As a child I thought that ... "one day we will look back to the 1900s and we will consider it equally unacceptable to release car exhaust to the air as to deface in the drinking water".

At one hand, things have gradually become better. We're no longer adding tetraethyl lead to the petrol, we have catalytic converters on the petrol cars removing most of the soot, CO and NOx from the exhaust ... as well as particle filters on most of the diesel cars.

At the other hand, air pollution is becoming a bigger and bigger problem worldwide, mostly in the urban centers but even on the country side - and no nations seems to be spared. It has become an acknowledged fact that air pollution is reducing the life span, the last I saw was even some research pointing out that people lose intelligence by being exposed to air pollution! And then I even haven't touched CO2, greenhouse effect, acidification of the oceans as well as the problems with extracting oil from shale, etc ...