New York City has released more than 170,000 pages of previously undisclosed records that raise fresh questions about what officials knew about toxic air around Ground Zero after the 11 September 2001 attacks.
The documents, made public through a new city portal, include air-quality reports, contamination records and internal correspondence. They indicate that concerns about hazardous pollution continued for months, even as officials repeatedly told New Yorkers the air was safe to breathe.
The first release includes 68 boxes of records recovered in 2025, the so-called Harding Memo and documents relating to the collapse of World Trade Centre 7. Further files are expected to be added over the next 12 months.
Among the records are reports showing that health officials were still finding asbestos at least 10 months after the attacks. Some tests recorded levels below limits set by environmental and workplace safety agencies, while others indicated higher concentrations but contained no written assessment explaining the results.
Mayor Zohran Mamdani said the files would help establish “what the city knew about the toxic air around Ground Zero, when they knew it, and how they acted to limit liability”.
He launched the portal at a news conference attended by city officials and 9/11 health advocates, including comedian and campaigner Jon Stewart. Mr Mamdani said the release was intended to provide greater transparency to survivors, families and first responders who had spent years seeking access to the records.
Mr Stewart accused officials of prioritising a return to normality over protecting people exposed to dust and debris. “There was poison in the air and on the ground,” he said, adding that the contamination remained for months.
Harding Memo and legal battle over 9/11 records
The Harding Memo was written just weeks after the attacks and discussed the potential for legal claims from people exposed to toxic air. Congressman Jerry Nadler said it suggested officials working under former mayor Rudy Giuliani anticipated severe health consequences for thousands of New Yorkers.
“The failure of government officials to share this information with the public and adequately respond to the dangers has had devastating and, in too many cases, fatal consequences,” Mr Nadler said.
The release follows the settlement of two lawsuits brought by 9/11 Health Watch, which had sought access to the records through freedom-of-information proceedings. The organisation said a New York court ruled in May that the city had acted improperly when it denied an earlier request for documents held by the Department of Environmental Protection.
Under the settlement, the city says further records concerning air quality, risk assessments and public messaging will be made available. The administration has committed more than $34 million to creating and maintaining the portal.
City Hall also plans to appoint staff to help eligible survivors and responders use the documents to demonstrate that they were present in the exposure zone when applying for federal health and compensation programmes.
A spokesman for former mayor Eric Adams said the records should be released and examined, but that Mr Adams “did not create, conceal or control records from prior administrations”. Representatives for former mayors Giuliani, Michael Bloomberg and Bill de Blasio were also approached for comment.
