Can EPA regain its scientific credibility?

It is fitting that William D. Ruckelshaus, the first administrator of the Environmental Protection Agency (EPA), has been appointed to rebuild the agency, for once again he will have to start anew. Many of the bright, young scientists and managers who came to EPA with ''a sense of mission'' in the early 1970s - when Mr. Ruckelshaus was assembling his team - have gone. The past two years have left the young agency in a shambles. Programs have been demolished, staff capriciously shuffled, divisions pointlessly reorganized, and enforcement activities nearly halted.

In the hands of a competent administrator - and Mr. Ruckelshaus is considered competent - these problems could be corrected and the EPA could get back to the business of protecting the environment if he has the President's support.

Mr. Ruckelshaus's managerial ability and President Reagan's intentions will be most conspicuously tested in their approach to that sector of EPA that has sustained the heaviest damage: research. While the other problems at EPA can be remedied by improved management and funding, the losses in the agency's research capabilities will be exceedingly difficult to recoup.

Everything EPA does is, or should be, based on the best and latest scientific information. Without a solid data base, environmental regulations can be ambiguous; possibly too lax, threatening public health, or too strict, causing consternation in the regulated business. The Reagan administration, in its efforts to ''get government off the backs of industry,'' has maintained that many environmental regulations should be scrapped because the data to back them up are lacking. At the same time the Reaganites have been defunding the research programs that would have produced the information needed to write, refine, or enforce environmental regulations.

EPA's research budget was $258 million in 1981. Although Congress has resisted some reductions, Mr. Reagan's budget benders have managed to squeeze EPA's science funds well below the minimum requirements. The President's 1984 budget request for EPA research was only $112 million. Even without adjusting for inflation, that's a 56 percent reduction.

Programs that have been cut back or scrapped include research on the effects of toxic chemicals on human beings, methods of toxic waste disposal, risk assessment, groundwater pollution, health standards, sampling for toxins, radiation, and air quality. Virtually every EPA research program has been affected and more laboratories are slated for oblivion in fiscal '84.

These reductions in data gathering come at a time when our need for such information is growing in quantum leaps. For example, EPA is responsible for determining what effect the production, use, and disposal of chemical products have on the environment and human health. According to a National Wildlife Federation study, there are over 55,000 chemical products in commerce and EPA receives about 1,000 new chemicals for testing each year. To deal with the backlog of applications, EPA scientists have been forced to apply abbreviated testing procedures to new chemicals and to rely on industry information.

Another example: Hazardous waste research is in its infancy, yet we now find that any of us could be sitting on a Love Canal or Times Beach. We need trustworthy research information on these ubiquitous, toxic materials and we need it fast. We are just beginning to realize that some chemicals we have casually incorporated into our everyday lives pose health risks. Yet, even with widespread chemical compounds like dioxin, we don't know what the safe exposure limits are or how to treat contaminated people and places. And dioxin is just one on a growing list of headline-grabbing substances that include PCBs, asbestos, formaldehyde, lead, and many pesticides.

Let's assume that Mr. Ruckelshaus is able to procure funding for the languishing EPA research programs. Then would we be back on the road to finding sensible and economical solutions to environmental problems? Unfortunately, it is no longer simply a matter of dollars.

In the early 1970s, when ecology was a sacred word and the EPA was new, the agency attracted scores of first-rate scientists who wanted to devote their talents to The Cause. Environmental science was the ''in'' field. Still, it took 10 years to assemble the interdisciplinary cadre necessary to deal with the complexities of environmental management. By 1980, EPA's science staff had won international respect and had established productive working relationships with scientists in industry and university labs. In some fields - fish and wildlife toxicology, environmental effects of atmospheric deposition (acid rain), marine pollutants - EPA had no equal.

That is all changed now; contracts with industry and university labs have been canceled and the credibility of EPA scientists punctured. Congressional committees investigating EPA have found that scientists who failed Mr. Reagan's political litmus test were placed on ''hit lists.'' Many were forced out or quit in disgust. Others were given menial, nonscientific tasks, such as punching holes in reports and filing. Some were exiled to remote areas. All were kept in constant suspense; they feared for the future of their projects, and their jobs.

Many fled to industry, and to much higher salaries; only dedication had held them before. They are not likely to return. To have an upwardly mobile career, scientists must work among their best peers, at modern facilities with good reputations. They must know that they will be allowed to see a project through and not lose years invested in long-term explorations.

Mr. Ruckleshaus has accepted an enormous responsibility and one of the toughest jobs in Washington. The acid test of his abilities and intent will be the restoration of EPA's scientific credibility. Congress and the American public will be watching his every move.