Facing court-ordered deadlines, the Occupational Safety and Health Administration yesterday proposed new rules to reduce the permissible levels of two suspected carcinogens in the workplace, but not before agreeing to compromises sought by Reagan administration budget officials, sources said.

The substances, benzene and formaldehyde, are used by an estimated 1.5 million industrial workers. They were the subject of lengthy litigation by more than a dozen labor unions seeking tougher standards because of medical evidence that emerged since current standards were adopted more than 10 years ago.

"With benzene and formaldehyde used throughout most industry, it is imperative that we assure that the levels of exposure are within safe bounds," acting OSHA chief Patrick R. Tyson said in announcing the proposed rules.

The new rules, which OSHA said could save hundreds of lives while costing employers more than$100 million, will be the subject of public hearings.

The conflict over regulating the substances involves debate over the reliability of the scientific evidence, and the role of the Office of Management and Budget in reviewing rules.

The rules would reduce the allowable exposure to benzene from its current 10 parts-per-million (ppm) of air to 1 part-per-million, averaged over an eight-hour workday. For formaldehyde, the current limit of 3 ppm would be reduced either to 1 or 1.5 ppm, under alternate proposals offered by OSHA.

But several sources in OSHA, along with union officials, warned that a key safeguard in current rules, the "short-term exposure limits" or STEL, is omitted from the proposed rules. Omitting such limits means that workers could be exposed to short bursts of the chemical at potentially lethal levels without companies being cited for violating the law, officials said.

Three OSHA officials, who asked not to be identified, said that OMB, which reviews proposed regulations, had pushed for eliminating the short-term limits. But Robert Bedell, OMB's deputy administrator for the office of information and regulatory affairs, said that his office had "raised concerns" about the benzene standard, not the formaldehyde standard. The new standards for both were proposed by OSHA officials, Bedell said.

Tyson, in an interview, said that he had not been pressured by OMB. He said he did not include short-term exposure limits "for the simple reason that right now, we do not have the scientific evidence before us to justify a STEL. There is some evidence, but just not enough . . . .If the evidence comes in to support it, a STEL can be done."

While formaldehyde has been linked to cancer in laboratory rats, a study by the National Cancer Institute is expected to provide the most conclusive evidence on whether it causes cancer in humans and at what doses, officials said.

Formaldehyde is a pungent gas used in variety of products, including building materials, dyes, and fabrics. More than 5 billion pounds of the substance are produced annually in the United States.

"The industry believes that formaldehyde has a long record of safe use and most companies are below the standard," said Ed Stana, a spokesman for the Formaldehyde Institute, representing major makers and users of the substance.

Benzene is used in the production of petrochemicals, refining, and tire manufacturing and has been linked in medical studies to leukemia deaths, OSHA said.

OSHA estimates that at the current legal ceilings, workers face a lifetime risk of between 71 and 620 "excess" cancers per 100,000 workers handling formaldehyde, and between 44 and 156 excess deaths per 1,000 workers exposed to benzene. Those risks would be sharply reduced with lower standards.

Randy Rabinowitz, a lawyer for the United Auto Workers, which initiated the formaldehyde case in 1982, said the union is pleased that OSHA has moved to propose a rule, but that "the absence of a STEL is outrageous."

Regarding formaldehyde, Rabinowitz said that studies showed that laboratory rats developed cancer from short exposures to 15 ppm. Without a STEL, Rabinowitz said, a human legally could be exposed to higher doses, such as 16 ppm for a half-hour period, because the eight-hour average might be below the permissible level.