“I have seen evidence that second hand smoke has an effect”
Actually it has a positive effect. Think of it as a vaccination process for the lungs. As proof you can simply look at the skyrocketing asthma and allergy rates in children today, which seems to be very much in line with with reduced exposure to tobacco smoke.
In fact the WHO proved that exposure to second hand smoke has positive correlations to the reductions of cancer and other ailments. Check out the DaveHitt link posted earlier in this thread for the actual study.
Well possibly, but then there are other possible reasons why asthma is on the increase - a general increase in atmospheric pollutants of all kinds over the same time period being an obvious one.