A new study has revealed one of the most detailed pictures to date of long-term air pollution in Addis Ababa, after researchers analyzed data collected by 10 air-quality monitoring stations as part of NASA’s Multi-Angle Imager for Aerosols (MAIA) project. The data cover the period from 2022 to 2025, focusing on fine particulate matter no larger than 2.5 micrometers in diameter, known as PM2.5, and on black carbon produced by fires, diesel vehicles, and other combustion sources.
The study’s findings were published in ES&T: Air. The average PM2.5 concentration in Addis Ababa over the three years was 30 micrograms per cubic meter, more than three times the U.S. Environmental Protection Agency’s health-based annual standard. Sensor data also showed that average black-carbon levels in the Ethiopian capital were approximately four to nine times higher than levels measured in three U.S. urban areas monitored by the mission.
Variations Associated with Congestion and Seasons
The network did more than measure averages; it showed how pollution levels change throughout the day and across seasons. Increases during certain periods were associated with traffic during rush hours, while the sensors recorded elevated black carbon during two major holidays in Addis Ababa that involve lighting fires. The researchers were able to distinguish particles produced by those fires from those resulting from fossil-fuel combustion.
These measurements are particularly important because the Addis Ababa metropolitan area is home to nearly 6 million people, and the United Nations expects its population to exceed 10 million by 2050. The data also provide a baseline that can be used to track changes in air quality as the city continues to grow. In 2024, Ethiopia banned the import of vehicles with internal-combustion engines, while its cities began adding bicycle lanes and electric-vehicle infrastructure.
Why Does This News Matter?
Long-term, multisite measurements help identify PM2.5 sources more precisely, since the composition of pollution varies from city to city according to geography, traffic, industry, and other factors. This knowledge is important for health, as the research cites estimates from the State of Global Air 2025 report linking exposure to PM2.5 to approximately 4.9 million deaths worldwide each year.
Sina Hasheminassab, a co-author of the study and deputy principal investigator of the MAIA project at NASA’s Jet Propulsion Laboratory, said the measurements provide an important baseline for understanding how pollution changes spatially and over time in rapidly growing cities. The research indicates that combining ground-sensor data with future satellite observations could expand the ability to map particle types and compare them with health data.
The Space-Based Phase of the MAIA Project
NASA supports MAIA research in approximately 12 urban areas around the world, including Los Angeles, Atlanta, and Boston in the United States. The project includes a network of ground sensors and a space observatory carrying a camera developed by the Jet Propulsion Laboratory. The Italian Space Agency (ASI) is scheduled to launch the camera on one of its satellites no earlier than late 2027.
The camera was designed to detect different types of aerosols associated with PM2.5 by analyzing how they reflect light and capturing data from multiple angles. The MAIA project also includes public-health researchers on a space-mission team for the first time in NASA projects, with the aim of studying potential links between particle types and their health effects.