Plastics are materials often made using fossil fuels, they are great for short term use, but are destructive to the environment in the long term, as they degrade over 500 years, and they mess up the areas where they degrade, the ocean is now our trash bin for many nations for the plastic, the Sealife is also suffering, as the life is killed in a very slow and painful way by either eating them or being trapped in them.
