World Trade Center (WTC)-exposed rescue/recovery workers endured massive respiratory insult from inhalation of particulate matter and gases, resulting in respiratory symptoms, loss of lung function, and, for many, bronchial hyperreactivity (BHR). The persistence of respiratory symptoms and lung function abnormalities has been well-documented, while persistence of BHR has not been investigated.
173 WTC-exposed firefighters with bronchial reactivity measured within 2 years after 9/11/2001 (9/11), (baseline methacholine challenge test [MCT]), were re-evaluated in 2013-2014 (follow-up-MCT). FEV1 measurements were obtained from the late pre-9/11, early post-9/11 and late post-9/11 periods. Respiratory symptoms and corticosteroid treatment were recorded.
Bronchial reactivity remained stable (within 1 doubling dilution) for most (n=101, 58%). 16 of 28 (57%) with BHR (PC20<8mg/ml) at baseline had BHR at follow up, and an additional 27 of the 145 (19%) without BHR at baseline had BHR at follow-up. In multivariable models, we found that BHR baseline was strongly associated with BHR follow-up (OR=6.46) and that BHR at follow-up was associated with an estimated 15.4 ml/year greater FEV1 decline than experienced by those without BHR at follow-up. Annual FEV1 decline was moderated by corticosteroid use.
Persistent BHR and its deleterious influence on lung function suggest a role for airway inflammation in perpetuation of WTC-associated airway disease. In future massive occupational exposure to inorganic dust/gases, we recommend early and serial pulmonary function testing, including measurements of bronchial reactivity, when possible, and inhaled corticosteroid therapy for those with symptoms or pulmonary function tests consistent with airway disease.