New York records show officials knew Ground Zero air was toxic after 9/11; Mamdani says leaders ‘lied’

New York City has made public more than 170,000 pages of long-withheld records on air quality after the September 11, 2001, attacks, with the documents showing that officials were aware of dangerous conditions around Ground Zero even as the public was repeatedly told the air was safe to breathe.

Mayor Zohran Mamdani announced the release of the documents at the New York City Hall on Tuesday, flanked by elected officials, 9/11 families and health advocates. He accused the erstwhile city leaders of failing those who lived, worked and responded in Lower Manhattan after the attacks. “People got sick because the leaders they trusted lied and told them they were safe to breathe in toxic air,” Mamdani said.

On September 11, 2001, al-Qaeda terrorists hijacked four planes, crashing two into New York’s World Trade Center and one into the Pentagon, while the fourth went down in Pennsylvania.

Nearly 3,000 people were killed, and thousands more later suffered illnesses linked to toxic dust and debris from the attacks.

The records, stored for years in 68 boxes in a city office and discovered last year, include air-quality reports, internal memos, audits, maps, spreadsheets, lab results and agency emails. Their release resolves a lawsuit filed by the advocacy group 9/11 Health Watch, which had sought access to the material.

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Zohran Mamdani: Now, close to 25 years later, more people have died from 9/11-related illnesses than were killed on the day itself. It would be one thing if government had stood alongside survivors and provided them with everything they needed at every step of the way. And yet,… pic.twitter.com/ayvVKRhSqa — Clash Report (@clashreport) September 8, 2026

“As the years pass and the human toll grows, we reckon with the cost of September 11th whenever another New Yorker is stolen from us too soon,” Mamdani was quoted as saying by CNN. He noted that more people have now died from 9/11-related illnesses than the nearly 3,000 killed on the day of the attacks.

The documents point to concerns being repeatedly raised inside government about toxins in and around Ground Zero. Some records show elevated levels of asbestos, benzene, dioxins and other dangerous substances in the weeks and months after the towers fell. A November 2001 audit, based on information from the city’s Department of Environmental Protection, found elevated benzene levels near Ground Zero and higher ambient asbestos concentrations on Staten Island. Ten months after the attacks, asbestos was still being detected around 15 John St, less than a mile from the World Trade Center site, reported New York Times.

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One environmental assessment of 90 Church St, a large office building damaged by debris and fires, found asbestos in settled dust and debris throughout the building. Dioxins were detected in all 11 samples taken, and other toxins, including mercury, were found inside filing cabinets. The report recommended disposing of porous materials such as carpets and ceiling tiles.

Magnesium removed from list of substances tested

A report by New York Times cites emails from October 2001 that show officials discussing what substances should be included in air-quality testing. In one message, a city health official wrote that not all listed substances would be tested and that magnesium would be removed from a revised plan. According to the Centers for Disease Control and Prevention, magnesium was among the substances that made World Trade Center dust hazardous to inhale, the report read.

Other records show officials were surprised that toxin levels had not fallen as expected. In an October 15, 2001, email, city environmental officials noted that dioxin levels were not decreasing and that “some high benzene levels were again found.” The concern appeared tied to fires that continued burning at the World Trade Center site for months.

‘Harding Memo’ that sought to reduce liabilities

The release also includes the so-called “Harding Memo,” sent to then-Deputy Mayor Robert Harding. The memo cited a Law Department estimate of about 35,000 potential plaintiffs, including roughly 10,000 expected claims, and outlined legislative options to reduce the city’s liability. It listed possible lawsuit grounds, including that health advisories may have caused people to return to the area too soon, exposing them to toxins, or too late, causing economic hardship.

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In the aftermath of the attacks, officials including then-Mayor Rudy Giuliani and then-EPA (Environmental Protection Agency) administrator Christine Todd Whitman assured the public that the air was safe. In February 2002, then-Mayor Michael Bloomberg said that “every test that has been done says the air quality was in acceptable limits.”

A spokesperson for Bloomberg declined to comment Tuesday. A spokesperson for Giuliani did not respond to a request for comment.

‘EPA neglected responsibility’

EPA administrator Whitman said in a statement that her remarks at the time were based on analysis by EPA scientists. She was quoted by NYT as saying that the EPA had made data public within days, frequently updated it, and sought transparency. She also said the agency distinguished between conditions at Ground Zero and elsewhere in the city, warned workers at the site about risks, and did not control the worksite or regulate indoor air quality.

The documents also include concerns raised by US Rep Jerry Nadler of New York, who wrote to Bloomberg’s office in February 2002 that the EPA had “neglected its responsibility for monitoring indoor air quality around Ground Zero.” Nadler cited research by University of California, Davis, scientists that found “startling concentrations” of ultra-fine particles capable of lodging deep in the lungs.

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At least 140,000 people from all 50 states are enrolled in the World Trade Center Health Program, and 49,000 have been diagnosed with certified WTC-related cancers, according to the 9/11 Memorial. Cancer was not covered when Congress created the health program in 2011, but was added in 2012 after advocacy efforts and research showing elevated cancer rates among New York firefighters who worked at Ground Zero.

Ben Chevat, executive director of 9/11 Health Watch, said the newly released material would help people seek federal assistance and support further research. “Mr. Mayor, I want to thank you for being the mayor who, after 25 years, begins to answer the question: What did the city know about the dangers from the toxic cloud at Ground Zero, and when did it know it?” CNN quoted Chevat as asking at a press conference.

Jon Stewart, who has long advocated for 9/11 responders and survivors, also attended the news conference. “There was poison in the air,” he said, adding that the documents made clear the city knew about the danger.

Three weeks after 9/11, the city chose a cover-up over public safety. Jon Stewart described poison in the air and ground, coating clothes, pets, and air conditioners for months. People who survived the attacks were sent into toxic dust because “business as usual” mattered more. pic.twitter.com/yfsQ2EGIrg — Lesley Abravanel 🪩 (@lesleyabravanel) September 8, 2026

The city has created a searchable portal where the documents can be viewed and downloaded for free. Officials said more records will be reviewed, redacted and released over the coming months.