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Background Attack Aftermath Evidence Misinformation Analysis Memorial

Ground Zero Gases

Months of Emissions of Gases and Fine Particulate Matter

The rubble piles emitted a toxic brew of gases and aerosols with periodic spikes of intensity going on well into 2002. One source of data was a monitoring program by the the Environmental Protection Agency (EPA) which recorded volatile organic compounds (VOCs) and other pollutants at a number of locations in and around Ground Zero. Some of the EPA's data are posted on its website, but the site contains numberous broken links and omissions, prompting researchers to file FOIA petitions to obtain data. 1  

A second source of data was a program by the UC Davis DELTA Group (Detection and Evaluation of Long-range Transport of Aerosols) using a rooftop air monitor one mile north-northeast of Ground Zero to record levels of airborne particles. 2  

In a 2008 paper published in The Environmentalist, Environmental Anomalies at the World Trade Center: Evidence for Energetic Materials, the independent researchers Kevin R. Ryan, James R. Gourley, and Steven E. Jones provide an in-depth analysis of anomalous features of the data. 3   They note, as do the UC Davis scientists, that the emissions exhibit a pattern of spikes with periodic episodes of very high emissions. The carcinogenic compound benzene registered a level of 180,000 on November 2001 -- hundreds of times higher than levels known to cause adverse health effects in humans. If the episodic pattern of emissions can be explained by flare-ups in the rubble pile during its excavation due to changes in air and fuel supplies to pockets of fire, another feature challenges such explanations: the pattern of emissions of VOCs shows no apparent relationship to the pattern of emissions of fine particulate matter. If rubble fires are the source of the VOCs and the particulate matter, then one would expect that the peaks in the two types of emissions would be strongly correlated.

emissions of five organic compounds
FIG. 3 from Environmental Anomalies: "EPA maximum daily detection of VOCs in air at GZ, September through November 2001"
emissions of very fine particulate matter
FIG. 4 from Environmental Anomalies: "Very fine PM detected in air by EPA near GZ in late 2001"

The authors of Environmental Anomalies advance a hypothesis to explain the lack of correlation between the VOC and paticulate emissions: whereas the particulate matter was produced by the ongoing combustion of conventional building materials and building contents in the rubble piles, the spikes in VOC emissions were produced by the periodic triggering of reactions of energetic materials in the pile -- the same materials used to destroy the buildings.


1,3-Diphenyl Propane

A study by a US EPA research office examining organic gases and particles in the air plumes emanating from Ground Zero noted the presence of 1,3-diphenyl propane (1,3-DPP) -- a compound that had never previously been detected in ambient air sampling. The compound was measured in concentrations that, according to EPA's Eric Swartz, "dwarfed all others", and, according to American Scientist, was "pervasive".

The EPA publication that reported the finding suggested that 1,3-DPP was produced by the decomposition of polyvinyl chloride materials in the debris. 4   Swartz offered another hypothesis -- that the compound was a combustion product of polystyrene. Both hypotheses beg the question of why this compound was never before observed in sampling of air from other fires of large commercial buildings, given that the EPA has monitored the emissions of many such events. Environmental Anomalies notes a series of other problems with these hypotheses:

However, the sources Swartz uses to support 1,3-DPP as a combustion product of polystyrene are not studies of polystyrene combustion, but of gases released in the long-term degradation of enclosed polystyrene food product packaging.

Other studies have shown trace amounts of 1,3-DPP as a secondary product of polystyrene combustion or thermolysis. But such studies suggest that 1,3-DPP may only form in negligible quantities and under certain conditions (Boettner et al. 1973 ; McCaffrey et al. 1996 ). In such experiments, the major product of the combustion or thermolysis of polystyrene, far outweighing others, is the monomer styrene. This leads us to the fact that, although styrene was a species of interest at 290 Broadway during the same time period as was 1,3-DPP, styrene detections were not reported in the FOIA provided data (EPA 2004 ). Therefore, it appears that Swartz’ first suggested hypothesis, that 1,3-DPP resulted from combustion of polystyrene, is not probable.

The possibility that 1,3-DPP was off-gassed as a result of the physical destruction of debris at GZ, as in Swartz’ second hypothesis, seems possible. But it is one thing to suggest that 1,3-DPP was “ encapsulated in large volumes of plastics in the buildings” and another thing to state in what exact materials this rare compound was encapsulated. Consumer plastics do not typically have large amounts of unusual organic compounds just simply “encapsulated” within them.

The authors of Environmental Anomalies go on to examine a more plausible explanation for the high levels of 1,3-DPP: that the gas was a product of the combustion of energetic nanocomposites. The paper provides a detailed hypotheses of the chemical reactions involved.


EPA on Ground Zero Metal Aerosols

Despite gathering evidence of toxic emissions, the EPA aggravated the public health disaster with its false assurances that the air was safe to breathe. The EPA's website continues to deny the hazardous effects of Ground Zero gas exposures, although its denials have become more sophisticated over time. Consider these excerpts from a 2002 and 2009 version of the page "Metals in Air",

Results as of mid-January, 2002:

About a third of these metals were not detected in any air samples. EPA detected fourteen metals: antimony, arsenic, cadmium, manganese, nickel, aluminum, barium, copper, iron, magnesium, sodium, calcium, vanadium, and zinc.

The first five of these metals are hazardous air pollutants (HAPs), also called toxic air pollutants, under the Clean Air Act. Although we detected these metals, their low concentrations mean they pose no potential for significant risk of long-term health problems from the WTC cleanup effort.

EPA continues to monitor and analyze these metals in the air surrounding the WTC. We do not, however, expect future results to be substantially different from the samples listed here. Subsequent sample results, however, will continue to be made available here.

Additional details are available.


The new version replaces the blanket denial that the metal vapors were a hazard due to their "low concentration" with a more nuanced denial claiming that the spikes in emissions were too infrequent to be of concern:

The following summarizes the results of monitoring for metals in air. Monitoring ended in May 2002.

EPA detected twenty-two metals: antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, nickel, selenium, aluminum, barium, calcium, copper, iron, magnesium, potassium, silver, sodium, thallium, vanadium, and zinc.

The first ten of these metals are hazardous air pollutants (HAPs), also called toxic air pollutants, under the Clean Air Act. Although we detected these metals, they were detected infrequently. When detected they were mostly at low concentrations. The infrequent detections above the screening levels for metals in ambient air mean they did not pose significant risk of long-term health problems to the general public.

Additional details are available.


On the 2009 version of the page, the link titled "Additional details are available" goes to a page declaring "File Not Found". The earlier version linked to a page that discloses that barium was among the ten metals detected most frequently in air sampling. Reports by the USGS also showed very high levels of barium.


1. Outdoor Monitoring, www.epa.gov,
2. Air quality scientists release WTC study, www-dateline.ucdavis.edu, 2/15/2002
3. Environmental Anomalies at the World Trade Center: Evidence for Energetic Materials, The Environmentalist, 8/4/2008
4. Monitoring Toxic Organic Gases and Particles Near the World Trade Center After September 11, 2001, [cached]
5. Metals in Air, epa.gov,
6. Metals in Air, epa.gov,

page last modified: 2013-03-21