But is there a difference between long term exposure to dirt (good) and diesel particulate emissions for instance? I don't think we can trust any of the data coming out of China at the moment.With regard to air quality I actually think that nations with poor air quality fare better than those with good air quality look at China although everyone doubts their figures it is unlikely they had anything like the death rate the U.K has despite a population 20 times as big but their cities are terribly polluted.If you have survived so far in smog your lungs are pretty resilient.Likewise here in Kenya most of us live in dirt and have a pretty good immune system plus the median age is about 20 rather than 40 plus in the UK as such there aren’t many care homes.