Chewing gum is forever

Although chewing gum was initially made from natural chicle, it is now made from synthetic rubber, the same rubber used in tire tubes. (Nice. Here is a picture of Niyati admiring years worth of chewing gum deposits in the NYC subway.) In fact, chewing gum is also made with some toxic materials, potentially carcinogens.  Furthermore, the switch from natural chicle to artificial rubber makes chewing gum non-biodegradable. Even though it doesn't stick to your teeth, it sticks to the ground, and costs a lot of money to clean up, if you wanted to.