The problem is that those populations lack the infrastructure and organization so they made the rivers ad-hoc trash disposal system. And it works too well for t

The problem is that those populations lack the infrastructure and organization so they made the rivers ad-hoc trash disposal system. And it works too well for them. It's not the plastic that's a problem. It's poverty and lack of organization of those regions. If humanity never invented the plastic those rivers would still be the most polluted (with population waste) rivers on the globe.