Nairobi has been ranked as Africa's third most polluted major city by Swiss air quality monitor IQAir, raising significant concerns about public health.

• Nairobi has an Air Quality Index (AQI) reading of 92, placing it in the ‘moderate’ category, and significantly exceeding the World Health Organization's (WHO) 5 µg/m³ annual PM guideline.
• The dominant pollutant in Nairobi is PM2.5, with an average concentration of 14.7 µg/m³ in 2020.
• Main drivers of pollution include a high number of older vehicles, factory emissions, construction, and open burning.