As noted above, pollution levels are actually
higher inside cars than out where you're cycling.
Much higher --
http://www.things.org/~jym/greenpeac...side-cars.html
I know that doesn't
seem true, but in fact it is. So if you're going to get a Darth Vader breathing mask, wear it when you drive, because that's when you're sucking in the nasties. Better yet would be to stop driving altogether....