Smoking must prevent asthma. I've also wondered why if lead is so dangerous and we've been getting rid of lead for many years, are learning and behavior disorders increasing?
I seriously doubt smoking prevents asthma............however if one chooses to utilize the same pseudo-science being used in many of these "studies" which all belie the fact that correlation does NOT equal causation, one could possibly reach that conclusion.
There does however seem to be a correlation between the increase in asthma and the increasingly sterile environment in which children are kept - they don't play outside as much, homes are much more energy efficient (less fresh air) and nearly all cleaning products are anti-bacterial.
As to lead and increased learning and behaviorial disorders, I really don't know. Of many of the anti-smoker contingency have claimed for years that both learning and behavioral problems are caused by exposure to SHS.