ACUTE EFFECTS OF NITROGEN-DIOXIDE AFTER ACCIDENTAL RELEASE

Objectives. Following an accidental release of nitrogen dioxide from a railroad tank car containing nitrous tetroxide, the authors undertook a study of the health effects of the release, measuring the associati on between acute low level exposure and pulmonary symptoms. Methods. T he authors reviewed the records of three emergency departments, survey ed 80 emergency department patients, 552 community residents, 21 chemi cal plant workers, and 29 emergency workers, and conducted a case-cont rol study. Pulmonary case status was defined as having an objective pu lmonary finding noted on the emergency department record, reporting th at the onset of symptoms was subsequent to the release, and being with in the city limits at the time of the release. Self-reported case stat us was: defined as reporting one or more symptoms consistent with expo sure;to nitrogen dioxide in the week after the release and having been within the city limits at the time of the release. Control subjects w ere survey respondents who reported no symptoms in the week after the release and had been within the city limits at the time of the release . Chemical exposure was characterized by proximity to, direction from, and being outdoors within one hour after the release, Duration oi pot ential exposure was not measured. Logistic regression was used to esti mate odds ratios and 95% confidence intervals for symptoms by adjusted for age, sex, smoking, and monary conditions. Results, Local emergenc y department visits increased fivefold in the week alter the release. The most common complaints recorded in a systematic sample of 528 visi ts in the first 30 hours after the release were headache (31%), burnin g eyes (30%), and sore throat (24%). Objective pulmonary findings were recorded for 41 (5%) patients in the week before and 165 (4%) in the week after the release. The odds of being a pulmonary case increased b y 40% for each quarter-mile increment in proximity to the release (odd s ratio [OR] 1.4; 95% confidence interval [CI] 1.1,1.7), while the odd s of being a self-reported case increased by 20% for each quarter-mile increment in proximity (OR 1.2, 95% CI 1.1,1.4). People who met the p ulmonary case definition were 2.5 times (Ci 1.3,4.8) more likely than control subjects to have been outdoors and 6.4 times (CI 3.2, 12.6) mo re likely to report a preexisting pulmonary condition. Self-reported c ases were 2.6 times (95% CI 1.8,3,8) more likely than control subjects to have been outdoors and 1.9 times (95% Ci 1.1,3.1) more likely to r eport a preexisting pulmonary condition. Conclusions, Emergency depart ment visits increased fivefold, but serious acute health effects were uncommon. People who met the pulmonary case definition were six times more likely to report pulmonary symptoms than those without preexistin g conditions. This study was not designed to determine any potential l ong-term effects of exposure.