In a decision with potentially broad implications, the Pennsylvania Supreme Court has disallowed scientific testimony in asbestos lawsuits asserting that even the tiniest exposure could cause cancer.

The unanimous opinion, written by Justice Thomas G. Saylor, said plaintiffs alleging asbestos-related disease could no longer argue that the mere exposure to even one fiber of the cancer-causing substance could be the basis for a claim. The court said plaintiffs would have to show some relationship between the amount of asbestos exposure and development of the disease.

"Simply put," the court said in its 53-page opinion, "one cannot simultaneously maintain that a single fiber among millions is substantially causative, while also conceding that a disease is dose-responsive."

The decision was hailed by the National Federation of Independent Business, which asserted that thousands of businesses around the country had been sued on the basis of the theory.

"This is a significant decision because it prevents the use of tenuous theories that have no basis in science," said the group's Pennsylvania director, Kevin Shivers. "We are grateful to the court for this decision because it makes the system objectively fairer."

The decision came in a 2005 lawsuit by a Western Pennsylvania auto mechanic against Ford Motor Co., Allied Signal Inc., and others alleging that, over 44 years, his exposure to asbestos through the repair of brake linings had caused mesothelioma, a cancer that in the overwhelming majority of cases is attributable to asbestos exposure. The Pittsburgh-area law firm that represented the mechanic, Charles Simikian, did not return a telephone call requesting comment.

The plaintiffs' team relied in part on expert testimony that exposure to even one asbestos fiber could cause the disease, known in the legal world as the "any breath" or "any fiber" theory. The defense attacked that explanation, saying it would be impossible to legally assign responsibility without showing that Simikian had been exposed to specific doses of asbestos known to cause the disease.

The trial court agreed with the defense, saying it could find no credible explanation for how the plaintiff's expert had determined that it was workplace exposure to asbestos and not another source.

The lower-court opinion was appealed to state Superior Court, which had said that the expert testimony was admissible, and was reversed. The Supreme Court in turn reversed the Superior Court, and sent the case back to the trial judge.

The Supreme Court said in its opinion that it had taken the Simikian appeal as a test case for establishing ground rules in similar litigation. Bill Anderson, a Washington-based lawyer with Crowell & Mooring, who filed an amicus brief on the case on behalf of the Pennsylvania Chamber of Commerce, said the any-fiber theory of causation in asbestos cases had been used increasingly across the country. Only one other state supreme court, that of Texas, has barred the theory, said Anderson, who defends businesses that have been sued in asbestos cases.

Contact Chris Mondics at 215-854-5957 or