10. Cigarette Filters
Cigarette filters, which may seem small and harmless, are actually made of cellulose acetate—a type of plastic.
These filters are among the most littered items on the planet and appear consistently in ocean plastic surveys.
Once in the water, they leach toxins and break down into tiny fibers, posing a threat to fish and birds alike.
For more about the environmental impact of cigarette butts, see this Ocean Conservancy post.