University of Texas at Dallas researchers have found a connection between Texas air quality and the severity of COVID-19 in certain Lone Star counties.
The researchers are taking advantage of satellites that orbit Earth every day, collecting information about our planet. Several of these satellites monitor the air around us. During the global outbreak of COVID-19, a disease that attacks the lungs, understanding the air we breathe may be crucial, according to the researchers.
Understanding air quality may help predict the severity of COVID-19 outbreaks over large swaths of Texas, the researchers found. Their work, recently presented at an international conference for computer scientists, was funded as part of a larger effort by NASA to encourage scientists to use the government agency’s satellite data to study the pandemic.
The UT-Dallas team looked at how well three aspects of Texas air might serve as predictors of COVID-19 severity in a given county: temperature, relative humidity and the amount of tiny particles, or aerosols, in the air.
They combined satellite air-quality data with COVID-19 hospitalization rates and fed that data into a complex computer program relying on geometric deep learning techniques, in collaboration with scientists at NASA. They found that relative humidity and aerosol concentration largely improved predictions of hospitalization rates across Texas in 2020, including Dallas County. Air temperature showed little to no connection with COVID-19 severity.
For the study, the research team used temperature and relative humidity observations provided by NASA’s Aqua satellite, while aerosol concentration measurements were provided by the agency’s Terra satellite.
These satellites only examine Texas a couple of times each week, making it tough to do a county-level assessment of air quality and COVID-19. As a workaround, the scientists averaged these satellite measurements over the past 20 years to create more of a climatological image of Texas air.
Aerosols — any microscopic particles that get suspended in the air — were a prime choice for the study because they are frequently connected to air pollution (though they can also be natural, like mist and dust).
The air pollutants we emit, such as from our cars, “create a lot of chemical reactions in the atmosphere and produce aerosols. That has an impact on us,” said Ignacio Segovia-Dominguez, a computer scientist at UT-Dallas and lead author of the study.
There has already been reason to believe that these pollutants may worsen COVID-19 symptoms.
“We know that when air quality is poor here in North Texas, we see more emergency department visits for asthma,” said Dr. John Carlo, a public health physician in Dallas and a member of the Texas Medical Association COVID-19 Task Force.
“We also know that asthma is one of the conditions that is known to cause more likelihood of coronavirus severity,” said Carlo, who was not involved with the study. “You have two interrelationships. But can you make the bridge from air quality to COVID-19 severity? I don’t know the answer to that. It’s an important question to be asking.”
Meanwhile, relative humidity more likely affects how well the coronavirus can survive.
But understanding exactly why humidity and COVID-19 severity are linked requires much more work. While the flu virus thrives in less humid environments, the novel coronavirus may behave differently, said Carlo. At this point, scientists just aren’t sure. “That is very complex and very interesting science that I think we’re going to learn a lot more from. We are very early on in our understanding of that,” he said.
While the recent study further demonstrates air quality’s direct tie to COVID-19, its design isn’t perfect. To get aerosol concentration, NASA’s satellite measures how much sunlight reflected by Earth gets scattered and blocked by tiny particulates — like the cloudy haze over a polluted city.
This translates to a measurement called “aerosol optical depth” or AOD, which is proportional to aerosol concentration. But the satellites are hundreds of miles above us. Thus, their measurements capture all of the aerosols in between, leading, in some Texas counties, to high AOD values that have little to do with pollution.
For example, measurements in Texas’ “coastal areas capture aerosols that are mostly in the upper layer, not the ground,” said Kyo Lee, an atmospheric scientist at NASA’s Jet Propulsion Laboratory and a co-author of the study. In those cases, “it doesn’t really worsen air quality on the ground.”
“That necessitates a follow-up study,” he said. “We can check the air quality measurements from ground stations and compare this with the aerosol optical depth map” to tease apart which parts of the map indicate poor air quality rather than a plume of particulates miles above us.
NASA is interested in more studies that use their atmospheric observations to probe public health problems, particularly as the frequency of pandemics is projected to increase.
“When people hear about NASA, they think about the Mars rover touching down on the surface of Mars or sending astronauts to an international space station,” said Lee. But with the COVID-19 pandemic, the government agency is encouraging more scientists to ask, “How can NASA data benefit society and people living on Earth?” said Lee. “We are also part of the Earth system. That aligns well with NASA’s overarching goal.”
Jordan Wilkerson is a science writer with a Ph.D. in atmospheric chemistry from Harvard University.
