In the nine years since 9/11, more than 238 scientific studies and medical reports in peer review journals have tried to measure the impact of the dust, smoke and ash of the collapsed twin towers on the health of the thousands who were exposed to the contaminated clouds. Cumulatively, hundreds of millions of dollars have already been spent screening and treating tens of thousands of responders, volunteers, residents and downtown workers who breathed in the pulverized building materials and hazardous compounds released by the disaster.
Despite all that, what is known with absolute certainty about the dust and its impact is limited, especially when it comes to the questions that most concern everyone who breathed in the dust: will it cause cancer and lead to deaths? Medical investigators readily admit that for many reasons they don't know the answers, and won't know with certainty for years, if ever.
But the more that scientists hedge their bets by saying they don't know, the less that elected officials seem able to say the same. In the face of uncertainty, they increasingly offer conclusions about complex medical mysteries, their false certitude keeping truth at a distance.
At a rally in Lower Manhattan earlier this month, Congressman Anthony Weiner urged passed of the James Zadroga bill (H.R. 847) to reopen the Sept. 11 Victim Compensation Fund and formally authorize long-term screening, monitoring and treatment programs for thousands of people exposed to 9/11 dust. "At least 900 people have died since September 11th, at least, from 9/11-related diseases," Mr. Weiner stated. In so doing, he repeated the chilling 900-plus figure that Senator Kirsten Gillibrand included in a letter urging Senate Majority Leader Harry Reid to bring the Zadroga bill up for a vote.
The problem is that no one -- not the officials, or the advocates of the bill, or the medical investigators -- yet knows how many people have died because they breathed in the dust. The senator got the statistic about ground zero deaths from advocates of the bill, who acknowledge that they extracted it from an ongoing study of deaths by the New York State Department of Health.
But the department has made no such conclusions. State health officials say they know that at least 836 people who worked a day or more at ground zero during the cleanup have died, but the causes listed on their death certificates include traffic accidents, fires, military action (in Iraq and Afghanistan) and suicide, along with cancers and other diseases that may or may not be related to exposure. The overall number of people who toiled at the site could exceed 90,000, and without further information, the 836 deaths over nearly a decade, in itself, tells us little about what happened at ground zero.
"We recognize that people want answers," said Kitty Gelberg, who heads the state's mortality study, "but the data just isn't there yet to provide answers that will satisfy them."
Ms. Gelberg concedes that that's not an easy message for people to accept, and that many have come to expect absolute certainty from science that science often simply cannot deliver.
Thanks to the work of Dr. Paul Lioy of the Environmental and Occupational Health Sciences Institute and others, we now know much more about the very fine particles in the dust. Asbestos, benzene and other known carcinogens were ground up in the complex mixture, but most of the dust was silica material from the pulverized concrete of the towers. Dr. Philip Landrigan of the Mount Sinai School of Medicine, which has screened and treated more responders than any other institution, said the dust penetrated deep into airways, scarring delicate lung tissue, stiffening air passages and decreasing the breathing capacity of thousands of people We know that the concentration of dust in the air on 9/11 and for days afterwards was so thick that the highly alkaline material -- as corrosive as strong lye -- burned throats and seared stomachs leading to severe acid reflux and recurring gastrointestinal disease. We know that many who witnessed the horrendous events of that day suffered post traumatic stress, which can have its own multiplying effect on a range of physical ailments.
But there is much more that we don't yet know, which is small consolation for those who are sick. That uncertainty also is complicating the passage of the Zadroga bill as well as clouding the outcome of historic litigation by thousands of responders who are suing the city of New York in federal court.
None of the peer-review studies has yet made a case that cancers have increased. In fact, all three major study groups -- the New York City Fire Department, the Mount Sinai Medical Center and the World Trade Center Health Registry -- the largest effort in U.S. history to track the health effects of a single event -- have not yet come to any conclusions about cancer.
Nor has any study found that responders are dying at rates that would call attention to a particular illness or ailment.
That's not to say that no one's died from the dust. Although New York City's Office of the Chief Medical Examiner has officially attributed just two deaths to the dust, the Police and Fire Department Pension Boards have authorized line of duty death benefits for scores who toiled at ground zero in 2001 and 2002. As standards of proof differ, so too do the results.
The studies continue. A recent one in the New England Journal of Medicine revealed while the overall number of respiratory cases among New York City firefighters has leveled off, and not many new cases are being added, the serious symptoms in certain groups of firefighters, have persisted since 9/11 and have not gotten better, suggesting that the conditions for some may be chronic.
"Recovery, if it's going to happen, is going to happen early on," said Dr. David Prezant, chief medical officer of the city's fire department. "The key thing was to document that it was pleateauing. That was unknown until a year ago."
As the number of respiratory ailments has leveled off, medical investigators now hope to focus on those responders who have not improved and ask why? Is it because they were on the scene in the first hours and days after the towers collapsed, when the dust cloud was thickest and the hazards greatest? Or is it because they put in more hours working on the debris pile than others? Or were they simply more genetically predisposed, and exposure to the dust was more likely to make them sick?
Finding the answers to this kind of questions will take more years of additional study. And for cancers, always the biggest worry among responders, conclusive answers may not come for 30 years because the latency period for cancers such as mesothelioma can last decades. Even then, the work will proceed slowly in large measure because it has become so difficult to know how to measure risk. Ground zero responders included firefighters, police officers and other professionals who tend to be more fit than the general population; construction workers, whose health varied widely; and volunteers, many of them retirees. Experts have advised the ground zero investigators to limit comparisons to within the group of responders rather than to the general population, weighing such factors time of arrival at the scene and duration of exposure along with such traditional factors as gender and age.
The elusive quest for certainty long predates ground zero. Vietnam veterans exposed to Agent Orange claimed a broad range of illnesses, and when they brought their class action case to federal court, the case was settled before anything could be proved. That provided some degree of compensation for those who became ill, but it left unanswered questions about causation and linkage. Eventually, presumption took the place of proof, and the list of illnesses presumed to be connected to Agent Orange -- though not proven -- has grown continuously over the last 40 years, with several additional diseases added within the past year.
The Zadroga bill is another response to the need for compassion to take the place of certainty. And it would also provide long-term funding for collecting data that can insure that we someday do have clear and conclusive answers. It is now expected to come up for a vote in the House on September 29. The Senate will have to wait until the lame-duck session after the Nov. 2 mid-term election to consider the bill.
In another search for the truth about the dust, seven years have passed since responders first sued New York City for not adequately protecting them from the dust during the recovery operation at ground zero, but the linkage between the dust and disease has never been proved in court.
The federal judge overseeing the litigation, Alvin K. Hellerstein, has acknowledged how difficult it would be to prove the dust's toxic legacy and has pushed both sides to agree to a settlement that could provide more than $700 million in compensation based on the severity of the injury and the likelihood that it is plausibly connected to 9/11. The responders have until Nov. 8 to decide whether to accept the settlement, and many have said they want to know the fate of the Zadroga bill before they decide whether to participate in the court-approved settlement.
In all this, some lessons about handling the aftermath of disasters have been learned. No list of workers was ever compiled for ground zero and that has limited greatly the kind of studies that could be done. In the recent BP oil spill in the Gulf of Mexico, Dr. John Howard, National 9/11 Health Coordinator and head of the National Institute for Occupational Safety and Health, has assembled a roster of workers involved in the months long cleanup. It seems like a simple step compared to complicated epidemiological studies that can last a generation, but Dr. Howard said such a list is critically important to tracking down disease.
Over 50,000 people have already registered in the Gulf. This will give federal scientists a chance that ground zero investigators never had to assess the universe of exposed people with accuracy. In turn, this detailed set of data could help tamp down expectations and heighten the ability of science to deliver conclusive and believable answers.
Still, in most cases science cannot provide the answers that people want when they want them. That limitation makes any answer initially seem more satisfying than none at all. But half truths and inconclusive proofs can unnecessarily frighten or give more hope than is warranted. Settling somewhere between the two extremes may be the only fair option, even if doing so almost always prolongs the anxiety of the victims and compounds the angst of the investigators.
Every time there's a mention in the news about deaths or cancers among ground zero workers, Dr. Prezant is flooded with calls from firefighters asking if the same thing is going to happen to them. He said that as a physician and a human being, (one who was himself buried by trade center debris on 9/11) his heart goes out to those who are sick and worried about their futures, and he'd much prefer to be able to give them definitive answers. But the proof is not there yet.
"As head of the department's health program," he said, "I need to make certain that I'm doing my best to collect all the numbers and analyze them properly." And by so doing, he said, science and truth will show the way.