The Environmental Protection Agency declared a public health emergency on Wednesday in and near Libby, Mont., where over the course of decades asbestos contamination in a vermiculite mine has left hundreds of people dead or sickened from lung diseases.

It was the first health emergency ever declared under the Superfund law, the 1980 statute that governs sites contaminated or threatened by hazardous substances. The Libby site has been designated a Superfund priority since 2002.

A spokeswoman for the E.P.A. said that in anticipation of the declaration, the Department of Health and Human Services had agreed to make $6 million available to the Lincoln County Health Clinic, which provides care to residents of the area, to finance treatment of people with asbestos-related conditions. She said the declaration also authorized the environmental agency to remove vermiculite, whose uses include insulating, from buildings there.

In addition, she said, the agency will begin an effort to inform Americans generally about the risks of insulation made from vermiculite, a natural silicate mineral that forms in flakes. She said that it was not known how many homes nationally contained asbestos-contaminated vermiculite but that estimates ran into the tens of millions.