Two years after the terrorist attacks on the World Trade Center in New York City, which claimed almost 3000 lives, researchers have gathered to assess the legacy of the giant plume of smoke and dust caused by the atrocity.
The composition of the plume was unique in its chemical composition and unprecedented in its complexity. As a result, no one yet knows the health effects of breathing them in and therefore how many more people may have been affected by the collapse of the Twin Towers.
鈥淭his was a fully functional building that was completely smulched into a burning pit,鈥� says Thomas Cahill, an atmospheric physicist at the University of California Davis, who has focused on the composition of the finest particles in the plume for the past two years.
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鈥淭hat鈥檚 never happened before, so we are in completely new territory. All we can say is we are worried about it,鈥� he says. 鈥淚t may take years before these effects show up, just like with radiation.鈥�
Astonishing complexity
The gathering on Wednesday at the American Chemical Society鈥檚 meeting in New York City was the first time chemists, atmospheric physicists and doctors from over 20 US institutions had got together to pool their results.
Paul Lioy, of the University of Medicine and Dentistry of New Jersey, emphasised to the meeting the sheer diversity of chemicals that were present in the dust. A mixture of plastics, computer hardware, synthetic furniture and hundreds of miles of wire burned to produce an aerosol of astonishing complexity. Out of 400 organic alkanes, pthalates and polyaromatic hydrocarbons he identified, the majority had never before been detected in the air, he says.
One such compound, detected by researchers from the US Environmental Protection Agency, was diphenyl propane, thought to have come from burning plastic. The health consequences of breathing it are totally unknown, says EPA scientist Leonard Stockburger.
快猫短视频s from the US Geological Survey showed that even among the well-known molecules and crystals, new shapes of particle were thrown up by the plume. 鈥淭hey detected fibrous, cylindrical materials, which have a totally different behaviour to spherical particles,鈥� says Michael Hays of the EPA, who attended the meeting. 鈥淗ow does that influence inhalation routes?鈥�
But the scientists were careful to be clear about their message. 鈥淲e don鈥檛 want people to get the wrong impression. For long term effects, we are simply in an area of unknowns,鈥� says Lioy.
Pollution map
Next, the chemists鈥� hope to produce a map of exactly what was in the air and when in the weeks and months after the September 11 attacks. Then, if people develop symptoms, the doctors will know exactly what they were likely to have inhaled.
The New York City Department of Health launched a survey last Friday that will follow the health of up to 200,000 people who were in the vicinity of the Twin Towers when they collapsed.
Some evidence of ongoing effects has already surfaced. A study published in August showed that pregnant women who were near Ground Zero on September 11 or up to three weeks later were twice as likely to give birth to smaller babies as women who were not.