Dr. Bailus Walker, head of the D.C. Environmental Health Administration, is leaving city government to become a U.S. Labor Department official with a major role in setting health standards affecting 62 million American workers.

Walker, who closed down several city restaurants for violations of cleanliness codes and exposed unsanitary conditions in city-run institutions, will become health director at the Occupational Safety and Health Administration on Sept. 10.

He will take over as OSHA health director as officials put the finishing touches on a controversial new policy regulating worker exposure to potential cancer-causing agents.

Walker's departure is "a great loss to the department and to the city," Herbert Tucker, director of the Department of Environmental Services and Walker's boss, said yesterday.

A spokesman for Mayor Marion Barry said the mayor had no comment on Walker's decision to leave. The city government did not announce the resignation. Walker is on leave and could not be reached for comment.

Perhaps Walker's best-known achievement was his vigorous enforcement of city regulations of food handling in restaurants and food stores.

He came to the city government in 1972 as city officials began a program to tighten restaurant inspections after a series of newspaper articles and congressional hearings spotlighted various unsanitary conditions.

Since last Oct. 1, Walker's office has suspended the operating licenses of about 17 percent of the city's 3,500 food establishments.

"When he came we were having difficulty with our restaurant inspection program," Tucker said. "He pulled it out and put it back on track.

"D.C. citizens and tourists now feel very comfortable that they can go into any place and eat and know it is meeting the health standards," Tucker added.

Last year Walker initiated the novel "truth-in-menu" inspections to ensure that restaurants are serving what they advertise. That program has "set the pace for the rest of the nation," Tucker said.

But Walker also criticized dirty conditions when he found them at city-owned and -operated institutions, a practice that made him unpopular with several department heads.

Four months ago Walker's inspectors found that more than 75 percent of the city's 22 public health clinics were dirty, cockroach- and mouse-infested places where some patients were given outdated drugs.

Walker's new job is potentially almost as controversial as his old one. He will be recommending standards for worker exposure to certain substances that are suspected of being dangerous to human health, an OSHA spokesman said.

Several industries have complained that OSHA standards, especially those concerning cancer, could cost them millions of dollars.