The U.S. Surgeon General says electronic cigarettes are a major health concern, especially for young adults.
A report released Thursday called "Know the Risks" says E-cigarette use is very popular with young people and their use has grown dramatically in the last five years -- and their use is higher among high school students than adults.
Surgeon General Vivek Murthy says nicotine exposure, even from E-cigs, can harm teens developing brains.
Murthy warns parents to protect their kids against e-cigs.