When scientists turned on the instrument on a new satellite this summer, they were able to take a sneak peek at what will soon become the first continuous record of air pollution in the country. The satellite will remain stationed above North America, providing scientists with hourly updates on air pollution throughout the day. Researchers recently released their initial images, which highlight changes in nitrogen dioxide pollution across the United States within a 24-hour period.
Xiong Liu, the deputy mission director and a physicist at the Center for Astrophysics associated with Harvard University and the Smithsonian Institution, expressed excitement at the instrument working as expected. The satellite instrument, known as TEMPO, will also be capable of measuring various other pollutants.
These images were captured during a summer marked by exceptionally poor air quality in the United States due to smoke from wildfires enveloping multiple cities and regions. However, even prior to this summer, the improvements in air quality that Americans have enjoyed since the implementation of the Clean Air Act in 1970 had started to level off.
Despite the progress in air pollution reduction over the years, Dr. Liu pointed out that “one-third of Americans are still living in unhealthy levels of air pollution.” Nitrogen dioxide, which is produced through fuel combustion and leads to the formation of other types of pollution through chemical reactions in the air, is prominently visible in the images. The gas concentration is higher around major cities and peaks during morning and evening rush hour traffic.
In addition to the satellite’s observations, scientists conducted extensive research throughout the country on foot and in research planes during July and August. The objective was to understand why air quality was no longer improving. Determining the primary sources of pollution on a nationwide scale has been challenging since pollutants can travel long distances through wind currents. The frequent updates from TEMPO are expected to revolutionize researchers’ ability to track air pollution from its origin.
Historically, car traffic has been a major contributor to air pollution, but tighter emission standards have resulted in reduced pollution from vehicles. At the same time, the relative significance of consumer products and materials emitting volatile organic compounds, such as paint and pesticides, has increased. These compounds react with nitrogen dioxide in the air to create harmful ground-level ozone, which remains persistently high in specific areas, particularly California and major metropolitan regions across the country. Ground-level ozone exacerbates or triggers respiratory conditions like asthma, bronchitis, and emphysema.
Another ongoing issue is fine particulate pollution, consisting of microscopic particles that can enter the bloodstream, leading to heart and lung diseases, strokes, and even premature death in severe cases. This pollution, also known as PM2.5, started increasing again around 2016 after years of decline. Last fall, a study indicated that more frequent and intense wildfires, resulting from climate change-induced hotter and drier conditions, were the primary cause of this resurgence. However, that research relied on an older satellite that provides daily measurements. TEMPO’s hourly data will provide a more comprehensive understanding of pollutant patterns.
TEMPO will offer high-resolution tracking of air pollution down to approximately four square miles. To complement the satellite’s data, coordinated field campaigns were conducted throughout this summer, including walks, drives, and flights. These efforts were designed to gather localized data and address the lack of coverage in certain neighborhoods within cities. Air pollution tends to be unevenly distributed within specific regions or cities.
For example, in New York City, researchers carried backpacks fitted with air quality sensors while walking around the city. These sensors collected air samples through long, thin tubes, resembling fishing rods, extending from the backpacks. One team member tracked the flight paths of NASA’s research aircraft to ensure coordination. The collected data sets will be compared later. The researchers covered various routes, including economically disadvantaged neighborhoods and areas with a higher percentage of residents of color. These regions often face disproportionate air pollution, but data collection is scarce.
The collected data, once analyzed in the coming months, will shed light on the link between climate change and air quality. The walks themselves highlighted this connection, with researchers enduring difficult conditions during the hottest parts of summer. Higher temperatures typically correspond to increased levels of ozone pollution. On the hottest sampling day, ozone readings surpassed the national standards set by the Environmental Protection Agency.
The general public can expect access to TEMPO’s data in spring 2024. However, more than 400 users, including state and federal agencies, have already signed up as “early adopters.” These users anticipate using TEMPO data for various purposes, such as studying the impact of air pollutants on children’s asthma symptoms or investigating the sources of high ozone pollution in specific states.
Dr. Yoshira Ornelas Van Horne, a TEMPO collaborator affiliated with Columbia University, hopes that the research conducted this summer will equip policymakers with the necessary information to address the lingering air quality issues in the nation. “We’re all in agreement that air pollution is bad,” Dr. Ornelas Van Horne stated.