Two federal agencies are preparing to take strong action against a chemical widely used as a soil, fruit and grain fumigant, nearly a decade after studies identified it as a powerful carcinogen.

Officials of the Occupational Safety and Health Administration and the Environmental Protection Agency confirmed yesterday that they are moving separately to crack down on ethylene dibromide, known popularly as EDB.

Both agencies are facing congressional hearings this month on their efforts to regulate EDB, which the National Cancer Institute identified as a cancer-causing chemical in 1974. More recent studies have linked it to birth defects and male sterility as well.

"It's a pretty bad-actor chemical, no doubt about that," said Edwin L. Johnson, director of EPA's Office of Pesticide Programs.

OSHA has asked the Office of Management and Budget to approve a drastic reduction in the maximum amount of EDB a worker can be exposed to in a day. The current limit is 20,000 parts per billion in the air, averaged over an eight-hour day. OSHA is asking for a new limit of 100 parts per billion.

The EPA, meanwhile, is preparing a final report that likely will recommend an immediate ban or phase-out of virtually all agricultural uses of EDB, according to agency officials. The agency proposed such a ban more than three years ago.

Neither action, however, will halt the major use of EDB--as an additive to leaded gasoline to prevent lead damage to engines. More than 330 million pounds of the chemical are used each year as a gasoline additive, compared with about 20 million pounds used for agricultural purposes.

The chemical has been turning up in drinking water supplies from Florida to California, as well as in fresh produce, meat and milk and in baked goods made from grains treated with EDB.

EPA officials said that it is possible some EDB may be entering ground water from underground gasoline storage tanks, but the agency has not conducted studies to confirm that. The recommendations for EDB will deal only with its pesticide uses, Johnson said.

EDB has been used for decades as a soil fumigant and to control root-attacking nematodes. Its use increased when the EPA banned most uses of DBCP, a cancer-causing pesticide that also was linked to sterility problems among chemical workers.

Two years ago, OSHA rejected a Teamsters union request for an emergency rule limiting EDB exposure, prompted by the widespread use of the chemical in the battle against the Mediterranean fruit fly.

In rejecting the request, OSHA chief Thorne C. Auchter turned aside a personal plea from J. Donald Millar, director of the National Institute for Occupational Safety and Health, who pointed out "the rapidly growing scientific evidence" of EDB's threat to human health.