I've been reading up on this stuff for a while. Most of the waste is actually single use plastics from products consumed in the emitting countries, that are disposed of improperly. For example, the Philippines has an issue with sachets.

Sources:

https://news.mongabay.com/2018/10/plastic-trash-from-the-sac...

https://www.scmp.com/lifestyle/health/article/2168819/philip...