Riverine plastic emissions
The annual mass of plastic waste transported by rivers into the ocean. Estimated at 0.8–2.7 million metric tons per year globally (Meijer et al. 2021).
Source: Meijer et al. 2021
Mismanaged plastic waste
Plastic waste that is not properly collected, sorted, or disposed of, and is therefore at risk of entering the environment.
Source: UNEP 2021
Modeled outfall
A point where a river discharges into the ocean, with plastic emission estimates derived from geospatial modeling rather than direct measurement.
Source: Meijer et al. 2021
Aquatic plastic leakage
All plastic entering aquatic environments from all pathways: rivers, coastal areas, and direct dumping. Broader than riverine emissions alone. Estimated at ~22 Mt/yr.
Source: OECD 2022
Ocean plastic stock
The accumulated mass of plastic in marine environments from all historical sources: floating debris, seafloor deposits, and microplastics.
Source: UNEP 2021
Watershed
The land area that drains into a particular river or body of water. Also called a drainage basin or catchment area.
Emission rank
The position of a river outfall relative to others, ordered by modeled annual plastic emission (mt/yr).
Source: Meijer et al. 2021
Distance to coast
A key variable in river plastic emission models. Rivers with shorter paths to the ocean deliver plastic more efficiently.
Source: Meijer et al. 2021
Microplastics
Plastic fragments smaller than 5 mm. Can result from fragmentation of larger plastics or be manufactured at small sizes (e.g. nurdles, microbeads).
Source: UNEP 2021
Confidence interval
A range of values that reflects uncertainty in a model estimate. The 0.8–2.7 Mt/yr range for riverine emissions represents a confidence interval, not imprecision.