05/16/2025May 16, 2025 Home to a population of over 20 million, Lagos has an air pollution problem, due to traffic, open fires, industrial emissions and landfills that release toxic gases. A citizen science project helps gather data on air quality. https://p.dw.com/p/4uRSG At the break of dawn in Lagos, Nigeria, a group of determined marathon runners sets out — not just to test their endurance, but to collect vital data on the city’s air quality.