The terrorist attack that destroyed the World Trade Center last
September exposed New Yorkers downwind to the most hazardous plumes of
extremely fine chemical and metal particles that experts have ever seen,
University of California scientists reported yesterday.
As the twin towers collapsed into flaming rubble after they were hit by two
hijacked airliners, wind gusts continued sending up thick clouds containing
millions of the particles for weeks afterward.
The unprecedented pollution was far worse than that from the Kuwait oil
field fires set by Iraq during the Gulf War or the soot-filled air from
Beijing's wintertime coal-burning furnaces, said UC Davis researcher Thomas
Cahill, a specialist in analyzing airborne particles who led a team
investigating the catastrophe's consequences for the Department of Energy.
"Those particles downwind over New York were like nothing we've ever seen
anywhere," Cahill said in an interview yesterday as he and his colleagues
released a preliminary report on the team's findings. Cahill heads the UC
Davis DELTA Group -- the term stands for Detection and Evaluation of Long-
Range Transport of Aerosols -- that has analyzed particulate hazards all over
The particles "were really weird: They came in great big spikes when the
wind blew, then they'd die down, then spike up again. And the particles that
aren't soluble -- like silicon from burning glass -- are the ones that can
lodge in your lungs and irritate them badly -- and stay there," he said.
Emphysema, asthma, other lung diseases and even heart disease are among the
health problems that can be aggravated or caused by pollutant particles that
lodge in the lungs. Workers at the site have complained of a variety of
To pin down the nature of the particles from the burning twin towers rubble, Cahill recruited researchers from UC's $100-million Advanced Light Source
facility at the Lawrence Berkeley National Laboratory for precise X-ray images
of the tiny particles, and UC's Lawrence Livermore National Laboratory for
that facility's ion microscopy and proton scattering devices.
Last Oct. 2, the team mounted a particle-collecting air monitor on a
rooftop at 201 Varick St. in Manhattan, a mile north-northeast of the trade
center complex, and samples were shipped back regularly to UC Davis through
the end of December. Yesterday's report covered the period through the end of
Although standards set by the Environmental Protection Agency for analyzing
particle size, their density, their composition and their hazards differ
somewhat from the DELTA Group's, the differences are largely technical.
Cahill's team collected particle samples ranging in size from "coarse," or
12 microns -- about the diameter of the period at the end of this sentence --
to "ultra-fine," or less than a tenth of that diameter. Their weight was
measured in "nanograms," or billionths of a gram.
"The ruins of the twin towers became a screamingly hot chemical reactor,"
Cahill said, "and for weeks, even as the flames eased and the core of the
towers cooled below 1,200 degrees, the steel was still glowing red at 800
degrees by November, and clouds of particles were still rising.
"Those particles simply shouldn't have been there, because it rained
heavily for six days in September after the attack, and the coarse particles
should have settled down. But they were probably still being generated from
the heat in the pile of debris."
Among the fine and very fine metal particles rising from the rubble, for
which the EPA has set no health guidelines, are iron from the girders,
titanium from the concrete, vanadium and nickel -- possibly associated with
burning fuel oil -- as well as copper and zinc.
Lead particles, most likely from the thousands of computers in the towers,
and mercury from the building's electrical circuits were detected in low
concentrations, Cahill reported.
The analysts found relatively few pulverized asbestos fibers from the
debris, he said -- probably because the twin towers contractors stopped using
asbestos half-way through construction of the 110-story buildings, which were
completed in 1972 and 1973.
By now, Cahill said, the evidence indicates that the air over New York City
is no longer affected by the World Trade Center disaster because the fires are
out and the debris pile has cooled.
California state and local officials already had been surveying members of
the state's Urban Search and Rescue Teams after receiving reports of health
problems among some of those members after they returned from New York.
According to Menlo Park Fire Protection District Capt. Harold Schapelhouman, of the 67 team members who went to New York, 70 percent had reported being
sick upon their return. Of those, 42 percent reported a chronic cough, and 3
percent reported pneumonia.
The team is now conducting more in-depth surveys, and Schapelhouman says he
is working with FEMA to coordinate a nationwide health survey of rescue team
Schapelhouman says he plans to send information about the UC Davis study to
his own affected team members as well as to other teams across the country.
"All these guys want is to be kept in the loop. . . . They want to know what
it is," he said. "They would all do it again, but . . . they took the chances,
and they deserve to know the truth."
Chronicle staff writer Matthew B. Stannard contributed to this report.
©2002 San Francisco Chronicle