NEW YORK (NYTIMES) - The Sept 11 terror attack on the World Trade Center has been remembered for the 2,753 lives lost that horrific morning. But that toll in New York has very likely been eclipsed by deaths from exposure to toxic pollutants in the air in the weeks and months after the collapse - and that number keeps growing.

Immediately after the twin towers fell, the roughly 90,000 firefighters, paramedics, police officers and others who selflessly rushed to the scene were hailed as heroes. But over the years, as the public's attention waned, health problems, like cancer, respiratory illnesses and other ailments, remained and have continued to emerge.

By some estimates, more than 400,000 people in lower Manhattan, including those who lived, worked and studied there, were exposed to toxic material from the pulverised towers, leading to health issues that were diagnosed many years later.

Of the 111,005 ground-zero responders and survivors enrolled in the World Trade Center Health Programme, 4,610 have died, according to officials at the Centres for Disease Control and Prevention. Although the programme does not collect information on cause of death, some health officials believe many died from 9/11-related illnesses - and that the toll is in fact higher, given the likelihood that many people have died who were not enrolled in the programme and did not know their illness was 9/11-related.

Most responders have registered for federal medical coverage and settlements. But only a small fraction of civilians affected by the toxins have done so. Many are unaware that they are able to, or even that the illnesses they are suddenly experiencing years after 2001 may be a result of the lethal dust and smoke of the smouldering rubble where the towers stood.

"I don't think even Al-Qaeda thought this would happen," said Mr John Mormando , 54, from Oakland, New Jersey, who was working as a commodities broker a few blocks from ground zero in 2001. "It was a bonus for them. They thought they killed 3,000 that day, but no one would have thought this would still be killing people."

He later underwent a double mastectomy after being diagnosed with breast cancer, an ailment suffered by a cluster of men who spent time near ground zero.

"We were told that the air was fine, and we needed to get back to work," he said. "There were buildings still on fire."

Ms Carrie Benedict Foley's husband, Mr Daniel Foley, died in 2020 at age 46 from pancreatic cancer believed to be linked to his exposure to airborne debris while he searched for survivors at ground zero, including his firefighter brother, Mr Thomas J. Foley, 32, whose body was found 10 days after the collapse.

Daniel's annual medical screenings never showed ailments until the cancer was diagnosed in 2019, four days after he crawled into a burning Bronx building to rescue two children, which earned him the Fire Department's Medal of Honour, Ms Foley said. Daniel knew his death would devastate their five young children, but he did not regret working on the pile at ground zero.

He would come home each night from ground zero with his clothes caked with toxic dust, said Ms Foley, 47, a funeral director from New Rochelle, New York.

"When he was diagnosed, he said, 'It wouldn't have changed what I did, even though it made me sick,'" she said.

Ms Barbara Burnette, 58, of Bayside, Queens, was a New York City police detective who helped for several weeks with recovery efforts at ground zero. Several years later, she could not walk up a flight of stairs because of the lung disease that was diagnosed in 2004. Then came lung cancer in 2017.

She now uses a wheelchair and oxygen. "We didn't even think about masks at the time," she said. "We were working so much that it didn't cross our minds we could get sick. What makes it so sad is, we would do it all again."

While aware of the toxic conditions at the time, "my mentality was, we were at war, and we initially thought we could rescue people", said Mr Tom Wilson, 52, of Bellport, New York, who was a New York City police sergeant.

He helped shut down the Williamsburg Bridge on Sept 11 before spending five weeks looking for remains in the rubble at ground zero and Fresh Kills Landfill for months following the attacks, all while inhaling toxic dust into his lungs.

Mr Wilson, who has five children, learnt he had oral cancer in 2008, which has left him plagued with chronic problems and ongoing treatments.

"Between 250 and 300 first responders are dying every year," said Mr Michael O'Connell , 45, of Westbury, New York, who worked on the pile and in 2007 developed sarcoidosis, an autoimmune disease. He retired from the New York City Fire Department in 2009 because of lung problems.

When Ms Val Velazquez-Stetz, 53, of Wall Township, New Jersey, assisted as a Jersey City police officer in the effort to recover remains at ground zero, the air was so laden with dust that it felt like a snowstorm, yet she wore no mask. Within months, she began having sinus and lung problems that worsened over the years. Then came skin cancer and severe reflux.

"I didn't know it was related - just thought I was an unlucky person," she said, adding that she has helped some 300 people, mostly responders from New Jersey, apply for the federal benefits.

For lower Manhattan residents, "we're one big cancer cluster at this point", said Ms Mariama James, 50.

She and her husband, Mr David James, 49, have three children - Abishai, 28, Armani, 25 and Alijah, 19 - who have had chronic 9/11-related illnesses largely from their exposure to ground zero dust in their apartment building five blocks from the site. Ms James was pregnant with Alijah on Sept 11.

"It was a hot day, over 80 degrees (27 deg C), so all the windows were open," she said, adding that the apartment got so dirty, she had to tear up the carpet in her children's room and throw out all of the furniture.

Mr Ken Muller, 62, who worked at Goldman Sachs in lower Manhattan, followed the government's guidance that the financial markets should reopen days after the attacks and that the air was safe.

"I came home every day with dust on my clothes," said Mr Muller. "Most people who worked in lower Manhattan were not thinking about this - they never connected the dots."

Along with a host of other 9/11-related illnesses, he learnt he had kidney cancer in 2015. After a year of daily chemotherapy, he still suffers from mental fogginess he attributes to "chemo brain".

"A lot of people believed this just happened to first responders, but a lot of us went to work every day and were inhaling the same dust," said Ms Yvonne Phang, 69, an accounting professor at the Borough of Manhattan Community College, several blocks from ground zero, where classes resumed weeks after the attacks.

"In my sixth-floor classroom, my students would have to cover mouths and noses, it smelled so horrible," she said. "The dust would blow through the windows."

"No one knew it could impact us that way," said Ms Phang, who had a double mastectomy for breast cancer.

Dozens of her colleagues have received diagnoses of 9/11-related illnesses, some of whom have died, she said. "Many people who got sick are embarrassed to talk about their illnesses," she said. "They avoid talking about 9/11 because they are so traumatised they want to forget it."

Ms Liz Wilson, 62, of Beacon, New York, was assigned to ground zero as a social worker for emergency medical workers and family members of victims. A non-smoker, she has since experienced lung and breathing problems, including asthma, and growths in her lungs, breast and nose.

"I was a very strong person and now I have anxiety attacks," she said. "If I see a lot of people running, I want to crawl under something."

Ms Lila Nordstrom, 37, was a senior at Stuyvesant High School, blocks away from ground zero on Sept 11, and fled with her fellow students away from the thick dust plume as the north tower collapsed. By Oct 9, they were back in class.

Her asthma quickly worsened and she developed rhinosinusitis and extreme acid reflux, which she believes is connected to the students' exposure that fall and winter. "As students we were told, 'Everything's fine, don't worry about it,'" she said. "We were minors, we shouldn't have been down there."

"A lot of people don't understand how bad the exposure was and how bad the issues are that we have," she said.

As years passed, she encountered more and more classmates with similar issues and founded the advocacy nonprofit StuyHealth to help other young survivors.

Mr Amit Friedlander, 37, was a senior at Stuyvesant High and was sent back several weeks after the attacks. In 2006, at age 22, he learnt that he had Hodgkin lymphoma, a white blood cell cancer. His cancer is in remission, but in March, he was told he had Parkinson's disease.

Ms Anne-Marie Principe, 62, who ran a modelling and talent agency near ground zero, got blanketed by debris the morning of the attacks. She suffered severe lung damage, had brain surgery to remove a tumour and is now battling breast cancer. She still has a flag that a soldier gave her when she was walking to her office on Sept 12.

Worried about ruining her nice shoes, she bought boots to walk through debris and continues to wear them two decades later. "They would spray down our shoes when we were leaving the area. They'd spray them with a hose and I said, 'Not my Pradas!'" Ms Principe said.

Mr Jose Santiago, 72, got doused with dust while reporting from ground zero for radio station WBAI. Within months, he began to develop a chronic cough and would later develop chronic pulmonary disorders, skin cancer and other ailments. "It was a knockout punch career-wise and every other way," he said.

"When we went back to work, people on the subway were coughing as it pulled into the station in lower Manhattan," he said. "People feel so betrayed by being told the air was safe."

Mr Martin Preston, 68, was a New York City employee who helped set up tables, chairs and other equipment at ground zero for months after Sept 11 and later developed fibrosis in his lungs as well as asthma and severe acid reflux. "It's the catastrophe that keeps on giving," he said.

Mr Andrew Pillay, 58, who worked at a printing and advertising firm near ground zero, helped work on the pile for several days and then sifted through heavy dust in his office. He now has sinusitis, lung disease, asthma, severe reflux and thyroid cancer.

He began being treated at the World Trade Center Health Programme at Mount Sinai in 2005 after he began to have health problems, and in 2013, he had surgery to rebuild his oesophagus, which was damaged by reflux.

"It's just a constant fight," Mr Pillay said. "Twenty years later, and I'm still suffering." He added, "Every time you think you have something fixed, something else kicks off."

Ms Mary Montgomery, 57, of Stroudsburg, Pennsylvania, said her husband, Mr Jeffrey Montgomery, died in 2018 at 59 from oesophageal cancer that she believes stemmed from his five months of emergency telecommunications work during the ground zero recovery.

"This man was like an iron horse," she said. "He was never sick. He worked 16 hours a day at ground zero and forbid me from coming anywhere near it."

She said he became a city bus driver after the telecommunications company laid him off along with other co-workers following their Sept 11 work. Several of the workers have also died, she said.

"His doctor said this type of cancer was an anomaly, given his medical history, and that he could only have gotten this type of cancer from exposure," she said. "He was like, 'That's why I have this?'"

"It's two decades later and people are still getting killed by it - the aftereffects are still happening," Ms Bridget Gormley said of the attacks. Her father, Mr William J. Gormley, was a New York City firefighter who died from lung cancer in 2017 at age 53, 16 years after responding to Sept 11 and helping in recovery efforts at ground zero for weeks.

"Everybody in the 9/11 community who doesn't have cancer is looking over their shoulder, wondering, 'When am I next?'" said Ms Gormley, who has 23-year-old triplet brothers: Billy Jr., Raymond and Kevin.