Recently, we applied Ashby's method of material selection to derive MIs for minimal environmental lifetime . With respect to mechanical performance, such MIs relate 𝑘 𝑑 to 𝐸 and 𝜎 𝑦 (Supplementary Table ). Low-density CDA foams optimized these MIs (Figure ). As for PS, foaming provided no benefit to reducing the environmental lifetime of items made of this material because the material was persistent.