Guardian: The air quality is officially good, 400ft above Paris in a balloon at rush hour. From that height you can see the ring road and many of the citys 37 bridges blocked with traffic, the commuting trains coming in, and on the first cold day of winter water vapour rising from several power stations as thousands of central heating systems fire up . A yellowish haze has formed on the horizon as air pressure builds, but the pollution from Pariss transport, construction sites and power stations is...