Potential impacts of atmospheric microplastics and nanoplastics on cloud formation processes

The presence of microplastics and nanoplastics (MnPs) in the atmosphere and their transport on a global scale has previously been demonstrated. However, little is known about their environmental impacts in the atmosphere. MnPs could act as cloud condensation nuclei (CCN) or ice-nucleating particles (INPs), affecting cloud formation processes. In sufficient quantities, they could change the cloud albedo, precipitation and lifetime, collectively impacting the Earth’s radiation balance and climate. In this Perspective, we evaluate the potential impact of MnPs on cloud formation by assessing their ability to act as CCN or INPs. Based on an analysis of their physicochemical properties, we propose that MnPs can act as INPs and potentially as CCN after environmental aging processes such as photochemical weathering and the sorption of macromolecules or trace soluble species onto the particle surface. The actual climate impact(s) of MnPs depend on their abundance relative to other aerosols. The concentration of MnPs in the atmosphere is currently low, so they are unlikely to make a substantial contribution to radiative forcing in regions exposed to other aerosols, either from natural sources or anthropogenic pollution. Nevertheless, MnPs will potentially cause non-negligible perturbations in unpolluted remote or marine clouds and generate local climate impacts, particularly in view of an increase in the release of MnPs to the environment in the future. Further measurements, coupled with better characterization of the physiochemical properties of MnPs, will enable a more accurate assessment of the climate impacts of MnPs acting as INPs and CCN. Microplastics and nanoplastics may affect cloud formation processes by acting as ice-nucleating particles and cloud condensation nuclei.