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9/11 dust still being studied

How dangerous was the dust released by the World Trade Center collapse?

BY TRAVIS DUNN | NEW YORK CITY | January 3, 2003


"In the early part of the event, people were exposed to a very complex mixture of dust and smoke."

—Dr. Paul Lioy


How dangerous was the dust released by the World Trade Center collapse? So far scientists disagree, and more research on the health effects is planned.

A study to be published in the February edition of Environmental Science and Technology shows the dust released by the collapse of the World Trade Center may not prove as dangerous as previously thought.

The study, funded by the American Chemical Society, found that 99 percent of the dust particles in the cloud were greater than 10 microns in width – large enough to get stuck in the upper respiratory tract and thus be quickly expelled.

"In the early part of the event, people were exposed to a very complex mixture of dust and smoke," said Dr. Paul Lioy, associate director of the Environmental and Occupational Health Sciences Institute, run by Rutgers University and the University of Medicine and Dentistry of New Jersey. Lioy is one of the principal authors of the study.

The most dangerous of these chemicals are known as polycyclic aromatic hydrocarbons, or PAHs, which the U.S. Environmental Protection Agency regards as potential carcinogens. While the study found a high level of PAHs, Lioy said these chemicals would not pose much of a health risk, since they were likely coughed out soon after inhalation.

Lioy and his colleagues also found that there wasn't much asbestos in the dust – a possibility about which many people were concerned.

But other studies, which focus on different aspects of the dust cloud, have arrived at less optimistic conclusions.

Scientists estimate that millions of tons of dust were generated by the collapse of the World Trade Center. If, according to the work of Lioy and his colleagues, 99 percent of the particles were larger than 10 microns, that means that one percent – or more than 10,000 tons – was composed of extremely tiny and easily respirable particles.

Dr. Thomas Cahill, professor emeritus of physics and atmospheric sciences at the University of California-Davis, is conducting a study of these extremely small particles.

Cahill is working with a groups of researchers known as the DELTA group (Detection and Evaluation of Long-range Transport of Aerosols), a scientific organization he founded in 1977.

On Feb. 23, 2002, at an Investigative Hearing of the National Ombudsman for the EPA in New York, Cahill testified that his measurements "indicated that the size of particles appearing at our site were both in high concentration and very fine, unlike any we had ever sampled before."

In an interview Jan. 2, Cahill said he can't say for sure what the possible health effects will be, but he can point out areas of definite concern.

Cahill's main worry is "ultra fine silica" – or vaporized glass and dirt – which the DELTA group found in high concentrations. Unfortunately, he said, the heatlh effects of aerosolized silica have received little study.

The health effects of inhaled vanadium have also received little scrutiny – and the DELTA group also found a lot of that, more than has ever before been recorded, Cahill said.

"That bothered me a lot," he said.

But Cahill said he is not particularly worried for the average New Yorker, because he thinks that the same process which generated the vaporized silica and vanadium – the slow, intense smoldering of World Trade Center rubble – also caused the resulting gas cloud to drift up and over the city.

The people who worked on "The Pile," are the ones who really need to worry, he said, since most of them worked with no breathing equipment, or with just dust masks, which were essentially useless.

“The very high temperatures that caused the strange chemical reactions also protected the people of New York, but unfortunately the same cannot be said for the people working on 'The Pile,'" he said. "A lot of people had their lungs really fried. That's a fact."

Dr. David Prezant of the New York City Fire Department is also particular concerned about the emergency workers, and he thinks they are likely to come down with serious long-term health problems.

"Even if that respirable airborne particulate matter does not include a single chemical, it is incredibly toxic at that level of exposure," said Prezant, during a telebriefing on Sept. 9, 2002, sponsored by the Centers for Disease Control. "There are voluminous data in the literature saying that exposure to airborne particulates may induce increasing rates of chronic obstructive pulmonary disease, asthma, emphysema, and heart disease."

Joann Hale, a disaster response and recovery liaison for Church World Service, more attention needs to be paid to the actual measurable health effect on people who have sought medical treatment.

That type of study is likely to get a major boost in the near future.

The New York City Department of Heath and Mental Hygiene recently announced that it would pour $20 million into a study of the health effects of the World Trade Center dust.

This new study is expected to survey as many as 200,000 New Yorkers.


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More links on September 11 2001

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