Two workplace health and safety cases, affecting millions of employes and thousands of employers, are before the Supreme Court as it opens its 1979 term today.

One case arose from a challenge by the government and the AFL-CIO to a ruling that federal standards intended to protect workers from cancer-causing substances must meet a cost-benefit test. The case is set for oral argument Oct. 10.

The second case involves a manufacturer's challenge to a Labor Department rule forbidding employers to retaliate against workers who refuse in good faith to do tasks they believe present an immediate danger of death or serious injury.

The challenge was filed by Whirlpool Corp., which seeks review of a ruling by the 6th U.S. Circuit Court of Appeals that conflicts with a ruling by the 5th Circuit. Solicitor General Wade H. McCree Jr. has joined Whirlpool in seeking review, making it probable that it will be granted.

These two cases have a common denominator: the intent of Congress in certain portions of the Occupational Safety and Health Act of 1970, which is administered by a Labor Department unit, the Occupational Safety and Health Administration.

The carcinogen case involves benzene, the 12th most widely used industrial chemical. It is an ingredient of other organic chemicals and is used in producing gasoline, detergents, pesticides and paint removers.

In 1971, the department adopted a standard permitting 10 parts per million of benzene to protect from nonmalignant diseases an estimated 629,000 workers at 150,000 worksites.

Later, however, the National Institute of Occupational Safety and Health warned that benzene also could cause leukemia. After a public hearing, Labor Secretary Ray Marshall in May 1977 tightened the standard to one part per million.

Actually, Marshall said, no safe level of exposure to benzene (or other carcinogens) has been shown. But, he said, one ppm was "the lowest feasible level," would save more lives than 10 ppm, and thus would achieve appreciable health benefits.

Consequently, Marshall said, the one ppm standard conforms with the mandate of the 1970 law to set an exposure level that "most adequately assures, to the extent feasible," that the health of no employe be impaired in the workplace.

He acknowledged that he was unable to pinpoint the benefits in reducing the permissible exposure to one ppm. But he did estimate the cost: Engineering controls costing $266 million, initial annual outlays of $187 million to $205 million, and subsequent yearly outlays of about $34 million.

The new standard drew legal challenges from the American Petroleum Institute and counterpart groups in the chemical, steel and rubber industries.

Last October, the 5th Circuit set aside the one ppm benzene standard with a 3-to-0 ruling.

In the opinion for the 5th Circuit, Judge Charles Clark of Jackson, Miss., agreed with Marshall that one ppm poses a lesser cancer risk than 10 ppm, that it is currently impossible to find an exact relationship between decreased exposure and decreased risk, that one ppm is feasible, and that the law seeks the "highest degree" of protection.

But the law doesn't give the secretary "unbridled discretion to adopt standards to create absolutely risk-free workplaces regardless of cost," Clark wrote.

The industry groups contend that the ruling doesn't conflict with the other decisions, is no threat to proper regulation of toxic substances and is "perfectly sensible."

By contrast, Solicitor General McCree said the ruling conflicts in reasoning and result with the others, particularly as they recognize the secretary's authority "to resolve doubts in favor of safety."

The AFL-CIO's Industrial Union Department said if the Supreme Court doesn't uphold the secretary's power to issue standards for the "myriad of carcinogens in the workplace," he'll be unable to proceed "with the congressionally mandated job of protecting American workers."

Judge Clark also wrote the opinion for a 2-to-1 majority in November 1977, when the 5th Circuit held that the secretary exceeded his authority by promulgating a rule forbidding employers to retaliate against workers refusing to perform particular tasks reasonably believed to present an immediate danger to life or limb.

Last February, however, the 6th Circuit ruled to the contrary in the Whirlpool case. Congress never intended to put workers in the "untenable position" of being forced by a boss to "choose between their jobs and their lives," Circuit Judge Damon J. Keith wrote.

The case came from Marion, Ohio, where Whirlpool makes household appliances in a plant with 13 miles of conveyors that carry parts overhead.

To protect workers from parts that occasionally fall from the conveyors, the company installed wire-mesh screening about 20 feet above the floor. Maintenance employes must walk on the screens to retrieve fallen parts, replace papers that catch grease drippings and care for the conveyors.

After several maintenance men fell through the screens, Whirlpool began to replace the screens with sturdier substitutes. But in June 1974, when the substitution was about one-third complete, an old section gave way under maintenance man George Cowgill, who fell about 20 feet into a parts box and was injured fatally.

Twelve days later, foreman Gale Price ordered two maintenance men to clean a section of screen except for areas he believed would not support them. They refused, saying they believed the section to be unsafe.

Price took them to the personnel director's office, where they received written reprimands, were sent home and docked six hours' pay. Another official noted their names and identification numbers when they requested OSHA's local phone number.

OSHA investigated, and the two men lodged a complaint that went to trial in Toledo before U.S. District Judge William J. Young.

Whirlpool claimed the men had rejected the work assignment not because they felt it to be unsafe, but because they wanted a pay increase for work on the screens. Young rejected the argument, saying that he "expressly finds that the employes refused to perform the cleaning operation because of a genuine fear of death or bodily harm."

Whirlpool won the case however, because Young ruled that the no-retaliation rule "is clearly inconsistent with the statute and therefore invalid." Congress, he said, had "squarely faced the issue as to whether . . . employes should be permitted to leave the job when faced with a dangerous situation and decided that they should not." He was reversed by the 6th Circuit.

Solicitor General McCree joined in seeking review for a different reason. He urged the court to recognize that "a limited right to self-help is necessary to deal with extreme situations for which the administrative and judicial processes are too slow, unless workers are to be left with the cruel choice between their safety and their job."

Here are some other major questions that confront the court, followed by the answer of a federal or state court. Each has been accepted for argument and will be decided by late June or early July 1980: ANTITRUST

Does the Sherman Act's ban on price-fixing cover an agreement among a city's real estate brokers to charge identical commissions for home sales? (No.) ENERGY

May Louisiana impose a tax on natural gas passing through the state from federal offshore fields to Illinois, Indiana, Maryland, Massachusetts, Michigan, New York, Rhode Island and Wisconsin, thereby imposing on consumers in these eight states an added charge of about $225 million annually? (Yes.) TAXATION

When a corporation does business but isn't based in a state, can that state tax the firm's dividends from foreign subsidiaries and investments? (Yes.) LABOR

Under the National Labor Relations Act, are university faculty members managers or supervisors -- and therefore exempt from the NLRA's protection -- because they participate in decisions on hiring, pay, Promotions and academic standards? (Yes.)