Induced sputum assessment in New York City firefighters exposed to World Trade Center dust

Abstract

New York City Firefighters (FDNY-FFs) were exposed to particulate matter and combustion/pyrolysis products during and after the World Trade Center (WTC) collapse. Ten months after the collapse, induced sputum (IS) samples were obtained from 39 highly exposed FDNY-FFs (caught in the dust cloud during the collapse on 11 September 2001) and compared to controls to determine whether a unique pattern of inflammation and particulate matter deposition, compatible with WTC dust, was present. Control subjects were 12 Tel-Aviv, Israel, firefighters (TA-FFs) and 8 Israeli healthcare workers who were not exposed to WTC dust. All controls volunteered for this study, had never smoked, and did not have respiratory illness. IS was processed by conventional methods. Retrieved cells were differentially counted, and metalloproteinase-9 (MMP-9), particle size distribution (PSD), and mineral composition were measured. Differential cell counts of FDNY-FF IS differed from those of health care worker controls (p < 0.05) but not from those of TA-FFs. Percentages of neutrophils and eosinophils increased with greater intensity of WTC exposure (< 10 workdays or greater than or equal to 10 workdays; neutrophils p = 0.046; eosinophils p = 0.038). MMP-9 levels positively correlated to neutrophil counts (p = 0.002; r = 0.449). Particles were larger and more irregularly shaped in FDNY-FFs (1-50 microm; zinc, mercury, gold, tin, silver) than in TA-FFs (1-10 microm; silica, clays). PSD was similar to that of WTC dust samples. In conclusion, IS from highly exposed FDNY-FFs demonstrated inflammation, PSD, and particle composition that was different from nonexposed controls and consistent with WTC dust exposure.

Figure 1. Correlation between concentrations of Ln MMP-9 and the percentage of neutrophils (A) and the percentage of macrophages (B) in induced sputum from all samples (n = 56). Values are expressed as the percentage of 200 cells as described in “Methods.”

Figure 2. Size and shape of four different particles found in an FDNY-FF specimen. Images (A and C) and shape of particles analyzed by a Cis-100 analyzer. Images (B and D) and shape of particles analyzed by X-ray spectrum. See “Methods” for details.

Figure 3. Comparison of the size distribution of particles between IS samples (n = 39) from FDNY-FFs and the settled material collected on Cortlandt Street, one block east of the WTC 7 days after the WTC collapse. Measurements were performed as described in “Methods.”

Figure 4. Intracellular phagocytized particles in a Giemsa-stained cytospin preparation from the IS sample of an FDNY-FF exposed to WTC dust. (A) Image showing a single macrophage with intracellular particles and two adjacent lymphocytes. (B) Image showing a mixed cell population with macrophages and intracellular particles. Light microscopy; magnification, ×100.

Figure 5. X-ray spectra of representative particles identified as Cu and Hg and Ag (A) and Zn (B) in FDNY-FF sample 35.