Novel approach to studying effects of inhalational exposure on lung function in civilians exposed to the World Trade Center disaster

Abstract

It is increasingly important to study the impact of environmental inhalation exposures on human health in natural or man-made disasters in civilian populations. The members of the World Trade Center Environmental Health Center (WTC EHC; WTC Survivors) had complex exposures to environmental disaster from the destruction of WTC towers and can serve to reveal the effects of WTC exposure on the entire spectrum of lung functions. We aimed to investigate the associations between complex WTC exposures and measures of spirometry and oscillometry in WTC Survivors and included 3605 patients enrolled between Oct 1, 2009 and Mar 31, 2018. We performed latent class analysis and identified five latent exposure groups. We applied linear and quantile regressions to estimate the exposure effects on the means and various quantiles of pre-bronchodilator (BD) % predicted forced expiratory volume in one second (FEV₁), forced vital capacity (FVC) and FEV₁/FVC ratio, as well as the resistance at an oscillating frequency of 5 Hz (R₅), frequency dependence of resistance R_5-20, and reactance area (AX). Compared with Group 5, which had low or unknown exposure and was treated as the reference group, Group 1, the local workers with both acute and chronic exposures, had a lower median of % predicted FVC (-3.6; 95% CI: -5.4, -1.7) and higher (more abnormal) measures of AX at 10th quantile (0.77 cmH₂O L^-1 s; 95% CI: 0.41, 1.13) and 25th quantile (0.80 cmH₂O L^-1 s; 95% CI: 0.41, 1.20). Results suggested heterogeneous exposures to the WTC disaster had differential effects on the distributions of lung functions in the WTC Survivors. These findings could provide insights for future investigation of environmental disaster exposures.

Figure 1

Patient flow diagram. ‘Acceptable’ means that the patients had all spirometry/oscillometry measures used in the analyses. LCA: latent class analysis.

Figure 2

Latent class analysis with five latent exposure groups. X-axis lists 15 exposure variables used in latent class analysis, and y-axis represents the percent of exposure categories in each latent group. The analysis was based on 3605 patients. Five latent exposure groups were identified: 1348 (37.4%) local workers with acute and chronic exposures (Group 1); 789 (21.9%) local residents with acute and chronic exposures (Group 2); 516 (14.3%) local workers with chronic exposures (Group 3); 247 (6.9%) local residents with unknown acute exposures but high home exposure risks (Group 4); and 705 (19.6%) mixed patients with unknown acute exposures and low home exposure risks (Group 5).

Figure 3

Quantiles of spirometry and oscillometry measures in five latent exposure groups. X-axis denotes five quantile levels, and y-axis is the quantile spirometry or oscillometry value within each group.

Figure 4

Estimates of absolute and relative effects on quantiles of % predicted FEV1, % predicted FVC, and FEV1/FVC ratio. X-axis denotes five quantile levels, and y-axis is the estimated absolute or relative difference on % predicted FEV1, % predicted FVC, and FEV1/FVC ratio. The colors represent four latent Group 1–4 vs. Group 5 (reference). The horizontal red dash line represents zero null effect. FEV1: pre- bronchodilator forced expiratory volume in one second. FVC: pre- bronchodilator forced vital capacity.

Figure 5

Estimates of absolute and relative effects on quantiles of R₅, R_5–20, and AX. X-axis denotes five quantile levels, and y-axis is the estimated absolute or relative difference on R₅, R_5–20, and AX. The colors represent four latent Group 1–4 vs. Group 5 (reference). The horizontal red dash line represents zero null effect. R₅: pre-bronchodilator total airway resistance to 5 Hz. R_5–20: pre-bronchodilator frequency dependence of resistance as difference between resistance at 5 Hz and 20 Hz. AX: pre-bronchodilator reactance curve area below zero.