The air we breathe...

Have you ever tried to understand what goes into air pollution and how governments are attempting to regulate the air we're supposed to breathe? It ain't simple. In my feeble attempts to understand, I've tried to concentrate in one specific area, that of particulates – also known as particulate matter (PM), the tiny little buggers that are tiny subdivisions of solid matter floating around.

While some of these particulates occur naturally (volcanoes, dust storms, forest and grass fires among others,) they're also the by-product of human activities, such as the burning of fossil fuels in cars and trucks, wood fireplaces, power plants and various industrial emissions that can generate significant amounts of particulates. These are supposed to be measured in micrograms per cubic meter and it seems to be quite difficult to find good tables that help folks like us compare where they stand. Has anyone any good suggestions on that topic?