"Never forget!" was the motto of the first responders who rushed to the burning World Trade Center on 9/11, but 10 years on some say they have been abandoned by their country to fight cancer and mounting medical bills.

Once hailed as heroes, thousands now say they have fallen victim to a host of ailments -- from asthma to cancer -- due to their exposure to the toxic debris pile left by the Twin Towers' collapse on September 11, 2001.

Compensation funds set up by the US government do not recognize cancer as a condition caused by exposure to the World Trade Center clean-up operation, and a political battle is brewing.

"This is almost 10 years later. I mean, how do you praise guys after 9/11 and then just turn your back?" asked Jeff Stroehlein, 47, a retired New York City firefighter who is battling brain cancer after working at Ground Zero.

Stroehlein and others with cancer have no doubt that their illnesses took root a decade ago as they scoured the debris for human remains and helped clean up the mess for time spans ranging from weeks to nearly a full year.

But until last week -- when a study in the Lancet showed that New York City firefighters who rushed to the doomed twin towers were 19 percent more likely to have cancer than their non-exposed colleagues -- there was scant scientific data to back up their claims.

In July, the government's first periodic review of cancer as part of the World Trade Center Health program found that there was "insufficient evidence" to add cancer to the list of WTC-related health conditions.

"Very little has been published addressing the association of exposures arising from the September 11, 2001, terrorist attacks and cancer in responders and survivors," said the WTC Health Program report.

According to the Fealgood Foundation, an advocacy group for first responders run by John Feal, a construction worker who was injured at the site, 1,020 of the estimated 40,000 WTC workers and volunteers have died from health complications.

A total of 345 members of the fire department and 45 police officers have since died from cancer, surpassing the death toll on the day itself when 343 firefighters and 23 police lost their lives, Feal said.

First responders now have revived hope for a reversal in the US government's decision that cancer would not be included in a list of health problems paid for by the US government in recognition of their service.

"The importance of its findings cannot be understated," said Feal, referring to the Lancet study led by David Prezant, chief medical officer of the Fire Department of the City of New York.

"This study now allows all 9/11 First Responder advocates to argue that these various forms of cancer should be monitored and treated in accordance with the James Zadroga Health & Compensation Act," he said of the legislation named for a fallen New York City police officer who died at age 34 of cancer.

Under the Zadroga Act, more than $4 billion has been allocated to pay for medical treatments and doctors' visits for asthma, post-traumatic stress, anxiety, back pain and carpal tunnel syndrome.

One major study of nearly 10,000 Ground Zero workers and residents released about five years after the attacks found that 70 percent of them faced new or worsening lung problems after 9/11.

In New York, about 5,000 responders regularly see doctors at the World Trade Center Medical Monitoring and Treatment Center on Long Island as part of an effort to track their health over time.

"Most often what we see are the breathing problems -- the sinus issues, the heart burn issues and mental health issues, those are quite common," said one of the doctors, Vrajesh Patel.

Some of the patients have medical insurance, others do not. Some who have fallen sick and lost their jobs face doctors' bills in the tens of thousands of dollars, said Feal.

In Stroehlein's case, he has insurance coverage but it does not include all his medication, so his prescriptions can cost hundreds of dollars each month.

For heavy equipment operator John Devlin, 50, who worked at the pile for almost 10 months, the problems began a few weeks after the attacks with the hacking that many workers experienced, coined "World Trade Center cough."

In 2009, he was diagnosed with stage four throat cancer. Haggling with insurance carriers, hospital billing departments, and state officials in charge of worker's compensation has become a regular part of his struggle to survive.

"I promised God, when I was dying in the hospital and I was in the cancer ward for two and a half months, that if I ever got out and had the ability to speak that I would stand up for my brothers and sisters who were down there," he told AFP.

"The government said that the air was clean. They lied to us."