Where the Air Is Dirtiest
When we think of air pollution, we often conjure up images of vast metropolises in the Far East, the sun blocked out by smog as people wearing facemasks hurry down the busy sidewalks. But air pollution is also a problem closer to home, in Germany, for example. Temporary driving bans don't just exist in Paris, but also in comparatively sedate Stuttgart.
Pollution includes particulate matter, which is made up of soot released by factories and cars, but it also contains tiny particles released through braking and tire friction. Even in tiny quantities, it is considered a health menace. The particles, which are smaller than 10 microns (or roughly one-fifth the width of a human hair), damage the lungs and the circulatory system. Furthermore, other carcinogenic materials can become attached to the particulate matter and then inhaled.