Plastics are flowing into the ocean nearly entirely from 3 major River systems
Yangtze (China)
Pear River (China)
Ganges/Brahmaputra (India Bangladesh)
This problem is NOT like global warming in that the cause is measurable and visible, but the problem is not with the USA or the West.
Until very recently, it was the West, we exported our re-cycling to China and India who did not re-cycle it but dumped in the water. Environmentalist have known this for years but looked the other way.
Sure it is. Have you ever looked along the streets of a typical neighborhood trash collection day? The amount of stuff being thrown away instead of reused is beyond comprehension. Think of all of the things that aren't reused anymore, how much packaging everything has.
You want to see open trash heaps and sewers? Take a cruise to a crowded port. Bright blue waters are becoming unusual, the beaches are littered with broken bottles, etc, in some places at sea there is visible trash.