The Labor Department yesterday extended "right-to-know" regulations to every industry in which workers are exposed to hazardous chemicals, requiring that employers make full disclosure of the danger of each such substance.

Mandated by court order, the regulations are expected eventually to cut by 20 percent the chemical-caused illnesses and injuries suffered by some of the 18 million employes exposed to toxic substances.

"The philosophy is that, if employes know what the hazards are, they will take steps to protect themselves," said Jennifer Silk, a health scientist for the department's Occupational Safety and Health Administration, which issued the rules.

"You can hand somebody gloves and say, 'Put them on,' " she said. "But if you tell them if they don't wear the gloves, their skin will be exposed to the bone, then they're more likely to understand why."

Last year, the OSHA imposed right-to-know requirements on 300,000 chemical manufacturers employing a total of 14 million workers. The requirements include labels identifying and revealing hazards of each substance, the posting of detailed expositions of risks and protective measures.

In May, the U.S. Court of Appeals ordered OSHA to extend the right to 18 million workers in 3.5 million industries that use but do not produce the chemicals. These include agricultural and construction businesses.

"The regulations are long overdue," said Margaret Seminario, associate director for occupational safety and health at the AFL-CIO, which brought the court case against OSHA. "Unfortunately, it's taken a court order and threat of contempt citation to get OSHA to act," she added.

Silk said the regulations, to be implemented over the next nine months, will cost industry $687 million to follow and more than $100 million a year to maintain.

But over the next 40 years, the disclosure provisions are expected to eliminate 750,000 illnesses and injuries each year. There are expected to be 148,400 fewer cancer cases, 74,200 fewer cancer deaths and 653 fewer non-cancer deaths caused by hazardous chemicals over the four decades, OSHA predicts.

Silk cited 1981 reports of 118,000 non-cancer illnesses and injuries due to toxic chemicals including poisonings, skin and respiratory diseases. She said such problems are grossly underreported.

In addition to apprising workers of chemical dangers, Silk said, the disclosure requirements are intended to help employers design programs to protect workers against the 575,000 hazardous chemical products in U.S. factories.

Chemical manufacturers are responsible for evaluating and labeling their products. Companies that merely use the substances are required to pass on the medical information and offer safety instructions.

The Carter administration proposed disclosure regulations for every work place, but the proposal was shelved in 1981 under President Reagan. In 1983, the OSHA published regulations for chemical manufacturers only, prompting the suit by Public Citizen and the U.S. Steel Workers of America.

In May 1985, the appeals court directed the OSHA to extend the regulations to all industry. Last May, the court ordered OSHA to speed up the process.

Seminario said that, while chemicals pose a great threat to workers, the Reagan administration "basically believes that the free-enterprise system can take care of these problems and that federal government doesn't have a role to play in this area."

But, she added, "employers left to their own haven't taken actions to protect workers."