Given almost anything can do something bad to you I've got a rule of thumb not to worry much about things unless they can quantify how many years they take off your life. There are still quite a lot of those around - smoking, air pollution and obesity being some of the top ones that can do >10 years. I'm not to bad on smoking and air pollution but could lose a pound or two. I figure central London has dropped from a couple of years off to maybe a couple of months over the time I've been around here.