For the firefighters and police officers who ran toward the fiery World Trade Center towers and breathed in the air on Sept. 11, the attacks are not just in their hearts or minds.
For them, 9/11 is in their lungs, their blood.
"It was like a black cloud over that whole area, and you couldn't see 10 feet in front of you," said John Walcott, a detective with the New York City Police Department.
"Basically I had no idea what -- how bad it was really gonna be until I got there," said Richard Volpe, another NYPD detective and Walcott's partner.
Toxic dust in the air around New York City's ground zero has made many first responders gravely ill.
Earlier this year, retired New York City firefighter Robert Ryan, who ran triathlons before Sept. 11, was forced to retire.
His lungs are so weak, he says, he can barely play catch with his son.
"After about 10 minutes, I always have to stop, catch my breath. And it's at the point now where he knows it, and he'll stop and say, 'Are you OK, Daddy? Do you need to stop?'" Ryan said.
A report released this week was shocking: Nearly 70 percent of 9/11 first responders have debilitating respiratory illnesses.
Many of them have been ill for years and will be for the rest of their lives.
Dr. Robin Herbert, who runs the World Trade Center medical monitoring program, called the report's findings sobering at a news conference earlier this week.
"Somebody has to take responsibility and make sure these folks get the care they need," he said.
In the last few months, state and federal officials have announced that millions of dollars will go to the treatment of first responders.
Many say it's still not enough.
"It's a drop in the bucket, and my worry is that money will be gone in a year, and what happens then," Herbert said.
Victims say they have little reason to trust what is being promised because the government's statements have not matched what the doctors have seen in their patients since the day of the attacks.
On Sept. 28, 2001, 17 days after the attacks, New York City Mayor Rudy Giuliani said, "The air quality is safe and acceptable."
The findings of this week's report paint a strikingly different picture.
"What we saw, in those first two months, was really very startling, and very, very disturbing. You could see that there were these chemical burns," Herbert said.
When asked by ABC News' Chris Cuomo whether he thought the government had reason to believe that the situation was worse than what had been announced publicly by officials, Herbert said, "I do not to this day understand the disconnect. Air that you can see probably isn't good for you."
A city health department memo, written a month after the attacks, shows that officials disagreed about air quality near ground zero.
According to the memo, while the Giuliani administration was "under pressure … from business owners" to reopen areas around the trade center site, officials from the city's Department of Environmental Protection were "'uncomfortable' with opening" certain areas.
The document also complains that the federal Environmental Protection Agency "has been very slow to make data results available and to date has not sufficiently informed … the public of air quality issues arising from this disaster."