Dr. Vivek Murthy, President Obama's nominee to be the next U.S. surgeon general, testifies Tuesday on Capitol Hill before the Senate Health, Education, Labor and Pensions Committee hearing on his nomination. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP

John Hartigan, proprietor of Vapeology LA, a store selling electronic cigarettes and related items, takes a puff from an electronic cigarette in Los Angeles. Reed Saxon/AP hide caption

itoggle caption Reed Saxon/AP