I'm not sure how the article goes from interesting hypothesis (which it is) to near certainty.

>If we rule out changes in cigaret design and environmental factors as explanations for the enormous increase in lung cancer, what are we left with?

Seems like a false dichotomy to me. It can't be X, so it has to be Y.

>All of these would affect smokers and non-smokers equally. And yet lung cancer rates have not gone up for non-smokers.

This isn't necessarily true. It could be a synergistic effect, where some external factor increases cancer rates when smoking is also involved.