The pulmonary sequelae associated with accidental inhalation of chlorine gas

Twenty previously healthy individuals were accidentally exposed to high concentrations of chlorine gas in 1975. Pulmonary function tests were performed on these individuals on several occasions over the next 12 years. On average, each subject was followed up for 8.5 years and 13 of the 20 exposed persons were tested 12 years following the exposure. Pulmonary function tests obtained one day following the accident were most notable for the high prevalence of airflow obstruction and air trapping. Over the ensuing years, the airflow obstruction persisted; however, the high prevalence of air trapping resolved. Of note, the prevalence of a low residual volume consistently increased during the follow-up period (p less than 0.001) and at year 12, 67 percent of those tested had residual volumes below 80 percent of their predicted value. We also found that five of 13 subjects tested at year 12 had an increase in airway reactivity (greater than 15 percent decline in FEV1) to inhaled methacholine. Those individuals with reactive airways were older (p = 0.004) and had more marked airflow obstruction (p = 0.03) and air trapping (p = 0.03) immediately following the exposure. These data suggest that exposure to high concentrations of chlorine gas may result in long-term pulmonary complications that are characterized by a reduced residual volume. Unfortunately, these data preclude us from determining whether the chlorine exposure led to the development of airway reactivity or the presence of reactive airways accounted for the air trapping that was observed following the exposure to chlorine gas.