Two days after arriving at ground zero to clear debris from the smoking ruins of the World Trade Center, David Miller could feel the physical effects.

"I was practically blind, I was coughing, I had blisters all up and down my arms," the National Guardsman said Sunday at a discussion about lingering health problems among first responders. "If I'd been smart, I wouldn't have gone back."

Nearly five years later, the 39-year-old suffers from hacking, bloody coughs, chronic lung infections, skin rashes and a 60 percent loss of lung capacity, he said.

Miller was among several first responders to speak Sunday at the event organized by the nonprofit group New York 9/11 Truth, which claims that the government covered up intelligence failures leading to the attacks and accuses officials of exposing rescue workers to toxic conditions at ground zero.

Kevin McPadden, a former Air Force medic, said his rescue and recovery work in the days after the Sept. 11, 2001, left him struggling with depression and anger.

"Every day is a challenge," he said. "I really don't feel alive. I'm a very bitter man."

Last week, a U.S. federal court judge heard arguments over whether the city and its contractors should be granted immunity against lawsuits filed on behalf of thousands of emergency workers who got sick after working in the dust of the World Trade Center. The city has argued it has legal immunity against the claims.

Les Jamieson, who organized Sunday's event at The Community Church of New York in Manhattan, said that, for some who felt they should have been financially compensated, the panel offered an opportunity to speak out.

"We're not just talking about health here," he said. "There are serious financial and psychological issues as well, and a lot of people are being left out in the cold."