[영문]Objectives. After a train derailment released approximately 60 tons of chlorinefrom a ruptured tanker car, a multiagency team performed a rapid assessmentof the health impact to determine morbidity caused by the chlorine and evaluatethe effect of this mass-casualty event on health-care facilities.Methods. A case was defined as death or illness related to chlorine exposure.Investigators gathered information on exposure, treatment received,and outcome through patient questionnaires and medical record review. Anexposure severity rating was assigned to each patient based on description ofexposure, distance from derailment, and duration of exposure. A case involvingdeath or hospitalization ？3 nights was classified as a severe medical outcome.Logistic regression was used to examine factors associated with severe medicaloutcomes.Results. Nine people died, 72 were hospitalized in nine hospitals, and 525were examined as outpatients. Fifty-one people (8%) had a severe medicaloutcome. Of 263 emergency department visits within 24 hours of the incident,146 (56%) were in Augusta, Georgia; at least 95 patients arrived at facilities inprivately owned vehicles. Patients with moderate-to-extreme exposure weremore likely to experience a severe medical outcome (relative risk: 15.2; 95%confidence interval 4.8, 47.8) than those with a lower rating.Conclusions. The rapid investigation revealed significant morbidity and mortalityassociated with an accidental release of chlorine gas. Key findings thatshould be addressed during facility, community, state, and regional mass-casualtyplanning include self-transport of symptomatic people for medical care andimpact on health-care facilities over a wide geographic area.