Chlorine Gas

The derailment

On January 6, 2005, a freight train carrying three tanker cars of chlorine was inadvertently switched onto an industrial spur, where it collided with a parked locomotive. The train derailed and one of the chlorine tankers was breached, releasing approximately 46 tons of chlorine immediately, and an additional 14 tons over the next three days until a patch could be applied. The incident occurred on the premises of a large textile mill, where approximately 180 employees were working, and in the center of a residential town of Granitveille, SC, with a population of 7,000.

Overall, 525 people were treated at emergency departments in South Carolina and Georgia, a total of 72 were hosptialized, and 8 died.

See Google News Timeline or News Archive of the disaster.

The Quick Response Program at the National Hazards Center at the University of Colorado supported an investigation of the disaster. The resulting article about evacuation behavior also offers additional details about the accident.


Chlorine is one of the most common toxic inhalants and is also among the most commonly manufactured and widely used chemicals in the United States. Much of the 13 to 14 million tons produced each year is transported by rail, often through densely populated areas, for use at tens of thousands of sites around the country. New federal regulations on the transport of rail cargo aim to avert a deliberate attack on a chlorine storage tank, which the Department of Homeland Security (DHS) included as 1 of its 15 National Planning Scenarios. If such an attack took place in an urban setting, an estimated 100,000 hospitalizations would occur. The intentional use of chlorine gas to cause widespread casualties has recently become a reality in Iraq, where there have been terrorist attacks using chlorine gas since January 2007.

The public health response

I was part of the team from CDC that went to South Carolina to help the South Carolina Department of Health and Environmental Control (SC DHEC) immediately begin documenting the health effects on area workers and residents.

We conducted a series of investigations which have been published in Public Health Reports and the American Journal of Emergency Medicine.

Rapid Assessment of Exposure to Chlorine Released from a Train Derailment and Resulting Health Impact  (Public Health Reports 2007; 122:784-792).

We performed a rapid assessment of the health impact to determine morbidity caused by the chlorine and evaluate the effect of this mass-casualty event on healthcare facilities. We gathered information on exposure, treatment received, and outcome through patient questionnaires and medical record review. The rapid investigation revealed significant morbidity and mortality associated with the expsoure, and highligthed the problem posed by self-transport of symptomatic people for medical care and the impact on healthcare facilities over a wide geographic area. This manuscript can be downloaded for free as a pdf from here.

Panel Classification of Self-Reported Exposure Histories: A Useful Exposure Index After a Mass-Casualty Event (Public Health Reports, 2007; 22;776-783)

Rapid epidemiological investigations of toxic exposures require estimates of individual exposure levels, but objective measures of exposure are often unavailable. We investigated whether the self-reported exposure histories we elicited from patients as part of the investigation could, when reviewed and classified by a panel of raters (who had no knowledge of the patient’s health effects), provide a useful exposure metric. We found that panel-assigned exposure ratings correlated well with health outcome, and may be useful for rapid epidemiologic investigations. The article is freely available as a pdf here.

Acute health effects after exposure to chlorine gas released after a train derailment (Am J Emerg Med 2009; 27:1-7).

Although occupational exposures and accidental releases of chlorine occur with some frequency, the typical clinical presentation and course of acute chlorine gas exposure in a large group of hospitalized persons has not been well described. The objective of this investigation was to characterize hospitalizations for chlorine inhalation injury resulting from this large-scale accidental release of chlorine gas in a community. The article (freely available as pdf here), provides information about the typical clinical presentation, treatment, and hospital course that occurred following this disaster, and is likely to result from future chlorine gas releases.