The New York City officials who withheld 68 boxes containing air-quality data and other information about toxins at Ground Zero put the health and lives of first responders and thousands of others in danger, officials from the FDNY’s largest union said Monday.

Uniformed Firefighters Association president Andrew Ansbro demanded to know who told his members and the public that the air quality was safe to return to lower Manhattan in the wake of the Sept. 11, 2001 attacks on the World Trade Center. He said the recently released documents could have helped public health officials diagnose and treat cancers and other diseases that have killed 400 New York City firefighters, in addition to the 343 who died on Sept. 11, 2001.

“We need to know who lied initially,” Ansbro said at a news conference just blocks from the World Trade Center site where 2,606 people died less than 25 years ago.

“I think it’s important for people to know that there were people back then that chose to protect the city’s interests and not protect the interest of New York City firefighters, and other responders and civilians that were down there,” Ansbro continued, urging Mayor-elect Zohran Mamdani to bring transparency and accountability to the issue.

Mamdani’s transition team did not respond to requests for comment.

City officials in recent months produced the 68 boxes of records from a Department of Environmental Protection office more than two years after an attorney for 9/11 Health Watch, an advocacy organization for first responders and other survivors, filed a Freedom of Information Act request in September 2023 seeking records about what the administration of then-Mayor Rudy Giuliani knew about the health impact of toxins at Ground Zero. DEP officials said they did not have the documents and denied the request.

Ansbro said the records may include data that could have identified the toxins his members and others inhaled at the site. Earlier access to the records may have helped his members get more accurate diagnoses and treatment, Ansbro said. His union was part of a yearslong effort to pass legislation that created the 2011 World Trade Center Health Program, which provides medical screening and treatment for 9/11 first responders.

“We could be looking at more illnesses that have latency periods of 25, 30 years, based on chemical exposure. These are all things that we could have been looking at and studying for the last 20 years,” said Ansbro, whose union represents about 20,000 active and retired firefighters. “The city chose to keep them hidden.”

A representative of Mayor Eric Adams declined to comment due to ongoing litigation but said the mayor has been “unwavering” in his commitment to 9/11 first responders.

“While we cannot comment on the specifics of pending litigation, the city has begun turning over documents to plaintiff’s counsel, and both parties are working out a schedule to continue this process,” the City Hall representative said in a statement.

The city has tried to have a subsequent lawsuit filed by 9/11 Health Watch dismissed for more than a year, said Andrew Carboy, an attorney for the advocacy group. City attorneys said no records were found “after a diligent search.”

But that changed after New York lawmakers passed legislation sponsored by City Council member Gale Brewer (D-Manhattan) directing the Department of Investigation to look into what officials knew about the toxins that killed and sickened thousands.

“I think it is a substantial factor in bringing this disclosure to light,” Carboy said.

Carboy and other attorneys and representatives of 9/11 Health Watch reviewed 20 boxes of documents last week. The reviewed records concerned air testing for asbestos, metals and other chemicals after the attack. One of the documents, from the city’s Law Department in 2002, directed agencies to preserve records that could be used in future litigation, Carboy said.

Carboy filed papers in New York State Supreme Court late Monday requesting to depose Russell Pecunies, the DEP’s Freedom of Information appeals officer. Carboy also requested a deposition with unspecified officials regarding  the existence of the recently released documents.

Ansbro called on the incoming Mamdani administration to push for answers.

“Everyone that was exposed, they need to know,” the union chief said. “Their families need to know who lied to them. They need to be held accountable.”

Michael O’Keeffe covers Suffolk County police and other Long Island law enforcement agencies. He is an award-winning journalist and the co-author of two books,”The Card” and “American Icon.”