Trade Center Debris Pile Was a Chemical Factory, Says New Study

Trade Center Debris Pile Was a Chemical Factory, Says New Study

September 10, 2003

	At Ground Zero in New York City, UC Davis Professor Emeritus Thomas Cahill describes his air-quality findings to reporters on Feb. 23, 2002, just before testifying at an EPA investigative hearing in Manhattan. (Sylvia Wright/UC Davis News Service file photo)

The
fuming World Trade Center debris pile was a chemical factory that
exhaled pollutants in particularly dangerous forms that could penetrate
deep into the lungs of workers at Ground Zero, says a new study by UC
Davis air-quality experts.

The
new work helps explain the very fine particles and extraordinarily high
concentrations found by an earlier UC Davis study, the first to
identify very fine metallic aerosols in unprecedented amounts from
Ground Zero. It will be essential to understanding the growing record
of health problems.

The
conditions would have been "brutal" for people working at Ground Zero
without respirators and slightly less so for those working or living in
immediately adjacent buildings, said the study's lead author, Thomas
Cahill, a UC Davis professor emeritus of physics and atmospheric
science and research professor in engineering.

"Now
that we have a model of how the debris pile worked, it gives us a much
better idea of what the people working on and near the pile were
actually breathing," Cahill said. "Our first report was based on
particles that we collected one mile away. This report gives a
reasonable estimate of what type of pollutants were actually present at
Ground Zero.

"The
debris pile acted like a chemical factory. It cooked together the
components of the buildings and their contents, including enormous
numbers of computers, and gave off gases of toxic metals, acids and
organics for at least six weeks."

Cahill,
an international authority on the constituents and transport of
airborne particles, will summarize the new study today (Sept. 10) at
the national meeting of the American Chemical Society, being held this
year in New York City.

Cahill
heads the UC Davis DELTA Group (for Detection and Evaluation of
Long-range Transport of Aerosols), a collaborative association of
scientists at several universities and national laboratories. The DELTA
Group has made detailed studies of small airborne particles, called
aerosols, from the trade-center collapse, 1991 Gulf War oil fires,
volcanic eruptions and global dust storms, and has most recently
finished a massive 21-site study of Asian aerosols for the National
Science Foundation.

The
new study reinforces and extends conclusions that DELTA Group reached
in February 2002 in what is still the most extensive analysis of the
dust and smoke from the hot collapse piles after the trade center
collapse.

In
the 2002 report, DELTA researchers described their analysis of over
8,000 air samples collected Oct. 2-30, 2001, on a rooftop at 201 Varick
St., one mile north-northeast of the trade center complex.

They
detailed very high levels of very fine airborne particles -- particles
that pre-Sept. 11 EPA summaries had showed could raise a person's risk
of lung damage and heart attacks. That analysis has been accepted for
publication in the peer-reviewed journal Aerosol Science and Technology.

Now
the researchers have added analyses of samples collected through May
2002, and constructed a timeline with physical and chemical
explanations for the results.

The
new study also confirms, Cahill said, that the very fine particles
observed were almost totally from the trade center debris pile and not
from other upwind sources, such as power plants and the diesel trucks
used to haul away the debris.

When
the trade center towers burned and collapsed, tons of concrete, glass,
furniture, carpets, insulation, computers and paper were reduced to
enormous, oxygen-poor debris piles that slowly burned until Dec. 19,
2001.

In
that hot pile, some of the debris' constituent elements combined with
organic matter and abundant chlorine from papers and plastics, and then
escaped to the surface as metal-rich gases. These then either burned or
chemically decomposed into very fine particles capable of penetrating
deeply into human lungs.

In
the trade-center air samples, Cahill identified four classes of
particles that have been named by the EPA as likely to harm human
health:

• Fine and very fine transition metals, which interfere with lung chemistry.
• Acids, in this case sulfuric acid, which attack cilia and lung cells directly.
• Very
  fine, un-dissolvable (insoluble) particles, in this case glass, which
  travel through the lungs to the bloodstream and heart.
• High-temperature organic matter, many components of which are known to be carcinogens.

"For
each of these four classes of pollutant, we recorded the highest levels
we have ever seen in over 7,000 measurements we have made of very fine
air pollution throughout the world, including Kuwait and China," Cahill
said.

After
the debris fire was out, pollution levels dropped, Cahill said. DELTA
Group measurements at the trade-center site made in May 2002, with the
American Lung Association of New York, showed that levels of almost all
of the very fine components had declined more than 90 percent,

Cahill
will report the new findings to the chemical society members today in a
special symposium on the trade center. The presentation is titled "Very
fine particles from the WTC collapse piles: anaerobic incineration?" It
is scheduled for 9:35 a.m. in Javits Convention Center, Room 1A22.

A news conference will follow the symposium at noon.

The
American Chemical Society is the world's largest scientific society.
Nine thousand people are expected to attend the Sept. 7-11 conference.

Cahill's
co-authors on the new study are: assistant research engineer Steve
Cliff, professor Jim Shackelford and researchers Mike Dunlap and Mike
Meier, all of UC Davis; Kevin Perry, assistant professor of meteorology
at the University of Utah, Salt Lake City.

Brad

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