Plastic debris litters our planet and can harm wildlife physically and chemically. Large debris entangles organisms and small fragments bioaccumulate. Several ingredients of plastic are hazardous and in aquatic habitats plastic debris sorbs priority pollutants from water. Thus, plastic debris is associated with a complex chemical mixture, including the material itself, ingredients and ambient contaminants. Here, we assessed how plastic debris acts as a multiple stressor in aquatic habitats. First, we quantified the relationship between different polymers and chemical contaminants in an urban bay. For organics, HDPE, LDPE and PP sorbed consistently greater concentrations of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) than PET and PVC. In contrast, for metals, all types of plastic tended to sorb similar concentrations of aluminum, chromium, manganese, iron, cobalt, nickel, zinc, cadmium and lead. Over a 12-month period, concentrations of all contaminants increased over time. Thus, hazards are not equal among plastic debris, varying by polymer, location and the length of time since becoming debris. Next, we exposed fish to low-density polyethylene (which sorbed relatively large concentrations of chemical contaminants) to assess the hazards of this complex mixture. After a laboratory dietary exposure, Japanese medaka (Oryzias latipes) exposed to the mixture of plastic + pollutants had greater concentrations of polybrominated diphenyl ethers (PBDEs) in their tissues (P < 0.05) and suffered liver toxicity and pathology. Furthermore, our results suggest that plastic debris may cause endocrine disruption—we observed reduced expression of vitellogenin and choriogenin genes and intersex. Moreover, fish fed virgin polyethylene material showed signs of stress, confirming that future assessments should consider the complex mixture of plastic and pollutants. Next, we examined the relationship between bioaccumulation and plastic contamination in the South Atlantic and found a positive relationship between plastic density and concentrations of PBDEs in the tissue of mesopelagic fish. This suggests that the bioaccumulation observed in the laboratory occurs in nature, and that plastic debris is another vector for pollutants to contaminate aquatic foodwebs. Finally, we evaluated the existing chemical, toxicological and ecological evidence about hazards of plastic debris and priority pollutants and found that at least 78% of the priority pollutants listed by the US EPA are associated with plastic debris as an ingredient or sorbed from the environment. The culmination of this and our own findings led us to conclude that current consumer practices and policy for managing plastic is scientifically outdated. We recommend reclassifying classes of plastic debris as "hazardous", providing a relatively simple mechanism, using existing legislation, to rehabilitate affected habitats and prevent further accumulations of hazardous debris.