New 9/11 Records Reveal What NYC Knew About Toxic Air After the Attacks

Newly released 9/11 records show New York City officials were discussing toxic exposure, health risks and potential legal claims within weeks of the attacks as residents, workers and students returned to Lower Manhattan.

Mayor Zohran Mamdani announced Tuesday that more than 170,000 pages of September 11 records are being made public, days before the 25th anniversary of the attacks. The release also resolves two lawsuits brought by 9/11 Health Watch after years of efforts to obtain the records.

Among the documents is the long-sought Harding Memo, prepared in October 2001 for then-Deputy Mayor Robert Harding during the administration of former Mayor Rudy Giuliani.

The memo estimated that the city could face approximately 35,000 potential plaintiffs and as many as 10,000 claims connected to September 11. Potential cases included allegations that residents were encouraged to return to Lower Manhattan too soon and later suffered health problems from toxic exposure, along with claims involving inadequate protective equipment for rescue workers.

At the same time, city health officials were publicly offering reassurance about environmental conditions downtown.

An October 2001 statement from the New York City Department of Health said particulate levels detected in Lower Manhattan did not pose long-term health risks to the general public. The department again said in February 2002 that testing did not indicate long-term health effects.

The records could provide a fuller account of how officials assessed those risks internally and how concerns over public health, cleanup efforts and potential liability developed after the World Trade Center collapsed.

The archive only became public after a years-long fight under New York’s Freedom of Information Law, commonly known as FOIL.

9/11 Health Watch filed a records request in 2023 seeking documents about what the Giuliani administration knew about toxic substances released by the collapse of the World Trade Center and when officials became aware of possible health risks.

The New York City Department of Environmental Protection initially said a diligent search had failed to locate responsive records. In 2025, the agency acknowledged that it had at least 68 boxes of September 11-related material, estimated to contain roughly 340,000 pages.

That discovery became a central issue in court.

On May 28, New York Supreme Court Justice James G. Clynes ruled in favor of 9/11 Health Watch, finding that the Department of Environmental Protection acted “arbitrarily and capriciously” when it denied the group’s appeal of the records request. Clynes found the agency’s reasoning vague and lacking individualized analysis.

The challenge was brought through an Article 78 proceeding, the New York court process used to review decisions by state and local agencies. In a public-records case, a judge can examine whether an agency properly searched for requested documents and followed FOIL when deciding whether records should be disclosed.

The Mamdani administration has now settled that case and a second lawsuit brought by 9/11 Health Watch as the city opens the records through a new public portal.

The archive includes material involving World Trade Center 7, contamination in Lower Manhattan and cleanup procedures after the attacks.

One document highlighted by city officials concerns warnings raised by Rep. Jerrold Nadler about conditions inside Lower Manhattan apartments and whether cleanup efforts adequately addressed asbestos and other contaminants.

The records could also help people still seeking federal 9/11 health care or compensation.

New York City plans to assign staff at the Department of Citywide Administrative Services and New York City Public Schools to help people locate records showing they were present in the New York City Exposure Zone.

Those documents could help some applicants establish eligibility for the World Trade Center Health Program or the September 11th Victim Compensation Fund, which serve people affected by illnesses and other harms tied to the attacks and their aftermath.

The city has committed more than $34 million to creating and maintaining the records portal and related access efforts.

Tuesday’s release represents only part of the archive. The New York City Law Department is expected to continue reviewing records over the next 12 months, with additional documents becoming public as files are processed and personally identifiable information is removed.

Twenty-five years after September 11, the expanding archive could offer one of the fullest public accounts yet of what New York City officials knew about toxic conditions around Ground Zero, when those concerns emerged and how the city responded as Lower Manhattan reopened.