In a letter two years ago to Vice President Bush, William D. Ruckelshaus attacked the Clean Air Act as "a complicated, pervasive law that is causing our society to spend very large sums of money for marginal benefits," and laid out a strategy for easing it.

Senate hearings on Ruckelshaus' nomination to head the Environmental Protection Agency, which enforces the clean air law, are scheduled to begin Tuesday. In an indication of the attitudes he may bring to that job, Ruckelshaus' 1981 letter told Bush:

* Congress is "largely ignorant" of the impact the Clean Air Act has had on industry, and congressional resistance to change is "reinforced by strong public support for the stated goals of the law . . . undergirded by a strong media bias in favor of continued stringent environmental regulations."

* The act's proponents are "dedicated, smart and experienced operators" who have "a solid public/media/congressional base of support."

* Any effort to ease the law would be "complicated by the rhetorical difficulty of advancing an argument which appears to place profit over public health," which would be compounded by the administration's "perceived bias against the environment."

* To move amendments through the Senate the administration should probably look for someone other than Robert T. Stafford (R-Vt.), chairman of the Senate Environment and Public Works Committee and a strong proponent of the law.

"If someone like Sens. Slade Gorton R-Wash. or Pete Domenici R-N.M. could be talked into strongly supporting the administration's position and carrying the bill, it would permit Bob Stafford to back away from his public position and save face with his constituents and the environmentalists," Ruckelshaus wrote.

The letter was written in June, 1981, as the Reagan administration was formulating its original position on the air pollution control law. It is now part of the voluminous record compiled by the Environment Committee in preparation for its hearings on President Reagan's nomination of Ruckelshaus to return to the job he held more than a decade ago as the EPA's first administrator.

The Senate file also includes a January, 1983, letter from Ruckelshaus to Ernie Minor, a member of the White House Council on Environmental Quality, in which Ruckelshaus indicates that he believes many environmental laws are "extreme" but no longer thinks they can be amended piecemeal through the legislative process.

Instead of proposing more amendments to the laws, which "will only cause further polarization on the issues to the detriment of change," Ruckelshaus suggested the appointment of a presidential commission to study and recommend basic changes in the way the government attempts to regulate health hazards.

Such a commission should be "made up of the most credible people we can find," Ruckelshaus wrote. " . . . A credible process must be found to educate the public and, in turn, the Congress on the lack of wisdom of the current system for regulating risk and the necessity for change."

Ruckelshaus, who has declined interviews until after the Senate votes on his nomination, could not be contacted to explain his letter to Minor, which apparently was written when the White House was considering a presidential speech on the subject of the environment.

But a fundamental change in the concept of risk assessment, as he appears to suggest, could affect dozens of laws--from the Food, Drug and Cosmetic Act to the Toxic Substances Control Act--that seek to protect the public from the potential health hazards of pollutants, chemicals, radiation and noise, whether in home, environment or work place.

The most stringent example of risk assessment is the Delaney clause to the food law, which forbids the use of any food additive that has been shown to cause cancer, no matter how small the risk or how large the dose needed to induce tumors in laboratory animals.

Industry has complained bitterly that this standard often results in enormously expensive regulations that are far more stringent than needed to safeguard the public.

Ruckelshaus suggested using the case of the Johns-Manville Co., which declared bankruptcy last year in the face of a swarm of asbestos-related lawsuits, as "the excuse" for the commission, whose recommendations "could lead to a more expansive review of social regulation in general."

In his letter to Bush nearly two years earlier, Ruckelshaus called the Clean Air Act the symbolic key to the administration's "struggle over social regulations."

He urged Bush to make amendments to the law a priority, noting that deregulation is "a central part of the administration's economic recovery program" and the Clean Air Act amendments would be "the first big test of how successful that program will be in coping with social regulations."

"It is my belief that the opportunity and hazard . . . in the Clean Air Act struggle greatly outweigh the importance of the issue of air pollution," Ruckelshaus wrote.

Ruckelshaus told Bush it would be useless to "tinker with" or "fine tune" the act. What was needed, he said, was "a straightforward approach with an aggressive communication effort" rather than "a mix of what ought to be done rationally and what can be done politically."

"There must be a clear upfront recognition that attempting to cope with air pollution by using health or environmental effects as the sole determinate of national policy is inherently irrational," he said.

In another letter to Bush, dated Jan. 30, 1981, Ruckelshaus jokingly referred to himself as the person who is "largely to blame for most of the bad things done to business by environmental regulations over the past decade."

Environmentalists said the letters do not, in their view, necessarily mean Ruckelshaus is unsuitable for the EPA job. But they characterized the documents as an important indicator of "what biases he brings to the job."

"His views are not that much different from his predecessor's," said Leslie Dach, a National Audubon Society official, referring to Anne M. Burford, who resigned March 9 amid allegations that the EPA had subverted environmental protection to the administration's political and economic goals.

"If he continues to take positions as EPA administrator as he took as a Weyerhaeuser executive, that clearly troubles us," Dach said. "That runs contrary to public desires for a strong Clean Air Act."

Although Ruckelshaus was named to the EPA job March 21, his nomination was not delivered formally to the Senate until yesterday, largely because of the need to come up with an acceptable plan to divest himself of stock in several firms regulated by the agency.

The Office of Government Ethics has formally approved that plan, which was released yesterday along with his financial disclosure statement.

Under its terms, Ruckelshaus agreed to divest himself of stock worth from $1,000 to $15,000 in Cummins Engine Co. Inc., Peabody International Corp. and Pacific Gas Transmission Co. He said he would exercise his right to buy, and then sell, shares of Weyerhaeuser stock worth between $100,000 and $250,000.

He also agreed to sell stock in United Siscoe Mines Ltd., valued at between $100,000 and $250,000, as soon as a Securities and Exchange Commission restriction on their sale expires in July.

Ruckelshaus, who listed salary and bonuses of more than $300,000 from Weyerhaeuser from Jan. 1, 1982, to last March 18, agreed to resign from that corporation and give up five corporate directorships that paid him nearly $60,000 last year.

He also promised not to participate in any EPA matters involving any of the companies that were pending while he had a financial interest in the company or involves a matter "with which I was directly and substantially involved while affiliated with that entity."

Additionally, Ruckelshaus said he might avoid participating "on a case-by-case basis" in other matters involving those companies if he thinks it is necessary to avoid any appearance of impropriety.