Plastics in the sea - the culprits
According to Britain's Economist magazine about 90 percent of all the plastic that reaches the world's oceans gets washed down just 10 rivers.
These are the Yangtze, the Indus, Yellow River, Hai River, the Nile, the Ganges, Pearl River, Amur River, the Niger, and the Mekong (in that order).
Very little plastic comes from North American, European and other first world countries. They have good water treatment systems.
If we want to reduce the amount of plastic in the oceans we need to put strong pressure on the countries that control the 10 rivers.
In Britain environmentalists have wasted their time on attempts to stop people using plastic straws and disposable coffee cups. Such campaigns are puerile and pointless when the potential benefits are compared to the amount of stuff being but in the oceans by China, India and other major polluters.