The city and its contractors are not immune from lawsuits brought by emergency workers sickened after toiling amid toxic dust at ground zero, a judge ruled, clearing the way for what he said should be the speedy resolution of thousands of claims.

In his decision Tuesday, U.S. District Judge Alvin K. Hellerstein said the city, its roughly 150 private contractors, and the Port Authority of New York and New Jersey were only partially immune from lawsuits, with the precise scope and extent of the immunity varying according to date, place and activity.

"If even a minority of the plaintiffs suffered serious injuries to their respiratory tracts arising from the acrid air of September 11, their claims deserve to be heard when a recovery could make a difference in their lives," the judge wrote, adding that the defendants are entitled to resolution at the earliest possible point.

A lawyer for the plaintiffs hailed the ruling as "an important decision, a first step forward in the legal system for these other victims of 9-11." Andrew J. Carboy, who represents 210 individuals, mostly firefighters, said the number of people making claims reaches as high as 8,000.

Michael A. Cardozo, the city's top lawyer, argued a close study of the facts surrounding the claims will show an absence of any legal liabilities by the city and its contractors.

Hellerstein did dismiss claims against the Consolidated Edison Co. and companies controlled by developer Larry Silverstein, saying they did not have legal control over the area and therefore weren't liable for damages.

The judge, who called the situation a "scar to the public interest," said he will appoint a special master to help eliminate unjustified claims and to otherwise manage a case that is "likely to become unmanageable."

The city and its contractors are trying to avoid damages in lawsuits filed on behalf of workers who cleaned up the World Trade Center site for months after the Sept. 11, 2001 terrorist attacks.

The lawsuits claimed the city and its contractors were negligent in monitoring the air and assuring appropriate safety in the workplace, particularly adequate respiratory equipment.

The judge noted that a study released in September by doctors at the Mount Sinai Medical Center showed that approximately 70 percent of the 10,000 workers who were tested reported that they suffer from new or substantially increased respiratory problems since 9/11.

"The workers at the site were presented with a dangerous environment, below and surrounding their work activities, threatening their health and safety," the judge said.