There are 22,000 toxic substances in use in American industry, many of them deadly - and in its six years of existence the Occupational Safety and Health Administration has published full-scale regulations limiting workers exposure to preeisely 17 of them.

Yet that same federal safety agency has 12 entire pages of regulations in force on the proper construction of portable wood ladders, including even a paragraph on knots.

"Knots shall not appear in narrow faces of side rails," paragraph 1910.25(b)(2)(ii) of title 29 of the Code of Federal Regulations solemnly warns America's employers. "Knots, if tight and sound and less than one-half-inch in diameter, are permitted on the wide face provided they are at least one-half inch back from either edge and not more frequent than one to any tahree feet of ladder length."

Not so good on industrial poisoning, but dynamite on rickety ladders - that is as good an introduction as any to OSHA.

Where Congress passed and President Nixon signed the Occupational Safety and Health Act of 1970, only specialists paid much aettention. Congress has passed so many regulatory acts in recent years that passage of one more hardly seemed a novel occasion. But OSHA has made a name for itself.

To business groups and conservatives generally, it has become the leading symbol of the federal regulatory presence. They alternately ridicule the agency and rail at it as a kind of industrial Gestapo threatening small businesses with extinction and larger ones with higher costs, which in turn will lead to higher prices. Last year the opposition was enough to elevate obscure OSHA into a political campaign issue.

The safety agency was a minor theme in the campaign for the Republican presidential nomination, a free punching bag that both candidates occasionally used to demonstrate their orthodoxy on the question of free enterprise. "OSHA is a four-letter word tht is giving businessmen fits and is helping drive up consumer costs," Ronald Reagan began one widely quoted syndicated column.

The agancy was a more important issue in the Wyoming senatorial election, in which Republican Malcolm Wallop defeated three-term Democrat Gale W. McGee. OSHA last year proposed field sanitation regulations for agricultural workers, according to which portable toilets would have to be placed "within a five-minute walk of each employee's place of work."

The proposal became an instant laughingtstock in farm and ranch states, and Wallop seized on it in his campaign. He ran a television commercial in which a weather-beaten cowboy was saddling up and riding off to roundup, leading a pack mule and muttering about the omnipresent federal government. "I think the government is going too far," the cowboy fumed as he moved off and the mule came into view. Tied to the mule's side was a toilet. "Now they say if you don't take the 'portable facility' along with you on a roundup, you can't go," the cowboy said.

The jokes are funny. But the intensity of the opposition to OSHA is strange. Some conservatives make is sound as if the OSHAcrats, as the John Birch Society has called them in its magazine, have swept through America's workplaces in the last few years, forcefully demanding all kinds of costly changes. Yet organized labor can marshal statistics that make the opposite point - that OSHA has been a puny force.

The labor groups say, first, that on important questions OSHA's standards are too low and its standard-setting is too slow. Industry is inventing new toxic substances faster than OSHA is issuing regulations on old ones. Thirteen of the 17 regulations the agency did issue came only after labor unions filed suits to force the government to act.

The unions are equally critical of the spread and sharpness of enforcement. OSHA and related agencies in the states have about 2,700 industrial safety and health inspectors. These inspectors are responsible for about 5 million places of business with about 65 million employees. They actually inspected about 75,000 workplaces last year - 1.5 per cent.The risk of being inspected is low.

The risk of having to pay a substantial fine is even lower. Inspectors found no violations last year in about a third of the establishments they inspected. In the other two-thirds - about 50,000 - proposed fines before appeals and litigation averaged about $26 per violation, $10.3 million in all.

In fairness, fines are only a minor part of the cost of compliance. The cost of changes required in machinery and procedures is much greater.

McGraw-Hill, Inc., economists estimate that total industry spending for safety and health equipment - items that would have been bought anyway, as well as those that will be bought because of OSHA - will be about $3.4 billion this year.

But uniions seethe at at the idea that these expenditures are a new and extra cost of production. They say the cost has simply been borne in the past by workers alone, in the form of injury and illness, rather than by society as a whole in higher prices. Their claim is that workers have subsidized society with their health.

"It's already costing," Anthony Mazzocchi, legislative director of the Oil, Chemical and Atomic Workers, union, says of worker safety and health. "They've socialized the cost. The worker, he goes off and dies, and the inducer of the disease, he's not charged.

Mazzocchi notes contemptuously that OSHA has not even issued an occupational chemical labeling regulation, though one has now been proposed. By law we must all be told the chemicals we eat and drink, but workers need not be told what chemicals they work with.

Simple labeling is also a goal of Dr. Sidney M. Wolfe of Ralph Nader's Health Research Group. In industrial health, "nothing's going to happen until we have a well-informed group of victims" Wolfe believes.

It is a sign of how our system of government has subtly changed in recent years that, in pressing for a "law" requiring chemical labeling, petitioners like Mazzocchi and Wolfe now turn not to the legislative but to the executive branch.

The OSHA legislation is one of literally dozens of regulatory acts that Congress has passed since the early 1960s, transferring to executive agencies essentially legislative powers over everything from pesticides to pension funds. Economist Murray L. Weidenbaum, assistante Treasury secretary in the first Nixon administration, has counted 29 acts of Congress that increased government regulation of business in the 12 years 1965-73. Former Labor Secretary John T Dunop once remarked to a group of reporters that in 1940, the Labor Department administered 18 regulatory programs; by 1960 the number had grown to 40; and by 1975 it stood at 134.

Dunlop is generally skeptical about the usefulness of regulation, or "legal compulsion," as the old labor mediator likes to call it. "The first problem," he was written, is that passage of a regulatory act "encourages simplistic thinking about complicated issues." You can legislate problems out of existence - that is the theory, and that is what Congress told itself and the voters with OSHA.

"Everyday we postpone passage means 55 more American workers will die; 8,500 will be disabled and 27,200 will be injured," Rep. Dominick V. Daniels (D-N.J.), floor manager of the bill, told the House in 1970 as he fended off amendments. The message was clear: if the House would only vote "aye," these numbers would be reduced.

It is hardly a new idea in this country to have a public agency issue safety and health regulations. The pure food and drug laws at various levels of government are one example; local fire laws are another. The traditional form of protection in the performance of work, however, has been worker compensation, which is not anticipatory regulation, but a kind of insurance, in which injured workers are compensated after the fact. In that sense, OSHA was a switch.