New York City on Tuesday released more than 170,000 pages of previously withheld records detailing air quality around Ground Zero in the aftermath of the September 11, 2001, attacks.

The documents, posted to a public online portal by Mayor Zohran Mamdani's administration, include air quality reports, internal memos, and contamination records showing that city officials detected elevated levels of toxins such as asbestos and benzene for months after the attacks.

Records indicate asbestos was still found at sites as far as a half-mile away 10 months later, even as officials including then-EPA Administrator Christine Todd Whitman declared the air safe to breathe before comprehensive indoor testing occurred.

One October 2001 memo, known as the Harding memo, discussed the city's potential liability for toxic exposure, highlighting early awareness of risks among officials under Mayor Rudy Giuliani.

The release stems from settlements in lawsuits by the 9/11 Health Watch group and follows the discovery of 68 boxes of documents last year. Multiple mayoral administrations had resisted full disclosure.

Mayor Mamdani, joined by comedian Jon Stewart and 9/11 families at a City Hall news conference, stated that the papers reveal what the city knew about the toxic air, when officials knew it, and how they acted to limit liability.

Stewart noted that the city only recognized the air as toxic in October 2001 and buried that information for 25 years.

More people have died from 9/11-related illnesses than in the initial attacks, according to federal monitoring data. The documents are expected to support ongoing health claims and add to the historical record ahead of the 25th anniversary commemorations this week.

The records provide further evidence that public assurances contrasted with internal findings of hazardous conditions persisting well into 2002.