Plastic debris is now a major source of anthropogenic pollution with >5 trillion fragments of micro-plastic in the world's oceans, and can lead to deleterious and often fatal consequences when ingested by seabirds and other marine animals, including hormonal disruption, chemical toxicity, or obstruction of digestive tract. In this action we propose to develop a standard method for characterisation of plastic fragments in the environment, using a combination of micro-CT scanning and FTIR, Raman spectroscopy to measure both physical parameters (size, shape, surface area) and chemical properties (primary polymers, additives, etc.) of individual fragments. We intend to apply the developed methodology to an existing collection of >10,000 plastic fragments extracted from living and dead seabirds over 10 years, and identify which properties of ingested plastics are associated with the greatest negative impact on seabird physiology and health outcomes. Analysis of preserved seabirds from spirit collections will provide historical context for the onset and rise of plastic contamination in seabirds over recent decades. The effect of environmental aging on plastics will be investigated by laboratory studies of several industrial polymers that comprise a major fraction of marine plastic pollution, identifying the spectroscopic signature of photo-chemical degradation under ambient marine conditions and in the acidic environment of seabird stomachs. With the increasingly ubiquitous presence of plastic debris in the environment, it is more important than ever that we understand the precise mechanisms by which that debris negatively impacts marine life so that we may mitigate those effects.