More than 345,000 federal workers and retirees in the District, Maryland and Virginia who are covered by Blue Cross-Blue Shield health insurance are waiting to see if the Office of Personnel Management will approve a multimillion dollar refund the insurance company would like to make in August.

The tax-free refunds would range from $18 for those with individual coverage to $374 for persons with high-option family coverage. Nationwide, 1.5 million civil servants, postal employes and retirees would receive $289 million in refunds.

At the same time, Blue Cross-Blue Shield is also proposing to refund $465 million to the federal treasury. The company said the refunds are possible because of a "major reduction in health plan utilization" by premium-payers.

Rival health plans oppose the rebates. They say the refunds should be plowed back into the health program and used to lower premiums and/or improve benefits for everybody next year. About 40 percent of the people in the federal health program have Blue Cross-Blue Shield insurance.

OPM can approve, reject or modify the Blue Cross-Blue Shield refund proposal. But if it decides against the rebates it will have lots of unhappy feds -- here and around the country -- on its back. Here are some of the numbers:

Nearly 71,000 federal workers and retirees in the Baltimore area would benefit from any refund. In Pennsylvania, more than 80,000 are eligible for it, as are 37,000 feds and retirees in New York City, 46,000 in Massachusetts, 28,000 in Michigan, 46,000 in Georgia, 32,000 in Cleveland and Cincinnati, 83,000 in Texas and 73,000 in Florida.

OPM has set no deadline for issuing its refund decision. But as a practical matter it will have to decide soon, because it has just begun negotiations with all health insurance plans for premiums they propose to charge, and benefits they will offer, in 1986.