The medical team leader studying the health of government workers exposed to PCBs says the workers' physical complaints may be traceable as much to public fear of the chemicals as to the PCBs themselves.

Dr. Edward Emmett, chief of the Johns Hopkins Medical School team, says media coverage of the possible hazards of PCBs has outpaced scientific research, leaving the public with more anxiety than knowledge.

"There hasn't really been a good and complete study of the effects on humans," he said. "We will consider the problems [of the workers] but I think that most of the complaints have come from the public's sensitivity to PCBs lately."

Forty-three government electricians have complained that daily, on-the-job exposure to PCBs have left them afflicted with nausea, headaches, dizziness and other symptoms of endangered health.

Their complaints -- and the report that PCBs have been leaking from drums stored at the GSA warehouse in Bladensburg and at P street SW -- have spurred a cooperative investigation by Johns Hopkins and the National Institute of Ocupational Safety and Health.

But even some of the complaining workers acknowledge that their concern is more with what they don't know than with what they do.

"I never really thought about PCBs being dangerous until I read about it in the newspapers, said Jim Edlen, a GSA electrician, as he leaned against a barrel of the chemical in the P Street warehouse earlier this week.

Edlen has been working for five years around a PCB-saturated chemical called Askarel, which is used as a coolant and lubricant in electrical transformers. The electricians say 75 percent of the electric transformers in federal buildings here, including the White House and the Pentagon, currently leak Askarel.

Edlen signed the electricians' complaint, but says he himself has never noticed any adverse effects from handling the chemical.

Other workers are less sanguine. Several in GSA's equipment repair shop adjacent to the Askarel storage room on P Street say Askarel fumes have caused symptoms that include numbness in their arms and hands and swelling in their feet.

John Hopkins' Emmett, however, while acknowledging the PCBs can be hazardous, is "not sure at this time that the symtoms the men are complaining of are a result of PCB exposure . . . My impression is that they may not be."

The question facing Emmett and other investigators is: At what point does PCB exposure become hazardous?

A group of 1,000 Japanese was made seriously ill by PCBs in 1968 after they ate rice oil containing high concentrations of the chemicals, which had contaminated the rice from which the oil was pressed.

According to Dr. Irving J. Selikoff, director of the Environmental Health Laboratory at Mt. Sinai Medical School, in New York, the victims of the so-called Yusho incident suffered "long continued sickness, illnesses of the skin, liver, birth defects and effects on the children."

But no one has suggest the government electrical workers have been eating PCBs, although it is possible some of the chemicals may have found their way from hand to mouth.

There are no data about the effect of industrial exposure to PCBs, said Selikoff, who is presently directing a study of workers at a General Electric plant in which generators being manufactured were filled with Askarel.

Despite repeated statements in the media that PCBs cause cancer in humans, Selikoff's study will be the first to examine that question in detail. There are, he said, no recorded cases of human death or cancer directly attributed although the chemicals have been manufactured more than 50 years to PCBs.

"Animal studies are clear," however, said Selikoff. "There are many effects on animals," including cancer, liver damage and birth defects. All of them were induced by feeding PCBs (polychlorinated biphenyls) in minute quantities -- quantities proportional, some scientists believe, to what humans might inhale or swallow in a contaminated industrial enviroment.

"But one of the problems we always have with environmental chemicals," he continued," is whether effects on animals should be of concern to us, or must we wait for [documented] disease in humans" before taking action.

According to Selikoff, more than 240 chemicals have been shown to cause cancer in animals -- chemicals "to which human beings are exposed and for which we have no studies to tell us what the effects on humans will be."

The difficulty, say scientists, is that the only way to determine the effect on humans is to study large numbers of persons who have been exposed to the particular chemical and compare their health and medical problems with those of a matched group of persons who have not.

Further complicating such studies is the fact that many cancers take decades to develope, so that a chemical or other substance may be in use for years before anyone even suspects that it may be a carcinogen.

According to Selikoff, scientists knew that smoking causes cancer in animals at least two decades before they proved the link between smoking and cancer in humans.

What has most concerned scientists and environmentalists about PCBs -- and led to a ban on their manufacture recently -- is that the chemicals are virtually indestructible, remain in the environment and are stored for years in the fatty tissue of animals and humans.

The chemicals were first manufactured in the late 1920s by Swann Chemical Co. -- later acquired by Monsanto -- and were used for numerous industrial applications.

The chemicals have been dumped into the environment for decades, and have been found in large quantities in Lake Michigan and the Housatonic River, in Connecticut.

Like the now-banned pestacide DDT, PCBs remain in the ground, and end up in the food chain. The chemicals have also been found in human breast milk, a result of their storage in the mothers' fatty tissues.

The result of such human exposure has not yet been determined. Cancer rates have soared in this country during the past 20 years, but so have the number of other chemical agents being used in every stage and function of life, including those commonly present in compounds also containing PCBs.

Precisely what agent causes which cancers may, in fact, never be determined.