Nairobi Air Quality Index (AQI)
Africa's fourth-largest city sits at 1,800m altitude, giving it natural ventilation advantages over low-lying cities. But rapid urbanization, 20,000+ diesel matatus, and charcoal cooking in informal settlements push PM2.5 well above WHO guidelines.
Monthly AQI Pattern
Long rains (Apr–May) are the cleanest months. July–August dry season peaks are worst.
Key Pollutants — Nairobi 2024
| Pollutant | Level | WHO Guideline | Primary Source |
|---|---|---|---|
| PM2.5exceeds WHO | 18 μg/m³ | 5 μg/m³ | Matatu diesel exhaust, charcoal cooking, open burning |
| PM10exceeds WHO | 42 μg/m³ | 15 μg/m³ | Construction dust, unpaved roads, dry season burning |
| NO₂exceeds WHO | ~30 μg/m³ | 10 μg/m³ | Diesel matatus, informal diesel generators, traffic |
| Black Carbon | Elevated | — | Charcoal burning, diesel exhaust — major public health concern |
| CO | Moderate | — | Vehicle exhaust, charcoal stoves in enclosed spaces |
Nairobi vs. Other African Capitals
Frequently Asked Questions
What is causing Nairobi's air pollution problem?
Nairobi's air quality challenges have three main drivers: (1) Matatu culture — an estimated 20,000+ diesel minibuses (matatus) circulate through the city, many running old, poorly maintained engines emitting black smoke; (2) Charcoal and biomass cooking — over 60% of Nairobi residents use charcoal or wood for cooking, generating significant PM2.5 and black carbon especially in informal settlements like Kibera and Mathare; (3) Rapid urbanization — construction dust from the city's fast expansion, plus the conversion of green spaces to impervious surfaces, increases dust loads.
How does Nairobi's high altitude affect air quality?
Nairobi sits at 1,795 meters (5,889 ft) above sea level — higher than most African capitals. This altitude provides two air quality benefits: cooler temperatures reduce secondary aerosol formation, and the elevated position catches trade winds that provide natural ventilation. On days with good wind flow, Nairobi's air can be remarkably clean. However, during calm, anticyclonic conditions (especially July–August dry season), pollution concentrates in valleys and low-lying areas like the Nairobi River corridor.
When is Nairobi's air quality worst?
The July–August dry season is typically worst. Rainfall stops, soils dry out, construction dust peaks, and farmers burn agricultural waste on the outskirts. The long dry season (Jan–Feb) also brings elevated pollution. Conversely, April–May (long rains) is the cleanest period — frequent rains wash particulates from the air, AQI regularly drops to 50 or below.
Is Nairobi safe from an air quality perspective?
By global standards, Nairobi is moderate — significantly cleaner than Cairo, Lagos, Delhi, or Beijing. However, PM2.5 at 18 μg/m³ annually exceeds WHO guidelines 3.6× and carries long-term cardiovascular and respiratory risk. The highest-risk populations are those who live near major roads (matatu exhaust), cook with charcoal in enclosed spaces (indoor black carbon), or work outdoors during dry season burning events.
What can Nairobi do to improve air quality?
Key interventions include: (1) Transitioning matatu fleet to CNG or electric — Kenya has begun piloting e-buses; (2) Promoting improved cookstoves and LPG access in informal settlements to replace charcoal; (3) Banning agricultural waste burning and providing affordable alternatives to farmers; (4) Paving unpaved roads that generate dust (a major PM10 source). Kenya's Air Quality Regulations of 2014 provide a legal framework, but enforcement capacity is limited.