The United Nations Environment Programme (UNEP) and the European Commission (EC) are implementing the project Identifying and quantifying plastic contaminant sources and leakages into the aquatic environment. The objective of this project is to establish a practical methodology to identify and quantify sources of plastic pollution in the aquatic environment. Three outputs are expected of the project: (i) a toolkit to identify and quantify sources/leakages of plastic waste entering aquatic environment; (ii) source/leakage inventory of plastics entering the aquatic environment in Kanya applying the toolkit, and (iii) communication and visibility of the project results through the existing water agreements and a future legally binding agreement on plastic pollution. A Working Group (WG) to assist the project implementation was established and a first meeting was held in Sept/2024, to agree on an initial conceptual framework in consideration of the project’s objective. The proposed methodology was named a toolkit, aiming to be a quick assessment tool for an initial estimation of plastic pollution sources and flows running into the environment, with particular attention to aquatic media.