Air pollution is one of those things, like weather and climate, that because it affects everyone we all have an opinion about it. This makes it an ideal area for "citizen" and "traditional" scientists to collaborate and work towards improving our lives. However, air pollution is not easy (I've been at it for 15 years and I still can't claim to get it) and clarity on the concepts used is key to maintain the communication and collaboration.
One of those concepts that is very easy to get confused about is particulate matter (PM).
