Effective reduction of land-to-ocean plastic leakage in Thailand from 2000 to 2019 and implications for low- and middle-income countries

Low- and middle-income countries (LMICs) normally lack reliable estimates regarding their long-term, land-to-ocean plastic leakage, hindering global endeavour in addressing marine plastic pollution. Here, we proposed a plastic flow framework for LMICs and applied it to estimate Thailand's plastic flows from production to marine deposition during 2000–2019. The results show that land-to-ocean plastic leakage decreased from 0.60 million tonnes (MT) in 2000 to 0.37 MT in 2019 (29% to 7% of generated), due to improved waste management. The leaked plastics amounted to 9.91 MT over two decades, with 47% being packaging materials and 76% polyethene. However, even substituting all packaging plastics with biodegradable ones, at least 39% of the two-decade leaked plastics remained in aquatic sediments by 2019. Our result indicated that improving waste management and biodegradable plastics substitution both are effective but have limits in mitigating marine plastic pollution. We thus suggest further harnessing the power of informal sectors and improving environmental infrastructure.