In a series of court filings late Tuesday, the city's legal team detailed several instances in which it said people who claimed to have been sickened by World Trade Center ash were already ill before the attacks.
One former Fire Department battalion chief who attributed respiratory problems to the dust had been granted a disability pension for the same type of breathing ailments in 1999, the city said.
A 400-pound utility worker who said he developed shortness of breath and other health problems after being deployed to ground zero had breathing problems diagnosed before 2001, the city said.
City lawyers also cited the case of a Staten Island construction worker who blamed a litany of health ailments on exposure to ground zero dust, even though he had previously filed a medical malpractice case blaming some of the same problems on a chronic gastrointestinal disease he'd had since the 1990s.
The city asked the judge presiding over the case to dismiss 17 suits on a variety of grounds.
Paul Napoli, the lead lawyer for more than 9,000 police officers, firefighters, construction laborers and other ground zero workers, dismissed the city's motions as posturing.
"He thinks these guys should go home and get no money," Napoli said of James Tyrrell, lead attorney for the city. "He does not think much of police officers or firefighters."
He predicted that some of the same cases criticized by the city as "baseless" would be embraced by jurors as compelling.
Tyrrell accused Napoli of repeatedly making "slipshod" filings that misstated how much time workers spent at ground zero or the severity of their illnesses, with few specifics on how the city was to blame.
"On the eve of trial, the time for boilerplate allegations and for more excuses has run out," Tyrrell wrote.
The Associated Press conducted its own review of some of the first cases headed toward trial in the legal battle and reported Feb. 7 that some contained inconsistent information about worker health problems or the time they spent at ground zero. Napoli called that investigation "misinformed."
Napoli's firm has been locked in a lengthy legal battle with the city and ground zero construction contractors over the health of workers who spent time at the trade center site.
They are arguing that thousands of workers were sent into toxic conditions without proper gear and are now sick with a variety of cancers and respiratory problems.
U.S. District Judge Alvin Hellerstein has adopted a strategy of selecting just a small number of cases for trials, with the intention of using those initial court battles to craft a settlement for the rest.
The initially picked 30 cases for trial, but that number is now being whittled to 12.
The city's filings Tuesday illustrate how difficult it might be for some of the plaintiffs to link their illnesses to service at ground zero.
Several of the cases involved people with limited exposure to trade center dust, including Consolidated Edison workers like Robert Galvani.
Galvani's lawyers had initially claimed that he was "never provided a respirator of any kind" when he was deployed to help repair the electrical grid in lower Manhattan after the attacks.
But in a deposition, Galvani said that was false. Every Con Ed worker, he said, was fitted with a full-face respirator with filters, cleaning pads, booties and gloves before they were allowed anywhere near the trade center site. He said he wore his respirator religiously.
The city also said Galvani weighed "between 400 and 450 pounds" at the time of the attacks, and had sleep apnea, hypertension, respiratory problems and diabetes diagnosed prior to 2001.
City lawyers also questioned the health claims of a former Fire Department battalion chief, Richard Ardisson.
In his suit filed in 2005, Ardisson blamed trade center dust for ailments including asthma, bronchitis, and other respiratory problems.
But the city said those conditions predated 9/11.
In fact, Ardisson retired from the Fire Department on a $110,000-per-year disability pension in 1999 after he performed poorly on a lung function test and was found to have severe bronchial asthma and obstructive airway disease.
Napoli and other lawyers working for the plaintiffs said they didn't have the details of Tuesday's individual cases at their fingertips, but said research has shown that some 9/11 responders with pre-existing asthma and other health problems saw their conditions worsen substantially as a result of exposure to trade center dust.
He said it should be left for a jury to decide the facts of each case.