A former director of the National Cancer Institute has told federal regulatory and health officials of new studies showing that formaldehyde a chemical to which an extimated 750,000 industrial workers are exposed, is "decisively" a cancer-causing agent in animals and a "likely" carcinogen in humans.

Saying that it is under consideration for regulatory action by agencies including the Occupational Safety and Health Administration, Dr. Arthur C. Upton warned that "it would be a mistake to ignore the evidence for carcinogenicity of formaldehyde . . . "

If the evidence is ignored, Upton said, "it would mean that no agent could be regarded as carcinogenic in the absence of positive evidence in humans. We hope that federal regulatory agencies will regard formaldehyde as a carcinogen and find ways to continue its important commercial and scientific uses in a sensibly safe fashion."

Upton, now professor and chairman of pathology at the Institute of Environmental Medicine of New York University Medical Center, said that 10 of 100 male rats developed highly destructive nasal cancers after 382 six hour exposures, over 588 days, to formaldehyde. None was found in control rats or in rats exposed to hydrochloric acid gases. Nine of 100 rats exposed to a mixture of formaldehyde and the gases developed tumors.

At OSHA, Deputy Assistant Secretary of Labor Mark D. Cowan told a reporter that the new evidence will be "very carefully" reviewed by agency and outside scientists and that a decision on regulation of formadehyde then will be made.

Three weeks ago, Cowan's boss, Thorne G. Auchter, beat a surprise retreat from the attempted firing of Dr. Peter F. Infante, OSHA's top specialist in carcinogen identification, who had argued that evidence available before the new studies showed formaldehyde to be a carcinogen in animals and a cancer risk in humans -- the same position taken by top government toxicity experts.

In response to Infante's finding, a trade association called the Formaldehyde Institute tried to target him for dismissal, alleging improper conduct.It sent OSHA a letter in which unpublished 1979 reseach data, on which Infante had relied in part, were challenged by Harry B. Demopoulos, an associate professor in Upton's department. The data showed that rats exposed to a combination of formaldehyde and hydrochloric acid gases developed nasal cancers.

Demopoulos engaged in "misrepresentations," Upton charged recently. Then, in the new letter to federal officials, dated Aug. 17 but made available only Tuesday, he said the new experiments confirmed the unpublished findings while going beyond them to deal with formaldehyde alone.

Upton sent his letter to OSHA, to four top officials of the Environmental Protection Agency, to officials of other agencies including the Consumer Product Safety Commission, to the Chemical Manufacturers Association, and to the AFL-CIO Industrial Union Department.