There is currently no standardized way to measure the extent of the plastic problem. Although there are various methods and tools to assess plastic pollution, it is difficult amongst others to measure how much plastic is entering the oceans and thus to compare this. Only when decision-makers have credible, meaningful, and legitimate data they can estimate and analyze the current state of the issue, set measurable goals, implement effective actions, and track progress towards set goals over time to tackle the problem of plastic pollution at source.

The purpose of this report is to conduct a review of the existing methodologies which assess plastic waste flows and leakage into the environment and more specifically, plastic leakage into waterways and entering oceans and seas.

By developing a comparative framework, the reader can find support in identifying the methodology which best enables monitoring projects or national programs to be assessed within their context of application and in terms of their added value for preventing plastic pollution and marine litter.