Summary of the development of a signature for detection of residual dust from collapse of the World Trade Center buildings

Our plain-English summary of Summary of the development of a signature for detection of residual dust from collapse of the World Trade Center buildings, by H.A. Lowers, G.P. Meeker, P.J. Lioy, et al (Journal of Exposure Science & Environmental Epidemiology, 2009).

The study

• Authors: H.A. Lowers, G.P. Meeker, P.J. Lioy, M. Lippmann
• Journal: Journal of Exposure Science & Environmental Epidemiology
• Published: 2009;19(3):325-35
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The collapse of the World Trade Center (WTC) towers on September 11, 2001, caused lower Manhattan and adjacent areas to be covered in millimeters to centimeters of dust. WTC dust penetrated into indoor spaces, and public health concerns remain regarding exposure to possible residual dust in the affected areas. The goal of the studies outlined in this review was to determine which, if any, components of the bulk WTC dust are sufficiently above typical background dust levels in New York City to develop an analytical method to screen for the component(s). Components of the <150-microm-size fraction of the dust are gypsum, phases compatible with crushed concrete, man-made vitreous fibers (MMVFs), silica, lead, chrysotile asbestos, and other materials. Slag wool was the most common WTC MMVF, whereas soda-lime glass and rock wool were minor to trace constituents. Most background samples also contained gypsum, phases compatible with concrete, and MMVF. However, the proportions of the various MMVF in background samples are typically unlike those characteristic of bulk WTC dust. Results indicate that slag wool can be used as a signature marker to identify areas that contain potential residual WTC dust contamination at concentrations that are less than average background levels for the material.

In plain English

This review summarized work by several agencies and groups on detecting leftover dust from the 2001 World Trade Center (WTC) collapse. Six WTC dust samples from 2001 were examined by electron microscope and compared with background dust from New York City residences. The WTC dust consisted mainly of gypsum, concrete-like material and man-made vitreous fibers. Chrysotile asbestos made up 0.01 to 1.76 area percent of particles across the six samples. Slag wool was the dominant man-made fiber in every WTC sample, averaging 9.4 million fibers per gram in three samples, but was the least common in background dust. In an EPA study, eight laboratories analyzed background dust spiked with a composite of USGS-collected WTC dust or diluted dust from 4 Albany Street. Results varied widely between laboratories, but all clearly distinguished the 5% and 10% USGS-composite spikes from the remaining samples. The authors concluded that slag wool can be used as a signature marker for residual WTC dust. They noted that the method's usefulness after so much time is unknown, that some false positives are unavoidable, and that background samples were limited.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review summarizing laboratory studies: microscopic analysis of bulk WTC dust, comparison with background dust, and an EPA interlaboratory study of spiked samples
• Who was studied: Six bulk WTC dust samples (four collected outdoors and two indoors, 0.25 to 0.80 km from the WTC site, September to November 2001), compared with background dust from six New York City residential locations collected November 2004 to January 2005 and with additional background samples
• Exposure: Components of WTC collapse dust, including gypsum, crushed concrete phases, man-made vitreous fibers (slag wool, rock wool, soda-lime glass), silica, lead and chrysotile asbestos
• Main results:
  • The major constituents of the six bulk WTC dust samples were gypsum, phases compatible with concrete, and man-made vitreous fibers
  • Chrysotile ranged from 0.01 to 1.76 area percent of particles across the six bulk WTC dust samples (1.76 in USGS 12, 0.72 in USGS 6, 0.73 in LM-2, 0.41 in USGS 4, 0.01 in L18-2, 0.05 in USGS 36)
  • Slag wool was the dominant man-made vitreous fiber in all WTC dust samples
  • Separate preparations of WTC samples USGS 6, 12 and 36 averaged 9.4 million slag wool fibers per gram (printed as 9.4 x 10 to the 6th; Table 3 lists 1.1 x 10 to the 7th, 9.3 x 10 to the 6th and 8.2 x 10 to the 6th)
  • In background samples analyzed by USGS, slag wool was not observed in two of six; the other four contained between 1,800 and 25,300 fibers per gram
  • Slag wool was the least common man-made vitreous fiber type identified in the background samples
  • In the EPA interlaboratory study, spiked and background samples were analyzed by eight laboratories
  • One spiking material was a composite of WTC dusts collected by USGS; the second was indoor dust collected in 2004 at 4 Albany Street, which appeared to represent diluted WTC dust
  • Interlaboratory variation in the EPA study was large
  • In all laboratories, the samples spiked with 5% and 10% of the USGS WTC dust composite were clearly distinguishable from the remaining samples
  • All laboratories found that the sample spiked with 10% 4 Albany dust had a slag wool content similar to the sample spiked with 1% USGS dust
  • The authors estimated the practical detection limit for residual WTC dust in indoor dust to be on the order of 0.1 weight percent
  • The background samples with the highest slag wool levels came from a North Carolina office building
• The authors' conclusion: The authors concluded that slag wool can be used as a signature marker to identify areas with potential residual WTC dust contamination at concentrations below average background levels
• Limitations the authors state:
  • The usefulness of the method for mapping WTC dust contamination is unknown, partly because of the time that had passed since the collapse
  • Some false-positive results are unavoidable
  • Only a limited set of background samples was compared with bulk WTC dust
  • The sample preparation method did not work well for man-made vitreous fibers
  • It was assumed, not shown, that WTC dust did not contribute to the background samples

Topics

Medical terms in this study, explained in our Lexicon: Vitreous, Chrysotile.

Related studies

• Characterization of the dust/smoke aerosol that settled east of the World Trade Center (WTC) in lower Manhattan after the collapse of the WTC 11 September 2001 — P.J. Lioy, C.P. Weisel, et al. (2002)
• Case report: Lung disease in World Trade Center responders exposed to dust and smoke: carbon nanotubes found in the lungs of World Trade Center patients and dust samples — M. Wu, R.E. Gordon, et al. (2010)
• Potential carcinogenic effects of world trade center dust after intratracheal instillation to Sprague-Dawley rats: first observation — M. Soffritti, L. Falcioni, et al. (2013)
• The legacy of World Trade Center dust — J.M. Samet, A.S. Geyh, et al. (2007)
• Evaluation of vacuum and wet-wipe methods for removal of World Trade Center dust from indoor environments — K.M. Tang, C.G. Nace, et al. (2004)
• Development of an exposure assessment method for epidemiological studies of New York State personnel who responded to the World Trade Center disaster — M.L. Herdt-Losavio, M.P. Mauer, et al. (2008)

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