Plastic and polystyrene never actually decomposes, it just breaks down into smaller and smaller pieces. Ever since I learned about that I've been picking up trash whenever I see it while outside but I can't always do it in large quantities. For example I tried grabbing a piece of styrofoam but it just broke apart and scattered tiny pieces all over the place that would have taken hours to pick up one by one. It's disgusting and nobody really seems to care about it.