As the United States pauses to commemorate the 10th anniversary of the 9-11 terror attacks, thousands of first responders are struggling to cope with debilitating illnesses they developed in the wake of their work at Ground Zero, and are still fighting to cover the costs of treatment.

While many have been hailed as heroes, the physical and mental health problems suffered by thousands of police, fire and other emergency services personnel who rushed to the site have been well documented.

Dr. Michael Crane, medical director of the World Trade Center Monitoring and Treatment Program at New York's Mount Sinai Hospital, says the most common health problems include upper and lower respiratory ailments, including rhinitis and asthma, as well as depression, post-traumatic stress disorder and anxiety disorders.

The program has evaluated more than 20,000 first responders, and every month sees between 50 and 100 Sept. 11 rescue workers for the first time.

According to Crane, many of the physical ailments can be blamed on the fine white dust breathed in by first responders and residents who lived near the World Trade Center in the days, weeks and months after the attack.

That dust was a mix of fibres, metals, concrete, noxious chemicals and gases, many of which are known carcinogens, or cancer-causing agents, he said.

The pH balance of that dust was also very alkaline, Crane told CTV News Channel, which made it especially irritating to mucus membranes.

Despite the catalogue of health problems, first responders say they have received little help from the U.S. government to cope with side effects of their ailments, as well as with the costs of treatment.

First responder John Devlin, who has stage 4 throat cancer, said he takes offense at the government's position on patients like him.

"There's too many responders like me that went down there for the love of our country that are dying right now, and our own country is turning their backs on us," he told CTV.

John Feal, founder of the Fealgood Foundation, which advocates for 9-11 first responders and raises funds to help with their medical bills, told CTV News that he still receives calls for help from emergency services personnel who worked at the site.

"I can't afford my medication, I can't afford gas to put in the car so I can get to my chemotherapy appointment, I'm losing my house," are just some of the concerns Feal hears.

After 10 years, the U.S. government announced earlier this year that it will offer $4 billion to cover medical costs and lost income among first responders. However, cancer patients are left out of the deal because officials argue that current research has not confirmed a link between work at Ground Zero and the risk of developing the disease.

The evidence suggests otherwise.

Firefighter John McNamara died at age 44 after developing aggressive cancers following his work at Ground Zero. McNamara spent two-and-a-half months on clean-up duty at the site.

His widow, Jenn McNamara, said her husband did not have a genetic predisposition to cancer and did not have any other risk factor for the disease.

"It's environmental, so what's the environmental factor?" she wondered to CTV News. "Clearly it was 9-11."

A new report from the New York fire department's chief medical officer backs up McNamara's belief. It found a connection between the dust at Ground Zero and the risk of developing cancer.

Dr. David Prezant and his colleagues found that firefighters who responded to the terror attacks were 19 per cent more likely to develop cancer compared to their colleagues who were not exposed to the dust.

That statistic, Prezant told CTV News Channel, will be backed up by further research.

"They made a commitment to us when they ran into those buildings. We've made a commitment to them. We're going to continue to collect and study these cancers," Prezant said.

"We can never take 9-11 away, but we can start and continue an aggressive cancer-prevention and cancer screening program."

Two more studies are due in the coming months that advocates hope will change the government's tune.

In the meantime, first responders like Kenneth George, who spent six months on search-and-rescue duty, fear for their health, and their future.

"The next thing I'm waiting for is just to die because when you've got lung disease and heart disease, those are the two biggest killers, there, and cancer," he said.

"I'm scared, wondering if I'm going to wind up with cancer now."

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip