Lack of essential data makes it impossible to say whether “Blue Water Navy” veterans -- who served aboard deep-sea vessels during the Vietnam War -- face higher, lower, or the same risk as other Vietnam veterans for long-term health problems associated with exposure to Agent Orange and other herbicides, says a new report from the IOM. It is plausible that service personnel assigned to deep-sea ships could have come into contact with the herbicides, the study committee noted, but the military carried out no measurements of herbicide concentrations in the atmosphere or waterways or of service members’ exposures during the war, so efforts to extrapolate from limited data on air and water currents and personnel locations provide insufficient information to make determinations.