Health, Education and Welfare Secretary Joseph A. Califano Jr. placed the issue of low-level nuclear radiation hazards high on the list of American public health priorities yesterday.

He called for expanding governmental studies to determine the dangers of exposure to a phenomenon that he described yesterday as a "serious public health issue."

Califano voiced his concerns in releasing the 800-page draft working papers of the White House Interagency Task Force on the Health Effects of Ionizing Radiation, which has been examining for nine months the controversy about existing levels of radiation that are considered safe.

Califano said recent studies, though not conclusive, do suggest that the incidence of leukemia produced by low levels of radiation may be higher than scientists thought.

The task force reviewed past and current research into radiation health and concluded: "Existing knowledge is insufficient to provide an unequivocal answer to the low-dose question." Moreover, it said that a definitive answer may never be found.

Nonetheless, the task force and Califano recommended that current health research be increased and coordinated.

A key element of the current radiation controversy is whether dose standards in government nuclear facilities and privately run nuclear power plants pose long-term health risks for employes.

Califano said HEW's Center for Disease Control will design within the next year "a comprehensive research program on occupational exposure to low-level radiation." In addition, the director of the National Institutes of Health, Dr. Donald Frederickson, will supervise all current government research in the low-level field "to insure that a comprehensive radiation research program is planned and conducted."

A task force study group has been unable to reach agreement on possible reorganization of the governmentwide health study. This is one of the few internal battles that was not settled by the time of yesterday's announcement. A report is expected in several weeks.

Of $78.5 million being spent now for this research, the Department of Energy accounts for over 63 percent -- a situation that some government officials think should be changed since DOE is an active promoter of nuclear weapons and power.

DOE is expected to announce today a new research study of low-level radiation effects on 250,000 past and present workers in the nation's nuclear submarine shipyards. To be carried out by The Johns Hopkins School of Public Health and Hygiene, the multiyear study would be the largest ever undertaken in this country.

In Califano's statements and in the task force papers, great care was taken to avoid creating an impression that all radiation is bad.

The HEW secretary said, for example, that "while the research and public discussion continues, we must take care neither to exaggerate nor to underestimate the degree of risk from radiation."

The task force study devoted to public information listed the following among the "basic messages" to be given the public: "the risk from an exposure to radiation must always be measured against the benefit," and such risks "need to be placed in the proper perspective alongside the health risks from exposure to other hazardous materials."

Not far below the surface of the task force papers lies the scientists' controversy over just how much risk is really involved in low-level doses.

The papers mention three studies released over the past 18 months that were "extensively criticized and vigorously defended."

One of the three was the CDC study of Smoky, the 1957 nuclear weapons test in Nevada where over 2,000 GIs were marched for maneuvers to ground zero of a 47-kiloton blast within hours of its detonation.

Califano yesterday confirmed a Washington Post report last month that eight leukemia cases among the participants were "more than twice what would have been expected in this population."

The secretary went on to say, however, that the numbers, don't automatically indicate that radiation at the site caused the subsequent leukemia.

The dilemma of the Smoky study and others was best summed up by the task force research group which found: "Because cancer has a long latent period and because clinical features of cancer do not reveal its cause, it is impossible to determine whether any given case of cancer was caused by radiation or by another factor."

Implications of such a finding are apparent in the task force study of possible benefits that could or should go to now ill veterans who participated in Smoky and other nuclear tests or to civilians exposed to fallout from the same tests.

"As a practical matter," the study says, "it is often virtually impossible to determine whether a particular injury has been caused by exposure to radiation or by other factors.

"It is statistically more probable in each case that the cancer was caused by other factors," and the "few who are 'entitled' to compensation or damages cannot be distinguished from the many who are not entitled."

The main recommendation of that group was that the federal government develop a single medical guideline outlining current knowledge on "the relationship between radiation exposure and disease including the issues in dispute." That at least would be a start for all benefit claimants that does not exist today.