What Was in the 9/11 Smoke Plume?

Photo: Stan Honda, AP

It has now been 14 years since 9/11.  We all have deeply personal feelings and views of the confusion, fear, and tragedy of that day and the days and weeks that followed.

Amongst my most vivid memories are the efforts of the first responders in the days following the attack to find survivors or just bring closure for those who had lost loved ones.  It was a heroic effort in an extremely difficult environment, with exposure to smoke and dust that was emitted from the smoldering pile long after the collapse of the towers.  

A team of scientists led by noted aerosol research Tom Cahill and including University of Utah Professor Kevin Perry collected and analyzed samples of particulate matter from very near the collapse site, with their results summarized in article entitled "Analysis of Aerosols from the World Trade Center Collapse Site, New York, October 2 to October 30, 2001", which appeared in the journal Aerosol Science and Technology in 2004 (click here for free access to the article).  

During the period investigated, plumes were typically elevated away from the collapse site, so exposure was greatest to workers at the collapse site.  As noted by the authors, "while the impacts of the plumes at sites away from the WTC collapse pile were episodic, that is not true for workers at the site itself." At the collapse site, concentrations of very fine particles (less than 1 micron in diameter), which can penetrate deep into the lungs, were extraordinarily high, described by the authors as "the highest we have recorded in a variety of studies, including on the ground in the oil fields of Kuwait, June 1991."  In addition, the composition of the dust and smoke produced by the smoldering collapse site was substantially different than that commonly associated with air pollution episodes, such as those we experience along the Wasatch Front.  Very fine particles consisted of sulfuric acid, polycyclic aromatic hydrocarbons (PAHs) and their derivatives (produced by incomplete fossil fuel and organic matter combustion), and glasslike silicon containing aerosols.  Larger particles included powdered concrete, gypsum from dry wall, glass shards, and man-made metals.  

It is clear that the heroic first responders at 9/11 were exposed to an unusual acrid mix of smoke and dust.  This is a major reason for elevated rates of respiratory problems amongst first responders and justifies careful monitoring for certain forms of cancer and other diseases.  Although linkages between dust and smoke exposure and cancer and other diseases are often difficult to establish, there is strong justification for ensuring that the 9/11 first responders receive more-than-adequate health support and treatment for their health challenges.