The United States top health official says electronic cigarettes can cause health problems for young people. Surgeon General Vivek Murthy released his first report on e-cigarettes this week. He called the devices a public health threat to Americas youth. The surgeon general is the U.S. governments top medical officer. He uses scientific information to give the best advice for improving health and reducing the risk of sickness and injury. Most electronic cigarettes use nicotine, a chemical found in tobacco plants, just like traditional cigarettes. But users do not light e-cigarettes because they are powered by a battery. They usually also contain flavoring and other chemicals. E-cigarettes have increasingly grown in popularity nationwide since 2010. Officials say the devices are now the most used tobacco product by American youth and young adults.