The U.S. military sprayed twice as much herbicide on Vietnam during the war there than previously estimated, according to a study published today in the journal Nature. Relying on previously unexamined military documents and new assessments of dioxin concentrations, the study found that an additional 1.8 million gallons of toxic herbicides, mostly Agent Orange, were used by the Armed Forces. From 1961 to 1971, more than 10 percent of what was then South Vietnam was sprayed with defoliants in an effort to destroy food crops and remove forest cover from combat areas. An estimated 14 percent of Vietnam’s forests were obliterated, and the herbicides have been blamed for birth defects and illnesses in both Vietnamese citizens and American veterans. The U.S. compensates veterans for diseases associated with the spraying in Vietnam but has refused recompense to the Vietnamese until more data are available.