NASA Study Reveals High Black Carbon Levels in Addis Ababa
A NASA-funded study has found that average black carbon concentrations in Addis Ababa are approximately 4 to 9 times higher than levels recorded in three U.S. metropolitan areas monitored by the same mission: Los Angeles, Atlanta, and Boston. The findings, published in Environmental Science & Technology: Air, are based on data collected between 2022 and 2025 from 10 air-quality monitoring sites across the Ethiopian capital under NASA's Multi-Angle Imager for Aerosols (MAIA) project.
Black carbon, commonly known as soot, is produced by incomplete combustion from sources including fires, diesel vehicles, and other fuels. The study found that pollution levels varied by time of day and season, with increases associated with rush-hour traffic and combustion activities. The research also detected increases in black carbon during two major Ethiopian holidays involving traditional bonfires. Researchers were able to distinguish particles originating from the fires from those associated with fossil-fuel combustion, helping identify different sources of particulate pollution.
The study found that Addis Ababa's three-year average concentration of fine particulate matter, known as PM2.5, was 30 micrograms per cubic metre — more than three times the annual health-based PM2.5 standard set by the U.S. Environmental Protection Agency.
"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 co-author of the study and deputy principal investigator of MAIA at NASA's Jet Propulsion Laboratory in Southern California. He said the measurements provide an important baseline for understanding how pollution changes across rapidly growing cities where long-term monitoring remains limited.
Araya Asfaw of Addis Ababa University, a co-author and MAIA's lead Ethiopian collaborator, noted that emissions remain significant at night due to charcoal and other fuel combustion.
Study Context and MAIA Mission
The MAIA project is monitoring air pollution in 12 metropolitan areas worldwide, including Los Angeles, Atlanta, and Boston. The satellite component of the mission is scheduled for launch on an Italian Space Agency satellite no earlier than late 2027. The space observatory uses a JPL-built camera designed to identify different types of PM2.5 aerosols based on how they reflect light. Mounted on a gimbal, the camera captures data from multiple angles using JPL-pioneered technologies. MAIA is the first NASA project to include public health researchers among a space mission's team; they will combine concentration maps with health data to study health impacts.
The monitoring network itself has provided a detailed long-term view of black carbon's role in the city, according to a separate account of the study. "This paper shows how valuable the air sensor data is on its own, but combining the sensor network and satellite observations will be a game-changer," said Kyan Shlipak, the paper's lead author.
The greater Addis Ababa urban area is home to nearly 6 million people, and according to United Nations projections, that figure is expected to surpass 10 million by 2050. Asfaw described Addis Ababa as "Africa's version of Brussels."
Policy Measures and Local Pollution Sources
Ethiopia has taken steps aimed at improving air quality. In 2024, the country became the first in the world to ban the import of internal-combustion-engine vehicles, while cities have been adding bike lanes and electric vehicle infrastructure. The MAIA project's measurements provide researchers with a baseline for understanding how air quality changes over time as Addis Ababa continues to grow and evolve.
The study focuses on PM2.5, particulate matter 2.5 micrometers or less in diameter, which is linked to health risks. The 2025 State of Global Air Report, cited in the paper, estimates that exposure to PM2.5 is associated with approximately 4.9 million deaths globally each year.
IQAir, an air quality monitoring organization, reported that on 6 August 2025, Addis Ababa ranked fourth globally among major cities with an Air Quality Index of 147 and a PM2.5 concentration of 54.2 micrograms per cubic metre, classified as "unhealthy for sensitive groups." According to IQAir, major sources of pollution in the city include vehicle emissions, biomass burning, construction dust, dust from unpaved roads, and open waste burning. Diesel vehicles were estimated to account for up to 29% of PM2.5 pollution. IQAir also noted that pollution levels during Hidar Sitaten celebrations reached more than eight times the World Health Organization guideline.
Seasonal weather conditions and Addis Ababa's high altitude can contribute to the accumulation of pollutants near the ground, further exacerbating air quality issues.