HAVING REACHED a dead-end of government inaction, Vietnam veterans have now joined together to try to discover through their own resources what harm may have been done to American servicemen who were exposed to Agent Orange during the war. Under the Air Force's Operation Ranch Hand, Agent Orange -- a mixture of two widely used herbicides, 2,4-D and 2,4,5-T -- was sprayed over Vietnam in an attempt ot destroy its jungles and crops. Now the "ranch handlers" want to know whether Agent Orange affected more than the crops. So far, neither the Pentagon, HEW nor the Veterans Administration has been of any help.

The vets' concern arises because preparations of Agent Orange used during the war were highly contaminated with dioxin, another dangerous chemical. It turns out that if the conditions of synthesis are not properly controlled, dioxin is produced instead of the chemically related herbicide. Though the extent of its effects on human beings is still an open question, dioxin has been proven to be extremely toxic to animals. For some species, in fact, dioxin is among the most lethal of all man-made substances. Generally, though not always or always to the same degree, human beings show the same kinds of health effects in response to a chemical that laboratory test animals do.

The Vietnam therefore have good reason to be worried. Thousands and thousands of them believe they are suffering from the aftereffects of exposure. Their symptoms include: nervousness and persure. Their symptoms include: nervousness and personality change, impotence, miscarriages and the producing of deformed children, and tingling and loss of sensation in parts of the body. These symptoms could be diagnosed as anything from a psychological syndrome to multiple sclerosis. The veterans don't know, and as any ex-patient can testify, uncertainty and fear of the unknown can be a large part of the problem.

The Air Force has promised to do a six-year study, beginning next fall. The vets want -- and surely deserve -- to know much sooner than that. Epidemiological evidence that would give many of the answers could, in fact, be collected from a properly designed study in no more than one year. It should be. In addition, such a study should be made outside the jurisdiction of the military, not because the military would cook the evidence, but because its own potential liability creates an apparent conflict of interest that would undermine confidence in its findings.

The responsiblity lies with HEW which has been strangely reluctant to face or to accept it. Part of the problem may be that the environmental effect of the herbicides that make up Agent Orange is still a fiercely debated issue, and the results of a study could well affect its outcome -- rightly or not. The chemical industry believes that these herbicides (uncontaminated with dioxin) have been shown to be absoultely safe. Whatever the truth of that matters simple justice demands that the veterans not be held hostage to its resolution. If HEW will not act on its own, Congress should require it act. The Senate has already passed such a bill. The house should waste not time in doing the same.