By Rachel Hicks
E-cigarettes entered the U.S. market in 2007 and have since become the most popular source of nicotine among the teenage demographic, the Centers for Disease Control and Prevention says. The electronic devices are marketed as safe because they don’t burn tobacco but turn nicotine and flavored liquids into vapor. The CDC says any consumption of nicotine is highly addictive and can lead to brain damage. Some students buy 40 cartridge refills for their e-cigarettes at gas stations every two weeks.