Satellites that stay over the same point could help provide faster and more accurate air quality alerts and save billions in health care costs per year, according to a study by GW’s Air, Climate and Health Lab.

Researchers from GW, the National Oceanic and Atmospheric Administration and the Environmental Protection Agency found that surveys of the same region taken from geostationary satellites — which stay in the same place relative to the surface of the Earth — provided more frequent air quality alerts than polar-orbiting satellites, which orbit around the poles of Earth. Susan Anenberg, the leader of the Air, Climate and Health Lab, said geostationary satellites better inform the public about poor air quality days, allowing people to reduce their exposure and avoid future health consequences like cardiovascular disease.

Anenberg, the chair of the Environmental and Occupational Health Department, said the study’s authors sought to demonstrate the public health value of geostationary satellites for air pollution monitoring before the tentative NOAA satellite mission GeoXO. The NOAA mission, planned for the 2030s, would place more geostationary satellites in orbit over the Western Hemisphere to improve weather, air pollution and climate change monitoring.

“The paper shows that if we had satellites that were geostationary, that hovered over the United States as the Earth spins and therefore were able to take measurements of the earth’s atmosphere every hour throughout the daylight hours,” Anenberg said. “If we had that capability, we would be able to provide better information to people to protect themselves on poor air quality days.”

Satellites measure air pollution in the atmosphere by observing the quantity of light that reaches the surface of the Earth and the amount that is reflected off of particles in the air. In contrast, ground monitoring systems chemically monitor air composition, drawing in air and measuring the concentration of particles.

Satellite and ground air pollution monitors measure levels of particulate matter in the atmosphere with a maximum diameter of 2.5 micrometers, or PM 2.5. Researchers have linked exposure to premature death, birth defects, lung cancer and more.

The researchers analyzed several air pollution data sets from ground sensors and polar and geostationary satellites to calculate the number of person-alerts, or the number of days under an air quality alert multiplied by the number of people in the affected region. They found geostationary satellites would generate 60 percent more person-alerts than polar satellites.

Researchers determined roughly 1,200 more people per year would avoid premature death by factoring in estimates of how people reduce their exposure to pollutants based on these alerts. The researchers combined the estimate with existing data on the costs of asthma and pollution-related hospital visits and showed that the satellites could reduce $13 billion per year nationally.

Anenberg said she hopes better air quality data collected from satellites will help individuals and policymakers make better health decisions like staying indoors and using air filters on poor air quality days or approving projects like GeoXO to improve air quality data.

“There had been a recent review done by the U.S. Environmental Protection Agency that shows that people do undertake behavior change when they know it’s a poor air quality day,” Anenberg said. “There’s a variety of things that people do. In some cases, they’re staying indoors and running their air conditioning with a filtration device. In other cases, they are just wearing masks when they’re outdoors.”

Experts in satellite air pollution monitoring said this study will contribute to the burgeoning literature on the subject, helping convince policymakers of the usefulness of satellite monitoring.

Jenny Bratburd, a researcher for NASA, said geostationary satellites could detect changes in fine particle pollution faster than polar orbiting ones, which would in turn provide more timely air quality alerts.

“People want information about when it’s near and when they should take action to protect themselves or even just the regular air pollution from say, like traffic, you know, that changes throughout the day,” Bratburd said. “So when you have geostationary satellites, you have a better ability to see those changes throughout the day.”

Yang Liu, a professor and the chair of Environmental Health at Emory University, said there needs to be more studies demonstrating the public health benefits of using satellites to monitor air quality, a relatively new technology, for policymakers.

“Remote sensing is very, very new. This level of modeling capabilities only became available probably for the past 10 years. Before that, we either don’t have the resolution, we don’t have the frequency or we simply don’t have the modeling tools to come up with accurate results,” Liu said.

Liu said the EPA uses ground monitoring instruments to assess air quality in accordance with the Clean Air Act of 1990. Though legally required by the act, the technology is limited by infrequent data collection and missing data for rural areas, which satellites help combat, he said.

“Two-thirds of the ground monitors only take samples once every three days, so that’s how you leave a big information gap in there. And again, because of its expensive operations, most of these monitors are only or mostly located in urban centers. We have 75 percent of U.S. counties without a single air quality mark,” Liu said.

Liu said emerging disasters that originate away from urban centers, like wildfires and dust storms, demonstrate the need for a method of detection without relying on costly ground monitors, which satellites could provide.

“That’s where I think remote sensing can provide the biggest value,” Liu said. “By nature, it has comprehensive spatial coverage.”