Washington — Recent developments concerning the herbicide Agent Orange show why this legacy of Vietnam is so difficult to deal with. And no matter how the issues surrounding it are resolved, it remains a cloud over Reagan administration efforts to increase United States chemical weaponry and to hold the Soviet Union accountable for using such weapons in Afghanistan and Southeast Asia.
Tens of thousands of veterans claim their exposure to the defoliant during service in Vietnam has caused a variety of illnesses in themselves and birth defects in their children. In a class action suit expected to come to trial next year, they seek billions of dollars from the manufacturers of Agent Orange.
But in a study released July 1, the US Air Force reported that personnel who handled the chemical in Vietnam have experienced no unusual death rate since the spraying was stopped more than a dozen years ago.
''They are not dying in increased numbers, at earlier ages, or by unexpected causes,'' the study said of the 1,269 men it surveyed who participated in what it called ''Operation Ranch Hand.''
At the same time, however, the Air Force cautioned that this does not mean close contact with Agent Orange was entirely free from potential harm. It said it would continue monitoring veterans for another 20 years.
Those critical of the Air Force study say it ignores other effects that may have been caused by the chemical, which contains the poisonous substance dioxin. And in the lawsuit brought in federal court in New York, there are new indications that the chemical manufacturers and the federal government may have suspected well before spraying was halted that Agent Orange was dangerous.
Internal documents made public this week from Dow Chemical Company and other defendants include warnings that Agent Orange and other substances containing dioxin could be harmful to humans. Some of this information apparently was reported to government officials several years before use of the herbicide in Vietnam was stopped.
All of this adds to the broad debate over the dangers of dioxin in hazardous waste. And it is an important factor in defense and arms control issues as well.
The United States, in pushing for new international limits on chemical and biological weapons, has been trying to publicize the alleged use of such weapons in Afghanistan, Laos, and Kampuchea by the Soviet Union and its allies. But it has not received much support from other nations. And Moscow continually reminds the world that the US dropped millions of gallons of toxic herbicides in Vietnam before political pressure and the suspicion that villagers may have been harmed forced it to stop.
Agent Orange was used not against people, but to destroy Viet Cong and North Vietnamese crops and jungle hiding places. President Ford ordered remaining stocks of Agent Orange incinerated on the ship Vulcanus in the mid-Pacific eight years ago.
But the substance still is associated with other chemical weapons. The administration has been pushing for a new generation of chemical bombs and artillery shells to replace and add to older weapons last produced in 1969. It is argued that the US is far behind the Soviets in this area and needs new chemical weapons to deter their use in time of conflict. But Congress so far has denied the Pentagon new chemical weapons.
As for the US veterans of Vietnam, it is likely to be some time before the Agent Orange issue is settled. It took considerable public pressure over several years before the Veterans Administration began investigating the subject. Studies by other agencies are expected to take months - if not years - as well. Among scientists, there remain widely differing opinions about the health effects of exposure.
And while the court battle in New York is much in today's news, observers see the latest developments there as just another chapter in a continuing saga.