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Cloud of gases from 9/11 still a mystery

Ten years later, what we know and don't know about the cough, respiratory ailments and cancer risks from the miasma and smoky dust following the collapse of the two towers.
Written by Janet Fang, Contributor on

Ten years later, we still don’t know exactly what was in the World Trade Center plume, and the residents and rescue workers remain uncertain of what they were exposed to after the towers collapsed. Scientific American’s David Biello reports.

"The debris pile acted like a chemical factory," says atmospheric scientist Thomas Cahill of the University of California, Davis. "It cooked together the components of the buildings and their contents.”

Millions of tons of cement, steel, lead, drywall, and window glass were scattered into the air. Add to that: crushed and incinerated computers, electrical cables, heating and cooling ducts, insulation and carpet fibers, and decades of human hair. And 91,000 liters of jet fuel. At 1,000 degrees Celsius.

And Paul Lioy of the Environmental and Occupational Health Sciences Institute in New Jersey, who collected samples of pulverized remains in the days following the attack, wants to know: What was the contribution of the gases from combustion?

We might never know… few direct measurements were taken of the plume that followed the disintegration of the two towers, though air samples were collected in subsequent weeks and months.

  • In dust samples the Environmental Protection Agency (EPA) analyzed in the first week, 25% showed asbestos levels above the 1% threshold that indicates ‘significant risk.’
  • Inside the towers were heavy metals such as lead that helps make electric cables flexible and poisons the human brain.
  • There were also polychlorinated biphenyls (PCBs) used in electrical transformers that are toxic on their own and become even more toxic when burned at high heat.
  • Pulverized glass became fibers that lodge in the lungs.
  • The levels of dioxin (chemical contaminants released by burning plastic) measured near the smoldering pile were the highest ambient measurements ever recorded anywhere in the world: at least 100 times higher than those found downwind of a garbage incinerator.

Science has revealed what was in the dust, but no one knows for sure what was in the cloud of gases released by the combustion of all that jet fuel and building material.

Knowing what was in the dust suggests what caused the ‘World Trade Center cough’ (as dubbed by the New England Journal of Medicine) that afflicted nearly half of those who worked at the site.

Besides inadequate protection, specifically respirators, the primary cause was that the dust was highly basic (versus acidic). People were bathed in particles ranging from millimeters to nanometers – the right size to be inhaled and embedded deep in the lungs. Both gypsum and calcite, found in drywall and cement, irritate the mucus membranes of the eyes, nose and throat.

  • Ultimately, the EPA determined in a 2007 report [pdf] that the air around Ground Zero was harmless: "Except for inhalation exposures that may have occurred on 9/11 and a few days afterwards, the ambient air concentration data suggest that persons in the general population were unlikely to suffer short-term or long-term adverse health effects caused by inhalation exposures."
  • As of last year, more than 12,000 of the 9/11 rescue workers continue to have trouble breathing, according to a study conducted by the World Trade Center Medical Monitoring Program.

In December 2010, New York State accountant Jerry Borg, who worked in a building a few blocks from the World Trade Center, died of an inflammatory disease of the lungs – and the third victim linked specifically to exposure to the toxic dust cloud.

And what about cancer risks? (Though, attributing cancer to being near the World Trade Center is extremely difficult since roughly one in 4 Americans will develop cancer in some form over the course of their lives.)

More than 70,000 have signed up for the World Trade Center Health Registry, which aims to track health outcomes of the exposed population. "The key is when you arrived, whether you were wearing a respirator or not, how long you were there and how high the concentrations were there that could lead to effects," Lioy says.

Via Scientific American.

Image via Wikimedia

This post was originally published on Smartplanet.com

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