A fire at the Doral waste-to-energy plant, which has been burning for a week and continues to send smoke into the air, raises questions about how to accurately assess air quality and its impact on the environment and human health.
Residents in the area are being told to stay indoors and keep windows closed in their homes and cars as they drive near the facility.
Faculty members at the University of Miami’s interdisciplinary Center for Aerosol, Science and Technology (CAST), which brings together experts from the Department of Chemical, Environmental, and Materials Engineering in the College of Engineering; the Rosenstiel School of Marine, Atmospheric, and Earth Sciences; and the Miller School of Medicine, share their insights about how air quality may be measured and how public health may be preserved in an incident like this.
While CAST students and faculty members regularly work with public and private groups to design studies and perform research on such events, no formal study has been undertaken yet by CAST researchers on the Doral fire.
Analyzing what you can’t see
Based solely on the information available to the general public about the Doral waste-to-energy plant fire, Chang-Yu Wu, professor and chair of the Department of Chemical, Environmental and Materials Engineering, said that “since it was an explosion and fire, the risk likely comes from the combustion products, such as soot—evidenced by the dark smoke—as well as some common hazardous pollutants.”
To determine the composition of the smoke, a variety of instruments may be used.
“CAST researchers have state-of-the-art instrumentation for aerosol measurements,” said Pratim Biswas, dean of the College of Engineering and a recognized pioneer in the field of aerosol science.
Those instruments include scanning mobility particle sizers, which are a type of spectrometer that measures particle number distribution by sizing particles in the air based on their electrical mobility diameter, as well as light scattering-based optical devices to determine the concentrations of the particles.
“We have a range of filter samplers that can collect the particles and then do a chemical composition determination,” Biswas said. “The size dependent chemical composition of the resultant combustion aerosol is a determinant of the eventual detrimental health effect. While these instruments are very precise, they are bulky and more viable for use in a research lab.”
But CAST researchers are nimble and may use available wearable and portable sensors to detect airborne particles in the field. This technology was useful in a study on protecting firefighters as well as monitoring the spread of COVID-19 and mapping ambient air quality, according to Biswas, who also serves as director of the College of Engineering’s Aerosol and Air Quality Research Laboratory.
Wu, whose research demonstrated aerosol transmission of SARS-CoV-2 and played a critical role in reshaping Centers of Disease Control and Prevention and the World Health Organization’s COVID-19 guidelines to protect public health, said “air sampling and modeling can also be used to ensure [a pollutant] is no longer in the air. If it’s still there, both tools can help determine if the concentration is going down and how fast. That information will allow policy makers to set better strategies to protect residents and properties (animals, etc.) from adverse exposure.”
Protecting the public health
While it’s not clear what environmentally protective equipment was in place at the time of the Doral fire, Biswas said, generally in such a facility “there should be gas and vapor trapping units. Furthermore, monitoring of combustion gases should be carried out,” he added. “Flow paths to exhaust the gas and use for co-generation by burning it in an engineered system should be designed.”
For individuals who live and work around the site of the fire, several protective measures may be in order, CAST faculty members said. First, people should avoid or at least minimize their time in the area.
“If time has to be spent in the vicinity where the air pollutant concentrations are high, it is best to wear masks similar to those used to prevent the spread of COVID-19 for protection against combustion aerosols,” Biswas said. “There are a range of masks with varying efficiencies, and some of the more protective ones are N-95 filters. If there are gaseous pollutants, it is best to use respirators as filter masks will only trap the particles.”
Wu also suggests that many HVAC systems include filters, which, depending on the grade and type, may remove the pollutants and make staying indoors safe.
“This principle is similar to advice given to the western states with wildfires in the past few summers or agricultural fires during harvest season,” he said.
Yang Wang, assistant professor in the Department of Chemical, Environmental, and Materials Engineering, noted that portable, indoor air purifiers may be useful for those without HVAC.
“During the COVID-19 pandemic, people made inexpensive, DIY air purifiers such as the ‘Corsi-Rosenthal Box,’” which is effective in filtering out airborne particles, he said. An activated carbon filter may be necessary to eliminate any odors from volatile organic vapors in the air, he added.
The incident in Doral highlights the importance of CAST’s work to assess and mitigate potential danger due to airborne particles and aerosols.
