Veterans Administration head Max Cleland, ignoring outraged congressmen and Vietnam veterans, yesterday insisted that a verdict still cannot be rendered about the long-term health effects of the herbicide Agent Orange.

Cleland, a triple amputee who was himself exposed to Agent Orange in Vietnam, told the House Commerce investigations subcommittee that the question of relating a low herbicide dose to chronic illnesses may never be completely answered. Three studies now planned or under way, however, could provide enough information in two or three years to justify a policy decision on it, he said.

"That is appalling," declared Rep. Andrew Maguire (D-N.J.). "Why do we have to have the last bit of evidence?" He said Cleland was "absolutely wrong" to insist on more studies.

Hundreds of the 2.5 million Vietnam veterans have sought VA compensation for skin, liver and nerve diseases, cancers or birth defects in their children that they claim resulted from exposure to Agent Orange, a defoliant used until 1970 in Vietnam. Maguire and Rep. Albert Core Jr. (D-Tenn.) urged Cleland to "make the reasonable presumption" that enough evidence now links Vietnam service to these diseases to warrant VA action on the claims.

"Just because there are uncertainties doesn't mean these people don't deserve a better performance from the VA than they are getting," Gore said. dMaguire angrily suggested that Cleland fire his chief medical officer, Dr. Donald L. Custis, who was sitting with Cleland at the witness table.

"The laboratory was not Vietnam," Cleland shot back. Although experimental animals suffer immediate health problems when fed or injected with dioxin, the toxic contaminant of Agent Orange, he said, the VA cannot conclude that a veteran who appeared healthy at the end of his service became ill a decade later as a result of Vietnam duty.

"What we're trying to establish is a very difficult case of scientific linkage," Cleland said.

Robert Muller, director of the Vietnam Veterans of America, told the panel that a toll-free information line on Agent Orange had drawn 10,000 inquiries from all over the country in 4 1/2 months of operation. He asked that the VA be required to begin a program informing veterans of its screenings and physical examination programs, and that any veteran with the skin condition chloracne, which is associated with dioxin exposure, be given automatic compensation whether it had been reported during Vietnam service or not.

"Most vets were too busy staying alive to report skin conditions," he said.

Joan Bernstein, general counsel of the Department of Heatlh and Human Services, and Dr. John Moore, deputy director of HHS' National Toxicology Program, testified that no further study results related to Agent Orange can be expected for two or three years, when three major reports will come in.

But a verdict may have to be given anyway, Bernstein said: "It will not be the first time that social policy decisions have had to be made on less than total scientific evidence."

One of the three major studies pending involves 1,160 Air Force personnel who handled the drums of Agent Orange in a defoliant operation called Ranchhand during the war, Moore said. Another concerns a comparison of birth defects among Vietnam veterans' children to those of ordinary children in Atlanta, where extensive records on malformed babies have been kept since 1962.

The third study is a broad review of all Vietnam veterans' health histories since the war, which is still being designed and is under court challenge to its eventual validity from the National Veterans Law Center.