Jeroen Sonke , Alkuin Koenig, Theo Segur, Nadiia Yakovenko

Plastics occupy a central role in the global economy, yet cause significant damage to ecosystems and human health. Recent studies and OECD reports have provided comprehensive roadmaps to reduce the environmental impacts of plastics, based on coordinated global action to reduce plastic consumption and improve waste management and recycling. Leakage of mismanaged plastic waste to aquatic environments, including the ocean, is a key policy variable, yet not well constrained in plastics life cycle analysis. Here we use a coupled land-ocean-atmosphere box model to simulate global plastic and microplastic dispersal for different policy scenarios. We update the global plastic and microplastic budget for the year 2015. Based on a revised estimate of the total marine plastic pool of 263 Tg, we constrain land to sea transport of plastics at 14 Tg y-1 for the year 2015, implying 4 to 7 times larger leakage than OECD estimates. Model simulation of two ‘global action’ policy scenarios, attaining near-zero mismanaged waste and >50% recycling by 2060, show a peak in land to sea transport of total plastics of 23 Tg y-1 around 2045 and a decrease thereafter. Land to sea transfer of microplastic, however, remains high during the 21st century due to its continued supply from the fragmentation of legacy mismanaged waste on land. Consequently, exposure to small microplastic, <300 μm, in air, terrestrial runoff, marine waters and sediment is estimated to increase 3 to 6-fold by 2060, compared to 2019, and can only be curbed by including remediation of terrestrial mismanaged plastic waste in policy scenarios.