Purple air monitors are privately owned highly sensitive pollution monitors. They connect to a nationwide network and show pollution levels in an easy to read format on a map. There are several around the Pittsburgh area. They show the PM 2.5 amounts in the air in the city. See the map in real time
The image on the left shows the pollution over Allegheny county. The color circles show density of pollution, red and orange being high, yellow is moderate and green is within EPA limits.
PM2.5 Causes heart attack and stroke