How many million tons of plastic are dumped in oceans every year?

12.7 mn tonnes.

Explanation:

Every year about more than 8 mn tonnes of plastic are dumped into the oceans in most of the coastal countries and the plastic that enters the oceans has larger identifiable microplastics and makes most of their ways through the sewer systems. Floating objects directly reach the sea from the river and then enter the oceans. Most of the plastics on the form of the paper and plastic pieces  foams, the glass pieces , the plastic food bags , plastic caps and lids , and the metal beverage cans , the plastic straws , the glass beverage bottles , and the plastic beverage bottles  etc. These are non-biodegradable these can enter directly into the soil and thus cause harmful effects on the terrestrial environments.