The acting director of the federal agency researching the health effects of Camp Lejeune's polluted water unexpectedly resigned Tuesday, according to a notice sent to the agency's senior leadership.It is not immediately clear why Dr. Tanja Popovic, who could not be reached to comment, stepped down. She has been acting director since Jan. 26.But her resignation comes after she told Congress on Feb. 26 that the Agency for Toxic Substances and Disease Registry lacked the authority and resources to launch a study into the incidence of cancer among veterans of the North Carolina base.The Tampa Bay Times reported earlier this month that ATSDR's own scientists said in a 2008 report that such a study was, in fact, feasible.Up to 1 million people, including about 20,000 Floridians, were exposed to cancer-causing chemicals in the base's drinking water from 1953 to 1987. Congress has dubbed victims "Poisoned Patriots."Popovic's assertion that ATSDR did not have authority to do the cancer-incidence study drew sharp criticism from some members of Congress, who noted the agency was created for the purpose of doing such research.Popovic's resignation also came after she threatened to cut off communication with members of a citizens panel advising the agency on Camp Lejeune issues.Popovic said the members were rude to her."I am kindly asking you again to please engage in a respectful manner of communications with me and my colleagues — that is, please state your issue and refrain from making unnecessary offensive comments about my agency," Popovic said in a recent email to retired Marine drill instructor Jerry Ensminger, a member of the citizens panel."Please note," she said, "that we will no longer be responding to any of the emails that contains disrespectful, condescending, and even offensive content."Ensminger's 9-year-old daughter, Janey, died of leukemia in 1985, a death he believes is linked to Lejeune's contaminated drinking water.Ensminger recently told Popovic he distrusted her commitment to continued Camp Lejeune research. He ended one email to her, "You just proved what I have suspected all along,"That prompted a bristling return volley from Popovic."What is it that you have suspected all along?" she asked. "That I have been recognized as a Fulbright Fellow, that I have been the lead laboratory expert for (the Centers for Disease Control) during the anthrax attacks with enormous trust placed on me during that trying time by the people of this country? That I am a member of 2 National Academies of Science with over 150 peer reviewed scientific publications? That I was trusted enough to chair the US Strategic National Stockpile Committee?"That I was trusted enough to serve on the President's Committee for Scientific Integrity? That I am recognized for my professional and scientific integrity at home and abroad? Or that I have received praise for my work directly from a U.S .President, a Senate Majority Leader, numerous senators and representatives? Or that a U.S. flag has been flown over the Capitol in recognition of my contributions to protect the country during 9/11 and anthrax attacks? What is it that you have suspected all along?"Popovic wrote, "I take attacks on my professional and personal integrity very seriously, and I am profoundly saddened to see that you will stop at nothing."Last week, U.S. Rep. John Dingell, D-Mich., in addition to U.S. Sens. Kay Hagan, a Democrat, and Republican Richard Burr, both of North Carolina, told Popovic's boss they expect her to repair the agency's relationship with the panel."For reasons we cannot yet discern, the desire for open communication seems to have waned within ATSDR in recent months," they said in a letter to Kathleen Sebelius, secretary of the Department of Health and Human Services.Popovic also serves as director of the National Center for Environmental Health. ATSDR and the center are part of the Centers for Disease Control and Prevention. Popovic is CDC's former associate director for science and its chief science officer.Ensminger, who told Popovic disagreement does not equate to disrespect, said the resignation is no guarantee ATSDR will conduct the cancer-incidence study."They have absolutely no justification for not performing this cancer-incidence study," he said. "None whatsoever."ATSDR last month released a mortality study showing veterans of Camp Lejeune from 1975 to 1985 died of cancer 10 percent more frequently compared to a Marine Corps base with clean water. But a cancer-incidence study would show the rates of cancer among veterans who did not die of the disease.William R. Levesque can be reached at [email protected],com or (813) 226-3432.