The point that's important here is that the mass of plastic is not a good measure for damage. surface area is a better measure. You can have a solid cubic meter block of plastic and it will do practically zero environmental damage. However, turn this block into a bunch of foil and bags and wrapping material and the damage will be extensive

Some weird semi-related news. A cargo ship spilled untold amounts of lentil sized plastic pellets off the coast on New Orleans during a storm in early August. https://weather.com/science/environment/video/nurdle-apocalypse-in-mississippi-river-after-plastic-spill