Concern is growing among public and private health experts that hundreds and perhaps as many as 1,000 school buildings constructed in the nation during the 1950s and 1960s contain hazardous amounts of the potential carcinogen asbestos.

Until it was outlawed by the Environmental Protection Agency in 1973 because it posed a cancer threat, asbestos was widely used to fireproof and soundproof schools and other public buildings.

Now inspectors who have looked at schools say they are finding asbestos everywhere.

In New York City this month school officials shut down two Harlem grade schools and transferred more than 300 pupils after an inspection found asbestoes flaking from ceilings and elsewhere. The city is now looking at the rest of its system, and officials said this week they have found 127 more schools where they suspect asbestos is present.

"The asbestos genie is out of the bottle," said Anthony Smith, head of New York City's school buildings department. "We're the first ones to really get hit hard by it, but it will occur all over. Ours is just going to be the biggest and most expensive problem."

An unpublished draft of a national survey of the asbestos situation in schools, which has been compiled by the EPA, shows that several hundred schools have been identified as containing asbestos in the few states where inspections are under way.

The survey notes that while a few states have been active in looking into the asbestos problem in schools, many others, particularly in the South and West, have ignored warnings because of objections over federal intrusion in what are looked on as local affairs. In Idaho, for example, the report notes "very conservative state. No program expected."

In August, Health, Education and Welfare Secretary Joseph A. Califano Jr. sent a carefully worded letter to all state governors warning that asbestos had been found in New Jersey schools and that the U.S. Public Health Service had warned that "any exposure probably carries some risk of disease." Califano noted that it was still not possible to identify the risk for schoolchildren in buildings with asbestos.

In another study done this year, Dr. Robert N. Sawyer, a Yale University occupational health expert and asbestos consultant, warned that schoolchildren have particular problems with asbestos because cancer caused by the fibrous mineral usually takes 20 to 30 years to develop.

Children, said Sawyer, have a longer period in which it may develop than persons exposed in middle age or later.

In addition, Sawyer said the concentration of children in schools and classrooms is likely to increase the exposure to asbestos in contaminated buildings.

"Some investigators," Sawyer wrote in his report to the New York Academy of Sciences asbestos conference in June, "feel that susceptibility is enhanced in youth with growth and high rates of cell replication."

In an interview, Sawyer said, "In any major urban area where a school was built or renovated between 1950 and 1975 it is suspect (of having asbestos)."

Other asbestos researchers place less emphasis on the immediate risk of exposure to the mineral by children. But asbestos experts like Dr. Irving Selikoff, who heads a team of researchers from Mt. Sinai Hospital's Environmental Sciences Laboratory in New York City, warn that the problem of asbestos exposure in children can greatly compound the cancer risk from smoking habits they may pick up later.

Selikoff and his coresearchers have also warned that asbestos in schools poses a danger for teachers who smoke. The cancer risk of asbestos and cigarettes combined has been shown by researchers to outweigh sum of the risks of either one taken separately.

Califano's warning in August and the report by Sawyer at the New York Academy of Sciences conference touched off a flurry of concern in some states.

In Indiana, investigators found asbestos in 260 of the state's 2,262 schools, with more locations expected to be identified. Connecticut has found the mineral in 45 of its schools, and Massachusetts identified it in nearly 100 schools. Three-quarters of the samples taken in Kentucky schools showed asbestos, and eight schools in St. Louis were found to contain it.

Only a few states have launched full scale searches for asbestos. "The potential cost of this problem could run into the millions of dollars," said Robert Raunch, an attorney for the Environmental Defense Fund, which has been active in pressing for federal action to speed up correction of school asbestos problems.

Rauch accused the EPA of dragging its feet on enforcing a provision of the federal Toxic Substances Control Act that could force asbestos manufacturers to pay for the cleanup in the schools. The provision has not been enforced, he said, because it has never been tested in court.

"Our position," said Rauch, who is planning on filing a formal petition with EPA calling for use of the act next week, "is that a law you are afraid to use is the equivalent of no law at all."

Finding someone to pay for the asbestos cleanup in the schools is important, Rauch and federal officials said. In New York City alone officials estimated this week it would cost them far more than $3 million the city had budgeted for asbestos removal.

Some states and cities are reluctant to look into the asbestos situation in their schools because of the potential cost, public and private experts said.

Asbestos manufacturers, already swamped under more than 1,000 lawsuits from asbestos victims, said this week that they are braced for a new round of suits from school districts and that they are prepared to fight them.

"We feel," said Richard Carter, an attorney for the Johns-Manville Corp., the nation's largest asbestos manufacturer, "that although these sprayed-on materials do not represent an appropriate use of asbestos fiber, at the same time there is no evidence to indicate the existence that these materials pose a health hazard."

Johns-Manville, he said, has offered to help locate asbestos in schools. But he said the company does not plan to pay for cleaning up the asbestos.

Most of the asbestos in schools, said Carter, came from smaller distributors who mixed their own soundproofing and fireproofing formulations. "Some were very satisfactory and some did not do very well," he said.

Johns-Manville, Carter said, did not make or sell asbestos products used in schools. But he added that "a certain small percentage" of the firm's asbestos output during the 1950s and 1960s may have been sold to other distributors who then resold it to firms active in school construction.

The attorney said "no more than 2 percent" of Johns-Manville's annual asbestos output was sold that way. The company, he estimated, annually produced several hundred thousand tons of asbestos.