If the U.S. Forest Service has its way helicopters will soon be spraying a deadly Vietnam-era payload over national forests in the West.

The choppers will be flying at about 50 miles an hour between 35 and 70 feet from the ground. They will emit a stream of chemical defoliant that will kill vegetation that competes with tree seedlings struggling to grow into commercial timber stands.

The matter is currently a raging issue in Idaho - with the Forest Service just having complete statewide hearings on the proposal to spray vast acreages in three national forests here - because some of the herbicides contain traces of chmicals known as diozins.

Dioxins are potent teratogens - that is, they cause birth defects. They also cause cancer in laboratory animals. The long range effects of dioxins on humans are not known, but officials of the California Health Department point out that they are so potent that researchers have been unable to specify a dose small enough to be considered safe. As a result the U.S. Environmental Protection Agency is considering stepping into the dispute.

A similar Forest Service proposal for Washington and Oregon is pending in the couts and plans are imminent to spray some small acreage in the Klamath National Forest in California.

"The Forest Service is putting its production above the safety of the people," charged Dale Snipes, Head of the Panhandle Environmental Lwague in Sandpoint, Idaho, which was formed recently to fight the proposal. Jeff Griggs, of the Kootenai Environmental Alliance here, says that because "the public in Idaho will be guinea pigs."

Forest Service and timber industry officials claim that the herbicides are safe and would be used on nearly 60,000 acres in Idaho in much lower concentrations than used in Vietnam. "We're not going to douse northern Idaho," says Kenneth P. Norman, supervisor of theClearwater National Forest at Orofin. He says the risk is minimal - "Like taking aspirin,"

Involve would be the use of 10 different herbicides in the Clearwater, Nezperce and Idaho Panhandle national forests, but mist of the controversy is over one of the herbicides called 2, 4, 5-T.

In combination with a chemical called 2, 4-D that the Forest Service also proposes to use 2, 4, 5-T.

In combination with a chemical called 2, 4-D that the Forest Service also proposes to use 2, 4, 5-T was used by the U.S. military as the notorious Agent Orange to defoliate jungles in Vietnam to expose enemy troops. The defense Department halted the defoliation program in 1970 after the findings that it caused birth defects in mice and rats.

At the same time the U.S. Agriculture Department banned household and other uses of 2, 4, 5-T. Forestry and some other uses are still allowed. In addition to Idaho, the Forest Service has proposed using the Chenical in Oregon and Washington, but a court injuction has halted any action because the agency's environmental study of the proposal was ruled to be inadequate. In Californa, the Kalamath Forest supervisor, Dan Abrams, says that he has as valid enviromental impact statement and that spraying will start as soon as the weather clears.

The forest Service wants to use the herbicides as a way to speed growth of trees so it can increase timber production. The chemicals would be sprasyed over cedar, grad fir and hemlock trees in Idaho at the rate of 10,000 acres a year for six years beginning this years.

Thje intent is to clear sites of vegetation prior to planting of tree seedlings and also to suppress weeds and shrubs competing with growing seedlings for light, water and nutrients. The spraying is needed "to meet long-range timber production goals," says Norman Hesseldashl, a Forest Service spokeman. "This is a too we can use kto grow more timber faster on the good growth sites," says Ralph Kizer, head of the Idaho Panhandle Forests.

Opponents of the plan, though, cite possible health hazards.

The forest Service's environmental study of the proposal says that "dioxin in its pure state is one of the most toxic chemicals known to man today."

Because of the toxcity, the Environmental Protection Agency has limited the dioxin concentration in 2,4,T-T to 0.1 part per million, a level much lower than that used in Vietnam.

Opponents of the herbicide use here such asrobert Kabler, a North Idaho College chemistry teacher and president of the Kootenal Environmental alliance, however, say that there is no safe level" of use for such a toxic chemical and that 2, 4, 5-T will get into the food chain like DDT did until it was banned. He proposes that the brush be cleared by hand as a way to "put some unemployed people in Idaho back to work."

Opposed to the plan too are local and state health agencies and an organisation of local governments in north Idaho. The proposal is generating emotion among residents near the forest lands. Says Ann Bacon of Hayden Lake: "I get my drinking water out of the lake and I like to pick huckleberries and mushrooms. I want to continue to do so."

The Forest Service has been holding hearings on the proposal in recent weeks and plans to adopt orreject it by late spring or early summer.