Science Inventory



Swartz, E C., L Stockburger, AND D A. Vallero. MONITORING TOXIC ORGANIC GASES AND PARTICLES NEAR THE WORLD TRADE CENTER AFTER SEPTEMBER 11, 2001. Presented at International Society of Exposure Analysis 2002 Conference, Vancouver, Canada, August 11-15, 2002.


The overall goal of human exposure research in air toxics is to develop the methods, data, and models of exposure that will provide the scientific basis for EPA to move to a risk-based program and that will enhance NATA. Specific objectives for this measurement task are to:

o Characterize exposure concentrations and variability in critical microenvironments using targeted measurement studies;

o Quantify the relationship of personal exposure to ambient and indoor concentrations;

o Identify critical microenvironments, human activities, and factors influencing exposure to air toxics;

o Develop methods to quantify exposure from background, point or area sources, and microenvironmental sources;

o Evaluate aggregate and cumulative exposures.


The September 11, 2001 attack on the World Trade Center (WTC) resulted in an intense fire and the subsequent, complete collapse of the two main structures and adjacent buildings, as well as significant damage to many surrounding buildings within and around the WTC complex. This 16-acre area has become known as Ground Zero. In response to this disaster, the US EPA quickly positioned air monitors and samplers around Ground Zero to characterize the resulting air plumes. One such instrument was a High Capacity Integrated Organic Gas and Particle (HiC IOGAP) sampler with a 2.5 mm cyclone for particle discrimination to collect semi-volatile gases and particles for speciation of organic compounds.

The results indicate that after the initial destruction of the WTC the remaining air plumes from the disaster site were comprised of many pollutants and classes and represent a complex mixture. This mixture includes compounds that are typically associated with fossil fuel emissions. The molecular markers for these emissions include the high levels of PAHs observed, the n-alkanes Carbon Prefix Index ~ 1 (odd carbon:even carbon ~ 1), as well as pristane and phytane as specific markers for fuel oil degradation. These results are not unexpected considering the large number of diesel generators and outsized vehicles used in the removal phases. The mixture also includes emissions of burning and remnant materials from the WTC site. The molecular markers for these emissions include retene and 1,4a-dimethyl-7-(methylethyl)-1,2,3,4,9,10,10a,4a-octahydrophenanthrene which are typically biogenic in origin. In addition, the compound 1,3-diphenyl propane [1',1'-(1,3-propanediyl)bis-benzene] is found in significant concentrations. This species has not previously been reported from ambient sampling. It has been associated with polyvinyl chloride materials, which are believed to be in abundance at the WTC site. These emissions lasted for over three weeks (9/26/01-10/20/01) after the initial destruction of the WTC.

This work has been wholly or in part by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Record Details:

Product Published Date: 08/11/2002
Record Last Revised: 06/21/2006
Record ID: 62021