October 19, 2010, 10:58 AM — In 1995, the subway system in Tokyo was the target of a domestic terrorism attack involving a potent gas called sarin, a chemical weapon that can cause neurological damage and even death. In five coordinated incidents, members of a radical-religious group known as Aum Shinrikyo released the sarin gas on five trains in the Tokyo subway system. The attack killed 12 commuters, seriously injured 54 and affected 980 more who experienced some health effect. The lesson learned in the tragedy was that chemical agents have the potential do widespread damage -- and a subway system provides an ideal environment for dangerous gas to travel fast.
See pictures from the DHS test in our slideshow: Images from a homeland security experiment
A terrorist attack on a U.S. subway system using biological agents is an ongoing concern for the U.S. Department of Homeland Security. Chemical weapons, particularly airborne contaminants, are usually invisible and not easily detected until after they have been released and have caused significant damage. As part of an effort to enhance emergency response and security in the country's transportation systems, DHS officials have been conducting a scientific study of airflow throughout the underground portion of the subway in both Boston and Washington.
While Washington D.C. has the newest subway system in America, Boston's MBTA subway system is the oldest of its kind in the country (Related: MBTA flaw disclosure: The students speak up). Inside the "T," as it is known to locals, a scientific team placed equipment - electronic monitoring devices used to gather data on the behavior of airborne contaminants if they were to be released into the subway. The research was conducted in two stages; the first portion was conducted in December 2009, the second in August 2010.
"The movement of airborne contaminants can be affected by differences in temperature and humidity, so a comprehensive study requires gathering data in both winter and summer months," said program manager Teresa Lustig. "In addition to comparing the effects of seasonal conditions, a second phase of the study also allows us to test the effectiveness of some of the proposed countermeasure and response strategies derived from analysis of the December tests."