The majority of plastic waste that enters the world's oceans via river currents is generated in Asian countries. This is evidenced by data from a recent study conducted by the organisation The Ocean Cleanup, published in the academic journal Science Advances. The study concludes that 81% of the total global riverine plastic emissions originated in Asian rivers, while on other continents this proportion remained in the single digits.

The study surveyed more than 1,600 of the world's rivers between 2017 and 2020, which together account for 80% of total plastic inflow into the oceans. The amount of plastic washed into each river depends on several factors. In addition to the size of the river, the concentration of the population near the river, the economic performance of surrounding regions, and the quality of waste management are also important. According to The Ocean Cleanup data, rivers are the largest source of plastic entering the world's oceans, which is why they play a vital role in curbing plastic pollution.

The study indicates that countries with long coastlines, despite having small land areas—such as islands or archipelagos—tend to disproportionately increase riverine plastic pollution. Seven of the ten rivers that discharge the most plastic into the sea are located in the Philippines, with the most problematic being the Pasig, which flows through the Manila metropolitan area. In 1990, the river was declared biologically dead, and it has since undergone renaturalisation. The country as a whole was also named the largest contributor to ocean plastic pollution, as the Philippines emits more than 36% of the plastic mentioned in the study, or 3.3 kg per capita per year, which is the highest figure in the study. Other countries with high per capita emission levels included Suriname (2.9 kg), Trinidad and Tobago (2.6 kg), and Malaysia (2.3 kg).