Can Plastics Form Clouds?

Micro- and nanoplastics (MnPs) are ubiquitous in the environment. There are several possible pathways for MnPs cycling in the atmosphere, from direct emissions or re-suspension from water and soil, or wet and dry deposition. However, their impacts in atmospheric processes is unknown. MnPs could act as cloud condensation nuclei (CCN) or ice-nucleating particles (INPs), affecting cloud formation. If present in sufficient quantities, they could perturb the cloud albedo, precipitation and lifetime, collectively impacting the Earth’s radiation balance and climate. We evaluated 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 influence cloud formation after environmental aging processes. Many aerosols play a role in cloud formation, but the (relative) concentration of MnPs compared to other (natural and anthropogenic) aerosols is key to understanding the importance of plastics to this process. 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.