New research shows the amount of the toxic chemical dioxin sprayed during the Vietnam war was much higher than previously thought. The study presents the clearest picture yet of when, where, and how much of the dioxin-contaminated herbicide called Agent Orange was sprayed in Vietnam. Scientists hope the new information can help answer decades-old questions about the health effects of the spraying.
During the Vietnam War in the 1960s, American and South Vietnamese forces faced frequent ambushes from communist fighters hiding in dense forest vegetation. The U.S. military came up with one way to deal with the problem. Spraying herbicides over trouble spots would deprive enemy forces of cover.
"I witnessed areas that were sprayed. And it certainly worked," says executive director John Sommer, of the American Legion's Washington office, who was an infantryman in Vietnam in 1968. He says in one area where he served, communist fighters had ambushed South Vietnamese convoys again and again. The military sprayed the area with herbicide. "It totally did away with anyplace for the North Vietnamese to hide in that area. So it did work," he says.
The U.S. military also sprayed herbicides to kill crops in villages suspected of supporting communist forces, and to clear vegetation around bases. From 1961 to 1971, Operation Ranch Hand sprayed more than 75 million liters of herbicides over Vietnam. Much of it was a chemical mixture called Agent Orange.
Mr. Sommer says in the late 1970s, Vietnam veterans began talking to the American Legion about problems with their health. "Different problems that could not be explained too easily, and it was determined after a lot of interviews and discussions that Agent Orange appeared to be a trigger for some of these problems," he says.
The active ingredient in Agent Orange, and some of the other herbicides used in Vietnam, was contaminated with a chemical called dioxin. Scientists discovered dioxin caused birth defects in laboratory animals. Dioxin may also cause birth defects in people, and it has been linked to several kinds of cancer.
"People were not doing this on purpose," says public health professor Jeanne Stellman, at Columbia University, who has been studying herbicide health effects on veterans for two decades. "In the early 1960s, dioxin had just been identified as a toxic agent. At the time that we were spraying Vietnam, we were using this chemical very, very freely in the United States," she says.
The United States banned the chemical in 1979.
But it has been extremely difficult for doctors to say for sure that the herbicides caused the health problems that Vietnam veterans suffered. Vietnam also says Agent Orange has affected its people. But the evidence has been lacking.
Veterans groups pushed for comprehensive studies. But Ms. Stellman says the U.S. government resisted. "There was a huge political decision to just not do the research. To just say there was no effects, that there were no exposures, and, furthermore, that the research could not be done," she says.
Ms. Stellman says it took an act of Congress to get serious research going on Agent Orange. The Agent Orange Act of 1991 instructed the National Academy of Sciences Institute of Medicine to look into the matter. The institute brougth in Ms. Stellman and her team.
Part of the problem has always been a lack of data on exactly when, where, and how much herbicide was sprayed. Researchers had not been able to put together comprehensive records of Operation Ranch Hand missions until Ms. Stellman found sets of forgotten and poorly-labeled records in the National Archives.
She says the turning point came when she recognized numbers in one set of files looked a lot like numbers with a different label in another set. "And it suddenly all started to make sense to me. And it turned the maps we could draw of the flight paths of the planes, it turned them from this crazy back-and-forth criss-crossing of Vietnam into really targeted efforts," she says.
The new maps are much better than previous versions at estimating herbicide exposure. The study also raises the estimate of how much herbicide was sprayed by about seven million liters, and the total amount of dioxin sprayed by nearly twofold. The study also estimates that between two and five million Vietnamese, in more than 3,000 hamlets, were sprayed directly during Operation Ranch Hand.
The study was recently published in the journal Nature.
Ms. Stellman says she could not believe the numbers were so high. "The night before the paper was supposed to be published, I got up at two o'clock in the morning I was so nervous. And I said to myself, I must have counted the hamlets more than once. I must have made a mistake," she says. She went back and checked her work, and there was no mistake.
The Vietnamese government says the study shows how serious the problem is in Vietnam. The Institute of Medicine says the new data makes possible the studies that will help answer lingering questions about the health effects of the herbicide program. For veterans and Vietnamese sprayed with dioxin-containing herbicides three decades ago or more, those answers can not come too soon.