A 'Chemical Factory' in Skies

By Laurie Garrett
STAFF WRITER

September 11, 2003

The air that hovered over New York in the months after by the collapse of the Twin Towers contained an unprecedented combination of chemicals, scientists said yesterday. As such, they said it may be impossible to forecast the long-term health impact.

Scientists from government and university laboratories gathered yesterday for the first time to compare findings about the dust, debris and polluted air in the aftermath of 9/11, in a conference at the annual meeting of the American Chemical Society.

The picture that emerged from the presentations depicted an unprecedented chemical event that evolved minute-by-minute, throwing a stew of compounds into the air. Researchers said one molecule detected had never been found in air before. The plume was marked by a mix so complex, the content varied centimeter by centimeter, researchers said.

Ground Zero fires smoldered for months and reached temperatures of 1,800 degrees, creating what a scientist characterized as a "chemical factory" that brewed new compounds. One effect was a sort of mini-ozone hole, in which chlorinated compounds scavenged hydrogen and other atoms off molecules, transforming them into volatile gases.

"The fact that the plume did not stay in one direction means the exposures to people were intermittent," said Paul Lioy of the Environmental and Occupational Health Sciences Institute of the University of Medicine and Dentistry in New Jersey. "Here it was, a catastrophic event. Initial exposures were basically a blackout - exposures people will, cumulatively, never see in a lifetime again. The problem we have now is we don't know the long-term, lifetime, health consequences. We just don't know."

There was a degree of disagreement among experts in attendance. Thomas Cahill, an air pollution expert from the University of California, said starting on Oct. 3, 2001, air monitored on the roof of a building in the West Village, a mile north of Ground Zero, showed "unprecedented ambient levels" of fine particulate matter, sulfur, acidic aerosols, heavy metals and other dangerous compounds. "I have sampled more than 7,000 samples of very fine aerosols for Kuwait [during the 1992 oil fires], China and so on," Cahill said, "and October 3 was the worst." But NYU environmental science expert George Thurston said most of the pollutants measured were normal for New York. Thurston's group started collecting air samples on Sept. 28 from NYU's Downtown Hospital, five blocks northeast of Ground Zero, and comparative samples from northern New Jersey and eastern Greenwich Village. He said by October, fires and dust contributed only a third of New York's pollution, and by January it had no real impact. Most scientists did not agree. The EPA's Joseph Pinto used optical density analysis of videos and photos shot on 9/11 to determine the wavelengths of light scattering to determine what chemicals and debris were present. "What I'm coming up with really should be viewed as lower limits," Pinto said. "You can see clear enhancement, one hundred to a thousand-fold, in pollution levels due to the World Trade Center."

Lioy's group is creating three-dimensional models of the plume and debris movement. The intense heat of Ground Zero blew the plume upwards, creating a "loft effect," he said, which actually protected New Yorkers from the worst of the chemical onslaught, though it also lifted the gases and particles over Manhattan and dropped them on Brooklyn and Sandy Hook, N.J. U.S. Census Bureau data are being added to the computer model, creating a neighborhood-by-neighborhood picture of human exposure that the researchers hope will help health officials determine locales at risk for long-term health problems. One molecule, described by the EPA's Erik Swartz, was present at levels "that dwarfed all others": 1,3-diphenylpropane. "We've never observed it in any sampling we've ever done," Swartz said. He said it was most likely produced by the plastic of tens of thousands of burning computers.

Roger Clark of the U.S. Geological Survey's Colorado laboratory led a team that provided the first strong pollution data for the White House, delivered on Sept. 17. The next day the White House announced operations would shift from rescue to recovery, because the heat level precluded the possibility of survivors beneath the rubble.

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