An Occupational Safety and Health Administration contractor has recommended that the agency propose a 200-fold reduction in its standard for worker exposure to the cancer-causing fumigant ethylene dibromide, which was used to check California's Mediterranean fruit fly infestation two years ago.

OHSA, which refused two years ago to tighten its standard on an emergency basis, expects to complete a proposed standard paralleling his recommendations this summer, according to an agency spokesman.

Before OSHA can publish such a proposal in the Federal Register, it must be approved by the Office of Management and Budget. It is not unusual for several months to elapse between publication of a proposed rule and final implementation.

Tens of thousands of dockworkers, grain handlers and workers involved in the storage and transportation of citrus products are exposed to the chemical, according to various government estimates. Ethylene dibromide is used as a soil fumigant in the Southeast, a fumigant for citrus fruit in California, Florida, Texas and Arizona, and for stored grain and some grain-milling machinery in the Midwest.

Several studies have implicated the chemical as a cause of nasal and liver cancers in laboratory animals. In humans, skin contact, inhalation and ingestion have caused everything from nausea to death.

California last fall, two workers who spent 15 minutes in a holding tank containing a two- to four-inch residue of a .3 percent mixture of the chemical in water died within 72 hours after suffering burns and extensive liver, heart and lung damage.

In a letter to columnist Jack Anderson, who publicized the Calfornia incident, John a. Attaway, a researcher for the Florida Department of Citrus, disputed the assumption that the chemical was the primary cause of those deaths.

Attaway wrote that "the chemical has been the mainstay of the [Agriculture Department's] fumigation program for over 30 years without illness or injury."

OSHA's current standard is 20 parts of the chemical per million parts of air. David R. Brown of Northeastern University, who did OSHA's risk assessment, recommended a standard of 100 parts per billion averaged over an eight-hour working day, with a 500 parts per billion ceiling for acute exposures.