Ten years after 54 workers were killed in twin Christmas week grain elevator explosions, the government yesterday adopted safety standards aimed at preventing explosive grain dust from claiming more lives.

The Occupational Safety and Health Administration said its new regulations, intended to prevent accumulations of grain dust, could save as many as 18 lives and prevent nearly 400 injuries annually among the nation's 155,000 grain handlers.

In the decade it took to develop the regulations after grain elevators near New Orleans and Galveston, Tex., burst into flames, 59 additional workers were killed and 317 were seriously injured in 190 other grain facility explosions.

Labor unions questioned the effectiveness of the new regulations, which the unions said had been watered down by OSHA and the president's Office of Management and Budget from strict recommendations made by a panel of the National Academy of Sciences.

The panel proposed in 1982 that the government adopt standards limiting accumulations of the grain dust to 1/64th of an inch on horizontal surfaces of all 23,770 grain-handling facilities in the United States.

A year later, OSHA submitted draft rules to the OMB that would have limited wall-to-wall dust accumulations to 1/8th of an inch in about 13,000 elevators, 525 terminals and nearly 9,400 grain and flour mills.

The OMB rejected these proposals after the National Grain and Feed Association claimed that meeting the 1/8th-inch standard through use of vacuum suction equipment would cost elevator operators $1.2 billion.

The rules issued yesterday, which take effect March 30, exempt grain and flour mills from the 1/8th-inch standard. They also say elevator and terminal operators must meet the standard only in areas within 35 feet of inside bucket elevators or near potential ignition sources.

Assistant Labor Secretary John A. Pendergrass estimated it will cost the grain industry between $5.9 million and $33.4 million a year to comply.

"The standard provides maximum flexibility for employers in limiting dust accumulations and controlling ignition sources, taking into account both facility size and type of operation," Pendergrass said.

Union officials said the standard is so vague that it may prove unenforceable, but they expressed surprise that it was issued at all, given the substantial opposition of large grain companies, mills and elevator operators.

Deborah Berkowitz, director of safety and health for the AFL-CIO's Food and Allied Service Trades Department, said that the Senate Labor and Human Resources Committee planned to examine the grain issue during oversight hearings on OSHA in February.

She said the new standard "is clearly a political expendiency, it's certainly not based on science."

The AFL-CIO department includes unions that represent about 30,000 grain millers and elevator workers. Its president, Robert Harbrant, said, "In the four years while OMB and OSHA catered to special-interest politics, another 16 workers have been killed and 74 injured. It makes a mockery of worker protection."

Berkowitz and Harbrant said they doubted that unions would challenge the regulations on the ground that going to court could delay implementation for another decade.

Randy Gordon of the National Grain and Feed Association said his group had not analyzed the new rules fully.