US Correspondent Emma Murphy reports on the rescuers who now face losing their own lives because of 9/11
So much about the 9/11 terror attacks remains shocking 20 years on. Not just the images of the day but the dreadful detail that has come out in the years since.
Shocking too are the detail of what has happened to those who were so much a part of it.
The people who thought they were lucky, thought they had survived, only to realise all these years on that 9/11 is their death sentence.
The date may not be etched on their graves but it will be what took them there.
The official toll of lives lost that day is 2,977.
'Get in the health programme before you find a lump in your neck or wherever in your body', says former New York City Police Officer, Tom Wilson
Yet since then 3,900 people have died of conditions they contracted when the towers fell in plumes of toxic dust.
At least 22,000 have cancer, 47,000 people have respiratory and digestive issues and thousands more have other life-altering or life-ending conditions.
They are the first responders, the people in the area that day and people who returned to that area thinking it was safe months on only unaware how much toxicity remained.
Hearing their stories proves that though 9/11 was one day for many, it is a life sentence for others.
'It's 20 years for everyone who watched it unfold but for those directly impacted by the aftermath of 9/11, it's the longest day in the history of days', says former rescue worker John Feal
John Feal was a rescue worker who lost part of his foot when a girder fell on it. As he recovered he saw his friends and colleagues become ill and die.
He began the fight to have the health conditions caused by 9/11 recognised by the US government.
It took 2,000 meetings and 300 trips to Washington but now there is provision for healthcare and an organisation devoted to those who became sick after. Sadly the science overtook the scepticism.
The more friends John lost, the more he was determined that something other than healthcare legislation would be their legacy and so he created the remembrance garden - a donated acre of land which he and others have developed to memorialise those who died after.
'It's scary, I never planned that I would be sick, I never thought it would hurt me as much as it has', says former New York City Police Officer, Glenn Tarquinio
It is his pride and joy and rightly so. It is a haven of peace for those who wish to remember.
It has taken 20 years of death to fill the existing walls - next week another 295 names will be added, they are the names of the recent dead.
The numbers are now increasing at faster pace than at any time before.
Twenty years on 9/11 is still killing people.