How about people driving those trucks that directly dump mixed waste into the ocean? That's a very common thing to do in South-East Asia. Plus, there are a zillion villages everywhere around there that dump all of their mixed waste into creeks going through them – to be brought "*away*". Into the oceans.

That's where almost half of all microplastic comes from. Then there's the other approximately half that comes from cars' tyres. And then a part of a percent that comes from drinking straws and such. Hooray.