Development of an exposure assessment method for epidemiological studies of New York State personnel who responded to the World Trade Center disaster

Our plain-English summary of Development of an exposure assessment method for epidemiological studies of New York State personnel who responded to the World Trade Center disaster, by M.L. Herdt-Losavio, M.P. Mauer, G.A. Carlson (The Annals of Occupational Hygiene, 2008).

The study

• Authors: M.L. Herdt-Losavio, M.P. Mauer, G.A. Carlson
• Journal: The Annals of Occupational Hygiene
• Published: 2008;52(2):83-93
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: An exposure assessment method was developed for use in assigning an exposure score to New York State personnel who responded to the World Trade Center disaster site after the 11 September 2001 terrorist attacks.

Methods: The method consists of an algorithm with two instantiations. Each represents a major component of the overall exposures at the site: dust and smoke. The algorithm uses US Environmental Protection Agency air monitoring data collected between 23 September 2001 and 28 February 2002, as well as information on duration, location and time period of work assignment and type and frequency of personal protective respiratory equipment (PPE) use, collected by a self-administered mailed questionnaire. These data were used to calculate an overall exposure score for each participant. For each time period/location combination, individuals provided average number of hours and number of days worked. This was multiplied by a weighting factor derived from the median of the air monitoring data for the time period/location. Calcium was chosen as a surrogate for the dust exposure, so the weighting factors for the dust instantiation were calculated from calcium air monitoring data. Total hepta-chlorinated dibenzo-p-dioxin was chosen as a surrogate for the smoke exposure and was similarly used in the smoke instantiation.

Results: More individuals in the highest exposure score category performed tasks such as search/rescue and hand digging than those in the lowest exposure category. Also, those in the highest exposure category had a higher mean number of hours at the site than other exposure groups.

Conclusions: The exposure assessment method presented accounts for PPE use, amount of time at the site, proximity to the site and ambient air monitoring results taken in the immediate vicinity. The algorithm can be used to rank individuals in the same study with very different patterns of exposure, such as high-level, short-term exposures and low-level, long-term exposures. The concepts could be modified for use in other epidemiological studies where long-term chronic exposure is a concern.

In plain English

This article described a method for scoring the likely relative exposure of New York State personnel who worked at the World Trade Center disaster site on or after 11 September 2001. It was not meant to estimate actual exposure to any specific substance. The score combined self-reported days, hours, locations, time periods and respirator use with US Environmental Protection Agency air monitoring results. One version scored dust, using calcium as a stand-in. Another scored smoke, using a group of dioxins. Asbestos, mentioned only as a dust ingredient, was not scored separately. It was applied to 1,341 participants in a medical monitoring-related study who gave work history; the response rate was 14%. In the highest dust-score quarter, 36.7% had worked on the debris pile, compared with 11.3% in the lowest. In the highest dust-score quarter, 22.7% had done emergency response tasks such as hand digging, compared with 7.1% in the lowest. Air monitoring did not cover all study locations until 23 September 2001, so the earliest, highest exposures were not adequately captured. The authors concluded the method can rank people with very different exposure patterns.

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: Exposure assessment methods development: a scoring algorithm with two versions (dust and smoke), applied to a cohort of responders using questionnaire data and air monitoring data, with a sensitivity analysis. It produces relative rankings, not actual exposure levels.
• Who was studied: New York State personnel assigned to work at the World Trade Center site between 11 September 2001 and 23 December 2001 who took part in an offered medical monitoring program. The algorithm data set included the 1,341 who agreed to join a medical monitoring-related study and gave work history information; the reported response rate was 14%.
• Exposure: Overall World Trade Center dust and smoke exposure. Calcium air monitoring data stood in for dust. Total hepta-chlorinated dibenzo-p-dioxins (total hepta-CDDs) stood in for smoke. These were combined with self-reported hours and days by location and time period, and with type and frequency of respirator use. Asbestos is mentioned only in the introduction as a dust component; it was not measured or scored separately.
• Main results:
  • Using dust-score quartiles, 123 of 335 (36.7%) in the highest quartile had spent time on the pile, compared with 38 of 336 (11.3%) in the lowest quartile.
  • Emergency response tasks (hand digging, firefighting, search and rescue, bucket brigade) were reported by 76 (22.7%) in the highest dust-score quartile, compared with 24 (7.1%) in the lowest dust-score quartile.
  • One-strap dust masks, which the authors describe as providing essentially no protection, were used at some time by 146 (43.6%) in the highest dust-score quartile, compared with 48 (14.3%) in the lowest dust-score quartile.
  • Mean total time spent at the site increased with exposure quartile. The underlying figures were not shown.
  • In the sensitivity analysis, all alternative versions of the algorithm were highly correlated with the original. The lowest Spearman correlation was 0.86, for back-extrapolated early weights in the dust version.
  • The dust and smoke versions correlated at 0.7445, so individuals could fall into different quartiles depending on which version was used.
• The authors' conclusion: The authors concluded that the method combines time period, duration on site, work location and respirator use with air monitoring data into one score. They said it can rank people with very different exposure patterns, such as high-level short-term and low-level long-term exposures.
• Limitations the authors state:
  • Air monitoring did not cover all study locations until 23 September 2001. Earlier data were excluded, and the earliest time periods were given the same weights as 17 to 30 September, so the earliest and highest exposures were not adequately captured and were likely underestimated.
  • Work history was self-reported on average 11 months after the event, which could introduce recall bias.
  • No information on respirator fit testing was available. The authors say this likely overestimated protection and underestimated exposure for some individuals.
  • Respirator use was collected by time period, not by specific day, location or task.
  • Using one stand-in substance each for dust and smoke may oversimplify a complex mixture of exposures.
  • Job tasks were not included in the score, which could underestimate exposure for some individuals.

Topics

Medical terms in this study, explained in our Lexicon: Air Sampling, Short-Term Exposure.

Related studies

• Assessing truck driver exposure at the World Trade Center disaster site: personal and area monitoring for particulate matter and volatile organic compounds during October 2001 and April 2002 — A.S. Geyh, S. Chillrud, et al. (2005)
• The legacy of World Trade Center dust — J.M. Samet, A.S. Geyh, et al. (2007)
• Occupational exposures during the World Trade Center disaster response — K.M. Wallingford, E.M. Snyder (2001)
• Health consequences of the September 11 World Trade Center attacks: a review — J. Moline, R. Herbert, et al. (2006)
• Health effects of World Trade Center (WTC) Dust: An unprecedented disaster's inadequate risk management — M. Lippmann, M.D. Cohen, et al. (2015)
• 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)

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