World Trade Center Dust Analysis Offers Good News For New Yorkers
The
rubble has been cleared from the World Trade Center site, but questions
still loom about the long-term health effects on people who survived
the terrorist attacks. A new study of dust samples taken from around
Manhattan in the days following Sept. 11, 2001, could offer some
much-needed good news.
A team of researchers tested debris from the collapsed towers for toxic
organic chemicals and found that the potential risk of exposure from
inhaling such compounds was lower than expected. The findings are
scheduled to appear in the Feb. 1 print edition of Environmental
Science & Technology, a peer-reviewed journal of the American
Chemical Society, the world's largest scientific society. The article
was initially published Dec. 18 on the journal's Web site.
The scientists were looking specifically for persistent organic
pollutants — highly stable compounds that pose a special problem
because they endure in the environment and can be toxic to humans and
wildlife. They found no evidence of high levels of two particular POPs:
pesticides and polychlorinated biphenyls, which were used in hundreds
of industrial and commercial applications until their production was
banned in 1977.
The team did, however, estimate that the dust covering lower Manhattan
contained between 100-1000 tons of polycyclic aromatic hydrocarbons — a
group of compounds containing some that are classified by the U.S.
Environmental Protection Agency as probable human carcinogens. But,
while the amount of PAHs was high, the dust particles to which the
chemicals stuck were large enough to stay out of a person's lungs,
according to Paul Lioy, Ph.D., associate director of the Environmental
and Occupational Health Sciences Institute in Piscataway, N.J., and an
author of the paper.
"The fact that the particles were primarily above 10 micrometers in
diameter would mean that the deposition was in the upper airways of the
respiratory system and more readily cleared than fine particles, which
would deposit deeper in the lung," Lioy says. "That means, in terms of
potential lifetime exposures, we're probably going to be very lucky in
that these may not be exposures of significant health risk."
Immediately after the attacks, the majority of people focused their
attention on asbestos, Lioy says. But he and his colleagues felt the
only way to understand the situation was to determine everything people
could possibly have been exposed to. "In contrast to what we normally
do every day in environmental sciences, this was a catastrophic event,"
Lioy says. "We had no clue what was in there and what size ranges, so
our goal was to do a full characterization of the entire aerosol."
Lioy and others were invited to Ground Zero to help assess the impact
on public health after the attacks. They took samples from 13 locations
around the World Trade Center site from Sept. 12-17. In an earlier
paper, published in Environmental Health Perspectives, the group
performed a more general analysis on the samples and reported that the
dust had a high level of glass fibers and a high pH. "Most of the acute
responses were probably due to the very long fibers which we reported
in our first paper and the high pH of the cement dust that was released
in the first few days," Lioy says.
Phase II of the experiment, which is reported in the current paper, was
led by John Offenberg, Ph.D., of Rutgers University. The team focused
mainly on the persistent organic pollutants and their potential for
long-term health risks. They also looked to see if there was some
uniformity in the way the PAHs were spread around Manhattan.
Three of the samples constituted a north-south transect down Church
Street, along the east side of the epicenter. The concentrations of
PAHs in these samples increased toward the south, which is in keeping
with the wind direction immediately after the disaster: The wind blew
to the east/northeast during the first 12-18 hours, carrying debris,
dust and smoke to the East River and beyond. Then the winds shifted to
the south, carrying the dust over Battery Park and south to New Jersey.
The research group plans to use this information along with samples
taken indoors to study potential health risks regarding the cleaning of
people's houses and apartments. "Although it's a big number — 100-1000
tons of PAHs — it's not the only health concern," Offenberg says.
"Simply having three inches of concrete dust in one's living room is a
very unique experience, in terms of cleaning up. You don't just get out
your vacuum cleaner and run it."
This story has been adapted from a news release issued by American Chemical Society.
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