> How much of it is their own waste? How much was produced for Western consumers and then off-loaded onto them?

From following ocean cleanup project, for plastic ending up in the ocean it's usually own waste. The issue is countries that don't have working waste collection systems, any rainpour will often wash out the trash into river/oceans.

(littering is also an issue in countries with waste management though, but to a smaller degree, I kinda hate when people don't realize that stuff they throw in the street will often end up in rain collectors and directly flow into rivers)

Thanks for the reply! I was able to find the source you mentioned. Is there room in the conversation to talk about how much of their "own use" plastic is sold to them by Western companies who control the local markets?