Journal of Hazardous Materials, a team of conservation biologists analyzed the digestive tracts of 30 freshly dead seabirds called flesh-footed shearwaters (Ardenna carneipes). "It is likely that plastic induces a swathe of sub-lethal effects which we were not able to capture in this study, such as introducing toxic chemical pollutants, changing gene expression, disrupting metabolism, or causing tissue dysfunction," the authors added. But part of the reason we don't have good data on this is because laboratory studies usually incorporate unused, "virgin" plastics such as spherical polystyrene, which is used to make Styrofoam