Nearly seven out of 10 Ground Zero workers have suffered lung problems during or after their work at the site, according to a study of health effects related to the 11 September 2001 attacks.
By Sarah Dale
BBC News, New York
Volodymyr Khomik's lung problems mean he can no longer work
Such findings may come as little surprise to the workers hired to clean the dust and debris from the buildings surrounding Ground Zero.
One such was 54-year-old Volodymyr Khomik. A lawyer in his native Ukraine, he was forced to take a manual labour job when he arrived in the US because of his lack of English language skills.
His employer joined the clean-up operation at Ground Zero on 12 September, 2001 and that afternoon Volodymyr set to work there.
"The first few days were emotionally devastating," he says, bowing and shaking his head. "There were so many things going on at the time, there was fire and body parts all over the place.
"It was extremely difficult for us to work there during the first few days and weeks because we were not prepared for this kind of job."
The work was physically very demanding, often 16 hours a day, seven days a week for the first three months.
Conditions on the site were extremely difficult, says Mr Khomik. "We had to work with our bare hands and we did not have the right equipment, right masks and nobody cared at that time.
Clean-up workers say they did not have adequate breathing apparatus
"There were places in Ground Zero where we could not breathe at all, we were suffocating and we couldn't hold our breath. So we had to wait for some time until the smoke went away."
He says it took a serious toll on his health, evident from the wheezing cough and the difficulty he has catching his breath.
"After two or three months working there, I started to have health problems and the situation just got worse and worse."
A CAT scan in 2002 showed dust in his lungs. "My doctor asked me why I had been smoking so much," says Mr Khomik.
"When I told him that I was working at Ground Zero he stopped asking questions.
"I have problems breathing now. I was also diagnosed with heart problems and my blood circulation is not working properly."
Unable to work since 2002, and without insurance, the Ukrainian faces hefty medical bills and fears he has become a burden on his family.
His vision of the future is bleak. "I am like an old man now. I don't know what will happen to me... I am thinking about whether I will live or pass away, it is the number one question for me now."
Lawyer Gregory Cannata says the scale of the health problems linked to 9/11 is enormous.
Thousands of people - firemen, policemen, residents and clean-up workers, both illegal and legal - have begun legal action, notably a class-action lawsuit against the Environmental Protection Agency.
Volodymyr is among a number who are suing the owners of the buildings they were employed to clean up, on the grounds that workers were not provided with adequate protective equipment on the premises.
Mr Cannata, who is acting for 60 workers, thinks there are still more lawsuits to come.
"We're talking about tens of thousands of workers. Thousands of them are ill and thousands of them are becoming ill," he says.
"I believe that more workers will actually die from the effects of the toxic substances that they were cleaning up than people who were actually killed on 9/11."
The dust that was left behind after the Twin Towers collapsed contained small particles of substances such as asbestos, lead, glass, and cement.
Breathing this in left people vulnerable to lung injuries. Many started with a chronic cough, referred to at the time as 'World Trade Center cough'.
Smoke and dust lingered over Manhattan for days after the attack
Others developed obstructive lung disease, nodules in their lungs, and scar tissue which all make it more difficult for the lungs to get oxygen into the bloodstream. And as the lungs become more damaged, the knock-on effect has been circulation and heart problems.
Some of the workers have developed cancers, although it is yet to be proven that these are related.
A study by the Mount Sinai Medical Center, based on the screening of 9,500 rescue and clean-up workers - the largest programme of its kind - said nearly 70% have had trouble breathing and many are likely to be affected for the rest of their lives.
"These were people who had been gainfully employed all their lives and now can't work and they're sick," says Mr Cannata.
"They are taking numerous medications - they are disabled as a result of this, they can't breathe, they can't catch their breath, they are constantly coughing - they're very uncomfortable and it's really destroyed and crippled their lives."