First responders still navigating health effects 25 years post-9/11

More than 9,400 people have died from 9/11-related illnesses.

When Michael O'Connell found out he had been accepted into the New York City Fire Department, he was elated. O'Connell had started his career as a police officer, but he always had more of an interest in becoming a firefighter.

"It was more my speed," O'Connell told ABC News. "It was like camaraderie, team, unity. It's where I wanted to be."

O'Connell was sworn into the FDNY as a probationary firefighter. Just four months later, he was deployed to lower Manhattan on Sept. 11, 2001, following the terrorist attack at the World Trade Center.

For several weeks, O'Connell said he didn't go home. He went back-and-forth between his firehouse and ground zero, extinguishing fires amid the rubble and engaging in search-and-rescue operations.

O'Connell started hearing about fellow firefighters who worked at the site being diagnosed with asthma or cancer but didn't experience any health problems himself until New Year's Day 2007, when he says he woke up in severe pain.

"My body inflamed two times the size of what it was," O'Connell said. "I didn't know what was going on ... and I had like bruises and blisters all over my body."

O'Connell said he was eventually diagnosed with sarcoidosis, a multi-system inflammatory disease that typically affects the lungs, skin and lymph nodes, and his doctors believe is linked to his exposure to toxins at ground zero.

It's estimated that 400,000 people were exposed to toxic dust, smoke and debris; risk of physical injury; and physically and emotionally stressful conditions from 9/11 and the aftermath, according to the World Trade Center Health Program.

At least 69 cancers -- including breast, prostate, skin and head and neck -- have been certified as being linked to 9/11 as have airway and digestive disorders, musculoskeletal disorders and mental health conditions, according to the WTC Health Program.

More than 9,400 people have died from 9/11-related illnesses -- according to recently published data from the WTC Health Program -- which is three times higher than the 2,977 who died in the attacks in New York, at the Pentagon and in Shanksville, Pennsylvania. Data from the WTC Health Program shows about 50,000 cancer diagnoses have been certified.

Many of these people are members of the FDNY and NYPD who responded to the attacks or assisted in cleanup operations, but they also include civilians -- those who lived, worked, went to school or passed through the area.

"The truth is, 9/11 didn't end on 9/11," Michael Barasch, managing partner at Barasch & McGarry, a law firm that specializes in helping 9/11 responders and survivors get compensation and health benefits, told ABC News. "I personally lost dozens of clients, mostly firefighters and police officers, on 9/11, but I have lost thousands of clients since."

"9/11 Tribute in Light: Live from Lower Manhattan," a one-hour ABC News multiplatform live special, premieres on Friday, Sept. 11, at 8:00 p.m. EDT across ABC, Disney+, Hulu, National Geographic, ABC Owned Television Stations livestreams and ABC News Live.

On the morning of 9/11, Thomas Wilson, an NYPD sergeant, was investigating a burglary of an elderly couple in Brooklyn when calls came in over his radio that an object had hit the World Trade Center. Wilson replied that he was heading to the Williamsburg Bridge.

"I said goodbye to that couple, 'I'll come see you later on to take that report,'" Wilson told ABC News. "Never did see them again."

Wilson said he shut down the Williamsburg Bridge on the Manhattan side while his colleague shut down the Brooklyn side. The assignment went from facilitating the movement of vehicles over the bridge to securing it as people fled from Manhattan over the bridge on foot.

"I don't know how many thousands upon thousands of people crossed the bridge that day," Wilson said. "I'm still haunted. Covered in dust. ... That mass exodus out of Manhattan still sticks with me."

When O'Connell, the firefighter, got down to the site, he said he was instructed to help shut down the water mains, and then he climbed on the rubble to assist in search and rescue.

Throughout the day, O'Connell remembers hearing alarms. He said that attached to the Scott Air-Pak, a self-contained breathing apparatus that firefighters wear, is a Personal Alert Safety System (PASS) Alarm, which sits on the chest and tracks movement.

If a firefighter stays still for 20 to 30 seconds, it emits a loud beep to help colleagues locate them.

"That's all you heard were those alarms when we first got there. Nothing but PASS Alarms," O'Connell said. "As a fireman, when you hear it, you're meant to act and try your best to get to that person. You couldn't. They were underneath that pile."

John Feal, a demolition supervisor at ground zero who arrived on site on Sept. 12, also remembers the PASS Alarms going off.

"I don't care who you are, you're not programed ... to see that kind of devastation of that magnitude," he told ABC News. "I've never witnessed anything like that in my life, nor do I wish I ever see anything like that again."

Wilson said he contributed to recovery efforts at ground zero, where he says he spent about 350 hours, and later as a sifter at Fresh Kills Landfill on Staten Island, which was temporarily reopened as a sorting ground for some of the ground zero rubble.

Wilson said he almost never thought about the dust and toxins he was inhaling.

"My mindset was just get the job done," Wilson said. "... Got to do what you got to do to keep things moving along."

At the landfill, Wilson said he was issued a disposable suit with boots, a hood, gloves and a respirator, but said the shifts were 12 hours, and that some respirator filters have an eight-hour limit.

Ivonne Sanchez, former FDNY emergency medical technician, arrived at ground zero after the towers fell and said she spent about 20 straight hours at the site. She said the dust was so thick that she couldn't get her bearings.

For the next several months, Sanchez worked on body identification and recovery efforts. She said she was motivated to continue responding at ground zero with the hope that she would find her friend, who died in the attacks.

Sanchez said she didn't receive a mask until October, when the site was visited by Occupational Safety and Health Administration inspectors for mandatory mask fittings.

O'Connell, the firefighter, said he didn't have a mask for the first few days until he received a painter's mask.

"You'd put them on but, quite honestly, you can't work with a painter's mask on for 24 hours straight and be a part of Bucket Brigade and talk to your guys and drink water," he said. "You're always pulling it on and off. Nobody was thinking, 'What's coming of this? Are we gonna get sick because we're breathing this stuff in?' That wasn't in anybody's head."

New York City Mayor Zohran Mamdani said this week that more than 170,000 pages related to the attacks were being made public , including about air quality.

Among the documents revealed is the "Harding Memo," an October 2001 memo from then-Deputy Mayor Robert Harding that indicated the city knew of the air quality dangers and the legal liability, even though the city publicly declared the air was safe.

The Environmental Protection Agency (EPA) also told the public at the time that the air around ground zero was safe to breathe. In an interview with The Guardian in 2016, Christine Todd Whitman, who was EPA administrator during 9/11, apologized for "whatever we got wrong" but denied that she knowingly lied about the air quality or knew at the time it was dangerous.