The scientists who first called new forms of genetic engineering a "possible danger" are now saying that the risks seem less than they believed and that Congress may soon impose unreasonable rules that would cripple American science.

The research involved splits apart, then rejoins the heredity-carrying material of various organisms - deoxyribonucleic acid, or DNA - to make "recombinant" hybrids that carry some of the traits of two unrelated forms.

The promise of such work is that it may create new medicines, vaccines, industrial chemicals or crops. The risk, many scientists have said, is that it could create unexpectedly dangerous new forms that start new ailments or epidemics.

Dr. Sherwood Gorbach of Tufts University told the National Institutes of Health in a letter Friday that 37 doctors and researchers have "unanimously" concluded that the danger of runaway epidemics from the bacteria now being used in such experiments has proved virtually non-existent.

The 37 scientists attended an NIH-financed workshop on potential risks to review research of the last four years. The workshop was chaired by Gorbach at Falmouth, Mass., in late June.

Another 137 scientists - 85 per cent of the participants in a 1977 version of the 1973 Gordon Research Conference, whose members first called attention to recombinant-DNA's possible hazards - have written an "open letter to Congress" saying "exaggerations" of the "hypothetical hazards" have gone "far beyond any reasoned assessment." Their letter says "the experience of the last four years," including many laboratory experiments, has shown no "actual hazards."

These and other scientists are alarmed at some sections of pending Senate and House bills to regulate the research. Among these are provisions that would fine them either $10,000 (in the Senate version) or $5,000 (the House version) each day they violated the proposed regulations.

Several scientific groups especially oppose the bill, introduced by Sen. Edward M. Kennedy (D-Mass.) and approved by the Senate Human Resources Committee last month. It would create an 11-member presidentially named commission to license laboratories.

A news report in the current Science, organ of the American Association for the Advancement of Science, says this bill's opponents claim "it smacks of Lysenkoism" - the kind of controls imposed on science in the Soviet Union by Josef Stalin and his scientific favorite. Trofim Lysenko - and could damage science here just as Lysenkoism did there.

Meanwhile, the same NIH committee that wrote the current safety guidelines for such research has recommended to NIH Director Dr. Donald Fredrickson that the guidelines be relaxed in several important ways.

But NIH's efforts to move quickly on experiments to test the new techniques' safety have been hampered.

Litton Industries - contractor to remodel laboratories and buildings at Fort Detrick, Md., to create a National Genetic Research Facility - has withdrawn from the work because it can't get liability insurance from insurers, who say they don't know enough to assess the potential dangers.

"This shows what can happen when the dangers get blown up," said an NIH official who declined to be identified." Almost no one is proposing that all the restrictions be removed.

"But we're suffering from all the word and TV pictures of bug-eyed monsters racing out of the labs as a result of our experiments."

There are also still some scientists who firmly believe that the research is moving ahead much too fast, and that the possible dangers are still frightening.

Two groups of scientists are to meet with Kennedy today. One, headed by Dr. Stanley Cohen of Stanford University, a leader of the original movement to curb the research, will argue that Kennedy's bill is too restrictive, tr add four

Another, headed by Dr. Halsted Holman of Stanford, is expected to back Kennedy.

The Kennedy bill could come to a Senate vote in late July or early August. A House bill sponsored by Rep. Paul G. Rogers (D-Fla.) is yet to be voted on by Rogers' Health Subcommittee, but is expected to reach the House floor by late summer.

The American Society for Microbiology and leaders of several other groups - including the Association of American Medical Colleges, Federation of American Societies of Experimental Biology and American Institute of Biological Sciences - back the Rogers bill, with some changes. It would have supervision of the rules to the Department of Health, Education and Welfare.

But both the Kennedy and Rogers bills would make the NIH safety guidelines mandatory for all laboratories, federal, academic and industrial, not just those financed by NIH funds. Both would leave approval of individual research projects to local committees.

Both would also allow states or cities to set tougher rules if they can show justifiable reasons. Most scientists feel this could create a regulatory patchwork that would force them to move from college to college to seek fewer restrictions - and might make it impossible for some universities to get liability insurance.