But the medical director for Brush Wellman, an Ohio-based company that supplied Rocky Flats with beryllium for nuclear weapons, and another company official dismissed the cases, saying they weren't "credible."

Four Rocky Flats workers and their wives are suing Brush Wellman in Jefferson County District Court, claiming the company failed to warn the nuclear-plant workers of beryllium hazards. The suit also alleges that the company conspired with the federal government to withhold information that showed workers became ill when exposed to levels below the federal safety standard.

The medical director's testimony opened a pivotal battle in the five-week trial over what company officials knew about the soundness of the federal safety standard and when they knew it.

The standard, in place since 1949, limits beryllium-dust exposures to an amount equivalent to crushing the tip of a pencil and dispersing the particles in a 6-foot-high room the length of a football field.

The federal government is currently considering lowering that standard and warned the public two years ago that it might not protect all workers.

The information about workers becoming sick from exposure even below the safety standard came from a Japanese company that also produced beryllium, and the cases of stricken workers eventually prompted the Japanese company to stop working with some forms of it.

Brush's medical director said he never told anyone outside the company about the Japanese research, including when he testified in 1977 before federal regulators considering lowering the decades-old standard.

"I don't know whom I should have talked to," said Otto Preuss, the company's medical director for 16 years until his retirement in 1987.

Preuss said he believed the Japanese cases stemmed from high dust exposures because the company had other workers ill from high exposures. But the Japanese never allowed Brush to review air sampling or other data about the cases.

Company officials traveled twice to Japan to try to change the Japanese doctor's position on the cases. Brush told officials with the Japanese company it would be best for the beryllium business to have a unified position on the safety standard, which also was in place in Japan, said Martin Powers, the Brush official in charge of beryllium safety information until he retired in 1986.

Rockwell International and Dow Chemical Co., which operated Rocky Flats for the government until 1989, also were not told, Powers said.

Powers also testified that the company believed the safety standard protected workers. But he acknowledged that as early as 1952, Brush knew some workers allergic to the metal could contract the lung disease even when exposed to levels below the standard.