Washington ? An avalanche of asbestos lawsuits many filed by people who are not extremely sick is overwhelming courts and threatening companies even though the cancer-causing substance has not been widely used in the United States for almost 30 years.

More than 60 companies have sought bankruptcy protection since 2000 as a result of mounting exposure claims and hefty settlements about asbestos, a fibrous mineral commonly used until the mid-1970s in insulation and fireproofing material. They include Kaiser Aluminum, Bethlehem Steel, Owens Corning and Armstrong World Industries.

“It’s a growing problem when a lot of people thought it was a diminishing problem,” said Mike Baroody, a lobbyist with the National Association of Manufacturers. His group has joined with the American Insurance Assn. to lead an alliance that is pressing Congress for relief.

The alliance is seeking legislation that would give priority to the claims of the most seriously ill while preserving the rights of others to sue if they should become very sick.

Inhaling asbestos fibers can cause lung cancer and other deadly respiratory ailments, sometimes decades later.

An estimated 200,000 claims are pending in courts, with more than 90,000 filed just last year. As more companies seek bankruptcy protection, new lawsuits target those that have only remote ties to asbestos.

“Claims are being put to anybody that’s got money to pay,” said David Bernick, a Chicago lawyer who represents two companies in bankruptcy W.R. Grace, a supplier of construction chemicals and building materials, and Babcock and Wilcox, an engineering company.

His clients also include automakers Ford, General Motors and Daimler Chrysler, which are fighting suits about asbestos once used in brakes.

W.R. Grace did not make asbestos, but used it in fireproofing material. The company filed for bankruptcy in April 2001 after seeing an 81 percent increase in asbestos claims the year before.

Only about 10 percent of the claims involve people working in the construction business, Bernick said. Most are from people who at one time were inside a building containing asbestos fireproofing material.