NEW YORK--Monday marks the fifth anniversary of the Sept. 11 terrorist attacks, an event that left an indelible mark on America's consciousness.

But for many first-responders and volunteers who helped that day at Ground Zero after the attack, the horror is more than just a memory--it is a physical reality they must deal with every day.

About 40,000 rescue and recovery workers were exposed to caustic dust and airborne toxic pollutants following 9/11, according to New York's Mount Sinai Medical Center. And a recent Mount Sinai report found that 70 percent of about 10,000 responders examined had a new or worsened respiratory symptom that developed during or after working at the World Trade Center.

Those numbers correspond with the experiences of companies like Farmingdale, N.Y.-based Homecare Concepts and Lake Forest, Calif.-based Apria Healthcare, two of the many national, regional and local HME providers that leapt into action immediately following the attacks, offering equipment and supplies to hospitals and other organizations.

"There were clinics that were set up in a variety of places, and many patients went in there initially, but what you're seeing now are the long-term problems that have occurred with the exposure to the dust," said Homecare Concepts co-owner Frank Brown, adding that, in particular, the company has seen an increased need for aerosol medications administered through nebulizers.

Lisa Getson, executive vice president of Apria, noted that "our branches in the greater New York City region have seen an increased need in respiratory oxygen products, primarily nebulizers and inhalation therapy, and that's held pretty consistent for the last five years."

After the attacks, Getson continued, "both in New York and Washington D.C., our branches provided as much relief equipment as they could ... but unfortunately, as [we] know, they didn't really need to use much of it."

According to the Mount Sinai report, illnesses have persisted in a high proportion of responders in the years since the attacks. In pulmonary function tests, for example, rescuers show abnormalities twice that of the U.S. population.

Of the responders that Mount Sinai has seen in the past year, 84 percent had upper respiratory illnesses such as sinusitis, laryngitis and vocal cord dysfunction; 47 percent had lower respiratory disorders, such as asthma and "World Trade Center cough;" 37 percent had psychological disorders, such as post-traumatic stress disorder and chronic depression; and 31 percent had musculoskeletal problems, often from injuries that occurred while working at the WTC site.

Volunteers are also having trouble paying for the illnesses they sustained as a result of responding to the tragedy. In one case reported by the New York Daily News, Vito Valenti, a volunteer in his early 40s, has pulmonary fibrosis and needs a double lung transplant. Due to legal restrictions preventing him from filing his case, he is unable to receive the help he needs, so Homecare Concepts is donating his oxygen.

On Thursday, HHS Secretary Mike Leavitt told the Associated Press that by the end of the month the government would fund $75 million for Sept. 11 health programs. If those funds aren't enough, he said, the government would "be part of a coordinated effort to solve whatever the balance of the problem is."

Some experts estimate that $75 million will only last for about a year, while many responders will probably need treatment for life.

Now, five years after the tragedy, Homecare Concepts still waits as its delivery trucks to Manhattan are delayed while officers with the National Guard open them up, checking oxygen tanks and the tubings of canes and other ADLs.

"The veil of 9/11 has never gone away," said Brown.