WHAT HAPPENED to Mark DeBlase -- the sudden emergence of a rapidly fatal lung disease -- is the nightmare that shadows the forgotten victims of 9/11.

Dec. 2, 2005: DeBiase was the picture of health -- but his lungs were rapidly dying.

And the story of how this 41-year-old husband and father of three descended to death in less than four months this year is a case study in why public health authorities must establish comprehensive medical screening and treatment programs for Ground Zero responders, complete with advisories about perils that may be coming.

Too many of the 40,000 people who served after 9/11 are sick now, and too many are at risk of more serious illnesses, and too many face even a chance of death to allow for further inaction. Even basic steps could save lives.

Chief among them: seeing to it that everyone who labored amid the pulverized remains of the Twin Towers has their lungs checked - and finding the money to test people who aren't covered by health insurance.

The procedure is simple - little more than breathing in and out of a hand-held tube - and at $150, relatively inexpensive. It measures how well lungs are functioning and, repeated over time, will signal whether they're deteriorating. (For more information, please see the explanatory graphic on opposite page.)

As Dr. Neil Schluger, chief of the division of pulmonary, allergy and critical care medicine at Columbia Presbyterian Medical Center, put it, "Every person who was down there should have a baseline lung function study, and be followed closely over the coming years for signs of pulmonary symptoms. They should see a doctor and get a lung function test."

DeBiase's death tragically proves the point.

Summoned to duty because he installed and maintained cellular networks for what was then AT&T Wireless, DeBiase worked for 64 hours at Ground Zero and at the Fresh Kills landfill, where the dust of the Trade Center was carted. Like most other recovery workers, he was not equipped with respiratory protection.

March 14, 2006: DeBiase shares 14th wedding anniversary with his wife, Jeanmarie, 26 days before his death.

According to his medical records, DeBiase spent 16 hours at The Pile on Sept. 12, when the air was thick with atomized concrete, glass fibers and particles of lead, chlorine, antimony, aluminum, titanium, magnesium, iron, zinc and calcium, among other toxins. In the ensuing days, he was stationed for 48 hours at the landfill as an endless convoy of trucks began arriving with the same materials.

Then he resumed life as a husband and father in Jackson, N.J., and more than four years passed without any sign that helping to establish emergency communications was taking a toll. DeBiase was active in Little League and the Knights of Columbus, and as late as last December he and his wife, Jeanmarie, enjoyed ballroom dancing lessons. By all outward appearances, he was robust and fit, as evidenced in the photograph to the right.

Actually, DeBiase was on the verge of death. Inch by inch, his lungs were turning into scar tissue, slowly losing the ability to infuse his blood with oxygen and to cleanse it of carbon dioxide.

As 2005 turned to 2006, he began to experience shortness of breath. He went to the doctor Jan. 10 for what became the start of a losing 89-day battle for air. He died April 9 while hoping for a lung transplant.

The cause of death was interstitial lung disease, or ILD, an insidious condition that typically shows up in workers who are exposed to concentrations of inhaled substances - coal miners, for example.

"It is my opinion to a reasonable degree of medical certainty that exposure to dust from the World Trade Center disaster site was the cause of Mr. DeBiase's respiratory disease, which was the cause of his death," wrote Dr. James Strauchen, a professor of pathology at the Mount Sinai School of Medicine who was retained by DeBiase's family to review why he had died such a sudden, suffocating death.

DeBiase's family declined an autopsy, the results of which could have pushed Strauchen's finding beyond a "medical certainty" into conclusive fact.

That DeBiase's death in the University of Pennsylvania Medical Center went unnoticed until now testifies to how poorly the public health system has tracked the aftereffects of 9/11. It comes to light only because his father contacted the Daily News after reading this series of editorials.

"I believe the same thing could happen to many others and they don't know it, just like my son had no reason to think anything was wrong," said Angelo DeBiase, a retired truck driver from Staten Island.

In fact, the same thing has happened to others: DeBiase is now the fourth World Trade Center responder known to have died of interstitial lung disease. Firefighter Stephen Johnson, Police Officer James Godbee and Detective James Zadroga all preceded him to the grave.

In fact, the same tragedy may well occur again: Numerous medical experts have predicted that interstitial lung disease will afflict an increasing number of World Trade Center recovery workers in the five to 20 years after they were exposed to the cloud at Ground Zero. The disease is rare enough that no one expects a vast outbreak, but, when the condition does show up - perhaps in just a relative handful of people - the consequences could be fatal.

To quell unwarranted fears, some distinctions are in order. More than 12,000 WTC responders are already sick, but not with ILD. The vast majority damaged their air passages by inhaling toxins, leaving them with inflamed sinuses, bronchitis and reactive airways dysfunction syndrome, or RADS, an irritant-induced asthma. These conditions do not transform into interstitial lung disease.

ILD, which has a variety of forms, attacks not the airways but the very tissues of the lungs. Typically, the body senses the presence of foreign particles and tries to combat them as it would fight a germ. The immune system surrounds the particles with cells that build up into nodule-like bodies known as granulomas. Granulomas lead to fibrosis, an irreversible scarring that prevents the lungs from extracting oxygen from the air. Some ILDs are very treatable. Others are uniformly fatal.

The need for a public health campaign is obvious. So, too, the need for someone to take charge. We have urged Mayor Bloomberg to be that person. Citing his long commitment to public health, his command of vast government resources and his ability to prod other levels of government into action, we have called on the mayor "to tackle the World Trade Center health crisis on all fronts - medical, legal, social, political and more."

Establishing full-scale health monitoring and treatment programs must be a priority, starting with a drive to have all 40,000 responders undergo lung function tests and building toward a sophisticated system for tracking the progress of the epidemic. For it is only by taking the measure of the epidemic that authorities can both tailor treatment strategies and provide reliable information to responders and physicians - perhaps saving the life of the next Mark DeBiase.

There's much work to be done. No one maintained a master list of the Ground Zero workers, making it impossible now to inventory their conditions. The U.S. Department of Health and Human Services began and disbanded a surveillance program for 10,000 federal workers. The state Health Department dropped a similar effort covering 9,800 state and National Guard personnel.

And despite a long battle by Sen. Hillary Clinton and Reps. Carolyn Maloney and Vito Fossella, the Bush administration and Congress have balked at providing the primary health resource for cops, construction workers and others - the World Trade Center Medical Monitoring Program at Mount Sinai Medical Center - with remotely sufficient funding.

Since 2001, it has had to beg for every dollar. And the federal government's latest promised funding will allow doctors to monitor and care for patients for only a year.

The program has affiliated doctors at medical centers around the metropolitan area and across the country. It is open to all responders except firefighters, who are covered by the FDNY, but it would quickly run out of money if large numbers began enrolling for yearly medical screening and treatment referrals. Even so, large numbers should consider taking advantage of the services. For information, call (212) 241-3355.

DeBiase's father speaks with bitterness about the fact that then-Environmental Protection Administrator Christie Whitman and Mayor Rudy Giuliani falsely assured the Ground Zero workers that the air was safe to breathe. And the family has consulted attorney Joseph Belluck about a possible suit.

Jeanmarie DeBiase said she and her husband had no sense he was in danger, or that services were available at Mount Sinai - until it was too late.

She said her three sons, Nicholas, 12, Christopher, 9, and Michael, 7, were, of course, hit hard by the death of a father to whom "everything was about the boys." And she described his decline as a bewildering, ever more painful downhill rush. First a worry about shortness of breath, then visits to doctors, then an attempt to keep working with an oxygen tank, then admission to the Deborah Heart and Lung Center in N.J., then a biopsy and a collapsed lung, then consultations with a doctor at the Mayo Clinic, then prayers for a lung transplant at the University of Pennsylvania Medical Center, then gasping for air, then organ failures as her husband's body was starved for oxygen, and then, finally, a decision to let go.

"I sometimes think it is a dream," said Jeanmarie DeBiase. "The only thing that gets us through is that it came from 9/11, and we had him five more years than the people who died that day."

Her son Christopher shares a similar gracious philosophy.

"Christopher's fear is that there are going to be a lot of other children who will lose a parent," she said. "He just feels that maybe this can help somebody."

It must.

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TELL US YOUR STORY Were you one of the brave men and women who became ill after answering the call to help your country at Ground Zero? Will you share your story? E-mail the Daily News at wtcvictims@nydailynews.com, or call us at (212) 210-1515

THE TEST THAT SAVES LIVES
A lung function test measures how well your lungs move air in and out. You inhale and exhale through a tube that gauges the speed and volume of your airflow. If you score below normal, doctors may order further tests, such as a chest X-ray or CT scan, that can diagnose interstitial lung disease, asthma and other respiratory illnesses. If your score is normal, you still would be retested periodically to check for declining lung function.

WHAT THE EXAM LOOKS FOR
Most of the 12,000 sick WTC responders suffered damage to their airways from inhaling toxic dust. In the upper airways, dust causes sinusitis and laryngitis. In the lower airways, it produces bronchitis and asthma. Interstitial lung disease attacks lung tissues. Irritating foreign particles cause the tissue to form nodules called granulomas that leads to scarring, called fibrosis. The scar tissue stops the lungs from putting oxygen into the bloodstream, leading, in the worst cases, to suffocation.

WHERE TO GET HELP Contact the Mount Sinai World Trade Center Medical Monitoring Program at (212) 241-3355.