What do we know about air quality in Nairobi?

A road packed with buses in central Nairobi

Packed streets at rush hour in downtown Nairobi (via the New York Times)

I went down a bit of a rabbit hole on Nairobi air quality the other weekend, after I went for a long bike ride, and ended up chugging up a steep hill alongside a matatu emitting black smoke directly into my face.  I wanted to know if I could pick specific areas or specific times of the week when it would be safer to ride.  (Research suggests that the health benefits of cycling probably outweigh the costs of pollution exposure in all but the most polluted cities, but I’m still not keen on breathing in matatu exhaust.)

What I found is that there’s a strong consensus that Nairobi’s air quality is poor, but very limited data about variations in air quality by neighborhood or time of day.  An MIT project shared data from five locations around the city collected from 2016 – 2017, and found that timing of the highest levels of pollution varied significantly between sites.  (Thus, no possibility of making a uniform recommendation like “avoid cycling in the afternoon” across the city.)

Three graphs showing pollution by time of day in Kibera, St Scholastika, and the United Nations in Nairobi

What about real-time data?  Air-quality.com offers data from two sensors in Kilimani and Kitisuru.  They’re currently suggesting that the air quality index is around 54 by US standards, which stands for “moderate pollution with mild impacts on extremely sensitive groups.”  However, these are also relatively wealthy neighborhoods that don’t see much traffic from buses and trucks, which tend to be the worst polluters.  We clearly can’t extrapolate from this to the whole city.

Another project called sensors.AFRICA is supposed to be launching an air quality monitoring network with 22 sensors across the city.  However, they don’t appear to be operating yet.  In short, Nairobi has a lot of work to do to provide adequate real-time data on its air quality.