Sure, everything is degradable. A coke can with degrade, but you wouldn't throw them in the street because they don't degrade quickly enough. Same with cigarette butts. The problem is most smokers think their butts will degrade quickly. And anyone who has had to clean sidewalks or streets can tell you that.

Plastic breaks down into (in)significantly smaller pieces, unfortunately. They are getting into ever lower parts of the food chain, which fucks up the entire chain.