WASHINGTON — The United States sprayed more than 19 million gallons of defoliant over the jungles of Vietnam, a tactic designed to kill the forests and deny cover to the enemy.
The chemical worked. Miles of vegetation withered and died.
It also exposed an estimated 3 million U.S. troops and millions more Vietnamese to dioxin, the same toxic chemical reportedly used to poison Viktor Yushchenko, a candidate in the disputed presidential election in Ukraine.
Experts say it is unlikely that many, if any, Americans absorbed the dose Yushchenko ingested. Tests confirmed by three labs in the Netherlands and Germany showed that Yushchenko had 100,000 units of the poison per gram of blood fat, the second-highest concentration on record.
Mark A. Brown, a toxicologist who heads the environmental agents service of the Veterans Affairs Department, said it is uncertain just how much dioxin U.S. troops absorbed from their exposure to dioxin-contaminated Agent Orange in Vietnam.
A study years after the war ended suggested that U.S. ground forces probably had blood levels of dioxin in the range of 5 parts to 10 parts per trillion.
Troops handling the herbicide — named Agent Orange for the color of a stripe on 55-gallon shipping drums — may have developed blood levels of about 20 parts per trillion.
While a small dose in comparison to that given Yushchenko, it was enough, according to some studies, to cause cancer, diabetes, nerve damage and other diseases in susceptible individuals. Studies also linked the toxin to a birth defect, spina bifida, in children of troops who served in Vietnam.
Based on these studies, Congress instructed the department to assume that any of a long list of diseases developed by Vietnam veterans could be considered as caused by Agent Orange.
In effect, the government decided that the diseases were at least as likely to have been caused by dioxin in Agent Orange as they were to have been caused by anything else. Therefore, veterans were entitled to compensation and medical care without having to prove their disorder was caused by the herbicide.
At first, the diseases were relatively rare cancers, Brown said. Over time, new disorders were added. Today, the list includes 23 types of soft tissue cancer, four respiratory cancers, multiple myeloma, Hodgkin’s disease, prostate cancer and a nerve disorder.
Under President Clinton, Congress added diabetes to the list. An estimate at the time, Brown said, was that the addition of diabetes — a lingering disease that is expensive to treat — added $3 billion every five years to the Agent Orange compensation costs to Vietnam veterans.
“Since all of the other diseases were relatively rare and less expensive to treat, the addition of diabetes completely dwarfed all the other disorders,” Brown said.
The government also began providing for the treatment of children with spina bifida who were born to Vietnam veterans. The coverage was virtually for a lifetime, said Brown, and covered rehabilitation, special training and even wheelchairs. He said about 1,000 children — now adults — receive that benefit.
Some veterans have been judged disabled because of their contact with Agent Orange. Disability payments can range from $108 a month to almost $3,000 a month, depending on the level of disability and the number of dependents supported by the veteran.
Just how much the VA is paying to compensate for Agent Orange exposure and for medical care of diseases linked to the herbicide is difficult to determine, department spokesman Jim Benson said, because agency records do not put Agent Orange exposure into a separate category from other types of medical or disability payments.