HAZARDOUS DUSTWhen the Dust Settles: Researchers Measure How Everyday Activity Spreads Hazardous Dust

By Marguerite Huber

Argonne researchers study the movement of dust particles from concrete surfaces during a simulated radiological contamination scenario, measuring how pedestrians and moving cars affect the spread of the particles.

Focusing on Safety: Why Accurate Particle Resuspension Estimates Matter
The resuspension of hazardous particles from the ground poses significant risks during chemical, radiological and biological contamination scenarios. Once the particles are kicked back up into the air, they can be inhaled. It raises the risk of exposure and complicates clean-up efforts.

Accurate modeling of resuspension helps develop contamination control strategies, guides emergency response and keeps people safe.

Older computer models underestimate the number of particles picked up into the air due to people and car activity. The models do not accurately predict resuspension factors. A resuspension factor is the amount of dangerous material in the air compared to the amount on the ground.

“We started to recognize that the radiation exposure models didn’t handle the dust that is thrown back up in the air very well,” said Mike Kaminski, Argonne senior nuclear chemical engineer and co-author of the paper. ​“There wasn’t any guidance on how to run that part of the model correctly, so we started looking into it.”

Putting it to the Test: Four Experimental Scenarios
To fill these gaps, the researchers conducted first-of-a-kind field experiments. They measured resuspension factors for activities that would likely happen during an emergency response.

“This is the only study that has quantitatively measured dust on concrete in this way,” Kaminski said. ​“Almost all of the data we have was collected from nuclear weapon detonation experiments in the desert early on during the Cold War and within uranium and plutonium nuclear facilities.”

The four scenarios were walking, marching, vacuuming and driving a vehicle. All experiments used Arizona Test Dust (ATD), which acts like contaminated environmental dust. Particle detectors measured how much dust was kicked up.

To replicate how people move, such as pedestrians or first responders, the researchers set up a long tent and walked and marched through the dust. Marching was included because it simulates the fast movements of emergency workers or an evacuation scenario.

The data showed that casual walking produced low resuspension factors, which match the results of earlier studies. Marching significantly increased resuspension.

The vacuuming experiments simulated a street sweeper or someone vacuuming at home. Vacuuming mainly resuspended smaller particles.

For the vehicle experiment, the team used a patch of road on Argonne’s campus. They spread ATD on the road and drove over it at different speeds with a sport utility vehicle (SUV). They measured both when the tires passed over the dust and when the bottom of the vehicle passed over it.

The vehicle tests showed that driving an SUV over dusted pavement produced substantial resuspension, especially larger particles.

Filling the Gap: How the Data Will Improve Emergency Response
Few have studied how people and vehicles affect resuspension factors.

“Previous studies on people’s movement exclusively focused on indoor activity and surfaces such as carpeting and hardwood flooring. Vehicle resuspension studies were looking primarily at everyday air quality,” Kaminski said.

Modelers could not accurately assess risks and help make informed decisions on emergency response safety with the data available. This study fills the gap.

The results show that resuspension during emergency operations is significantly higher than many models had predicted. Argonne’s data now supplies previously unknown resuspension rates to experts around the world.

This new data will help improve many parts of emergency response. It will help inform contamination control and improve decisions on protective gear and emergency response strategies, such as evacuation or shelter-in-place protocols. Now when emergency crews prepare for a radiological event, not only will they have the tools, but they will also have the accurate resuspension data they need to keep responders and the public safe.

Marguerite Huber is a science communicator at Argonne National Laboratory covering nuclear technologies and national security. The article was originally posted to the website of Argonne National Laboratory.