Once known as the “City of Smoke,” Pittsburgh has come a long way since the days when filthy air turned downtown streets dark at mid-day. But in struggling communities near the remaining steel plants, high levels of air pollution persist.
The World Health Organization estimates that outdoor ambient air pollution caused 4.2 million deaths in 2016. While many of these deaths are in low- and middle-income countries, the health effects are felt by people all around the world.
