NASA Study Provides First Long-Term Air Pollution Baseline for Addis Ababa

A NASA-funded research project has produced one of the most detailed long-term assessments of air pollution in Addis Ababa, Ethiopia, using a network of 10 ground-based sensors deployed across the city. The Multi-Angle Imager for Aerosols (MAIA) mission collected continuous measurements of fine particulate matter (PM2.5) and black carbon between 2022 and 2025. The findings, published in the journal ES&T: Air, represent the first multisite, long-term study of its kind in Ethiopia, according to researchers at NASA's Jet Propulsion Laboratory.

The study found that Addis Ababa's three-year average PM2.5 concentration was 30 micrograms per cubic meter, more than three times the U.S. Environmental Protection Agency's annual health-based standard. Average black carbon levels were approximately four to nine times higher than those measured in the three U.S. metropolitan areas—Los Angeles, Atlanta, and Boston—also monitored by the MAIA project. The 2025 State of Global Air Report estimates that PM2.5 exposure is associated with roughly 4.9 million deaths globally each year.

The sensor network captured how pollution varies by time of day and season, detecting spikes during rush-hour traffic and during major holidays involving bonfires. Researchers were able to distinguish between black carbon particles originating from biomass burning, such as charcoal and wood fires used for cooking and heating, and those from fossil fuel combustion, including diesel vehicles. The data also showed elevated emissions persisting into the night from residential fuel burning.

Addis Ababa, a metropolitan area of nearly 6 million people projected to surpass 10 million by 2050, presents a complex pollution profile shaped by rapid urbanization, traffic, and household energy use. The MAIA measurements provide a baseline for evaluating future air quality changes as Ethiopia implements new policies, including a 2024 ban on the import of internal combustion engine vehicles and expansions of bike lanes and electric vehicle infrastructure.

The MAIA mission combines the ground sensor network with a planned satellite observatory carrying a JPL-built multi-angle camera, scheduled for launch no earlier than late 2027 on an Italian Space Agency satellite. The instrument is designed to identify different types of PM2.5 aerosols by analyzing how they reflect light from multiple angles, enabling city-wide mapping of particle concentrations. MAIA is the first NASA mission to include public health researchers on its core team, who will correlate the pollution maps with health data to study links between specific particle types and health outcomes.

Scientists emphasize that the composition and sources of PM2.5 differ substantially between cities due to geography, traffic patterns, industry, and household practices. Long-term surface monitoring remains limited in many regions globally. By establishing a detailed baseline in Addis Ababa, the MAIA project aims to improve understanding of urban air pollution dynamics in rapidly growing cities and support more targeted air quality management strategies.