Respiratory symptoms and lung function 8-10 months after community exposure to chlorine gas: a public health intervention and cross-sectional analysis

We implemented a community based interventional health screening for individuals located within one mile of a 54 metric tons release of liquid chlorine following a 16 tanker car train derailment on 6 January, 2005 in Graniteville, South Carolina, USA. Public health intervention occurred 8-10 months after the event, and provided pulmonary function and mental health assessment by primary care providers. Its purpose was to evaluate those exposed to chlorine for evidence of ongoing impairment for medical referral and treatment. We report comparative analysis between self-report of respiratory symptoms via questionnaire and quantitative spirometry results.

Health assessments were obtained through respiratory symptom and exposure questionnaires, simple spirometry, and physical exam. Simple spirometry was used as the standard to identify continued breathing problems. Sensitivity, specificity, positive and negative predictive values were applied to evaluate the validity of the respiratory questionnaire. We also identified the direction of discrepancy between self-reported respiratory symptoms and spirometry measures. Generalized estimation equations determined prevalence ratios for abnormal spirometry based on the presence of participant persistent respiratory symptoms. Covariate adjustment was made for participant age, sex, race, smoking and educational status.

Two hundred fifty-nine people participated in the Graniteville health screening; 53 children (mean age = 11 years, range: <1-16), and 206 adults (mean age = 50 years, range: 18-89). Of these, 220 (85%) performed spirometry maneuvers of acceptable quality. Almost 67% (n = 147) displayed abnormal spirometry, while 50% (n = 110) reported persistent new-onset respiratory symptoms. Moreover, abnormal spirometry was seen in 65 participants (29%) who did not report any discernible breathing problems. This represented a net 16.8% underreporting of symptoms. Sensitivity and specificity of questionnaire self-report of symptoms were low at 55.8% and 61.6%, respectively. Persistent cough (41%) and shortness of breath (39%) were the most frequently reported respiratory symptoms.

Eight to ten months after acute chlorine exposure, the Graniteville health screening participants under-reported respiratory symptoms when compared to abnormal spirometry results. Sensitivity and specificity were low, and we determined that relying upon the self-report questionnaire was not adequate to objectively assess the lung health of our population following irritant gas exposure.