NASA-funded air quality monitoring reveals how black carbon and PM2.5 pollution vary across Addis Ababa. The long-term monitoring network offers one of the most detailed views yet of soot pollution from fires, diesel vehicles and other combustion sources in Ethiopia’s capital. The findings show how air pollution changes by time of day and season, with notable increases during rush hours and holiday celebrations. The research could also provide valuable insights for cities worldwide, including those in the United States.
In a new paper published in ES&T: Aviation, scientists analyzed air quality data collected across Addis Ababa from 2022 through 2025. The data came from 10 monitoring sites deployed as part of NASA’s Multi-Angle Imager for Aerosols (MAIA) mission.
The study comes as Ethiopia takes steps to improve air quality and reduce transportation emissions. The country announced plans to become the world’s first to ban imports of internal-combustion-engine vehicles, while cities are expanding bicycle lanes and electric-vehicle infrastructure. MAIA’s measurements will establish an important baseline for tracking how air quality changes as Addis Ababa continues to grow and develop.
Researchers focused on fine particulate matter measuring 2.5 micrometers in diameter or smaller, known as PM2.5. The 2025 World Atmospheric State Report cited in the study estimates that PM2.5 exposure is associated with approximately 4.9 million deaths worldwide each year. Black carbon, one of the many components of PM2.5, is of particular concern because of its potential effects on human health and the climate.
The study found that Addis Ababa’s three-year average PM2.5 concentration was 30 micrograms per cubic meter—more than three times the U.S. Environmental Protection Agency’s annual health-based PM2.5 standard. MAIA ground-sensor data also showed that average black carbon concentrations in Addis Ababa were approximately four to nine times higher than levels measured in the three U.S. metropolitan areas monitored by the mission.
“To our knowledge, this is the first long-term, multisite study of continuous PM2.5 and black carbon measurements in Ethiopia,” said paper co-author Sheena Hasheminassab, MAIA deputy principal investigator at NASA’s Jet Propulsion Laboratory in Southern California. “Many rapidly growing cities have limited long-term air quality monitoring, so these measurements provide an important baseline for understanding how pollution changes over time and across urban areas.”
The sources and chemical composition of PM2.5 can differ significantly from one city to another, depending on factors such as geography, transportation and industry. Desert cities, for example, may experience elevated dust pollution, while communities near coal-fired power plants can have higher sulfate concentrations. In many regions, however, long-term ground-based air quality measurements remain limited.
NASA supports MAIA air pollution research in 12 metropolitan areas worldwide, including Los Angeles, Atlanta and Boston in the United States. The mission combines an operational ground-based sensor network with a space-based observatory. The JPL camera is planned for launch aboard an Italian Space Agency (ASI) satellite by the end of 2027.
The camera is designed to distinguish different types of PM2.5 aerosols by analyzing how they reflect light. This capability will allow MAIA to map particle concentrations and characteristics in each city included in the mission. Mounted on a gimbal, the camera collects observations from multiple angles using pioneering JPL technology that makes atmospheric particles more visible against the surface background. The data can provide information about particle size, shape and composition.
MAIA is NASA’s first mission to include public health researchers as members of a space mission team. These researchers will combine MAIA’s PM2.5 concentration maps with health data to investigate potential links between specific particle types and health outcomes. The research could improve scientific understanding of particulate pollution and support more effective air quality management.
“This paper shows how valuable air sensor data can be on its own, but combining sensor networks with satellite observations will change the game,” said lead author Kaian Schlipak, who worked on the study during an internship at JPL.
Tracking black carbon pollution in Addis Ababa
Approximately 6 million people live in the Addis Ababa metropolitan area, and the population is expected to surpass 10 million by 2050, according to United Nations projections.
“This is a cosmopolitan city with a large international community,” said Alaya Asfaw of Addis Ababa University, a co-author of the paper and the lead Ethiopian collaborator on the MAIA project. “Think of it as the African version of Brussels, the home of the European Union.”
“Even at night, when there is less traffic, burning charcoal and other fuels generates substantial emissions,” Asfaw said.
The MAIA sensor network detected elevated black carbon levels during two major holidays in Addis Ababa that included bonfires. The monitoring system also helped researchers distinguish particles produced by fires from those generated by fossil-fuel combustion. These findings show how detailed air quality measurements can help identify pollution sources and reveal how particulate matter changes across neighborhoods, seasons and times of day.
For more information about NASA’s MAIA mission and its air pollution research, please see the resources below.
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Source: www.nasa.gov