By Manas Mishra (Reuters) – An estimated 2.55 million U.S. middle and high school students reported using e-cigarettes during the early part of this year, health officials said on Thursday, a level they described as concerning. One in four of those students said they used e-cigarettes daily, according to a national survey conducted between Jan. 18 and May 31, the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention (CDC) reported on Thursday. “Adolescent e-cigarette use in the United States remains at concerning levels, and poses a serious public health risk to …