A new document submitted Wednesday to the Environmental Protection Agency by Union Carbide Corp. indicates that 190 chemical leaks occurred in five years in the methyl isocyanate unit of its pesticide plant at Institute, W.Va.

The company said none of the spills -- 61 of methyl isocyanate, 107 of phosgene and 22 of a mixture of the two -- was of sufficient size to endanger health or the environment or large enough to require reporting to the EPA at the time.

Production of methyl isocyanate was halted after a massive leak of the chemical last December at Carbide's plant in Bhopal, India, killed at least 2,000 people, in the worst industrial accident in history.

The West Virginia facility was the only place in the United States where the highly toxic methyl isocyanate (MIC) was manufactured. Phosgene, known as mustard gas during World War I, is used to make methyl isocyanate, an intermediate compound in the pesticide Sevin.

Union Carbide said its earlier report, made public last week, of 28 leaks of MIC at Institute since Jan. 1, 1980, was incomplete because it was hurriedly assembled for a Dec. 14 hearing at Institute by the House subcommittee on health and the environment.

"On short notice from the congressman's staff, and given the priorities of shutting down the MIC unit and meeting with investigators of four federal and state agencies after Bhopal ," the statement said, " . . . the company was unable to complete a search for all relevant documents. That has since been done."

An aide to subcommittee Chairman Henry A. Waxman (D-Calif.) said the revised report "raises questions about whether anyone really knows" what amount of the toxic chemicals was released at the plant.

"Clearly EPA does not know, and this gives the impression Carbide doesn't know either," he said.

In a letter to Mary Letzkus, an EPA regional enforcement officer, Insitute plant manager H.J. (Hank) Karawan said Union Carbide was going beyond what the law required in reporting in-plant leaks, "even as little as one drop."

EPA regulations require reporting MIC leaks of one pound or more and phosgene losses of 5,000 pounds or more that go beyond plant boundaries in a 24-hour period.

Some in-plant leaks must be reported to the Occupational Safety and Health Administration, whose investigation at Institute continues.

A spokesman for the EPA's regional office in Philadelphia, which recieved the company's revised report Wednesday night, said it was being studied yesterday.

The EPA said it particularly wants to clarify the extent of a previously reported spill, on Dec. 31, 1983, which Union Carbide first listed as 840 pounds of MIC. After release of the Waxman committee's report last week, the company said the correct amount was five pounds.