St. Louis ? A federal warning is set to go out to millions of home and business owners whose attics and walls may have insulation that could cause lethal exposure to asbestos.

The Environmental Protection Agency plans to announce Wednesday that vermiculite insulation should be handled as if it contained cancer-causing asbestos. The warning comes after two years of the agency’s being pressured by Congress, public interest groups and its own employees.

The presence of the material is not cause for “needless anxiety,” said Stephen Johnson, assistant administrator of the EPA’s Office of Prevention, Pesticides and Toxic Substances, in a press statement prepared for the announcement. But, he said, “It is important that people be informed so they can identify the product and properly manage it.”

The recommendations for handling the material were hammered out by scientists and regulators from the EPA and the Agency for Toxic Substances and Disease Registry, a health research division of the Centers for Disease Control.

Among the recommendations:

• Property owners should not disturb vermiculite attic insulation; any disturbance has the potential to release asbestos fibers into the air.
• Homeowners should limit the number of trips to attic space and shorten the length of those trips. People should not store boxes or other items in attics if retrieving the material will disturb the insulation.
• Children should not be allowed to play in an attic with open areas of vermiculite insulation.
• Homeowners should never attempt to remove the insulation. Instead they should hire professionals trained and certified to safely remove the material.

The agencies warned that the “insulation can sift through cracks in the ceiling, around light fixtures or around ceiling fans.” The cracks should be sealed, they said.

Vermiculite is a natural mineral that when heated expands into accordion-shaped, feather-weight pieces of material usually tan-gold in color. It is flameproof and absorbent, which makes it useful as insulation and in garden products.

But the insulation that the agencies are most concerned about is called Zonolite. It came from vermiculite ore in a now-closed, 80-year-old mine that was last owned by W.R. Grace & Co.

In the material being released this week, the agencies warn: “If you removed or disturbed the insulation, it is possible that you inhaled some asbestos fibers.”

The exposure can cause asbestosis, lung cancer and a fast-killing cancer of the linings of the lungs, heart and other organs called mesothelomia. Disease symptoms can take years to surface after exposure.