"Lingering" is certainly the mot juste—45 years after we quit spraying it around, we're still trying to figure out what Agent Orange's effects on the body are. If it seems surprising that the U.S. has yet to fully flush a Vietnam-era toxic agent from its system, consider that nobody's figured out how to get rid of Henry Kissinger either.
First, to recap: Faced with a peasant army fighting out of the dense forests of South Vietnam, the U.S. military resolved to simply destroy the forests via mass herbicide spraying, thereby forcing the guerrillas out into the open. A simple plan. What could go wrong? For this initiative—codenamed Operation Ranch Hand, and running from 1962 until 1971—the military relied on a few different herbicides, identified by a color and differentiated by their chemical composition. The most heavily used, to the tune of 12 million gallons dispersed, was Agent Orange.
Agent Orange contained equal parts of two plant-killing chemicals, 2,4-D and 2,4,5-T. Getting basted with 2,4-D wouldn't be a walk in the park, of course, but the latter component is the bad actor here. The manufacture of 2,4,5-T, it turns out, also produces a contaminant: the dioxin TCDD, a notably persistent chlorine compound that's been linked—but, as we'll see, with varying degrees of confidence—to spina bifida and related neural birth defects, cancer, skin disease, and a host of other unpleasant conditions.
The collective realization that our super-defoliant might be even more harmful than intended wasn't particularly gradual—it's not like we woke up to the corollary effects only decades down the road. As early as the mid-'60s, scientists were warning against the long-term uncertainty of what might be wrought by herbicidal warfare. By 1969 researchers had discovered the dioxin in Agent Orange, and in 1970 the surgeon general issued a warning about it. The Vietnamese, meanwhile, were seeing these fears come to life—local dispatches reported rising rates of birth defects, stillbirths, premature births, and miscarriages. You asked about U.S. troops, and that's where we'll confine our discussion here, but the Vietnamese-civilian angle is another, frankly ghastlier, story. Servicemembers' exposure was incidental; noncombatants on the ground were the ones being hosed down with the stuff.
What was gradual was an understanding of the exact link between Agent Orange and the afflictions that started showing up in Vietnam vets and their children—a devilish connection to make, even over decades of study. Why so tricky? An array of factors: for one, early research didn't track things like alcohol and tobacco use, which can also cause natal health problems. Another reason was a poor understanding of the paternal relationship to birth defects, and yet another is the presence of dioxins in some commercial herbicides—who's to say for sure where the exposure happened?
Nonetheless, after years of veteran activism, and plenty of anecdotal data—namely a lot of veterans getting sick—enough dots had been connected that in 1991 Congress passed the Agent Orange Act. This established a few conditions suspected of being linked to dioxin exposure, such as soft-tissue sarcoma, as "presumptive diseases"—that is, if a Vietnam vet was diagnosed with one of them, the connection to herbicide exposure could be presumed without anyone having to prove it, and Veterans Affairs would provide compensation. Through the 1990s and 2000s, cycles of Congressional hearings, further study, and legislation followed, lengthening the list of presumptive diseases and thus broadening eligibility for VA money and care. The government remained reluctant, though, to spell out any links between defoliant and health trouble: a benefits act passed in 2000, granting compensation to female vets whose kids had birth defects, didn't mention Agent Orange, dioxin, or herbicides at all—it just talked generally about service in Vietnam.
And that about brings us to the present, where the scope of the Agent Orange problem is still under debate. In 2010 the Obama administration issued a rule further expanding the presumptive-disease circle to include Parkinson's, ischemic heart disease, and other conditions; it estimated that an additional 150,000 vets would be able to submit claims. Any chance a President Trump will take up the cause? Well, he has promised to beef up the VA, and there are opportunities here—Congress has lately been considering extending benefits to "blue-water sailors," personnel who served on ships off the Vietnamese coast where Agent Orange may have been handled, but never got any closer to where it was used. (The VA's current position is that there isn't enough evidence for their disability claims; blue-water vets have to demonstrate direct exposure.) But we've heard nothing about this or any other Agent Orange-related topic from the White House, which hosts no relevant policy papers on its website. A general Internet search, meanwhile, for the phrases "Donald Trump" and "Agent Orange," yields ... well, I'm sure you can guess.
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