engagement. Within the proposed framework, we propose how we can use research experiences gained so far to carry out the different steps of the assessment process, and we define priorities for further research.

The present study aims to explore the degradation process of compostable, starch-based (i.e., Mater-Bi^®) shopping bags in the marine environment using isotope ratio mass spectrometry and Fourier-transform infrared spectroscopy (FTIR). The mixing model applied to the isotopic data suggested that the compostable shopping bags had a mixed composition with a higher percentage of polyesters (61% to 72%). Changes in the isotopic composition over a 73-day period of marine water immersion showed a decrease in the corn starch constituent (of 14% to 13%), with a similar rate in both types of bags in accordance with the evidence derived from the infrared spectra. The time required for complete degradation of the starch fraction was estimated by an isotopic approach from 124 to 180 days, following zero-order kinetics. The coupled application of these two analytical methodologies promises to (i) show complementary evidence regarding the time-course degradability of different polymers via FTIR changes, and (ii) infer potential degradation mechanisms via carbon isotope analyzes. We encourage the use of this information to support advancements in the development of more sustainable-by-design plastic materials.