EVERY TIME A TRAIN RACES THROUGH A SUBWAY
station in New York City, it sends a blast of air rolling through the 100-year-old system’s enormous network of tunnels. That blast kicks up and carries a whole slew of particles. They swirl and float and fly. And then they deposit themselves all over everything. Over five days this past May, the US Department of Homeland Security (DHS) conducted a massive test to find out what would happen if those particles weren’t just harmless pieces of dust or lint: What if they were something more dangerous, like anthrax? How would they move around and where, exactly, would they land?“New York is the largest subway system in the US and one of the largest in the world. They have over 5.5 million people on average on weekdays. It’s an enormous system, very complex, and it’s high on the target list of our adversaries,” says the project’s lead scientist Don Bansleben, a programme manager at the DHS Science and Technology Directorate.
The trains, he says, act like pistons when they move through the system. “They push material in front of themselves and pull material from outdoors behind them. The material basically goes everywhere. And during rush hours there are 4,000 subway cars in the system.”
Experimenters spray an aerosol release of particles on the 4/5/6 train line platform at New York City’s Grand Central Station.
For the test, 115 people from the DHS and several partners (including the US Environmental Protection Agency and seven American laboratories) set themselves up at 55 train stations (including two in Queens, one in Brooklyn, and one in New Jersey) and inside 10 different trains. Using air compressors, they shot one gram of a harmless, aerosolized, analogue of anthrax into the air every minute for 20 minutes. The subway system was running as normal the whole time.
With subways’ low security threshold and high passenger count, they’re especially vulnerable spots for a bioweapon attack. Similar tests that studied airflow within the NYC subways have been done before—those focused on gases, and how air flows from outdoors to indoors via station entrances. But this study is the first large-scale one that focuses on particles, which behave differently than gases, and which also include different kinds of bioweapons that aren’t gaseous, like anthrax.
It’s an enormous system, very complex, and it’s high on the target list of our adversaries.
The anthrax analogue, called DNATrax, was developed by one of those DHS partners, Lawrence Livermore National Laboratory, located about 70km from San Francisco. DNATrax is a material that comes from wheat and corn starch and has been used in the past to help the US Centers for Disease Control and Prevention (CDC) track food poisoning outbreaks. For this test they made two sets of particles—one at 2 microns and one at 5 microns (anthrax particles are about 10 microns). They then attached a series of very short chains of DNA onto each particle. The DNA, which is derived from a microscopic deep sea creature that’s clearly not often found in the subway, acts as a tiny barcode. – READ MORE
