The city medical examiner’s recent decision to list World Trade Center dust as a factor of death on a death certificate could prompt quick action on a number of fronts.

For one, it is likely to energize lobbying efforts to get federal funding for the thousands who say they are ill from exposure to contaminants from ground zero. It also could prompt further requests for the city to similarly amend additional death certificates.

But the effects of this recent medical finding are not likely to be immediately found in the federal courts, where the city is dealing with suits filed by nearly 10,000 rescuers and construction workers who labored at ground zero and now say the city failed to protect them from toxins.

An attorney for the plaintiffs, Marc Bern, has said he intends to mention the amended death certificate in an upcoming court brief. But Mr. Bern added that it was possible that “any medical issues might not be talked about” at this stage in the litigation.

Lawyers familiar with the case say that at least for the moment any medical findings are unlikely to sway the course of the lawsuits. The 2nd U.S. Circuit Court of Appeals will decide whether to dismiss them in the coming months.

Whether the lawsuits survive will depend on the court’s answer to an abstract legal question: Is the city immune from such lawsuits because it was acting in the wake of an emergency?

The recent decision by the city to amend the death certificate “in no way changes the calculus as to whether the city is liable or immune from suit,” the lawyer who directed the September 11 Victim Compensation Fund, Kenneth Feinberg, told The New York Sun.

In a 102-page brief filed this week to the court, the city exclusively focuses on this question of immunity.

“If these immunity laws do not extend to the single largest public/private emergency response in American history, then what do they cover?” the brief, written by an outside lawyer, James Tyrrell Jr. of Patton Boggs LLP, said.

Last year, a lower court judge, Alvin Hellerstein, said the lawsuits should go forward, partially rejecting the city’s claim of immunity.

Should the 2nd Circuit agree with Judge Hellerstein, lawyers say that the recent death certificate amended by the city’s medical examiner, Charles Hirsch, could emerge at the center of the plaintiffs’ case. The death certificate was for a government attorney, Felicia Dunn-Jones. Dr. Hirsch recently added exposure to World Trade Center as a “contributory” cause of her death.

“The legal significance of this is profound,” Mr. Feinberg, who is not involved in the case, said of the change to the death certificate. “It is one more weapon in the plaintiffs’ arsenal to demonstrate medical causation.”

A spokeswoman for the city law department declined to comment on what effect the death certificate could have on the litigation.