King's College have made this handy website to show daily levels of various air pollutants around London so you can see how bad, or not, your commute or local street are.  Quite useful if you are concerned about the long term effects on you or your families' health, or if you have a chronic lung condition. There is also useful info on there about their research, advise on exercise route planners etc

http://www.londonair.org.uk/LondonAir/nowcast.aspx