Re: too late.
The air in our country is cleaner than it ever was.
Here's one chart showing how we're doing more with less pollution every year (sorry I couldn't find a bigger copy):
Why do you think environmentalists had to finally back themselves into a position where the very chemical process of combustion itself - fuel releasing energy and carbon dioxide - had to become a crime?
Incidentally, CO2 does not cause asthma. Nobody really knows why rates are increasing, and why there are so many geographical and other differences. There are as many theories as there are scientists.