Summary
A NASA-funded network of 10 ground sensors measured PM2.5 and black carbon across Addis Ababa from 2022 to 2025. The data show pollution patterns linked to traffic, fuel burning and holiday bonfires, creating a baseline for future satellite observations.
A NASA-funded network of 10 ground sensors has produced a detailed three-year record of fine-particle pollution in Addis Ababa, Ethiopia. The measurements show how PM2.5 and black carbon vary by time of day, season and local activity, including increases associated with rush-hour traffic and holiday bonfires.
The findings come from a paper published in ES&T: Air, based on measurements collected between 2022 and 2025 by NASA’s Multi-Angle Imager for Aerosols (MAIA) project. The network provides a baseline for tracking air-quality changes as Addis Ababa grows and Ethiopia expands measures such as bike lanes and electric-vehicle infrastructure.
What the Addis Ababa network measured
PM2.5 is particulate matter with a diameter of 2.5 micrometres or less. Because these particles are small enough to enter deep into the respiratory system, long-term exposure is an important air-quality concern. The paper cites an estimate from the 2025 State of Global Air report associating PM2.5 exposure with approximately 4.9 million deaths globally each year.
The study reports a three-year average PM2.5 concentration of 30 micrograms per cubic metre in Addis Ababa. NASA says that is more than three times the U.S. Environmental Protection Agency’s health-based annual PM2.5 standard.
The sensors also measured black carbon, a soot-like component produced by combustion, including fires, diesel vehicles and other fuel-burning sources. Average black carbon levels in Addis Ababa were approximately four to nine times higher than levels measured in the three U.S. metropolitan areas being monitored by MAIA: Los Angeles, Atlanta and Boston.
The network’s time-resolved measurements helped distinguish different pollution patterns. Black carbon increased during periods associated with heavy traffic, while elevated levels were also detected during two major Addis Ababa holidays involving bonfires. The measurements allowed researchers to differentiate particles linked to those fires from particles associated with fossil-fuel combustion.
That source information matters because PM2.5 is not a single substance. Its composition can vary with local geography, traffic, industry and fuel use. Dust may contribute more in some desert cities, while areas near coal-fired power plants may have higher concentrations of sulfate. Long-term surface measurements remain limited in many parts of the world.
How MAIA will extend the measurements
MAIA currently combines the Addis Ababa sensor network with a planned space-observation system. Its JPL-built camera is designed to identify different types of PM2.5 aerosols by observing how they reflect light. Mounted on a gimbal, the camera will collect observations from multiple angles, using techniques intended to make airborne particles more distinguishable from the surface below.
The space observatory is scheduled to launch on an Italian Space Agency satellite no earlier than late 2027. Once operating, its observations are intended to map particle concentrations over the metropolitan areas studied by the mission and complement the detailed measurements collected at ground level.
MAIA is also notable for including public-health researchers as part of a space mission team. Those researchers plan to combine PM2.5 maps with health data to investigate potential relationships between particle types and health outcomes. The Addis Ababa paper itself is an environmental monitoring study: its main contribution is documenting pollution levels, timing and likely sources rather than reporting health outcomes in the monitored population.
With the greater Addis Ababa urban area home to nearly 6 million people and projected by the United Nations to exceed 10 million by 2050, the sensor record gives researchers a reference point for evaluating how air quality changes as the city develops. The measurements may also help other cities design monitoring systems that distinguish not only how much particulate pollution is present, but where it comes from and when it is most concentrated.