Air pollution is the world’s second-largest cause of death globally, leading to 8.1 million premature deaths annually from lung cancer, heart disease, and emphysema, among other diseases. Regular forest fires are a reminder for many in the U.S. that our air quality can be precarious, but in much of the world’s cities, foul air has been a fact of life for decades.Tracking air quality is a critical step toward preventing air pollution related illnesses, yet monitoring is nowhere near granular enough.