Work at the National Institute for Occupational Safety and Health (NIOSH) in Rockville has come to a virtual standstill because agency heads refuse to replace employes who left over a proposed, but now congressionally blocked, transfer to Atlanta, a union official charged this week.

NIOSH is the research arm of the Centers for Disease Control in Atlanta that studies job hazards and recommends exposure limitations for toxic chemicals in the work place. Enforcement is left to such agencies as the Occupational Safety and Health Administration.

Darlene Christian, vice president of the NIOSH unit of the American Federation of Government Employees, said in an interview that since the move of the NIOSH headquarters to Atlanta was proposed 15 months ago, the work force at the agency on Fishers Lane has dropped from 177 to fewer than 90, one of the most severe declines in workers among federal agencies.

Shortly after the move was announced, the agency decided to temporarily not replace the workers. As a result, Christian charged, research at the facility has dropped off dramatically, with only one worker safety recommendation having been completed and approved in more than a year.

In contrast, she said, about 115 recommendations were developed at the Rockville facility during the agency's previous 12 years -- or nearly 10 a year.

Christian contended it is important to continue research here because of the proximity to other federal research facilities and related interest groups.

At NIOSH, "everything has come to a standstill because people left who were afraid their jobs were going to be moved, and they (CDC) refuse to let us hire replacements," Christian said. "We're putting in 10- and 12- hour days and still not getting anywhere."

But agency officials disputed Christian's charges. Instead, they said, research previously done at Rockville is being shared at branches in Cincinnati and Morgantown, W. Va., and at Atlanta. They said that, in fact, 18 recommendations have come out of all NIOSH facilities in the past year. They said the branch facilities are at full staff.

Congressional observers also said controversy over the proposed move has thrown the Rockville facility into a quagmire of uncertainty. Workers there are "a group of people who are being asked to make bricks out of straws," said Bob Honig, director of the Federal Government Services Task Force, a congressional group concerned with federal workers.

"Top researchers are in despair. People are getting physically sick because of the uncertainty. They're desperate," he said. "You're not talking about regular government workers. You're talking about top-of-the-line government scientific researchers who are doing something vitally important."

However, Thomas Shamblee, NIOSH executive officer stationed in Atlanta, said: "There is no work slowdown from our standpoint. If they (Rockville personnel) are doing less work, it is not because management has directed them to do less."

When the proposed transfer was announced, Reagan administration officials said the agency would operate more efficiently if it was closer to its parent body, the disease control centers.

But union officials countered that the proposal was designed to accommodate NIOSH director Dr. J. Donald Millar, who lives in Atlanta and who has stated he will not move to Rockville.

NIOSH's administrators work in Atlanta, while top research scientists are in Rockville, a split that resulted when Millar -- a disease control official already stationed in Atlanta -- was appointed last year.

Union officials also described the proposed transfer as another attempt by the Reagan administration to dismantle a business watchdog agency.

Congress temporarily blocked the proposal late last year when it voted to prohibit the expenditure of federal funds to finance the move. Attempts to reverse that by officials at Department of Health and Human Services -- the umbrella department -- prompted resignations by employes uncertain over the future of their jobs, Christian said.

Until the issue is resolved, no permanent employes will be hired, said Carl Crittenden, director of personnel at the disease control centers.

Honig said the hiring freeze makes NIOSH one of the hardest hit in percentage terms in recent federal employment declines. In comparison, the Public Health Service, which has recorded the largest total loss of positions and which oversees NIOSH, was required last year to reduce its workforce 17 percent, from 48,000 to 40,000 nationwide.

Last week, Congress failed in an attempt that would have permanently blocked the move to Atlanta by making the research agency part of the Bethesda-based National Institutes of Health. The measure is expected to be reintroduced next year.