An initial estimate for the social cost of plastic pollution was proposed to range between 4.58 to 45.8 $USD/yr-kg plastic. Based on the range of values for the social cost of plastic pollution, 2-18% of CDA foam food trays and 15-100% of CDA foam takeaway containers would need to leak into the environment for the social cost of plastic pollution to exceed the social costs of CO2 (Supplementary Figure ). A rough estimate for the leakage frequency of plastic foam is ~2% (calculated as the product of the global plastic leakage frequency, ~11% 1 , and the proportion of leaked plastic that is plastic foam, ~15% ). Conversely, for persistent PS foams, only 0.02-0.2% of food trays and 0.2-2% of takeaway containers would need to leak for the social cost of plastic pollution to outweigh that of CO2 (Supplementary Figure ). The difference in the range of leakage frequency for food trays and takeaway containers was because of their ten times difference in thickness, which results in different environmental lifetimes and thus different social costs of plastic pollution (Supplementary Figure ).