They said the release from the plant that makes materials used in the production of nuclear weapons did not pose a hazard to the public.

But even material at that level may pose a problem for the estimated 95 million Americans with poor reading skills.

The union contends that the materials cause cancer in field workers and pose other serious health risks.

When burned or buried, toxic materials also pose a serious threat to public health and the environment.

On the other hand, heavy materials pose problems as well.

Intact, undisturbed asbestos-containing materials generally do not pose a health risk.

"There is simply no truth to the baseless suggestions that the material poses any risk," he said.

Environmental officials said the material posed no health risk.

Knit material, which is easily stretched, poses other challenges for cutting.

Federal scientists said several years ago that the material could break down in a woman's body and pose a cancer threat.