The Labor Department yesterday launched a review of the policy it uses to decide whether a workplace chemical may cause cancer. The department, which seems poised to make fundamental changes, also will look at how it determines which potential carcinogens should be reviewed first and how best to protect workers exposed to them.

This so-called carcinogen policy, spelled out by the Carter administration, was bitterly opposed by industry and targeted for review in the early days of the Reagan administration. It had evolved over the years as the Occupational Safety and Health Administration found itself facing the same basic questions of scientific policy over and over as it wrote regulations for a variety of suspected or proven carcinogens.

The policy gives OSHA some rules of thumb for assessing scientific evidence about workplace chemicals. For example, it says that chemicals shown to cause cancer in one kind of animal should be listed as potential human carcinogens. It also says that any dose of a potential carcinogen should be considered dangerous--rejecting the idea of a "threshold" or "no-effect" exposure level.

Such basic elements of the OSHA policy eventually became a model for a government-wide carcinogen policy for such disparate agencies as the Food and Drug Administration, the Environmental Protection Agency and the Agriculture Department's Food Safety and Quality Service.

The proposal in yesterday's Federal Register said this reconsideration of the standard is designed to incorporate such new developments as the Supreme Court's benzene decision (saying OSHA must show a chemical presents a substantial risk before regulating it) and President Reagan's Executive Order 12291 (saying that regulations should prescribe the least costly means of accomplishing their objective).

James Foster, an OSHA spokesman, emphasized yesterday that the agency was reevaluating only its January, 1980, carcinogen policy; no changes were proposed in nine existing or proposed OSHA standards regulating workplace exposure to such chemicals as lead, arsenic and asbestos.

Foster also noted that whether or not the agency has a carcinogen policy doesn't affect its ability to write rules for potential workplace carcinogens. OSHA is in the process of developing two such standards at the moment, he added.

Since the list of chemicals to be examined for carcinogenicity has never been sorted to rank them as potential hazards, no chemical has ever been regulated under the policy, Foster said.

OSHA yesterday also solicited comments on what to do with 257 chemicals awaiting further study under the original policy. Comments on what to do with the standard are due April 5; comments on what to do with the list of chemicals are due Feb. 19.

A series of industry challenges to the existing standard, currently pending before the 5th U.S. Circuit Court of Appeals, have been stayed while OSHA takes a second look at the policy. "You've got a whole lot of things to crank into the policy now," said Foster.

The original policy met with mixed reviews from labor groups, some of whom didn't think it went far enough in pressing for quick regulation of potential workplace hazards. "It was just a classification scheme . . . . To us at the time it didn't change things any. It didn't regulate one chemical," said Steve Wodka, an attorney specializing in occupational health issues.

"What they're doing now is destroying any hope of having any chemical appropriately regulated," Wodka added.

"It didn't look as if the Reagan administration would implement the policy already on the books," said Peg Semenario, an industrial health expert for the AFL-CIO. She added that she feared changes on such questions as the best way to protect workers could lead to changes in the regulation of all occupational hazards, putting more burden on workers to protect themselves rather than having employers build in protections.

Industry scientists and health experts welcomed the move toward changing the policy, though some felt OSHA has not moved quickly enough. "The OSHA policy is scientifically unsound and in conflict with the benzene decision and Executive Order 12291," said Ronald Lang, executive director of the American Industrial Health Council, one of the groups challenging the policy in court.

"Unless they stay some of the portions of the policy, in theory they're still bound by this," he said.

The policy "essentially freezes science at that time, 1978," said Dr. Bruce W. Karrh. "It sets unrealistic criteria for considering animal tests and epidemiological studies," he added. (Epidemiological studies of the effects of a substance on a population of workers are acceptable only if they cover a 20-year period, according to those familiar with the policy.)