NASA researchers have published one of the clearest long-term pictures yet of air pollution in Addis Ababa, Ethiopia. Measurements collected across the capital between 2022 and 2025 show how fine particulate matter changes by time of day, season and source, offering a detailed baseline for a city where long-running air-quality monitoring has been limited.
The findings come from 10 ground-based monitoring sites connected to NASA’s Multi-Angle Imager for Aerosols, or MAIA, project. In its official report, NASA says the network recorded pollution linked to traffic, fuel combustion, fires and holiday celebrations. The measurements are important because they show not only how much pollution is present, but also when it rises and what kinds of combustion may be contributing to it.
A detailed view of PM2.5 and black carbon
The study focuses on PM2.5, particles measuring 2.5 micrometres or less across. These particles are small enough to remain suspended in the air and are widely used in air-quality research because they can penetrate deep into the respiratory system. One component of PM2.5, black carbon, is produced by incomplete combustion from sources including fires, diesel vehicles and other fuels.
NASA reports that Addis Ababa’s three-year average PM2.5 concentration was 30 micrograms per cubic metre. That is more than three times the annual health-based standard used by the U.S. Environmental Protection Agency. The comparison is not a health diagnosis for any individual resident, but it places the measured citywide average in a range that underlines the scale of the monitoring challenge.
The ground sensors also recorded black-carbon levels approximately four to nine times higher than those measured in the three U.S. metropolitan areas that MAIA is monitoring. NASA cautions that pollution profiles differ from city to city because geography, traffic, industry and fuel use all affect the mix of particles. The comparison therefore points to a substantial difference in measured black carbon, rather than suggesting that the cities have identical conditions.
Pollution changes with daily and seasonal activity
One of the most useful results is the timing information. The Addis Ababa network detected increases associated with rush-hour traffic, while evening measurements showed that emissions did not disappear when traffic declined. Researchers observed continuing black-carbon signals from charcoal and other fuels used at night.
The sensors also identified increases during two major holidays that involve bonfires. Because the network measured changes across multiple sites and times, researchers could distinguish patterns associated with open fires from those more consistent with fossil-fuel combustion. That kind of source information can help researchers understand which interventions might reduce exposure, although the NASA report does not present a policy programme or claim that any single measure will solve the city’s air-quality problem.
The work is especially relevant as Addis Ababa grows. NASA notes that the wider urban area is home to nearly 6 million people and that United Nations projections put the population above 10 million by 2050. A stable record of pollution levels gives researchers a reference point against which future changes can be assessed as transport, energy use and urban development evolve.
What the MAIA satellite will add
The current results come from instruments on the ground, not from the MAIA satellite camera. NASA describes the sensor network as a valuable dataset in its own right, while the space-based part of the mission is designed to extend the observations across each metropolitan area. The camera will use multiple viewing angles to help identify different aerosol types from the way they reflect light.
NASA says the camera is scheduled to launch on an Italian Space Agency satellite no earlier than late 2027. Once operating, it is intended to map particle concentrations across the cities studied by MAIA and to distinguish characteristics such as particle shape and size. The project also includes public-health researchers, who will examine how concentration maps can be used alongside health data to study possible relationships between particle types and outcomes.
That future satellite coverage will not replace local monitoring. Instead, it is meant to complement the fixed sensors by showing how pollution varies across a wider urban area. The Addis Ababa measurements demonstrate why that combination matters: a citywide average can describe the overall burden, but detailed measurements reveal the daily peaks, seasonal patterns and local sources hidden behind the average.
For now, NASA’s announcement is best understood as a reporting milestone rather than a finished satellite result. The agency has documented a rare multi-year baseline for Addis Ababa and shown how ground observations can identify pollution patterns before space-based mapping begins. The dataset should give future researchers a reference for judging whether air quality changes as the city and its transport systems continue to develop.
