DHS Hoping To Understand, Limit Impact Of Chemical, Biological Agent Release In Subway Systems

Millions of commuters in America rely on subway systems to travel. This makes mass transit an attractive target for terrorists, as proven by the Tokyo subway terrorist attack in 1995 in which sarin was released on several train cars, killing 12 and injuring thousands.

To limit the impact of similar attacks and determine the best actions to take during a chemical or biological agent release, scientists are investigating how these contaminants would travel through a subway system’s underground tunnel network.

The Department of Homeland Security Science and Technology Directorate is studying the way gasses and particulates behave by conducting a series of airflow tests in subway systems.

Boston’s Massachusetts Bay Transportation Authority subway was host to the latest experiment in December. DHS S&T conducted controlled releases of harmless substances – sulfur hexafluoride and perfluorocarbon  gas, as well as sodium fluorescein particles – to simulate a chemical or biological agent’s movement, according to Teresa Lustig, the program manager leading the study for DHS S&T’s Chemical and Biological Division. Scientists released the gases and particles into the MBTA subway system during a seven-day test.

The data from the testing will help researchers test and refine models that predict how chemical and biological agents spread through subway systems as well as how they escape into the streets above.

The results could help first responders act more effectively to evacuate subway stations, adjust ventilation, and modify train movements to save lives after an attack or accidental release of hazardous substances.

“We need to better understand airflow and how that affects transport so that we can then better develop technologies to support [chemical and biological] detection, as well as planning and response strategies, in case there is a terrorist attack,” Lustig said.

Researchers from Argonne National Laboratory, Lawrence Berkeley National Laboratory, ICx Technologies, the Defense Science and Technology Laboratory of the United Kingdom, and Chemistry Centre of Australia tracked the tracer gases and particles in the MBTA system. About 40 gas samplers and more than 25 particle counters placed throughout the underground system monitored the concentration of the tracer gases and particles DHS S&T used to simulate a chemical or biological attack, said David Brown, a research scientist from Argonne National Laboratory, which designed and led the test.

Preliminary findings from the December 2009 tests showed that chemicals and biological agents can spread quickly through a subway system, according to Lustig. There are differences in how these materials transport in the underground subway environment. The particles simulating biological agents tend to deposit on surfaces and were less likely to round corners than gases.

MBTA Transit Police plan to use the airflow test’s findings to enhance strategic response and preparedness, said Deputy Chief Lewis Best. Understanding how substances travel through the subway’s five lines will help the MBTA Transit Police fine tune evacuation plans to protect the subway’s more than 1.3 million daily riders. Other transit systems will be able to use the airflow models researchers create from the data to draft their own preparedness plans.

The data also will help scientists design more effective chemical detectors to alert police quickly to any spill or attack.

“It’s obviously going to help scientists and researchers develop next-generation detection systems,” Best said.

Researchers plan to combine the MBTA airflow test data with findings from similar tests conducted in the Washington D.C. Metro system in December 2007 and August 2008. Lustig explained that the tests will allow scientists to see if there is a difference between the way chemicals travel through an older subway system, like Boston, and a newer one, like the Washington D.C. Metro.

Scientists plan to return to Boston to repeat the testing in August  to determine if there is any seasonal variation in airflow. The researchers will complete a final report on the subway tests in late 2010 or early 2011, Brown said. The data will not be made public for security reasons, but it will be provided to the Transportation Security Administration and first responders, according to Lustig.

Researchers had developed models for subway airflow, but these experiments were the first to examine whether those predictions held true during a system-wide, rush-hour test, according to Brown. Previous models indicated chemicals would spread quickly through a subway system.

The MBTA and D.C. Metro tests will help first responders judge how serious a threat chemical and biological releases are and determine how best to prepare for them.

“They know these data are going to help them plan for not only terrorism-type events but accidental spills and fire and smoke events,” Brown said. “This type of data is very useful for them to gauge vulnerabilities in their system.”


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