(AP) -- Of all the illnesses people fear might be caused by toxic dust from the World Trade Center, nothing scares people like cancer.
Hundreds of people are suing New York City over cancer diagnoses they received after working at ground zero. A judge last week rejected a $575 million legal settlement for thousands of sick 9/11 responders in part because he thought it should contain more money for cancer victims.
Yet, statistics show that cancer rates among those who worked in trade center rubble are in line with rates among the general public.
The three major research efforts tracking the health of ground zero responders have so far failed to turn up evidence linking any type of cancer to the dust.
Many of the cancers now afflicting ground zero workers are common. There are plenty of theories as to how the dust might cause cancer, but little proof. Even the scientists most concerned about a potential tie say the length of time it takes for many cancers to develop means it could be years before cases related to 9/11 begin to emerge.
That lack of evidence has complicated efforts to craft a compensation package for sick workers.
With as many as 10,000 workers claiming illnesses, the lawyers trying to hammer out a settlement and lawmakers working on a 9/11 health bill in Washington have faced a tough question: Do they dedicate the bulk of money to people with ailments where there has been stronger evidence of a tie to ground zero, like asthma and other respiratory diseases? Or, do they set aside more for people with deadly, but common, cancers that may or may not be related to the attacks?
U.S. District Judge Alvin Hellerstein noted the dilemma last week when he shot down a settlement that would have resolved nearly 10,000 lawsuits over post-9/11 illnesses.
"Cancer is a very difficult injury," he said. "Who can really say how a cancer is caused?"
In the end, the judge suggested he was willing to give the benefit of the doubt to the sick.
"The people who went in to 9/11 did not make calculations on cancers and whether they would get or wouldn't get cancer. ... They responded," he said. He said a part of the settlement that capped payments at $100,000 for people who develop the disease in the future was inadequate.
"I think there is more money to pay for the cancers, given all the issues, given all the problems with it," the judge said.
There is no doubt that cancer has claimed the lives of many responders.
New York's state health department, which tracked fatalities for several years among the roughly 40,000 ground zero workers, confirmed at least 250 cancer-related deaths though June 2009. Analysis of other deaths is ongoing.
Many other police, firefighters and construction workers who worked with the dust have fallen ill.
Candiace Baker, a retired New York City police detective, said at a court hearing last week that she was diagnosed with breast cancer after spending many days sifting rubble at a Staten Island landfill. She said she wore a particle-filtering respirator, but is convinced the dust gave her cancer anyway.
"It is not a coincidence," she said.
Doctors note, however, that cancer causes nearly one of every four deaths in the U.S. and is a frequent killer even among people in their 40s and 50s. And a woman's average lifetime risk for breast cancer is one in eight.
"In any population of 40,000 people over an 8 1/2-year span, there is going to be cancer. That is a known fact," said Dr. Philip Landrigan, who oversees the World Trade Center Medical Monitoring and Treatment Program at Mount Sinai Hospital, one of the three major efforts to study the health of the workers.
Mount Sinai has found no notable spike yet in cancers among the 27,000 ground zero workers it has been tracking, Landrigan said.
Top doctors for the Fire Department, who are conducting a second big study involving 15,000 firefighters, have said they also found no clear increase in cancers. The third and biggest effort, being conducted by the city's health department also hasn't found elevated cancer rates among 71,000 Lower Manhattan residents.
That doesn't mean there is no danger, Landrigan said.
"We know full well that there were carcinogens at ground zero. There was asbestos. There was benzene. There were other things," Landrigan said.
He said he and other researchers had "big concerns" that cancer clusters will emerge as the years go by.
Scientists think environmental toxins cause cancer by damaging cells, which then go through a series of mutations before becoming malignant. That mutation process usually takes place very slowly.
Malignant mesothelioma caused by exposure to asbestos, for example, can take 30 years to manifest, which means that if trade center dust does indeed cause cancer, it would likely not start appearing until after the present court cases are resolved.
All of those uncertainties had been reflected in the court fight.
An analysis performed by two court-appointed officials in September said that of the 802 plaintiffs then involved in the case who claimed to have cancer, 188 said they had skin cancer, 107 said they had lung cancer, 95 said they had lymphoma, 68 had prostate cancer and 66 had liver cancer. Those five types of cancer are all common.
One defendant in the case, the Port Authority of New York and New Jersey, had asked the judge to order the plaintiffs to provide more proof of a link between cancer and the trade center dust.
"Even if WTC debris were potentially carcinogenic, it is unlikely - indeed, without compelling evidence, scientifically impossible - that numerous cancers would have already arisen from the plaintiffs' relatively recent and short-term exposures to WTC debris," lawyers for the agency wrote.
Before the settlement was announced, a dozen cases were set to go to trial, starting in May.
One involved a firefighter who died of esophageal cancer in 2007 at age 47. His lawyers were prepared to argue that ingested dust from the trade center gave him acid reflux, which in turn damaged the cells in his throat, which then caused his cancer.
A number of studies have documented high rates of acid reflux disease among ground zero responders.
Those trials are now on hold, as is the settlement, while the lawyers on each side decide what to do next.