Asthma is a disease directly related to high living standards. Studies show that kids that are brought up in sterile-like clean enviroment do not develop necessary antibodies at young age and therefore develop asthma.
There is a direct relation between high living standard and asthma.. Of course the pollution doesn't help either. If you protect your kid from all possible dirt at young age, chances are that he'll develop asthma sooner or later in his life. Things are only made worse by the fact that many modern women don't breast feed their babies long enough (or at all) which deprives the child from the natural protection. They want perky titties.