SAN FRANCISCO, DEC. 17 -- City supervisors today approved the nation's broadest video display terminal safety law, rejecting the arguments of opponents who had said the law would be too expensive for employers.

"It's historic," Supervisor Angela Alioto said of the ordinance. "It's on the cutting edge of an extremely important area for all workers in America."

The supervisors voted 7 to 4 in favor of the law. Mayor Art Agnos has said he is sympathetic to the need for VDT safety, but he is uncertain about signing the ordinance in its present form because of its cost.

The law would require city government and businesses with 15 or more employees to provide those who work on video display terminals at least four hours a day with adjustable chairs, glare shields, detachable keyboards, tables with sufficient leg space and special lamps to reduce vision impairment.

VDT workers also would be allowed 15-minute breaks every two hours, and an advisory committee would monitor data about the health effects of VDT use, including the possible effects of radiation.

Companies would have two years to implement the law. After that, violators could be fined up to $500 per day.

Agnos said he would meet with business and labor leaders over the next couple of weeks. He has 10 days to act on the legislation and the board can still make changes. "I plan to listen carefully to the concerns of both sides before making up my mind," Agnos said.

Even if Agnos rejects the measure, the 11-member board of supervisors could overturn the veto with eight votes.

City budget analysts estimate that San Francisco would have to spend $1.4 million to $6 million during the next two years to comply with the bill, and private businesses would have to spend $31.5 million to $76.5 million.

"This is a message to the nation that this is the next wave of worker safety issues," said Supervisor Nancy Walker, who cosponsored the ordinance with Alioto.