About CUSP The European Commission’s Research Cluster to Understand the Health Impacts of Micro- and Nanoplastics (CUSP https://cusp-research.eu) is now three years into its endeavour to develop new analytical tools, share data, conduct inter-laboratory comparisons, and communicate and disseminate research results on the health impacts of micro- and nanoplastics (MNPs). To date, thefive research projectshave published more than 60 scientific peer-reviewed research papers and reports, and much more research is underway. The findings from CUSP have already contributed to filling key knowledge gaps. It is clear that MNPs are a public health concern, although the health risks remain unclear and the hazards, exposures and risks of individual types of plastics and their specific chemical additives still need to be determined. This is particularly the case in the long term. Key messages for Policy Makers: 1. CUSP researchers have documented the potential carcinogenicity, mutagenicity and reproductive toxicity (CMR) of micro- and nanoplastics (MNPs), primarily in vitro and with polystyrene.2. The effects of nanoplastics have been observed to be more pronounced than those of microplastics.3. The main routes of exposure of MNPs to the human body appear to be inhalation and ingestion. Small MNPs have been found to translocate into the blood.4. Most of the studies conducted so far are short-term studies and there is a significant gap in understanding the long-term effects of MNPs on human health. More effort is also needed to better establish dose-responses and modes of action.5. It is important that future studies are conducted on representative MNPs of different chemical compositions, and with physico-chemical characteristics better resembling those MNPs found in the environment.