The dust and debris that billowed into the air when the World Trade Center towers collapsed after the 9/11 terror attacks has had long-reaching detrimental health effects, most notably on firefighters, experts said.

At a conference Thursday at Montclair State University, health experts discussed the effects of air quality after 9/11 (search), specifically on firefighters working in the area and children born to pregnant women living nearby.

Firefighters have had serious, long-term respiratory problems from the particles of pulverized concrete or glass they inhaled, according to Dr. David Prezant, who has been leading a program to study the health effects of 9/11 on New York City firefighters.

"This isn't just 'Oh, I have a cough,'" said Prezant. Prezant said the study of approximately 14,000 firefighters and emergency medical personnel is looking at "who was ill and who continues to be ill."

Prezant's work and the other studies discussed — most of which have already been published — focused on the immediate days and weeks after the buildings' collapse when fine particles of dust and debris were thick in the air.

The researchers said the biggest area of concern was the effects of inhaling or ingesting the particulate matter (search) as opposed to having it touch the skin.

According to Prezant, the firefighters are a good group to study because so many were affected and because they had pre-9/11 health data with which to compare.

According to the researchers, the rescuers often only had basic face masks, which didn't keep out most of the dust particles. This was partly because the firefighters quickly went through the air in their breathing tanks, designed for short trips into burning buildings. The rescuers also needed to be able to communicate in the dangerous situation, often impossible while wearing a bigger mask.

Prezant said the result has been a dramatic increase in the number of firefighters receiving respiratory disability after 9/11, a classification he said is extremely difficult to get.

According to Prezant, the department would average less than 30 people per year out on respiratory disability before 9/11. After Sept. 11, at least 450 people have met the classification.

Prezant said it's too early to tell whether the bad air quality and respiratory problems might lead to increased instances of malignancies or growths.

Another researcher, Dr. Sally Ann Lederman from Columbia University, studied pregnant women living within two miles of the World Trade Center in the four weeks immediately following the 9/11 attacks.

There were about 300 women in the group, many in their first or second trimester. Lederman found that the babies tended to be lighter and shorter than other babies.

While Lederman said lower birth weight can sometimes translate into health problems, it's impossible to know whether those post-9/11 children would be more likely to have lower IQ's or development problems — questions she often receives from mothers who gave birth after the terrorist attacks.

"They look like perfectly normal children," said Lederman about the babies in the study.

According to the experts, people in New Jersey would not necessarily be affected by the air quality following 9/11 unless they were rescue workers on or near the "pile," as the remains of the World Trade Center are often called.

The experts said one of the problems with measuring the air quality effects after 9/11 is that most of the testing mechanisms are designed to test air quality over a long period of time and not from a catastrophic event like the towers' collapse.

The experts also said while gases like fumes from the burning jet fuel may have affected health, there was no way to measure it.

"No matter how much we know there are always going to be uncertainties," said Dr. Paul J. Lioy, from the University of Medicine and Dentistry of New Jersey.