The Reagan administration is considering a drastic overhaul of the Clean Air Act, including possible elimination of nationwide standards for air pollutants and the "margin of safety" required in defining a health hazard.

This could bring the president into collision with key members of Congress who have vowed to permit only fine-tuning of the controversial 1970 legislation. Whilte professing to agree with that approach, those who are preparing the administration position have not ruled out major changes, according to documents obtained by The Washington Post.

The proposed changes include transferring to state governments the power to set standards, eliminating the program to prevent significant deterioration of air quality in clean areas, and redefining health goals so that they safeguard the public only against "significant risk of adverse effects." Current law bases its pollution standards on the level of air purity required to protect children and asthmatics.

Working papers from early April reveal major divisions within the White House, however. During his campaign, Reagan criticized the act as an impediment to energy development, but the degree of unbuckling he will seek is still being hammered out.

The process involves a series of meetings with trade associations and industry lobbyists that began two weeks ago to gather ideas for the rewrite. Work on the amendments is divided among at least four groups.

One, headed by Interior Secretary James G. Watt, is the Clean Air Act Working Group set up under the Cabinet Council on Natural Resources and Environment, which appears to be in overall charge. Another is Vice President Bush's Regulatory Policy Office, a third is the natural resources team at the Office of Management and Budget, and the fourth is the Environmental Protection Agency, which will take the lead in presenting the administration proposals to Congress.

In an April 7 memo, the Watt group outlined seven "issues for review" on which Congress could be asked to hold hearings. They included methods by which the act sets pollution standards, the deadlines for compliance, the federal-state relationship, programs to preserve clean air and to control acid rain, and the impact of the act on the auto industry and coal-burning industries.

But discussion papers sent to the working group from different parts of the administration varied greatly in their approach to those issues. One of the toughest, from Bryan Mannix of Bush's regulatory policy analysis team, titled "Federalism and Clean Air," recommended elimination of national air quality standards for various pollutants, which form the basis of the act. He called them "inappropriate, as they take no account of local conditons."

Instead, Mannix wsrote, the federal government could inform the states about health effects of various levels of pollutants, tohelp the states set their own standards. Mannix agreed in an interview that the shift would be "a major overhaul" of the Clean Air Act, but, he said, "I haven't heard any talk that the administration position will be just a fine-tuning. The administration is looking at basic, fundamental change."

However, another paper, unsigned but apparently from EPA, assumed national standards will continue to exist and discussed the pros and cons of easing them. Another EPA paper -- the unpublished draft outline of its positin, which has yet to be approved by the new EPA head, Anne M. Gorsuch -- also retains federal standards. The administration verdict on this issue is not yet in.

A third unsigned issue document, thought to be from the Office of Management and Budget, said swift administrative deregulation of air pollution control would be faster than waiting for Congress to do it: "As the agency [EPA] begins dismantling the federal regulatory structure, it will become clear that there are no adverse consequences of federal deregulation."

But other papers in ther series ignored that approach. They discussed auto emission standards, regional costs and benefits of air pollution control and the possible effect of changes in the act on the coal market, clearly relating all of them to the congressional debate.

White House officials said the papers represented only "thinking out loud" and would not necessarily be reflected in the final proposals.

The EPA draft proposes loosening health standards to protect the public only from "significant risk of adverse effects" instead of "with an adequate margin of safety," a phrase aimed at safeguarding asthmatics and children. Such a change is a goal of the Business Roundtable, the steel and auto industries and the Chemical Manufacturers' Association, but is anathema to environmental groups.

EPA's draft also recommends further research on acid rain instead of the reduction in pollution emissions that Canada and environmental groups have asked for. It would give major polluters a three-year extension in their 1982 deadline for compliance with the law and would replace the current alphabet soup of site-specific technical rules with one performance standard for new pollution sources. These are all major changes.

But Sen. Robert T. Stafford (R-Vt.), chairman of the Senate Environment and Public Works Committee, where the act will be rewritten, has made it clear he wants only "fine-tuning" of the law he helped to write. His counterpart in the House, Rep. Henry A. Wxman (D-Calif.), chairman of the energy subcommittee on health and the environment, echoes that sentiment.

In fact, staff aides to both chairmen said hearings on Clean Air Act issues should be completed before the administration submits its bill. That is not expected until June 30; meanwhile, industry chieftains are making their case to the working group.

Representatives of the coal, electric utility and mining industries were among those who trooped into the Office of Management and Budget recently to dispense ideas, documents and chart.

The only complete set of proposed amendments to the act so far before Congress is a 37-page bill full of major changes, offered May 6 by Rep. James T. Broyhill (R-N.C.), ranking Republican on the Energy and Commerce Committee that has a major say in the final outcome. His measure would follow EPA on health standards and compliance deadlines, and would also eliminate federal sanctions against states that do not comply.

It would all but eliminate the program to prevent significant deterioration (PSD) of air quality where air is now clean. The issue, one of the most explosive, is listed as "unresolved" in the EPA draft, and the parade of industrialist has denounced the exisiting setup. But at least one of the White House documents notes that the PSD program would not hinder industrial growth in the West.