The chief sponsor of a measure to compensate asbestos victims said on Tuesday its introduction had been delayed for a week while senators discuss how to handle claims of injury by another mineral, silica.

Pennsylvania Republican Sen. Arlen Specter, chairman of the U.S. Senate Judiciary Committee, told reporters the panel would hold a hearing Feb. 2 to try to establish medical criteria for silica claims.

Specter had planned to introduce this week his proposal to take asbestos claims out of the courts and compensate them from a $140 billion privately funded trust instead.

But he said the ranking Democrat on the Judiciary Committee, Vermont’s Sen. Patrick Leahy, asked him to delay the introduction while they worked on some of the language.

“We’ve got a problem on mixed dust,” Specter said. “The issue is, if you have a trust fund to pay all people from asbestos, and then some of the cases are allegedly being repackaged as silica cases, it’s not solving the problem.”

They should work out medical criteria for injuries caused by each mineral so as not to compensate people twice, he said.

Asbestos, a fire-retardant mineral, was once widely used for insulation and construction purposes. Scientists say inhaled fibers are linked to cancer and other diseases.

In recent years an explosion of asbestos injury claims have clogged U.S. courts and bankrupted dozens of companies.

Manufacturers have urged senators to write the trust fund law so lawyers could not repackage asbestos claims into claims involving other airborne fibers like silica.

But Sen. Leahy said on Tuesday he was concerned that some “last-minute” provisions in the bill would impair the legal rights of victims of other airborne minerals in the workplace.

“My two grandfathers worked as stonecutters in the granite quarries of Vermont and both suffered from silicosis because of their workplace exposures to stone dust,” Leahy said in a statement. “One of my grandfathers died at the age of 35 because of that exposure.

“Asbestos legislation should focus on compensating asbestos victims and not denying the legal rights of victims of other airborne dust, fiber or other minerals,” Leahy said.