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Lessons Learned about Airway and Respiratory Illness at the World Trade Center

August 5, 2015
Impedance oscillometry

Impedance oscillometry

There are few events in our collective consciousness that have united us as a country like the events of 9/11. Everyone knows where they were on the day, what they were doing and how they felt.

Lessons learned by early responders on that day have taught us a great deal about dealing with disaster and managing the aftermath. The following abstract is interesting in the context of our knowledge of the health effects on the men and women who stayed onsite to clean up the rubble. At the time it was well understood that the dust must be toxic or that breathing the dust would have some detrimental impact on the health of the cleanup teams. Following is an excerpt from a report by the City of New York entitled “What we know about the health effects of 9/11”.


Respiratory Illness

  • Those exposed to WTC-related dust were more likely to develop respiratory symptoms, sinus problems, asthma or lung problems. One in 10 Registry enrollees developed new-onset asthma within six years of 9/11, three times the national rate. New cases were highest during the first 16 months after 9/11.
  • Intense dust cloud exposure on 9/11 increased the risk of developing asthma. These groups were especially at risk:
    • Rescue, recovery and clean-up workers who arrived early at the WTC site or worked at the WTC site for long periods of time
    • Lower Manhattan residents who didn't evacuate their homes
    • Lower Manhattan residents and office workers who returned to homes or workplaces covered with a thick coating of dust
    • People who both lived and worked in lower Manhattan after 9/11
  • Steep declines in pulmonary function first detected among firefighters and emergency medical service (EMS) workers within a year of 9/11 have largely persisted, even among those who never smoked. It is estimated that four times as many firefighters and twice as many EMS workers had below-normal lung function for their ages six to seven years after 9/11 as they did before the attacks. Among the few active smokers, pulmonary function declines were even greater than for non-smokers.
  • Studies also have identified persistent abnormal pulmonary function in other WTC rescue and recovery workers, including police, and in Lower Manhattan residents and area workers.
  • Seven to eight years after 9/11, continuing lower respiratory symptoms were identified in area workers and people living in Lower Manhattan at the time of the attack. The prevalence of symptoms correlated with the degree of WTC disaster exposure and abnormal pulmonary function.
  • Both epidemiologic and clinical studies demonstrate substantial co-morbidity (co-occurrence) of respiratory illness and mental health conditions in WTC-exposed groups.

 This abstract set out that testing done onsite using forced spirometry the standard of care to measure lung function at the time, appeared normal. It is very possible that the early diagnosis of diminished lung function of this kind requires much more specific diagnostic protocol such as Impedance oscillometry (IOS).



Oppenheimer BWGoldring RMHerberg MEHofer ISReyfman PALiautaud SRom WNReibman JBerger KI.


Division of Pulmonary and Critical Care Medicine, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.



Following collapse of the World Trade Center (WTC), individuals reported new-onset respiratory symptoms. Despite symptoms, spirometry often revealed normal airway function. However, bronchial wall thickening and air trapping were seen radiographically in some subjects. We hypothesized that symptomatic individuals following exposure to WTC dust may have functional abnormalities in distal airways not detectable with routine spirometry.


One hundred seventy-four subjects with respiratory symptoms and normal spirometry results were evaluated. Impedance oscillometry (IOS) was performed to determine resistance at 5 Hz, 5 to 20 Hz, and reactance area. Forty-three subjects were also tested for frequency dependence of compliance (FDC). Testing was repeated after bronchodilation.


Predominant symptoms included cough (67%) and dyspnea (65%). Despite normal spirometry results, mean resistance at 5 Hz, 5 to 20 Hz, and reactance area were elevated (4.36 +/- 0.12 cm H(2)O/L/s, 0.86 +/- 0.05 cm H(2)O/L/s, and 6.12 +/- 0.50 cm H(2)O/L, respectively) [mean +/- SE]. Resistance and reactance normalized after bronchodilation. FDC was present in 37 of 43 individuals with improvement after bronchodilation.


Symptomatic individuals with presumed WTC dust/fume exposure and normal spirometry results displayed airway dysfunction based on the following: (1) elevated airway resistance and frequency dependence of resistance determined by IOS; (2) heterogeneity of distal airway function demonstrated by elevated reactance area on oscillometry and FDC; and (3) reversibility of these functional abnormalities to or toward normal following administration of a bronchodilator. Since spirometry results were normal in all subjects, these abnormalities likely reflect dysfunction in airways more distal to those evaluated by spirometry. Examination of distal airway function when spirometry results are normal may be important in the evaluation of subjects exposed to occupational and environmental hazards.

Chest. 2007 Oct;132(4):1275-82. Epub  2007 Sep 21.

This is another article on the same topic; Respiratory Symptoms and Physiologic Assessment of Ironworkers at the World Trade Center Disaster Site

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