Research aims to mitigate airborne chemical and biological threats | MIT News


When the air contains harmful materials, such as a virus or a toxic chemical, it is not always easy to detect this danger quickly. Whether spread maliciously or accidentally, how fast and far can dangerous plumes travel through a city? What could emergency managers do in response?

These are questions that scientists, public health officials and government agencies probed with a recent New York City airflow study. At 120 locations across the city’s five boroughs, a team led by MIT Lincoln Laboratory collected particles and safe test gases released earlier at subway stations and on the streets, tracking their journeys. The exercise measured the distance the materials traveled and their concentrations when they were detected.

The results should improve atmospheric dispersion models and, therefore, help emergency planners improve response protocols in the event of a real chemical or biological event.

The study was conducted as part of the Department of Homeland Security’s (DHS) Science and Technology (S&T) Directorate’s Urban Threat Dispersion Project. The project is largely driven by Lincoln Laboratory’s Counter Weapons of Mass Destruction (CWMD) systems group to improve homeland defenses against airborne threats. This exercise followed a similar, albeit much smaller, study in 2016 that focused primarily on the Manhattan subway system.

“The idea was to examine how particles and gases move in urban environments, starting with a focus on subways,” says Mandeep Virdi, a researcher at CWMD Systems Group who helped lead both studies.

The particles and gases used in the study can be dispersed safely. The particles are primarily made up of the sugar maltodextrin and have been used in past public safety exercises. To allow researchers to track the particles, the particles are modified with small amounts of synthetic DNA which acts as a unique “barcode”. This barcode corresponds to the location from which the particle was released and the day of the release. When these particles are then collected and analyzed, researchers can find out exactly where they came from.

The lab team led the process of releasing the particles and collecting particle samples for analysis. A small sprayer is used to aerosolize particles in the air. As the particles move through the city, some are trapped in filters installed at the many scattered collection sites.

To make processes more efficient for this large study, the team built special filter heads that rotated through multiple filters, saving time spent revisiting a collection site. They also developed a system using NFC (near field communication) tags to simplify cataloging and tracking of samples and equipment via a mobile app.

The researchers are still processing the approximately 5,000 samples that were collected during the five-day measurement campaign. The data will feed into existing particle dispersion models to improve simulations. One of these models, from Argonne National Laboratory, focuses on subway environments, and another model from Los Alamos National Laboratory simulates aerial urban environments, taking into account buildings and airflows from urban canyons.

Together, these models can show how a plume would move from the subway to the streets, for example. This information will allow New York City emergency officials to develop more informed response strategies, as they did following the 2016 Subway Study.

“The big question has always been, if there is a release and law enforcement can detect it in time, what do you actually do? Do you shut down the subway system? What can you do to mitigate these effects? Knowing that’s the end goal,” says Virdi.

A new program, called Chemical and Biological Defense Testbed, has just started to delve into these questions. Trina Vian of Lincoln Laboratory leads this program, also funded by S&T.

“Now that we know more about how materials are transported in the metro, this test bed examines ways to mitigate this transport without regret,” says Vian.

According to Vian, emergency officials have little option but to evacuate the area when a biological or chemical sensor is triggered. Yet current sensors tend to have high false alarm rates, especially in dirty environments. “You really can’t afford to make that evacuation call by mistake. Not only are you undermining people’s trust in the system, but also people can get hurt, and it can actually be a situation non-threatening.”

The objective of this testbed is to develop architectures and technologies that could enable a range of appropriate response activities. For example, the team will look for ways to restrict or filter airflow on site, without disrupting traffic, while responders validate an alarm. They will also test the performance of new chemical and biological sensor technologies.

Both Vian and Virdi stress the importance of collaboration in carrying out these large-scale studies and in tackling the problem of aerial hazards in general. The testbed program already benefits from the use of equipment provided by the CWMD Alliance, a partnership between DHS and the Joint Program Executive Office for Chemical, Biological, Radiological, and Nuclear Defense.

A team of nearly 175 people worked together on the air traffic exercise, covering the Metropolitan Transportation Authority, New York City Transit, New York City Police Department, Port Authority of New York and New Jersey, New Jersey Transit, New York City Department of Environmental Protection, New York City Department of Health and Mental Hygiene, National Guard Weapons of Mass Destruction Civilian Support Teams, Environmental Protection Agency and the Department of Energy’s National Laboratories, in addition to S&T and Lincoln Laboratories.

“It was really about teamwork,” recalls Virdi. “Programs like this are the reason I came to Lincoln Laboratory. Seeing how science is applied in a way that has real, actionable results and how much agencies appreciate what we do has been rewarding. It’s exciting to see your program come to fruition, especially one as intense as this.”


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