NASA-Funded Sensors Reveal Detailed Picture of Soot Pollution in Addis Ababa

A NASA-funded air pollution monitoring network has produced one of the most detailed long-term views yet of black carbon - soot from fires, diesel vehicles and other combustion sources - in Ethiopia's capital, Addis Ababa. Scientists analyzed data collected between 2022 and 2025 from 10 air-quality monitoring sites deployed by NASA's Multi-Angle Imager for Aerosols (MAIA) project, in a study published in ES&T: Air. The measurements show how pollution changes by time of day and season, including increases tied to rush-hour traffic and holiday bonfires.

The study focused on particulate matter 2.5 micrometers or smaller, known as PM2.5, which the 2025 State of Global Air Report estimates is linked to roughly 4.9 million deaths worldwide each year. Addis Ababa's three-year average PM2.5 concentration was 30 micrograms per cubic meter, more than three times the US Environmental Protection Agency's health-based annual standard. Average black carbon levels in the city were roughly four to nine times higher than those measured in the three US metropolitan areas the MAIA project also monitors: Los Angeles, Atlanta and Boston.

"To our knowledge, this is the first long-term, multisite study of continuous PM2.5 and black carbon measurements in Ethiopia," said Sina Hasheminassab, a coauthor of the paper and MAIA's deputy principal investigator at NASA's Jet Propulsion Laboratory. "Many rapidly growing cities have limited long-term monitoring, so these measurements provide an important baseline for understanding how pollution changes across space and time." The sensor network detected black carbon increases during two major holidays involving bonfires and could distinguish particles from those fires from particles produced by fossil fuel combustion.

The greater Addis Ababa area is home to nearly 6 million people, a figure UN projections suggest will surpass 10 million by 2050. In 2024, Ethiopia became the first country in the world to ban the import of internal combustion engine vehicles, while cities have been adding bike lanes and electric vehicle infrastructure. "Even at night, when traffic dies down, you see high emissions from the burning of charcoal and other fuels," said Araya Asfaw of Addis Ababa University, the project's lead Ethiopian collaborator.