In 1992, Singapore banned the sale and import of chewing gum. The ban was due to improper disposal of gum by disrespectful citizens and tourists. The disposal of gum in mailboxes, elevators, or on the seats or doors of buses and trains was expensive to clean up. The Singaporean government introduced the ban when transportation was disrupted a few times due to gum on the door sensors of its modern trains. In 2004, following the Singapore-US Free Trade Agreement, the chewing gum ban was changed slightly, allowing dentists and pharmacists in Singapore to sell medicinal gum. Pharmacies have to be licensed to sell chewing gum, and pharmacists must check the ID of the buyer and record who bought the gum. The act of chewing gum is not illegal in Singapore; however, tourists can be charged with “gum smuggling” if they try to bring large amounts of chewing gum into the country.