Environmental Protection Agency Administrator William D. Ruckelshaus yesterday called for major revisions in the way public health and environmental laws attempt to regulate risks, saying that the "emotionalism" of the debate about toxic substances has created a "paralysis of honest public policy."

In his first policy address since beginning his second stint as EPA administrator last month, Ruckelshaus told scientists and engineers at the National Academy of Sciences that he endorses a "government-wide process for assessing and managing health, safety and environmental risks."

The process Ruckelshaus outlined would entail statutory changes in many of the nation's broadest laws, including the Federal Food and Drug Act and many of the pollution laws administered by the EPA.

Ruckelshaus said that he envisions a two-step process: the first an assessment of risks to human health or the environment from a given substance, and the second a balancing of that risk against the costs of reducing or eliminating it.

While some laws permit balancing a regulation's cost against its expected benefit, many require regulation on the basis of risk alone. The Delaney clause in the Food and Drug Act, for example, forbids the use in food products of any substance shown to cause cancer in laboratory rats, no matter how small the risk.

Conceding that "legislative change in the current climate is difficult," Ruckelshaus asked his audience of more than 150 distinguished scientists for help.

"The polls show us that scientists have more credibility than lawyers or businessmen or politicians, and I'm all three of those," he said. "The truth is, I need your help."

Ruckelshaus supported risk-benefit analysis as a Weyerhaeuser Co. executive and testified at his confirmation hearings that he intended to press to implement the concept.

But in his address yesterday to an audience that included some scientists who have accused the EPA of attempting to manipulate scientific data to support its decisions, Ruckelshaus said that risk assessment "must be based on scientific evidence and scientific evidence only."

"Nothing will erode public confidence faster than the suspicion that policy considerations have been allowed to influence the assessment of risk," he said.

In another olive branch to the scientists, Ruckelshaus said that he intends to bolster the EPA's research program, which has been cut sharply in the last two years, and "will be asking the advice of the outside scientific community as how best to focus those research efforts."

He also asked his audience to "take a larger role" in explaining environmental risks to the public.

"We are now in a troubled and emotional period for pollution control," he said. "Many communities are gripped by something approaching panic. And the public discussion is dominated by personalities rather than substance."

Part of the scientists' role, Ruckelshaus suggested, will be to tell Americans that they can no longer count on avoiding the potentially hazardous effects of toxic substances.

"Since these substances are widespread in the environment and since we can detect them down to very low levels, we must assume that life now takes place in a minefield of risks from hundreds, perhaps thousands, of substances," he said. "No more can we tell the public: 'You are home free with an adequate margin of safety.' "